Precast pile, combined pile and construction method

Abstract

The invention provides a precast pile, a combined pile and a construction method, and relates to the technical field of pile foundation construction.The precast pile comprises a first pile body, a second pile body and a third pile body, the first thickened protrusions are fixed to the peripheral wall of the first pile body and arranged in the length direction of the first pile body at intervals; the first annular protrusion is fixed to the first pile body in a surrounding mode, and the at least one first thickened protrusion is located between the first annular protrusion and the second end; when the precast pile is placed in the drill hole, the projection of the inner peripheral wall of the drill hole in the length direction of the first pile body surrounds the outer side of the projection of the combination body of the first pile body and the first thickened protrusion in the length direction of the first pile body, and the projection of the first annular protrusion in the length direction of the first pile body completely covers the projection of the inner peripheral wall of the drill hole in the length direction of the first pile body. After construction of the combined pile comprising the precast pile is completed, the bearing capacity of the combined pile can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation construction, and in particular to a prefabricated pile, a combined pile and a construction method. Background Art

[0002] With the increase in urban building density, more and more pile foundation construction projects, both new and expanded, need to reduce or even eliminate the impact of soil squeezing on the surrounding environment, which has also led to the development of implanted pile technology. Implanted pile technology was early applied to my country's coastal soft soil areas. After drilling, the soil in the hole needs to be stirred and liquefied, and then the pile is driven into the soil. At this time, the liquid level in the hole rises and is partially discharged, which will not produce soil squeezing effect. Therefore, the implantation method is very suitable for soft soil foundations.

[0003] Under the existing construction process of implanted piles, there are two failure interfaces in the pile body under the vertical load, namely, the interface S1 between the core pile 7 and the solidified soil 6 around the pile, and the interface S2 between the solidified soil 6 around the pile and the original soil 5 around the hole wall. Figure 1 As shown. According to the bearing capacity calculation formula, Q uk =u∑ξ si q sik l i +q pk A p Only by simultaneously increasing the limit friction resistance of the above two failure interfaces S1 and S2 can the single pile bearing capacity of the implanted pile be effectively improved.

[0004] In order to improve the single pile bearing capacity of the implanted pile, bamboo piles were developed on the basis of conventional pipe piles. They are a special-shaped pipe pile, see patent CN2611433Y. The bamboo pile has "bamboo nodes" protruding from the pile body at intervals, so it is also called bamboo pile. Unlike pipe piles, bamboo piles are difficult to cast on site. Although some literature points out that cast-in-place piles can also be made into a shape similar to bamboo piles, the bamboo piles formed by casting are significantly different from prefabricated bamboo piles in size, surface burrs and bearing performance due to the uncertainty of drilling technology and foundation construction conditions. The two cannot be confused. The technology of forming special-shaped piles similar to bamboo piles by casting has no reference and reference significance in the production and construction of prefabricated bamboo piles, and in addition to production tests in the industry, there have been no actual construction projects of cast-in-place bamboo piles. Prefabricated bamboo piles are very suitable for implantation construction. When traditional static pressure and hammering methods are applied to bamboo piles, the soil squeezing effect is very prominent. When the implantation method is used, the diameter of the drill hole is larger than the bamboo part, so the bamboo pile can be sent into the foundation in a "non-soil squeezing" manner. After the bamboo pile is completed and combined with the pile surrounding solidified soil 6, the pile surrounding solidified soil 6 not only contacts the pile body, but also contacts the surface of the bamboo, effectively increasing the peak shear stress of the interface S1. Compared with ordinary prefabricated piles of the same diameter, the interface S1 between the pile surrounding solidified soil 6 and the core pile 7 is less likely to be damaged.

[0005] However, under the implantation construction method, the interface S2 between the solidified soil around the pile and the original soil around the hole wall has not been improved compared with the ordinary precast piles of the same diameter, and has become a limiting factor for the bearing capacity of the single bamboo pile constructed by the implantation method. Although increasing the pile diameter can improve the bearing capacity, the amount of concrete will inevitably increase greatly with the increase in the pile diameter, and the transportation, construction difficulty and maintenance time of the bamboo pile will also increase accordingly. The increased cost is not competitive in industrial applications. Therefore, under the premise of not changing the pile diameter or the borehole diameter, in order to further improve the single pile bearing capacity of the implanted pile, it is necessary to solve the problem of how to increase the boundary friction between the solidified soil around the pile and the original soil around the hole wall. Summary of the invention

[0006] The technical problem to be solved by the present application is how to increase the boundary friction resistance between the solidified soil around the pile and the original soil around the hole wall. In view of this, the present application provides a prefabricated pile, a combined pile and a construction method.

[0007] In a first aspect, a prefabricated pile comprises:

[0008] A first pile body, wherein two ends of the first pile body along the length direction are respectively a first end and a second end;

[0009] a plurality of first thickened protrusions fixed to the outer peripheral wall of the first pile body and arranged at intervals along the length direction of the first pile body; and

[0010] A first annular protrusion is fixed around the first pile body, and at least one of the first thickened protrusions is located between the first annular protrusion and the second end;

[0011] When the prefabricated pile is placed in the drilled hole, the inner circumferential wall of the drilled hole is projected along the length direction of the first pile body around the outer side of the first pile body and the first thickened protrusion combination projected along the length direction of the first pile body, and the first annular protrusion is projected along the length direction of the first pile body to completely cover the inner circumferential wall of the drilled hole projected along the length direction of the first pile body.

[0012] Compared with the prior art, the prefabricated pile of the present application has the following advantages: when the prefabricated pile is implanted in the borehole, the lower end face of the first annular protrusion forms a closed cavity with the outer peripheral wall of the first pile body and the side wall of the borehole, squeezing the cement soil on the lower side of the first annular protrusion in the borehole to increase the pressure on the lower side of the lower end face of the first annular protrusion in the borehole, and the cement soil enters the gaps in the soil around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the prefabricated pile is implanted. In addition, the cement soil around the first thickened protrusion is squeezed by the first annular protrusion, and the density increases, and the interaction force between the first thickened protrusion and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the prefabricated pile and the solidified soil around the pile, and further improving the bearing capacity of the single pile after the prefabricated pile is implanted.

[0013] In a preferred embodiment, the prefabricated pile further comprises at least one second annular protrusion fixed around the circumferential wall of the first pile body, the second annular protrusion is located between the first annular protrusion and the second end, the projection of the first annular protrusion along the length direction of the first pile body covers the projection of the second annular protrusion along the length direction of the first pile body, and the projection of the outer circumferential wall of the second annular protrusion along the length direction of the first pile body is located outside the projection of the borehole along the length direction of the first pile body, or the projection of the outer circumferential wall of the first annular protrusion along the length direction of the first pile body at least partially overlaps the projection of the outer circumferential wall of the second annular protrusion along the length direction of the first pile body.

[0014] In a preferred embodiment, at least one pressure relief channel is provided on the second annular protrusion, and the pressure relief channel penetrates the second annular protrusion along the length direction of the first pile body;

[0015] And / or, at least one of the first thickened protrusions is disposed between the first annular protrusion and the second annular protrusion.

[0016] In a preferred embodiment, the second annular protrusion is provided with two or more pressure relief channels spaced apart along the circumferential direction, and / or at least one of the pressure relief channels is a through hole or a notch.

[0017] In a preferred embodiment, the first pile body, the first thickened protrusion, the first annular protrusion, and the second annular protrusion are prefabricated in one piece;

[0018] The first pile body is arranged in a hollow round pile, and the plurality of the first thickened protrusions are arranged in a bamboo-joint shape along the length direction of the first pile body. The first annular protrusion and the second annular protrusion are both arranged in a circular ring shape. The first thickened protrusion, the first annular protrusion, the second annular protrusion and the first pile body are arranged coaxially.

[0019] In a preferred embodiment, the first pile body, the first thickened protrusion, the first annular protrusion, and the second annular protrusion are prefabricated in one piece;

[0020] The first pile body is arranged as a hollow square pile, the first thickened protrusion, the first annular protrusion and the second annular protrusion are all arranged in a square ring shape, and the first thickened protrusion, the first annular protrusion and the second annular protrusion are all parallel and surround the outer side of the first pile body.

[0021] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as a whole, the first pile body is arranged as a hollow round pile, and a plurality of the first thickened protrusions are arranged in a bamboo-like shape along the length direction of the first pile body;

[0022] The first annular protrusion and the second annular protrusion are both arranged in a circular ring shape, the first thickened protrusion, the first annular protrusion, the second annular protrusion and the first pile body are coaxially arranged, the first annular protrusion and / or the second annular protrusion include more than two arc-shaped protrusions that can be spliced ​​together to form a circular ring shape, and the arc-shaped protrusion is welded and fixed or detachably fixed to the first pile body.

[0023] In a preferred embodiment, a groove is provided on the inner peripheral wall of the arc-shaped protrusion, and when the arc-shaped protrusion is fixed on the first thickened protrusion, the outer peripheral wall of the first thickened protrusion and the inner side wall of the groove fit each other to limit the axial position of the arc-shaped protrusion.

[0024] In a preferred embodiment, the arc-shaped protrusion is prefabricated from concrete, and a first embedded steel part extending in a circumferential direction is pre-embedded in at least one of the two ends of the inner circumferential wall of the arc-shaped protrusion along the length direction of the first pile body, and a second embedded steel part extending in a circumferential direction and corresponding to the first embedded steel part is pre-embedded on the first pile body, and the first embedded steel part is correspondingly welded to the second embedded steel part.

[0025] In a preferred embodiment, a plurality of first steel bars, first connecting bars and radial bars are embedded in the arc-shaped protrusion, the plurality of first steel bars are evenly arranged along the circumference of the arc-shaped protrusion, the first steel bar extends along the axial direction of the arc-shaped protrusion, one end of two first connecting bars are respectively connected to the two ends of one first steel bar, the other ends of two first connecting bars are respectively welded and fixed to two first embedded steel parts, the plurality of radial bars are all connected to the first steel bar and evenly distributed along the length direction of the first steel bar, and the radial bars extend radially along the arc-shaped protrusion;

[0026] The first pile body is pre-embedded with multiple second steel bars and second connecting bars, the multiple second steel bars are evenly distributed along the circumference of the first pile body and fixed on the prestressed main bars of the first pile body, the second steel bars are arranged corresponding to the first thickened protrusions, one ends of two second connecting bars are respectively connected to the two ends of one second steel bar, and the other ends of the two second connecting bars are respectively welded and fixed to the two second embedded steel parts on the axial sides of the first thickened protrusion.

[0027] In a preferred embodiment, the arc-shaped protrusion is prefabricated from concrete, and is provided with a through hole extending radially, the through hole passing through the inner and outer circumferential walls of the arc-shaped protrusion, and a bolt hole is provided on the outer circumferential wall of the first thickened protrusion, and the bolt hole is equipped with an expansion bolt passing through the through hole to fix the arc-shaped protrusion to the first thickened protrusion.

[0028] In a preferred embodiment, the first annular protrusion and / or the second annular protrusion includes a first conical surface, a cylindrical surface and a second conical surface connected in sequence from the first end to the second end of the first pile body, the cylindrical surface extends along the length direction of the first pile body and surrounds the outer side of the first pile body, the end of the first conical surface facing the first end is connected to the first pile body, the end of the second conical surface facing the first end is connected to the first pile body, and the second conical surface cooperates with the first pile body to form an annular cavity with an opening arranged toward the second end.

[0029] In a preferred embodiment, the first annular protrusion and / or the second annular protrusion both include a first conical surface, a cylindrical surface, and a second conical surface sequentially connected from the first end to the second end of the first pile body, the cylindrical surface extends along the length direction of the first pile body and surrounds the outer side of the first pile body, the end of the first conical surface facing the first end and the end of the second conical surface facing the second end are both connected to the first pile body, the diameter of the first conical surface gradually increases from the first end to the second end of the first pile body, and the diameter of the second conical surface gradually decreases from the first end to the second end of the first pile body.

[0030] In a preferred embodiment, the angle between the second conical surface and the length direction of the first pile body is greater than 45° and less than 90°.

[0031] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated in one piece;

[0032] The outer peripheral wall of the end plate at the first end is projected along the length direction of the first pile body around the outer side of the first thickened protrusion projected along the length direction of the first pile body, and the part of the end plate at the first end extending out of the first pile body forms the first annular protrusion.

[0033] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated in one piece;

[0034] The first annular protrusion is arranged in an end plate shape, and a plurality of spaced-apart through holes are provided on the first annular protrusion, and the through holes penetrate through the two end surfaces of the first annular protrusion along the length direction of the first pile body, and a threaded hole corresponding to the through hole is provided on the end plate at the first end of the first pile body, and a bolt passing through the through hole is assembled in the threaded hole to fix the first annular protrusion on the first pile body.

[0035] In a preferred embodiment, the threaded hole is an anchor hole of an end plate at the first end of the first pile body, and the anchor hole is used for a heading to pass through from the first end to the second end.

[0036] In a preferred embodiment, the length of the first pile body is defined as L, the first end is defined as a starting point, and the first annular protrusion is located within the interval [0, L / 2] of the first pile body.

[0037] In a preferred embodiment, the first annular protrusion is located within the interval [0, L / 4] of the first pile body.

[0038] In a preferred embodiment, the first thickened protrusion and the first annular protrusion are both parallel and surround the outer side of the first pile body, and the distance from the outer edge of the first thickened protrusion projected along the length direction of the first pile body to the outer edge of the first annular protrusion projected along the length direction of the first pile body is a fixed value, and the fixed value is not less than 40 mm and not more than 150 mm.

[0039] In a preferred embodiment, the first pile body is arranged in a hollow round pile, the first thickened protrusion and the first annular protrusion are arranged in a circular ring shape, the first thickened protrusion, the first annular protrusion and the first pile body are arranged coaxially, the outer diameter of the first annular protrusion is 0 to 50 mm larger than the diameter of the drilled hole, and the outer diameter of the first thickened protrusion is 40 mm to 100 mm smaller than the diameter of the drilled hole.

[0040] In a preferred embodiment, the first pile body is arranged in a hollow round pile, the first thickened protrusion and the first annular protrusion are arranged in a circular ring shape, the first thickened protrusion, the first annular protrusion and the first pile body are arranged coaxially, the outer diameter of the first pile body is 350mm to 750mm, the outer diameter of the first annular protrusion is 90mm to 200mm larger than the outer diameter of the first pile body, the outer diameter of the first thickened protrusion is 50mm to 150mm larger than the outer diameter of the first pile body, and the outer diameter of the first annular protrusion is 40mm to 150mm larger than the outer diameter of the first thickened protrusion.

[0041] In a second aspect, the present application provides a combined pile, comprising:

[0042] A top precast pile consisting of a precast pile as described above; and

[0043] at least one bottom precast pile connected to the lower end of the top precast pile;

[0044] The bottom prefabricated pile comprises a second pile body extending vertically, wherein a projection of an outer peripheral wall of the second pile body along a length direction of the first pile body completely overlaps with a projection of an outer peripheral wall of the first pile body along the length direction of the first pile body.

[0045] Compared with the prior art, the composite pile of the present application has the following advantages: when the top prefabricated pile is implanted into the borehole, the lower end face of the first annular protrusion forms a closed cavity with the outer peripheral wall of the first pile body and the side wall of the borehole, squeezing the cement soil on the lower side of the first annular protrusion in the borehole to increase the pressure on the lower side of the lower end face of the first annular protrusion in the borehole, and the cement soil enters the gaps in the soil around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted. In addition, the cement soil on the lower side of the first annular protrusion is squeezed by the first annular protrusion, and the density increases, and the interaction force between the first thickened protrusion, the concrete pile and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, and further improving the bearing capacity of the single pile after the composite pile is implanted.

[0046] In a preferred embodiment, the bottom precast pile also includes a plurality of second thickened protrusions fixed around the outer peripheral wall of the second pile body, the second thickened protrusions are prefabricated integrally with the second pile body, the plurality of second thickened protrusions are arranged at intervals along the length direction of the second pile body, and the outer peripheral wall of the first annular protrusion is projected along the length direction of the first pile body around the outer side of the projection of the second pile body and the second annular protrusion combination along the length direction of the first pile body.

[0047] In a preferred embodiment, the second pile body and the first pile body are both arranged in the form of hollow round piles, the first thickened protrusion, the first annular protrusion and the second thickened protrusion are all arranged in a circular ring shape, the first thickened protrusion, the first annular protrusion, the second thickened protrusion, the second pile body and the first pile body are arranged coaxially, and multiple second thickened protrusions are arranged in a bamboo-joint shape along the length direction of the second pile body, and the outer diameter of the second annular protrusion is equal to the outer diameter of the first thickened protrusion.

[0048] In a preferred embodiment, the bottom precast piles are tubular structures with an inner cavity, and a blocking structure for at least partially blocking the inner cavity is fixed to at least one of the bottom precast piles; or at least one of the bottom precast piles is a solid structure.

[0049] In a preferred embodiment, the blocking structure is an end blocking plate provided at the end of the bottom precast pile.

[0050] In a preferred embodiment, it also includes a uniform cross-section pipe pile connected to the upper end of the precast pile, the uniform cross-section pipe pile extends vertically and is prefabricated in one piece from concrete, and the projection of the outer peripheral wall of the uniform cross-section pipe pile along the length direction of the first pile body coincides with the projection of the outer peripheral wall of the first annular protrusion along the length direction of the first pile body.

[0051] In a preferred embodiment, the first annular protrusion is arranged at the uppermost end of the first pile body and is connected to the uniform-section pipe pile, the first annular protrusion and the first pile body are prefabricated as one piece, the upper end face, the outer peripheral face and the lower end face of the first annular protrusion are connected in sequence from top to bottom, the upper end face of the first annular protrusion extends from the outer peripheral face to the first pile body, the upper end face of the first annular protrusion is coplanar with the upper end face of the first pile body, the outer peripheral face of the first annular protrusion extends vertically and surrounds the outside of the first pile body, the lower end face of the first annular protrusion extends from the outer peripheral face to the first pile body, the lower end face of the first annular protrusion is conically arranged, and the diameter of the lower end face of the first annular protrusion gradually decreases from top to bottom.

[0052] In a third aspect, the present application provides a precast pile construction method, using the precast piles as described above or the combined piles as described above.

[0053] In a fourth aspect, the present application provides a construction method using the above-mentioned combined piles, comprising the following steps:

[0054] S1. Drilling hole setting: the drilling hole size is designed according to the cross-sectional size of the first pile body of the precast pile, the orthographic projection of the inner circumferential wall of the drilled hole in the horizontal plane surrounds the outer side of the orthographic projection of the first pile body and the first thickened protrusion combination in the horizontal plane, and the orthographic projection of the inner circumferential wall of the drilled hole in the horizontal plane is completely covered by the orthographic projection of the second annular protrusion in the horizontal plane;

[0055] S2, drilling construction: drilling according to the drilling settings;

[0056] S3, bottom prefabricated pile planting and grouting: including placing at least one of the bottom prefabricated piles into the borehole and injecting solidified slurry into the borehole;

[0057] S4. Top precast pile planting: place the precast pile on the upper end of the bottom precast pile and press the precast pile into the borehole, wherein the first annular protrusion and the second annular protrusion squeeze the soil around the borehole wall and / or the solidified slurry during the process of placing the precast pile into the borehole.

[0058] Compared with the prior art, the composite pile construction method of the present application has the following advantages: a precast pile is used as the top precast pile of the composite pile. When the precast pile is implanted into the borehole, the lower end face of the first annular protrusion forms a closed cavity with the outer peripheral wall of the first pile body and the side wall of the borehole, and squeezes the cement soil on the lower side of the first annular protrusion in the borehole to increase the pressure on the lower side of the lower end face of the first annular protrusion in the borehole, and the cement soil enters the gap of the soil body around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted. In addition, the cement soil on the lower side of the first annular protrusion is squeezed by the first annular protrusion, and the density increases, and the interaction force between the first thickened protrusion, the precast pile and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, and further improving the bearing capacity of the single pile after the composite pile is implanted.

[0059] In a preferred embodiment, the grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the precast pile is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact the second annular protrusion or the first annular protrusion.

[0060] In a preferred embodiment, at least four second thickened protrusions are distributed over the bottom 2.6 m of a section of bottom precast piles first placed into the borehole.

[0061] In a preferred embodiment, step S2 further comprises expanding the diameter of the borehole at the bottom, wherein the borehole cavity of the expanded diameter borehole accommodates at least four second thickened protrusions at the bottom of the first section of bottom precast piles inserted into the borehole.

[0062] In a preferred embodiment, the depth of the expanded borehole is greater than 2 m and less than 3 m, preferably greater than 2.4 m and less than 2.8 m. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a bearing capacity analysis diagram of the implantation construction in the prior art;

[0064] Figure 2 This is a schematic diagram of the structure of the prefabricated piles of Example 1 of the present application;

[0065] Figure 3 It is a schematic projection diagram of the drill hole, the first annular protrusion, the second annular protrusion and the first thickened protrusion along the length direction of the first pile body in Example 1 of the present application;

[0066] Figure 4 The QS curves of the prefabricated piles, pipe piles and bamboo piles in Example 1 of the present application are compared;

[0067] Figure 5 It is a full cross-sectional schematic diagram of a prefabricated pile in which a first annular protrusion is welded to a first pile body according to Example 1 of the present application;

[0068] Figure 6 for Figure 5 A partial schematic diagram of the connection between the first annular protrusion, the first pile body and the first thickened protrusion;

[0069] Figure 7 This is a full cross-sectional schematic diagram of a prefabricated pile in which a first annular protrusion is detachably fixed to a first pile body according to Example 1 of the present application;

[0070] Figure 8 This is a schematic structural diagram of a first annular protrusion integrally prefabricated and formed on the upper end of the first pile body in Example 1 of the present application;

[0071] Fig. 9 This is a schematic structural diagram of the first annular protrusion in Example 1 of the present application being detachably fixed to the upper end of the first pile body;

[0072] Fig.10 This is an exploded schematic diagram of the first annular protrusion of Example 1 of the present application being detachably fixed to the upper end of the first pile body;

[0073] Fig.11 for Fig.10 Enlarged view of part A in the middle;

[0074] Fig.12 This is a schematic structural diagram of a prefabricated pile in which a pressure relief channel is provided on the first annular protrusion of Example 1 of the present application;

[0075] Fig.13 This is a schematic structural diagram of a prefabricated pile in Example 1 of the present application, which is a square pile;

[0076] Fig.14 This is a schematic diagram of the structure of the combined pile in Example 2 of the present application. Figure 1 ;

[0077] Fig.15 This is a schematic structural diagram of a composite pile in Example 2 of the present application that is pressure-regulated by an end sealing plate;

[0078] Fig.16 This is a schematic diagram of the structure of the combined pile in Example 2 of the present application. Figure 2 ;

[0079] Fig.17 The construction process of the combined pile in Example 3 of this application Figure 1 ;

[0080] Fig.18 The construction process of the combined pile in Example 3 of this application Figure 2 ;

[0081] Fig.19 for Fig.18 Schematic diagram of the bottom precast pile that is first placed in the borehole being implanted into the bottom of the expanded diameter borehole.

[0082] Description of reference numerals:

[0083] 1. Precast pile; 10. First pile body; 11. First thickened protrusion; 111. Concave groove; 112. Bolt hole; 12. First annular protrusion; 120. Arc protrusion; 121. First embedded steel part; 122. First conical surface; 123. Cylinder; 124. Second conical surface; 122', first conical surface; 123', Cylinder; 124', second conical surface; 125. Concave groove; 126. First steel bar; 127. First connecting bar; 128. Radial bar; 129. Through hole; 129', through hole; 13. The second annular protrusion; 131, pressure relief channel; 14, second embedded steel part; 15, prestressed main reinforcement; 151, hoop; 16, second reinforcement; 161, second connecting reinforcement; 17, expansion bolt; 18, bolt; 19, threaded hole; 191, reinforcement hole; 192, large diameter hole; 193, small diameter hole; 2, bottom precast pile; 20, second pile body; 21, second thickened protrusion; 3, end sealing plate; 30, pressure regulating hole; 4, uniform cross-section pipe pile; 5, original soil around the hole wall; 6, solidified soil around the pile; 7, core pile. DETAILED DESCRIPTION

[0084] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0085] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0086] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0087] The following is combined with Figures 2 to 18 The present application is further described in detail with specific embodiments.

[0088] Example 1

[0089] See also Figure 2 to Figure 13 As shown, an embodiment of the present application discloses a prefabricated pile.

[0090] See also Figure 2 The prefabricated pile of the present embodiment comprises a first pile body 10, a plurality of first thickened protrusions 11 and a first annular protrusion 12. The first pile body 10 is prefabricated integrally with concrete. The first pile body 10 can be a pipe pile or a solid pile. In the present embodiment, the first pile body 10 is introduced by taking a pipe pile as an example. The two ends of the first pile body 10 along the length direction are respectively a first end 10' and a second end 10", and a plurality of first thickened protrusions 11 are all located between the first end 10' and the second end 10", and the first thickened protrusions 11 are fixed on the outer peripheral wall of the first pile body 10 and are arranged at intervals along the length direction of the first pile body 10, and the first thickened protrusions 11 can be a circumferentially closed and continuous annular shape, or can be composed of a plurality of block-shaped protrusions distributed at intervals in the circumferential direction, and the first thickened protrusions 11 and the first pile body 10 are combined to form a special-shaped pile with alternating thickness along the length direction, such as a bamboo pile, a special-shaped square pile with alternating thickness along the length direction, etc. In this embodiment, the vertical extension of the first pile body 10 is taken as an example, that is, the length direction of the first pile body 10 is arranged vertically, the first end 10 ′ is the uppermost end of the first pile body 10 , and the second end 10 ″ is the lowermost end of the first pile body 10 .

[0091] According to the implantation method, before the prefabricated pile 1 is implanted into the foundation, it needs to go through the process of drilling, bottom expansion, mixing and grouting, and finally realize the foundation structure of "core pile - solidified soil around the pile - original soil around the hole wall". Due to the effect of the first thickened protrusion 11, the contact surface of the interface S1 between the core pile and the solidified soil around the pile is increased, the force direction becomes more, and the peak shear stress of the interface is improved; however, due to market competition considerations, without changing the diameter of the first pile body 10 or the borehole diameter during implantation, the interface S2 between the solidified soil around the pile and the original soil around the hole wall is not improved compared with ordinary prefabricated piles of the same diameter, which is a key factor limiting the bearing capacity of a single pile of a special-shaped pile with alternating thickness along the length direction constructed by the implantation method. Therefore, in order to further improve the bearing capacity of a single pile of an implanted pile, it is necessary to solve the problem of how to improve the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall.

[0092] In this embodiment, the first annular protrusion 12 is fixed around the first pile body 10, and at least one first thickened protrusion 11 is located between the first annular protrusion 12 and the second end 10", that is, the first annular protrusion 12 is located above at least one first thickened protrusion 11. In order to increase the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, the outer peripheral wall of the first annular protrusion 12 is projected along the length direction of the first pile body 10 and surrounds the outer side of the first thickened protrusion 11 projected along the length direction of the first pile body 10.

[0093] According to the implantation method, when the prefabricated pile 1 is implanted into the borehole, since the outer peripheral wall of the first annular protrusion 12 is projected along the length direction of the first pile body 10 and surrounds the outer side of the first thickened protrusion 11 projected along the length direction of the first pile body 10, during the downward implantation process, the lower end face of the first annular protrusion 12 squeezes the cement soil located below the first annular protrusion 12 in the borehole, and the cement soil diffuses to the soil around the borehole by increasing the pressure, and part of the cement soil enters the soil gaps around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, and improving the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, thereby improving the single pile bearing capacity of the prefabricated pile 1 after implantation.

[0094] The first annular protrusion 12 located above the first thickened protrusion 11 has an outer peripheral wall projected along the length direction of the first pile body 10 and surrounds the outer side of the first thickened protrusion 11 projected along the length direction of the first pile body 10, so that during the downward implantation process, the cement soil around the first thickened protrusion 11 is squeezed by the first annular protrusion 12, the density increases, and the interaction force between the first thickened protrusion 11 and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the precast pile 1 and the solidified soil around the pile, and further improving the single pile bearing capacity of the precast pile 1 after implantation.

[0095] During the downward implantation process, the squeezing effect of the lower end of the first annular protrusion 12 on the cement soil below the first annular protrusion 12 in the borehole is affected by the physical properties of the first annular protrusion 12. In order to improve the squeezing effect of the lower end of the first annular protrusion 12 on the lower cement soil during the construction process, preferably, in some examples, the projection of the first annular protrusion 12 along the length direction of the first pile body 10 completely covers the projection of the inner peripheral wall of the borehole along the length direction of the first pile body 10.

[0096] Preferably, the first annular protrusion 12 is located above all the first thickened protrusions 11 or the first annular protrusion 12 is located at the same height as the top first thickened protrusion 11, and most of the first thickened protrusions 11 are located below the first annular protrusion 12. During construction, the lower end surface of the first annular protrusion 12 can effectively squeeze the cement soil in the borehole below it, but cannot squeeze the cement soil above it. Therefore, most of the first thickened protrusions 11 are located on the lower side of the first annular protrusion 12, so that the cement soil around most of the first thickened protrusions 11 can be squeezed, thereby improving the overall bearing capacity of the precast pile 1 after implantation.

[0097] According to the implantation method, when the prefabricated pile 1 is implanted in the drill hole, the inner peripheral wall of the drill hole is projected along the length direction of the first pile body 10 around the outer side of the first pile body 10 and the first thickened protrusion 11 combination projected along the length direction of the first pile body 10, and the implantation action can be completed by relying on the weight of the prefabricated pile 1 and the pile holding and pressing down of the pile driver. In these examples, the first annular protrusion 12 is projected along the length direction of the first pile body 10 to completely cover the inner peripheral wall of the drill hole projected along the length direction of the first pile body 10, which means that when the first annular protrusion 12 is to be implanted in the drill hole, additional pressure from the pile driver is required.

[0098] In these examples, when the precast pile 1 is implanted in the borehole, especially when the first annular protrusion 12 enters the borehole, the lower end surface of the first annular protrusion 12 forms a closed cavity with the outer peripheral wall of the first pile body 10 and the side wall of the borehole.

[0099] In these examples, as the precast pile 1 descends, the first annular protrusion 12 gradually increases the pressure in the closed cavity, driving the cement soil to diffuse to the soil around the hole wall. Because it is a closed cavity, the squeezing effect is significant, and the cement soil can more effectively enter the gaps in the soil around the hole wall to improve the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increase the boundary friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improve the single pile bearing capacity after the precast pile 1 is implanted. Different from the natural diffusion between cement soil and the original soil around the hole wall in the ordinary implantation construction method, in this example, since the first annular protrusion 12 is projected along the length direction of the first pile body 10 to completely cover the inner wall of the borehole along the length direction of the first pile body 10, when the first annular protrusion 12 enters the borehole, the formed closed cavity can significantly enhance the squeezing effect of the lower end of the first annular protrusion 12 on the lower cement soil, and the cement soil can actively diffuse to the soil around the hole wall with the help of the soil gaps, and the boundary friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall is significantly enhanced.

[0100] Preferably, the first pile body 10 is set as a hollow round pile, a plurality of first thickened protrusions 11 are set in a bamboo-like shape along the length direction of the first pile body 10, the first annular protrusion 12 is set in a circular ring shape, and the first pile body 10 and the first thickened protrusion 11 and the first annular protrusion 12 are set coaxially as an example. In order to make the first annular protrusion 12 completely cover the inner peripheral wall of the borehole along the length direction of the first pile body 10, the outer diameter of the first annular protrusion 12 is set to be 0 to 50 mm larger than the borehole diameter. According to the experimental data of the early test pile, once the outer diameter of the first annular protrusion 12 exceeds the borehole diameter by more than 50 mm, the additional static pressure load to be applied during construction is too large, and the construction difficulty is greatly increased. At the same time, during the maintenance period after the completion of the test pile construction, according to the monitoring of the surrounding soil, it can be seen that the soil squeezing effect it brings is too obvious, especially not suitable for soft soil foundation. In addition, based on the single pile load test of the engineering rigid composite pile, the FLAC3D finite difference software was used to establish a three-dimensional model, and the ultimate bearing capacity of the single pile after the implantation construction was compared. The outer diameter of the test pile body was 450mm, the outer diameter of the first thickened protrusion 11 was 500mm, the outer diameter of the first annular protrusion 12 was 550mm, the outer diameter of the bamboo pile body was 450mm, the outer diameter of the bamboo part was 500mm, and the outer diameter of the pipe pile was 500mm. The pile length was calculated to be 40m, the gravel sand layer was used as the pile end bearing layer, the borehole diameter was 550mm, and the pile end was not expanded. The single pile bearing capacity comparison chart of the test pile, bamboo pile and pipe pile was obtained, as shown in the figure below. Figure 4As shown in Table 1, it can be seen that the amount of concrete used in the test pile is no more than 2.4% higher than that of the conventional 450mm / 500mm bamboo pile, the bearing capacity of the single pile is 28.57% higher than that of the conventional 450mm / 500mm bamboo pile, and there is no soil squeezing around the pile after the curing period. Considering the construction difficulty, implantation effect and raw material cost, it has more competitive advantages than bamboo piles of the same size or larger sizes on the market.

[0101] Table 1 Comparison between 450mm / 500mm / 550mm test piles and 450mm / 500mm bamboo piles

[0102] Pile Type Pile size Bamboo size Single pile concrete dosage Single pile bearing capacity Soil squeezing effect Test pile 450mm 500mm / 550mm 4.70 4500kN No soil squeezing Bamboo pile 450mm 500mm 4.59 3500kN No soil squeezing

[0103] In addition to the above-mentioned test piles, optionally, the outer diameter of the first pile body 10 is 350 mm to 750 mm, the outer diameter of the first annular protrusion 12 is 90 mm to 200 mm larger than the outer diameter of the first pile body 10, the outer diameter of the first thickened protrusion 11 is 50 mm to 150 mm larger than the outer diameter of the first pile body 10, and the outer diameter of the first annular protrusion 12 is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion 11.

[0104] See also Figure 2 In some examples, the length of the first pile body 10 is defined as L, the first end 10' is defined as the starting point, the first annular protrusion 12 is located within the interval [0, L / 2] of the first pile body 10, and further, the first annular protrusion 12 is located within the interval [0, L / 4] of the first pile body 10. The first annular protrusion 12 is provided at the upper portion of the first pile body 10, and the upper end of the precast pile 1 is more closely connected to the soil around the hole wall through the first annular protrusion 12, and the first annular protrusion 12 is stronger than the cement soil structure and can withstand a larger horizontal load, thereby improving the horizontal bearing capacity of the precast pile 1 after implantation. In addition, the first annular protrusion 12 is provided at the upper portion of the first pile body 10, and there is more cement soil located below the first annular protrusion 12 and capable of vertically supporting the first annular protrusion 12, so that the precast pile 1 is not easy to settle after implantation, thereby improving the vertical bearing capacity of the precast pile 1 after implantation.

[0105] Further, see Figure 2 The prefabricated pile 1 also includes at least one second annular protrusion 13 fixed around the outer peripheral wall of the first pile body 10, and the second annular protrusion 13 is located between the first annular protrusion 12 and the second end 10". The second annular protrusion 13 can be one or more than two. When there are more than two second annular protrusions 13, the more than two second annular protrusions 13 are arranged at intervals along the length direction of the first pile body 10.

[0106] See also Figure 2 and Figure 3The projection of the first annular protrusion 12 along the length direction of the first pile body 10 covers the projection of the second annular protrusion 13 along the length direction of the first pile body 10, or the projection of the outer peripheral wall of the first annular protrusion 12 along the length direction of the first pile body 10 at least partially overlaps the projection of the outer peripheral wall of the second annular protrusion 13 along the length direction of the first pile body 10. The outer peripheral wall of the first pile body 10 is projected as S3 along the length direction of the first pile body 10, the outer peripheral wall of the first thickened protrusion 11 is projected as S4 along the length direction of the first pile body 10, and the first thickened protrusion 11 is projected as the annular space between S3 and S4 along the length direction of the first pile body 10; the inner peripheral wall of the borehole is projected as S5 along the length direction of the first pile body 10, and the borehole is projected as the space within S5 along the length direction of the first pile body 10; the outer peripheral wall of the second annular protrusion 12 is projected as S6 along the length direction of the first pile body 10, and the second annular protrusion 12 is projected as the annular space between S6 and S3 along the length direction of the first pile body 10; the outer peripheral wall of the first annular protrusion 12 is projected as S7 along the length direction of the first pile body 10, and the first annular protrusion 12 is projected as the annular space between S7 and S3 along the length direction of the first pile body 10. When the first annular protrusion 12 is projected along the length direction of the first pile body 10 and covers the second annular protrusion 13 projected along the length direction of the first pile body 10, due to the action of the second annular protrusion 13, the contact surface of the interface S1 between the precast pile 1 and the solidified soil around the pile is increased, the force direction becomes more, and the peak shear stress of the interface is improved; at the same time, the cement soil on the lower side of the first annular protrusion 12 in the borehole is squeezed by the first annular protrusion 12, the density increases, and the interaction force between the second annular protrusion 13 and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the precast pile 1 and the solidified soil around the pile, and further improving the single pile bearing capacity of the precast pile 1 after implantation.

[0107] When the projection of the outer peripheral wall of the first annular protrusion 12 along the length direction of the first pile body 10 completely overlaps with the projection of the outer peripheral wall of the second annular protrusion 13 along the length direction of the first pile body 10 and both the first annular protrusion 12 and the second annular protrusion 13 are solid rings, or the projection of the first annular protrusion 12 along the length direction of the first pile body 10 covers the projection of the second annular protrusion 13 along the length direction of the first pile body 10, and the projection of the outer peripheral wall of the second annular protrusion 13 along the length direction of the first pile body 10 is located outside the projection of the borehole along the length direction of the first pile body 10, the first annular protrusion 12 and the second annular protrusion 13 can separate the cement soil in the borehole into a closed cavity, which is formed by the first annular protrusion 12, the second annular protrusion 13, the outer peripheral wall of the first pile body 10, and the side wall of the borehole. As the precast pile 1 is implanted, the cement soil on the lower side of the second annular protrusion 13 overflows into the closed cavity on the upper side of the second annular protrusion 13. Since it is a closed cavity, as the cement soil in the closed cavity increases, the pressure in the closed cavity continues to increase. Therefore, the squeezing effect on the cement soil in the cavity is significant during the construction process, and the cement soil can more effectively enter the soil gaps around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the single pile bearing capacity after the precast pile 1 is implanted.

[0108] Furthermore, at least one first thickened protrusion 11 is provided between the first annular protrusion 12 and the second annular protrusion 13, so as to fully utilize the pressurization and compaction effect of the first annular protrusion 12 on the cement soil in the closed cavity. The force between the cement soil after compression in the closed cavity and the first thickened protrusion 11 located in the closed cavity increases, and the boundary friction resistance of the interface S1 between the part of the pile body of the precast pile 1 and the solidified soil around the pile increases, thereby further improving the single pile bearing capacity of the precast pile 1 after implantation.

[0109] In addition, since the drilling hole in the implantation method is different from the conventional lead hole, the pile body may be skewed during the implantation process after the grouting is completed due to the environmental factors of the actual construction. The first annular protrusion 12 and the second annular protrusion 13 are arranged in cooperation. When the prefabricated pile 1 is implanted in the borehole, since the projection of the first annular protrusion 12 along the length direction of the first pile body 10 completely covers the projection of the inner peripheral wall of the borehole along the length direction of the first pile body 10, the projection of the outer peripheral wall of the first annular protrusion 12 along the length direction of the first pile body 10 at least partially overlaps the projection of the second annular protrusion 13 along the length direction of the first pile body 10, or the projection of the first annular protrusion 12 along the length direction of the first pile body 10 covers the projection of the second annular protrusion 13 along the length direction of the first pile body 10 and the projection of the outer peripheral wall of the second annular protrusion 13 along the length direction of the first pile body 10 is located outside the projection of the borehole along the length direction of the first pile body 10, the coaxiality of the prefabricated pile 1 and the borehole can be improved, and the technical problem of the prefabricated pile 1 being planted skewed due to the construction environment when the implantation method is used is solved.

[0110] Please continue to see Figure 2 Optionally, in some examples, the first pile body 10 is arranged in a hollow round pile, a plurality of first thickened protrusions 11 are arranged in a bamboo-joint shape along the length direction of the first pile body 10, the first annular protrusion 12 and the second annular protrusion 13 are both arranged in a circular ring shape, the outer diameters of the first annular protrusion 12 and the second annular protrusion 13 are equal, and the first thickened protrusion 11, the first annular protrusion 12, the second annular protrusion 13 and the first pile body 10 are coaxially arranged.

[0111] The first pile body 10 and the first thickened protrusion 11, the first annular protrusion 12, and the second annular protrusion 13 are prefabricated and centrifugally formed as a whole using a steel mold. In this way, no later assembly is required, and the production process is simple to operate. The first annular protrusion 12, the second annular protrusion 13 and the first pile body 10 are prefabricated and formed as a whole. The first annular protrusion 12 and / or the second annular protrusion 13 each include a first conical surface 122, a cylindrical surface 123, and a second conical surface 124 connected in sequence from top to bottom, wherein the upper end of the first conical surface 122 and the lower end of the second conical surface 124 are both connected to the first pile body 10, the cylindrical surface 123 extends vertically and surrounds the outer side of the first pile body 10, the diameter of the first conical surface 122 gradually increases from top to bottom, and the diameter of the second conical surface 124 gradually decreases from top to bottom, so as to facilitate demoulding when the first pile body 10 and the first annular protrusion 12 are prefabricated as a whole.

[0112] When using a steel mold to produce a prefabricated pile 1, due to centrifugal one-piece molding, it is easy to encounter the problem of demolding difficulty during demolding. For bamboo piles with protrusions on the outer wall, this problem is particularly prominent. The industry has developed different types of molds to improve the yield rate. In the present invention, the first thickened protrusion 11 is similar to the bamboo part of a conventional bamboo pile, and the first annular protrusion 12 is projected along the length direction of the first pile body 10 to completely cover the inner wall of the drilled hole along the length direction of the first pile body 10. The first annular protrusion 12 is projected along the length direction of the first pile body 10 to cover or at least partially overlap the second annular protrusion 13 along the length direction of the first pile body, that is, the outer diameters of the first annular protrusion 12 and the second annular protrusion 13 are both larger than the outer diameter of the first thickened protrusion 11, which changes the distribution of stress in the prefabricated pile 1 as a whole, which brings new challenges to demolding.

[0113] In order to solve the above technical problem of demoulding difficulty, the angle between the first conical surface 122 of the first annular protrusion 12 and the second annular protrusion 13 and the horizontal plane is set to be 45°, and the angle between the second conical surface 124 of the first annular protrusion 12 and the second annular protrusion 13 and the vertical plane is greater than 45° and less than 90°. The above setting makes the upper and lower end surfaces of the first annular protrusion 12 no longer symmetrical. From a local point of view, there is a stress difference between the upper and lower end surfaces of the first annular protrusion 12, but from the perspective of the entire pile body, this part of the stress difference can just weaken or offset the problem of uneven stress distribution caused by the size and position factors of the first annular protrusion 12 to a certain extent, thereby improving the yield rate. At the same time, the angle between the second conical surface 124 of the first annular protrusion 12 and the second annular protrusion 13 and the horizontal plane is reduced, so that when the precast pile 1 is implanted, the extrusion of the first annular protrusion 12 and the second annular protrusion 13 can act as much as possible on the cement soil under the first annular protrusion 12 in the borehole, thereby improving the extrusion effect of the first annular protrusion 12 and the second annular protrusion 13 on the cement soil under the first annular protrusion 12 in the borehole.

[0114] Usually when preparing bamboo piles, the bamboo protrusions should be symmetrical up and down to adjust the stress distribution, such as Figure 2 As shown, the first thickened protrusion 11 is conventional with symmetrical upper and lower end faces. However, when the first annular protrusion 12 and the second annular protrusion 13 surround the outside of the first pile body 10, and the size of the first annular protrusion 12 and the size of the second annular protrusion 13 are larger than the size of the first thickened protrusion 11, from the perspective of the entire pile body of the first pile body 10, uneven stress distribution occurs. At this time, setting the first annular protrusion 12 and the second annular protrusion 13 as asymmetrical upper and lower end faces can weaken or offset the defect of uneven distribution, solving the technical problem of demoulding difficulty.

[0115] See also Figure 5 and Figure 6 In other examples, in order to solve the problem of demoulding difficulty caused by the above-mentioned uneven stress distribution and expand the applicable scenarios of the prefabricated pile 1, the first pile body 10 and the first thickened protrusion 11 are prefabricated as a whole, and the first annular protrusion 12 and / or the second annular protrusion 13 are welded and fixed or detachably fixed on the first pile body 10. Preferably, the first annular protrusion 12 and / or the second annular protrusion 13 include more than two circular arc protrusions 120 that can be spliced ​​to each other, and the arc protrusion 120 is prefabricated from concrete, which is convenient for mass production, not easy to be corroded, low cost and long service life. In this way, in the centrifugal prefabrication molding stage, it can be the same as the existing bamboo pile, the existing production mold and production operation can remain unchanged, the stress distribution of the entire prefabricated pile 1 pile body is uniform, and the pile body part is not easy to collapse during demoulding, which can effectively reduce the adverse effects of the first annular protrusion 12 and the second annular protrusion 13 on the stress distribution of the pile body during the centrifugal molding stage.

[0116] Since the first annular protrusion 12 and the second annular protrusion 13 of relatively large size are avoided during production, the first pile body 10 and the first thickened protrusion 11 can be demoulded relatively easily. On this basis, the shapes and sizes of the first annular protrusion 12 and the second annular protrusion 13 can also have more choices. Figure 5 Preferably, the first annular protrusion 12 and / or the second annular protrusion 13 includes a first conical surface 122', a cylindrical surface 123' and a second conical surface 124' which are connected in sequence from top to bottom, the cylindrical surface 123' extends vertically and surrounds the outer side of the first pile body 10, the end of the upper end of the first conical surface 122' is connected to the first pile body 10, and the end of the lower end of the first conical surface 122' is connected to the cylindrical surface 123'; the end of the upper end of the second conical surface 124' is connected to the first pile body 10, and the end of the lower end of the second conical surface 124' is connected to the cylindrical surface 123', the diameter of the first conical surface 122' gradually increases from top to bottom, and the diameter of the second conical surface 124' gradually increases from top to bottom, and the second conical surface 124' cooperates with the first pile body 10 to form an annular concave cavity with an opening facing downward. When the precast pile 1 is implanted, the second conical surface 124' of the first annular protrusion 12 guides the cement soil to gather toward the first pile body 10, thereby reducing the cement soil from overflowing from the lower side of the first annular protrusion 12 to the upper side of the first annular protrusion 12, or from overflowing from the lower side of the second annular protrusion 13 to the upper side of the second annular protrusion 13. At the same time, the action force of the second conical surface 124' of the first annular protrusion 12 and the second annular protrusion 13 can completely act on the cement soil in the borehole, further improving the squeezing effect of the first annular protrusion 12 and the second annular protrusion 13 on the cement soil in the borehole.

[0117] In addition, the lower surface of the arc-shaped protrusion 120 can also be set horizontally. With this setting, when the precast pile 1 is implanted, the force of the lower end surfaces of the first annular protrusion 12 and the second annular protrusion 13 can be kept vertically downward as much as possible, so as to fully act on the cement soil in the borehole, further improving the squeezing effect of the first annular protrusion 12 and the second annular protrusion 13 on the cement soil in the borehole.

[0118] See also Figure 6 Furthermore, the inner peripheral wall of the arc-shaped protrusion 120 has a groove 125 adapted to the first thickened protrusion 11, and the groove 125 is located in the middle of the inner peripheral wall of the arc-shaped protrusion 120. When the arc-shaped protrusion 120 is fixed on the first pile body 10, the outer peripheral wall of the first thickened protrusion 11 and the inner side wall of the groove 125 of the arc-shaped protrusion 120 fit each other, and the arc-shaped protrusion 120 is axially limited, so as to improve the firmness of the connection between the arc-shaped protrusion 120 and the first pile body 10, so that when the prefabricated pile 1 is implanted in the drilled hole, the arc-shaped protrusion 120 is not easy to move relative to the first pile body 10 in the axial direction.

[0119] Optionally, the first annular protrusion 12 and / or the second annular protrusion 13 are welded and fixed to the first pile body 10. Specifically, at least one of the two ends of the arc-shaped protrusion 120 is pre-embedded with a first embedded steel part 121, and the first embedded steel part 121 can be an arc-shaped steel part, or can be composed of a plurality of arc-shaped steel sheets uniformly arranged along the circumference of the arc-shaped protrusion 120. In this example, the first embedded steel part 121 is a plurality of arc-shaped steel sheets uniformly arranged along the circumference of the arc-shaped protrusion 120, and the inner diameter of the arc-shaped steel sheet is equal to the inner diameter of the arc-shaped protrusion 120. Specifically, the arc-shaped steel sheet is embedded in a specific position of the steel mold in advance during production, and is prefabricated and formed integrally with the arc-shaped protrusion 120.

[0120] The first pile body 10 is pre-embedded with a second embedded steel part 14, which may be an annular steel part or may be composed of a plurality of arc-shaped steel sheets uniformly arranged along the circumference of the first pile body 10. In this example, the second embedded steel part 14 corresponds to the first embedded steel part 121 and is arranged as a plurality of arc-shaped steel sheets uniformly arranged along the circumference of the first pile body 10, and the outer diameter of the arc-shaped steel sheet is equal to the outer diameter of the first pile body 10. Specifically, the arc-shaped steel sheet is embedded in a specific position of the steel mold in advance during production, and then centrifugal integrated prefabrication is performed. The first embedded steel part 121 is welded to the second embedded steel part 14 to fix the arc-shaped protrusion 120 to the first pile body 10.

[0121] To ensure the firmness of the connection, preferably, both ends of the arc-shaped protrusion 120 are pre-embedded with first embedded steel parts 121, the upper end surface of the upper first embedded steel part 121 is not lower than the upper end of the first annular protrusion 12, and the lower end surface of the lower first embedded steel part 121 is not higher than the lower end of the first annular protrusion 12. Two second embedded steel parts 14 are provided corresponding to the first embedded steel parts 121, and the two second embedded steel parts 14 are respectively located on both sides of a first thickened protrusion 10, and the two first embedded steel parts 121 are respectively welded to the two second embedded steel parts 14.

[0122] Furthermore, a plurality of first steel bars 126, first connecting ribs 127 and radial ribs 128 are embedded in the arc-shaped protrusion 120. The first steel bar 126 extends along the axial direction of the arc-shaped protrusion 120, and the plurality of first steel bars 126 are evenly arranged along the circumference of the arc-shaped protrusion 120; two first connecting ribs 127 are connected to one first steel bar 126 correspondingly, and one end of the two first connecting ribs 127 are respectively connected to the two ends of the first steel bar 126, the first connecting rib 127 at the upper end is parallel to the upper end surface of the arc-shaped protrusion 120, and the other end of the first connecting rib 127 at the upper end is welded and fixed to the upper first embedded steel part 121; the first connecting rib 127 at the lower end is parallel to the lower end surface of the arc-shaped protrusion 120, and the other end of the first connecting rib 127 at the lower end is welded and fixed to the lower first embedded steel part 121. The first steel bar 126 and the first connecting rib 127 are completely embedded in the arc-shaped protrusion 120, and the bonding force with the arc-shaped protrusion 120 is stronger. The first embedded steel part 121 is connected to the first connecting rib 127, so that the first embedded steel part 121 and the arc-shaped protrusion 120 are more firmly connected. A plurality of radial ribs 128 are also welded to the first steel bar 126, and the radial ribs 128 extend in the radial direction of the arc-shaped protrusion 120. The plurality of radial ribs 128 are evenly distributed along the length direction of the first steel bar 126. The first steel bar 126 and the radial ribs 128 cooperate as the skeleton of the arc-shaped protrusion 120, strengthen the structure of the arc-shaped protrusion 120, improve the load bearing capacity of the arc-shaped protrusion 120, and make the arc-shaped protrusion 120 not easy to crack and be damaged when the prefabricated pile 1 is implanted in the drilled hole.

[0123] Furthermore, a plurality of second steel bars 16 and second connecting bars 161 are embedded in the first pile body 10, the second steel bars 16 extend vertically, and the plurality of second steel bars 16 are evenly distributed along the circumference of the first pile body 10, and the second steel bars 16 are fixed to the prestressed main bars 15 of the first pile body 10 by the hoop 151. Two second connecting bars 161 are connected to one second steel bar 16 correspondingly, and one end of the two second connecting bars 161 is connected to the two ends of the second steel bar 16 respectively, and the other end of the second connecting bar 161 at the upper end is welded and fixed to the second embedded steel member 14 at the upper side, and the other end of the second connecting bar 161 at the lower end is welded and fixed to the second embedded steel member 14 at the lower side. The second steel bar 16 and the second connecting bar 161 are completely embedded in the first pile body 10, and have a stronger bonding force with the first pile body 10. The second embedded steel member 14 is connected to the second connecting bar 161, so that the second embedded steel member 14 is more firmly connected to the first pile body 10, and it is convenient to fix the second embedded steel member 14 on the prestressed main bar 15 of the steel cage for fixing and positioning before embedding.

[0124] Compared with the first annular protrusion 12 and the second annular protrusion 13 being prefabricated integrally with the first pile body 10, the welding molding method can well expand the applicable scenarios. Due to different construction environments, the physical properties of the foundation are also different. By adjusting the size specifications of the first annular protrusion 12 and the second annular protrusion 13, a balance can be achieved between improving the extrusion effect and controlling the soil squeezing effect. For example, the first annular protrusion 12 and the second annular protrusion 13 (two or more arc-shaped protrusions 120 spliced ​​together) of different sizes are welded and fixed to the second embedded steel part 14 of the first pile body 10. Usually, when the foundation contains soil layers of sand, gravel, pebbles and larger stones, drilling is difficult and the hole wall is easily disturbed by external forces. At this time, it is suitable to use smaller-sized first annular protrusions 12 and second annular protrusions 13 to extrude the cement soil; and when the foundation contains soil layers with more clay and silt, there are fewer gaps in the soil layers and cement soil penetration is more difficult. At this time, it is suitable to use larger-sized first annular protrusions 12 and second annular protrusions 13 to extrude the cement soil.

[0125] See also Figure 7 Optionally, both the first annular protrusion 12 and the second annular protrusion 13 can be detachably fixed to the first pile body 10. Specifically, a bolt hole 112 extending in the radial direction is provided on the first thickened protrusion 11, and a through hole 129 corresponding to the bolt hole 112 is provided on the arc-shaped protrusion 120. After the arc-shaped protrusion 120 abuts against the outer side of the first thickened protrusion 11, the expandable end of the expansion bolt 17 is inserted into the bolt hole 112 through the through hole 129, and the nut of the expansion bolt 17 is rotated to fix the two arc-shaped protrusions 120 to the first thickened protrusion 11. In order to ensure the extrusion effect, preferably, the first annular protrusion 12 is detachably fixed to the outer side of the first thickened protrusion 11 on the side of the first pile body 10 closest to the cap.

[0126] In this example, since the relatively large-sized first annular protrusion 12 and the second annular protrusion 13 are avoided during production, the first pile body 10 and the first thickened protrusion 11 can be demoulded relatively easily. On this basis, there are more choices for the shapes of the first annular protrusion 12 and the second annular protrusion 13. At the same time, since the embedded parts such as the second embedded steel part 14 and the first embedded steel part 121 are avoided during production, the first pile body 10 and the first thickened protrusion 11 can be prefabricated as a whole relatively easily, and the first annular protrusion 12 can also be prefabricated separately relatively easily. Moreover, the first annular protrusion 12 and the second annular protrusion 13 are connected to the first thickened protrusion 11 by expansion bolts 17, which makes assembly easier.

[0127] Based on the above ideas, in order to further solve the problem of demoulding difficulties caused by uneven stress distribution and expand the applicable scenarios of precast piles 1, see Figure 8In some examples, the projection of the outer peripheral wall of the end plate at the first end 10' of the first pile body 10 along the length direction of the first pile body 10 surrounds the outer side of the projection of the first pile body 10 along the length direction, and the portion of the end plate at the first end 10' of the first pile body 10 extending out of the first pile body 10 forms a first annular protrusion 12. Specifically, when the prefabricated pile 1 is prefabricated in one piece, a standard end plate is connected to one end of the steel cage of the first pile body 10, and the outer diameter of the standard end plate is equal to the outer diameter of the first pile body 10, and a larger end plate is connected to the other end of the steel cage of the first pile body 10, and the outer diameter of the larger end plate is greater than the outer diameter of the first pile body 10.

[0128] Since the first annular protrusion 12 of relatively large size is not prefabricated during production, the first pile body 10 and the first thickened protrusion 11 can be demoulded relatively easily without the need for subsequent assembly. On this basis, the shape of the first annular protrusion 12 can also have more choices.

[0129] Based on the above ideas, in order to further solve the problem of demoulding difficulties caused by uneven stress distribution and expand the applicable scenarios of precast piles 1, see Fig. 9 and Fig.10 In some examples, the first annular protrusion 12 is arranged in an end plate shape, and a plurality of spaced through holes 129' are provided on the first annular protrusion 12, and the through holes 129' pass through the upper and lower end surfaces of the first annular protrusion 12. Correspondingly, a threaded hole 19 is provided on the end plate of the first end 10' of the first pile body 10, and the stud of the bolt 18 passes through the through hole 129' and is threadedly connected with the threaded hole 19 to fix the first annular protrusion 12 to the first end 10' of the first pile body 10.

[0130] Since the first annular protrusion 12 of relatively large size is avoided during production, the first pile body 10 and the first thickened protrusion 11 can be demoulded relatively easily. During construction, the first annular protrusion 12 is detachably fixed to the first end 10' of the first pile body 10 by bolts 18, and the first annular protrusion 12 can be installed after the first end 10' of the prefabricated pile 1 passes through the pile clamp box, so as to avoid interference between the first annular protrusion 12 and the pile clamp box, and there is no need to modify the pile clamp box, so as to reduce the construction cost of the prefabricated pile 1; at the same time, it is convenient to disassemble and recycle the first annular protrusion 12 before the foundation construction after excavation, so as to further reduce the construction cost of the prefabricated pile 1.

[0131] See also Fig.10 and Fig.11Furthermore, the threaded hole 19 is an anchoring hole of the end plate of the first end 10 ′ of the first pile body 10 . Specifically, taking the end plate of the first end 10' as a circular end plate as an example, the end plate of the first end 10' is provided with an anchor hole, and the anchor hole is a threaded hole 19, so as to be connected with the tensioning bolt, so as to facilitate the tensioning of the steel cage; the threaded hole 19 passes through the two end surfaces of the end plate of the first end 10' along the length direction of the first pile body 10, and the diameter of the threaded hole 19 is larger than the diameter of the upsetting head, so that the upsetting head can pass through the threaded hole 19 in the direction from the second end 10" to the first end 10'. The end plate of the first end 10' is also provided with a rib hole 191 arranged in a long strip shape, and the rib hole 191 passes through the two end surfaces of the end plate of the first end 10' along the length direction of the first pile body 10, and the rib hole 191 extends along the circumference of the end plate of the first end 10', and one end of the rib hole 191 is connected to the anchor hole, and the width of the rib hole 191 is larger than the diameter of the main reinforcement and smaller than the diameter of the upsetting head. The end plate of the first end 10' is also provided with a hanging The rib hole is connected to the other end of the rib hole 191, and the rib hole is a stepped hole. The rib hole includes a large diameter hole 192 and a small diameter hole 193. The opening of the large diameter hole 192 is set away from the first pile body 10, and the opening of the small diameter hole 193 is set toward the first pile body 10. The diameter of the large diameter hole 192 is larger than the diameter of the small diameter hole 193, the diameter of the large diameter hole 192 is larger than the diameter of the upsetting head, and the diameter of the small diameter hole 193 is larger than the main rib. The diameter of the main reinforcement is smaller than the diameter of the pier head, and the upsetting head can be clamped in the large diameter hole 192. When the main reinforcement is assembled with the end plate of the first end 10', the upsetting head passes through the threaded hole 19 in the direction from the second end 10" to the first end 10', and then the end plate of the first end 10' is rotated, the main reinforcement moves to the other end of the reinforcement hole 191, and the end plate of the first end 10' is moved in the direction from the second end 10" to the first end 10', and the upsetting head is clamped in the large diameter hole 192.

[0132] The first annular protrusion 12 is directly fixedly connected to the first end 10 ′ of the first pile body 10 using the anchor hole and the bolt 18 , without the need to additionally process the threaded hole 19 on the end plate, thus simplifying the processing steps and reducing the production cost of the prefabricated pile 1 .

[0133] When the outer diameters of the first annular protrusion 12 and the second annular protrusion 13 are larger than the borehole diameter, additional downward pressure is required to implant the prefabricated pile 1 into the borehole. As mentioned above, a closed cavity is formed between the second annular protrusion 13, the outer peripheral wall of the first pile body 10 and the borehole wall. In this case, it may be difficult to push the pile downward when applying pressure. For this reason, see Fig.12In some examples, at least one pressure relief channel 131 is provided on the second annular protrusion 13, and the pressure relief channel 131 passes through the second annular protrusion 13 along the length direction of the first pile body 10. Furthermore, the second annular protrusion 13 is provided with more than two pressure relief channels 131 evenly distributed along the circumferential direction, and the pressure relief channels 131 can all be through holes or notches, or a combination of through holes and notches, and the specific combination can be set according to the degree of influence of the pile foundation construction environment on the surrounding environment. When the pressure relief channel 131 is a notch, the radial dimension of the pressure relief channel 131 is not less than 50 mm, and the arc length of a single pressure relief channel 131 is not greater than 1 / 15 of the circumference of the drilled hole and not less than 1 / 20 of the circumference of the drilled hole. When the pressure relief channel 131 is a notch, the projection of the outer peripheral wall of the first annular protrusion 12 along the length direction of the first pile body 10 partially overlaps with the projection of the outer peripheral wall of the second annular protrusion 13 along the length direction of the first pile body 10; when the pressure relief channel 131 is a through hole, the projection of the outer peripheral wall of the first annular protrusion 12 along the length direction of the first pile body 10 completely overlaps with the projection of the outer peripheral wall of the second annular protrusion 13 along the length direction of the first pile body 10.

[0134] When the first pile body 10 is sent downward, a part of the cement soil can be transferred to the upper end of the second annular protrusion 13 through the pressure relief channel 131, thereby reducing the pressure load on the lower end surface of the second annular protrusion 13 to a certain extent, which is conducive to achieving pressure control, thereby achieving a balance between reducing the holding pressure applied when the precast pile 1 is implanted and improving the extrusion effect. Whether the pressure relief channel 131 is opened on the second annular protrusion 13 and the number and size of the pressure relief channel 131 can be set according to the degree of influence of the pile foundation construction environment on the surrounding environment. Furthermore, in this example, the second annular protrusion 13 with a pressure relief channel 131 is suitable for using the first pile body 10 and the first thickened protrusion 11 to form the second annular protrusion 13 by welding or bolting, and at the same time, the lower end surface of the second annular protrusion 13 is set horizontally or concavely. When the precast pile is implanted, the force on the lower end surface of the second annular protrusion 13 can be kept vertically downward as much as possible, so as to fully act on the cement soil in the borehole, and further improve the extrusion effect of the second annular protrusion 13 on the cement soil in the borehole. According to the actual situation of the soil layer, the soil squeezing conditions during construction and the squeezing effect of cement soil, the second annular protrusion 13 with different sizes and shapes and the pressure relief channel 131 is selected and installed on the first pile body 10 of the precast pile 1. This can effectively balance the soil squeezing effect and the squeezing effect on cement soil, while taking into account the operational complexity of construction and production preparation.

[0135] In addition, the first pile body 10 may also be configured with a cross-sectional outer contour being a regular polygon, such as a square. The first thickened protrusion 11, the first annular protrusion 12 and the second annular protrusion 13 may all be configured as circular rings, or may be configured as regular polygonal rings corresponding to the cross-sectional outer contour of the first pile body 10. When the first thickened protrusion 11, the first annular protrusion 12 and the second annular protrusion 13 are configured as regular polygonal rings corresponding to the cross-sectional outer contour of the first pile body 10, the first thickened protrusion 11, the first annular protrusion 12 and the second annular protrusion 13 are all parallel and surround the outside of the first pile body 10. However, it should be noted that no matter what shape is configured, in order to ensure the squeezing effect of the first annular protrusion 12 on the cement soil in the hole and to improve the squeezing effect by using a closed cavity, the first annular protrusion 12 is projected along the length direction of the first pile body 10 to completely cover the inner circumferential wall of the borehole projected along the length direction of the first pile body 10. See. Fig.13 In some examples, the first pile body 10 is arranged as a hollow square pile, the first thickened protrusion 11, the first annular protrusion 12 and the second annular protrusion 13 are all arranged in a square ring shape, the first thickened protrusion 11, the first annular protrusion 12 and the second annular protrusion 13 are all parallel and surround the outer side of the first pile body 10, the distance from the outer peripheral wall of the first pile body 10 to the outer peripheral wall of the first thickened protrusion 11 is 50mm to 150mm, the distance from the outer peripheral wall of the first pile body 10 to the outer peripheral wall of the first annular protrusion 12 is 90mm to 200mm, and the distance from the outer peripheral wall of the first thickened protrusion 11 to the outer peripheral wall of the first annular protrusion 12 is 40mm to 150mm. A concave groove 111 is provided on the outer peripheral wall of the first thickened protrusion 11, and the concave groove 111 extends in the horizontal direction. Due to the provision of the recessed groove 111, on the one hand, after the precast pile 1 is implanted into the drilled hole, the cement soil will fill the recessed groove 111, thereby improving the embedding effect between the precast pile 1 and the cement soil, and increasing the boundary friction resistance of the interface S1 between this part of the pile body of the precast pile 1 and the solidified soil around the pile, thereby further improving the single pile bearing capacity after the precast pile 1 is implanted; on the other hand, during the holding and pressing construction, the friction coefficient between the first pile body 10 and the transverse clamp can be increased.

[0136] To sum up, the working principle of the precast pile in the above embodiment is as follows: as the precast pile 1 is continuously implanted into the borehole, the lower end faces of the first annular protrusion 12 and the second annular protrusion 13 continuously squeeze the cement soil in the lower borehole to increase the pressure in the borehole below the lower end faces of the first annular protrusion 12 and the lower end faces of the second annular protrusion 13, thereby causing the cement soil to diffuse into the soil around the borehole, and the cement soil ions to enter the soil voids, thereby increasing the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the precast pile is implanted; in addition, the density of the cement soil increases after being squeezed by the first annular protrusion 12 and the second annular protrusion 13, which can increase the force between the first thickened protrusion 11 below the first annular protrusion 12 and the cement soil, thereby increasing the limit friction resistance of the interface S1 between the precast pile and the solidified soil around the pile, and thereby improving the bearing capacity of the single pile after the precast pile is implanted.

[0137] On the basis of improving the squeezing effect on cement soil, in order to take into account factors such as construction complexity and squeezing effect, the above embodiment also specifically sets the size of the first annular protrusion 12 and the second annular protrusion 13, or the relationship between the size of the first annular protrusion 12, the second annular protrusion 13 and the first thickened protrusion 11 and the borehole diameter. On the basis of improving the squeezing effect on cement soil, the squeezing effect is controlled and the construction complexity is reduced.

[0138] On the basis of improving the squeezing effect on cement soil, in order to improve the yield rate during product production and reduce the complexity of the preparation operation, the above embodiment also specifically sets the shape of the upper and lower end faces of the first annular protrusion 12 and the second annular protrusion 13, and uses the stress difference formed on the upper and lower end faces to weaken or offset the problem of uneven stress distribution caused by the size of the first annular protrusion 12 and the second annular protrusion 13. In addition, it also provides a method in which the first pile body 10 and the first thickened protrusion 11 are prefabricated in one piece, and the first annular protrusion 12 and the second annular protrusion 13 are fixed by welding or bolts to avoid the problem of demoulding difficulty caused by the above-mentioned uneven stress distribution.

[0139] Taking into account the complexity of construction operations, the complexity of preparation operations, the soil squeezing effect and the squeezing effect on cement soil, the above embodiment also provides a preferred method, which is to prefabricate the first pile body 10 and the first thickened protrusion 11 as a whole, and then form the second annular protrusion 13 with a pressure relief channel 131 by welding or bolting the second annular protrusion 13, thereby controlling the complexity of construction and preparation operations to a minimum and balancing the soil squeezing effect and the squeezing effect on cement soil.

[0140] Example 2

[0141] See also Figure 14 to Figure 16As shown, an embodiment of the present application discloses a combined pile.

[0142] See also Fig.14 The composite pile of this embodiment includes a top precast pile and at least one bottom precast pile 2 connected to the lower end of the top precast pile. The top precast pile 1 is composed of the precast pile 1 described in Example 1, and the precast pile 1 includes a first pile body 10, a plurality of first thickened protrusions 11 and a first annular protrusion 12. The first pile body 10 is a pipe pile and is precast integrally from concrete. The first pile body 10 extends vertically, and the plurality of first thickened protrusions 11 are fixed on the outer peripheral wall of the first pile body 10. The plurality of first thickened protrusions 11 are arranged at intervals along the length direction of the first pile body 10. The inner peripheral wall of the drilled hole is projected along the length direction of the first pile body 10 to surround the outer side of the projection of the combination of the first pile body 10 and the first thickened protrusion 11 along the length direction of the first pile body 10. The first annular protrusion 12 is fixed around the first pile body 10, and the first annular protrusion 12 is located above at least one first thickened protrusion 11. The first annular protrusion 12 is projected along the length direction of the first pile body 10 and completely covers the inner peripheral wall of the borehole projected along the length direction of the first pile body 10. The first annular protrusion 12 can be prefabricated integrally with the first pile body 10 and the first thickened protrusion 11, or can be prefabricated first and then welded or bolted to the first pile body 10, or can be directly formed by the part of the first end 10' extending out of the first pile body 10 or bolted to the end plate of the first end 10' of the first pile body 10 in the form of a metal end plate. For details, please refer to the relevant records in Example 1, which will not be repeated here.

[0143] In some examples, the bottom precast pile 2 includes a second pile body 20, which extends vertically and is integrally precast from concrete, and the projection of the outer peripheral wall of the second pile body 20 along the length direction of the first pile body 10 completely overlaps with the projection of the outer peripheral wall of the first pile body 10 along the length direction of the first pile body 10. Optionally, both the first pile body 10 and the second pile body 20 can be provided as hollow circular piles, or as pipe piles with a cross-sectional outer contour being a regular polygon, or as solid piles, which can be selected according to construction needs.

[0144] When the prefabricated pile 1 is implanted in the borehole, the lower end surface of the first annular protrusion 12 is used to squeeze the cement soil in the borehole below the first annular protrusion 12, so as to increase the pressure in the borehole below the lower end surface of the first annular protrusion 12, thereby causing the cement soil to diffuse to the soil around the borehole, and the cement soil ions to enter the soil gaps, thereby increasing the bonding strength between the solidified soil around the pile and the original soil around the hole wall, thereby increasing the boundary friction resistance S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted. Moreover, the force between the cement soil in the borehole after being squeezed and the first thickened protrusion 11, the first pile body 10 and the second pile body 20 increases, and the boundary friction resistance of the interface S1 between this part of the pile body of the composite pile and the solidified soil around the pile increases, further improving the bearing capacity of the single pile after the composite pile is implanted.

[0145] In some examples, the bottom precast pile 2 includes a second pile body 20 and a plurality of second thickened protrusions 21. The second pile body 20 extends vertically and is prefabricated integrally with concrete, the second thickened protrusions 21 are prefabricated integrally with the second pile body 20, the plurality of second thickened protrusions 21 are evenly distributed along the length direction of the second pile body 20, and the projection of the outer peripheral wall of the second thickened protrusion 21 along the length direction of the first pile body 10 coincides with the projection of the outer peripheral wall of the first thickened protrusion 11 along the length direction of the first pile body 10. Optionally, both the first pile body 10 and the second pile body 20 can be arranged as hollow round piles, can also be arranged as hollow square piles, can also be arranged as solid square piles or solid round piles, which can be selected according to construction needs.

[0146] Due to the effect of the second thickened protrusion 21, the contact area of ​​the interface S1 between the composite pile and the cement soil is increased, the force direction becomes more, the interface peak stress is increased, and the boundary friction resistance of the interface S1 between this part of the composite pile body and the solidified soil around the pile is increased, further improving the single pile bearing capacity of the composite pile after implantation.

[0147] In other examples, the multiple bottom precast piles 2 can also be a combination of pipe piles and special-shaped piles with alternating thickness along the length direction, that is, the bottom precast piles 2 at the lowest end are special-shaped piles with alternating thickness along the length direction, such as bamboo piles, and multiple cylindrical pipe piles or a combination of bamboo piles and cylindrical pipe piles are connected between the bottom bamboo pile and the top precast piles. The specific configuration can be selected according to the actual construction environment and construction requirements.

[0148] See also Fig.15In some examples, the bottom precast pile 2 is a tubular structure with an inner cavity, such as a hollow round pile or a hollow square pile. A plugging structure that at least partially blocks the inner cavity of the bottom precast pile 2 is fixed on at least one bottom precast pile 2 to adjust the pressure in the borehole below the first annular protrusion 12 and control the squeezing effect on the cement soil in the borehole. The plugging structure is an end sealing plate 3 arranged at the end of the bottom precast pile. The end sealing plate 3 is welded and fixed to the end of one of the bottom precast piles 2. The end sealing plate 3 is provided with a pressure regulating hole 30 that passes through from top to bottom. The pressure regulating hole 30 is connected to the inner hole of the second pile body 20. The diameter of the pressure regulating hole 30 is smaller than the inner diameter of the second pile body 20. The pressure regulating hole 30 is used to prevent cement slurry from passing through the pressure regulating hole 30 while allowing air to pass through the pressure regulating hole 30, so as to adjust the pressure in the borehole below the first annular protrusion 12 and control the squeezing effect on the cement soil in the borehole. Under the same conditions, the closer the position of the end sealing plate 3 is to the bottom of the borehole, the more cement soil there is between the outer peripheral wall of the first pile body 10, the outer peripheral wall of the second pile body 20 and the side wall of the borehole, and the greater the pressure in the borehole below the first annular protrusion 12. The height of the end sealing plate 3 can be adjusted according to the impact of the pile foundation construction on the surrounding environment.

[0149] In addition, the sealing structure can be replaced by setting one of the bottom precast piles 2 as a solid pile to adjust the amount of cement slurry entering the bottom precast pile 2, adjust the pressure in the borehole under the first annular protrusion 12, and control the squeezing effect on the cement soil in the borehole.

[0150] See also Fig.16 In some examples, the composite pile also includes a uniform cross-section pipe pile 4, which extends vertically and is prefabricated in one piece with concrete. The projection of the outer peripheral wall of the uniform cross-section pipe pile 4 along the length direction of the first pile body 10 completely overlaps with the projection of the outer peripheral wall of the first annular protrusion 12 along the length direction of the first pile body 10, and the uniform cross-section pipe pile 4 is welded and fixed to the upper end of the top prefabricated pile. Specifically, one of the first annular protrusions 12 is arranged at the uppermost end of the first pile body 10, the first annular protrusion 12 is prefabricated integrally with the first pile body 10, the upper end face, the outer peripheral face and the lower end face of the first annular protrusion 12 are sequentially connected from top to bottom, the upper end face of the first annular protrusion 12 extends from the outer peripheral face to the first pile body 10, the upper end face of the first annular protrusion 12 is coplanar with the upper end face of the first pile body 10, the outer peripheral face of the first annular protrusion 12 extends vertically and surrounds the outside of the first pile body 10, the lower end face of the first annular protrusion 12 extends from the outer peripheral face to the first pile body 10, the lower end face of the first annular protrusion 12 is arranged in a conical surface, the diameter of the lower end face of the first annular protrusion 12 gradually decreases from top to bottom, and the upper end of the first annular protrusion 12 has an end plate for connecting the uniform cross-section pipe pile 4. Preferably, the first annular protrusion 12 of the prefabricated pile 1 in this example is one and is arranged at the uppermost end of the first pile body 10.

[0151] The first annular protrusion 12 is made into an enlarged head of the prefabricated pile 1, which is used to connect the equal-section pipe pile 4 with the same outer diameter as the first annular protrusion 12. The equal-section pipe pile 4 is tightly matched with the soil around the borehole wall, and the cement soil is not easy to overflow upward. On the one hand, the extrusion effect of the composite pile on the cement soil in the borehole is improved, so that the amount of cement soil entering the soil gap around the hole wall is increased, the bonding strength between the solidified soil around the pile and the original soil of the hole wall is improved, and the boundary friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall is improved, thereby improving the bearing capacity of the single pile after the composite pile is implanted; on the other hand, On the one hand, as the squeezing effect of the composite pile on the cement soil in the borehole increases, the density of the cement soil on the lower side of the first annular protrusion 12 is further increased, and the interaction between the first thickened protrusion 11, the first pile body 10 and the second pile body 20 and the surrounding cement soil is strengthened, thereby increasing the limit friction resistance of the interface S1 between the precast pile 1, the precast pile 2 and the solidified soil around the pile, and further increasing the single pile bearing capacity of the composite pile after implantation; in addition, the upper end of the composite pile is more tightly connected to the soil around the hole wall through the uniform cross-section pipe pile 4, thereby increasing the horizontal bearing capacity of the composite pile after implantation.

[0152] In summary, the working principle of the combined pile of the above embodiment is as follows: the drilling size is designed according to the cross-sectional size of the first pile body 10 of the precast pile 1, the inner circumferential wall of the drilling hole is projected on the horizontal plane around the outer side of the first pile body 10 and the first thickened protrusion 11 combination on the horizontal plane, and the inner circumferential wall of the drilling hole is completely covered by the first annular protrusion 12 on the horizontal plane; the drilling rig is in place and the hole is drilled to the designed depth; a certain volume of solidifying slurry is injected into the pile end; a certain volume of solidifying slurry is injected into the part above the pile end, and after mixing with the soil in the hole, a state between liquid and solid is formed; the bottom precast pile 2 is implanted into the borehole in sections in sequence by relying on its own weight and pile pressing force; the precast pile 1 is welded to the upper end of the uppermost bottom precast pile 2, and the precast pile 1 is pressed into the borehole. As the precast pile 1 is continuously implanted During drilling, the lower end face of the first annular protrusion 12 continuously squeezes the cement soil in the lower borehole to increase the pressure in the borehole below the lower end face of the first annular protrusion 12, thereby causing the cement soil to diffuse into the soil around the borehole, and cement soil ions to enter the soil voids, thereby increasing the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted; in addition, the density of the cement soil increases after being squeezed by the first annular protrusion 12, which can increase the interaction force between the first thickened protrusion 11, the first pile body 10 and the second pile body 20 below the first annular protrusion 12 and the cement soil, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, and thereby improving the bearing capacity of the single pile after the composite pile is implanted.

[0153] Example 3

[0154] The present application embodiment discloses a construction method using the combined piles described in Example 2, comprising the following steps:

[0155] S1, drilling setting: the drilling size is designed according to the cross-sectional size of the first pile body 10 of the precast pile 1, the inner peripheral wall of the drilling hole is projected on the horizontal plane around the outer side of the first pile body 10 and the first thickened protrusion 11 combination on the horizontal plane, and the inner peripheral wall of the drilling hole is completely covered by the first annular protrusion 12 on the horizontal plane.

[0156] S2. Drilling construction: Drill holes according to the drilling settings; see Fig.16 In (1), drilling to the designed design depth;

[0157] S3, planting and grouting of bottom precast piles 2: including injecting solidified slurry into the borehole and placing at least one bottom precast pile 2 into the borehole; see Fig.17 In (2) to (4), a certain volume of solidifying slurry is first injected into the pile end, and then a certain volume of solidifying slurry is injected into the part above the pile end, and after mixing with the soil in the borehole, a state between liquid and solid is formed, and then at least one bottom prefabricated pile 2 is sequentially placed into the borehole in sections by relying on its own weight and pile pressure;

[0158] S4, top precast pile planting: the precast pile 1 is placed on the upper end of the bottom precast pile 2 at the uppermost end, and the precast pile 1 is pressed into the borehole, wherein the first annular protrusion 12 and the second annular protrusion 13 squeeze the soil around the borehole wall and / or the solidified slurry during the process of the precast pile 1 being placed into the borehole, see Fig.16 (5)~(6).

[0159] When the prefabricated pile 1 is implanted into the borehole, since the orthographic projection of the first annular protrusion 12 on the horizontal plane completely covers the orthographic projection of the inner wall of the borehole on the horizontal plane, during the downward implantation process, the lower end face of the first annular protrusion 12 squeezes the cement soil located on the lower side of the first annular protrusion 12 in the borehole, and the cement soil diffuses to the soil around the borehole by increasing the pressure, and part of the cement soil enters the soil gaps around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, and improving the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, thereby improving the bearing capacity of the single pile after the composite pile is implanted.

[0160] Further, in step S3, the planting of the bottom precast pile 2 also includes that one of the bottom precast piles 2 is a solid pile, or the bottom precast piles 2 are all hollow piles, an end sealing plate 3 is welded at the end of one of the bottom precast piles 2, the outer peripheral wall of the end sealing plate 3 along the length direction of the first pile body 10 is completely overlapped with the outer peripheral wall of the second pile body 20 along the length direction of the first pile body 10, and the end sealing plate 3 is provided with a pressure regulating hole 30 that passes through from top to bottom, the pressure regulating hole 30 is connected to the inner hole of the second pile body 20, and the diameter of the pressure regulating hole 30 is smaller than the inner diameter of the second pile body 20, so as to prevent cement soil from passing through the pressure regulating hole 30 from bottom to top. The end sealing plate 3 or the solid pile is used as a blocking structure to adjust the volume of cement soil entering the bottom precast pile 2, thereby adjusting the squeezing effect of the first annular protrusion 12 of the precast pile 1 on the cement soil in the borehole. In addition, when the bottom precast pile 2 is a hollow pile, a blocking structure can also be arranged in the inner hole of the bottom precast pile 2 to adjust the squeezing effect of the first annular protrusion 12 of the precast pile 1 on the cement soil in the borehole.

[0161] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact the second annular protrusion 13 or the first annular protrusion 12 .

[0162] In some examples, in step S3, the injection amount of the solidifying slurry is the borehole volume within a height range of 2.5 m to 3 m at the lower end of the borehole.

[0163] In some examples, at least four second thickened protrusions 21 are distributed over a 2.6-meter length of the bottom section of the bottom precast pile 2 that is first placed into the borehole, see Fig.18 Middle (2) to (3);

[0164] In some examples, step S2 further includes expanding the diameter of the borehole at the bottom, wherein the borehole cavity of the expanded borehole accommodates at least four second thickened protrusions 21 at the bottom of the first section of the bottom precast pile 2 placed in the borehole, see Fig.19 .

[0165] In some examples, the depth of the expanded borehole is greater than 2 meters and less than 3 meters, preferably greater than 2.4 meters and less than 2.8 meters, wherein the ratio of the expanded borehole diameter to the borehole diameter is between 1.2 and 1.4.

[0166] Furthermore, in step S3, the injection amount of the solidifying slurry is the volume of the expanded borehole. Expanding the borehole at the bottom of the borehole can increase the injection amount of the solidifying slurry, and the lower second thickened protrusions 21 of the first bottom prefabricated pile 2 placed in the borehole are arranged more densely, which can further improve the bearing capacity of the lower end of the composite pile, thereby improving the vertical bearing capacity of the single pile after the composite pile is implanted.

[0167] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0168] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0169] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A prefabricated pile, characterized in that: include: A first pile body (10), wherein two ends of the first pile body (10) along the length direction are respectively a first end (10') and a second end (10"); A plurality of first thickened protrusions (11) fixed on the outer peripheral wall of the first pile body (10) and arranged at intervals along the length direction of the first pile body (10); and A first annular protrusion (12) is fixedly mounted on the first pile body (10), and at least one of the first thickened protrusions (11) is located between the first annular protrusion (12) and the second end (10"); When the prefabricated pile (1) is placed in a borehole, the inner peripheral wall of the borehole is projected along the length direction of the first pile body (10) around the outer side of the first pile body (10) and the first thickened protrusion (11) combination projected along the length direction of the first pile body (10), and the first annular protrusion (12) is projected along the length direction of the first pile body (10) to completely cover the inner peripheral wall of the borehole projected along the length direction of the first pile body (10).

2. The prefabricated pile according to claim 1, characterized in that: The prefabricated pile further comprises at least one second annular protrusion (13) fixed around the outer peripheral wall of the first pile body (10), the second annular protrusion (13) being located between the first annular protrusion (12) and the second end (10"), the first annular protrusion (12) being projected along the length direction of the first pile body (10) covering the second annular protrusion (13) being projected along the length direction of the first pile body (10), and the outer peripheral wall of the second annular protrusion (13) being projected along the length direction of the first pile body (10) being located outside the projection of the borehole along the length direction of the first pile body (10), or the outer peripheral wall of the first annular protrusion (12) being projected along the length direction of the first pile body (10) at least partially overlapping the outer peripheral wall of the second annular protrusion (13) being projected along the length direction of the first pile body (10).

3. The prefabricated pile according to claim 2, characterized in that: At least one pressure relief channel (131) is provided on the second annular protrusion (13), and the pressure relief channel (131) penetrates the second annular protrusion (13) along the length direction of the first pile body (10); And / or, at least one of the first thickened protrusions (11) is provided between the first annular protrusion (12) and the second annular protrusion (13).

4. The prefabricated pile according to claim 3, characterized in that: The second annular protrusion (13) is provided with two or more pressure relief channels (131) spaced apart along the circumferential direction, and / or at least one of the pressure relief channels (131) is a through hole or a notch.

5. The prefabricated pile according to claim 2, characterized in that: The first pile body (10), the first thickened protrusion (11), the first annular protrusion (12), and the second annular protrusion (13) are prefabricated in one piece; The first pile body (10) is arranged in the form of a hollow round pile, a plurality of the first thickened protrusions (11) are arranged in a bamboo-joint shape along the length direction of the first pile body (10), the first annular protrusion (12) and the second annular protrusion (13) are both arranged in a circular ring shape, and the first thickened protrusion (11), the first annular protrusion (12), the second annular protrusion (13) and the first pile body (10) are arranged coaxially.

6. The prefabricated pile according to claim 2, characterized in that: The first pile body (10), the first thickened protrusion (11), the first annular protrusion (12), and the second annular protrusion (13) are prefabricated in one piece; The first pile body (10) is arranged in the form of a hollow square pile, the first thickened protrusion (11), the first annular protrusion (12) and the second annular protrusion (13) are all arranged in a square ring shape, and the first thickened protrusion (11), the first annular protrusion (12) and the second annular protrusion (13) are all arranged in parallel around the outer side of the first pile body (10).

7. The prefabricated pile according to claim 2, characterized in that: The first pile body (10) and the first thickened protrusion (11) are prefabricated as a whole, the first pile body (10) is arranged in a hollow round pile, and a plurality of the first thickened protrusions (11) are arranged in a bamboo-like shape along the length direction of the first pile body (10); The first annular protrusion (12) and the second annular protrusion (13) are both arranged in a circular ring shape; the first thickened protrusion (11), the first annular protrusion (12), the second annular protrusion (13) and the first pile body (10) are arranged coaxially; the first annular protrusion (12) and / or the second annular protrusion (13) include more than two arc-shaped protrusions (120) that can be spliced ​​to each other in a circular ring shape; the arc-shaped protrusion (120) is welded and fixed or detachably fixed to the first pile body (10).

8. The prefabricated pile according to claim 7, characterized in that: A groove (125) is provided on the inner peripheral wall of the arc-shaped protrusion (120); when the arc-shaped protrusion (120) is fixed on the first thickened protrusion (11), the outer peripheral wall of the first thickened protrusion (11) and the inner side wall of the groove (125) fit each other to limit the axial position of the arc-shaped protrusion (120).

9. The prefabricated pile according to claim 7, characterized in that: The arc-shaped protrusion (120) is prefabricated from concrete, and a first embedded steel part (121) extending in the circumferential direction is embedded in at least one of the two ends of the inner peripheral wall of the arc-shaped protrusion (120) along the length direction of the first pile body (10), and a second embedded steel part (14) extending in the circumferential direction and corresponding to the first embedded steel part (121) is embedded in the first pile body (10), and the first embedded steel part (121) is correspondingly welded to the second embedded steel part (14).

10. The prefabricated pile according to claim 9, characterized in that: A plurality of first steel bars (126), first connecting bars (127) and radial bars (128) are embedded in the arc-shaped protrusion (120); the plurality of first steel bars (126) are evenly arranged along the circumference of the arc-shaped protrusion (120); the first steel bars (126) extend along the axial direction of the arc-shaped protrusion (120); one end of two first connecting bars (127) are respectively connected to two ends of one first steel bar (126); the other ends of the two first connecting bars (127) are respectively welded and fixed to two first embedded steel parts (121); the plurality of radial bars (128) are all connected to the first steel bars (126) and evenly distributed along the length direction of the first steel bars (126); and the radial bars (128) extend radially along the arc-shaped protrusion (120); The first pile body (10) is pre-embedded with a plurality of second steel bars (16) and second connecting bars (161); the plurality of second steel bars (16) are evenly distributed along the circumference of the first pile body (10) and fixed to the prestressed main bars (15) of the first pile body (10); the second steel bars (16) are arranged corresponding to the first thickened protrusion (11); one end of two second connecting bars (161) are respectively connected to the two ends of one second steel bar (16); and the other ends of the two second connecting bars (161) are respectively welded and fixed to two second pre-embedded steel parts (14) on both axial sides of the first thickened protrusion (11).

11. The prefabricated pile according to claim 7, characterized in that: The arc-shaped protrusion (120) is prefabricated from concrete, and is provided with a through hole (129) extending in the radial direction, and the through hole (129) passes through the inner and outer peripheral walls of the arc-shaped protrusion (120). A bolt hole (112) is provided on the outer peripheral wall of the first thickened protrusion (11), and an expansion bolt (17) passing through the through hole (129) is installed in the bolt hole (112) to fix the arc-shaped protrusion (120) to the first thickened protrusion (11).

12. The prefabricated pile according to claim 7, characterized in that: The first annular protrusion (12) and / or the second annular protrusion (13) comprises a first conical surface (122'), a cylindrical surface (123') and a second conical surface (124') which are sequentially connected from the first end (10') to the second end (10") of the first pile body (10); the cylindrical surface (123') extends along the length direction of the first pile body (10) and surrounds the outer side of the first pile body (10); the end of the first conical surface (122') facing the first end (10') is connected to the first pile body (10); the end of the second conical surface (124') facing the first end (10') is connected to the first pile body (10); the second conical surface (124') cooperates with the first pile body (10) to form an annular cavity with an opening facing the second end (10") 13. The prefabricated pile according to claim 5 or 7, characterized in that: The first annular protrusion (12) and / or the second annular protrusion (13) both comprise a first conical surface (122), a cylindrical surface (123) and a second conical surface (124) which are sequentially connected from the first end (10') to the second end (10") of the first pile body (10); the cylindrical surface (123) extends along the length direction of the first pile body (10) and surrounds the outer side of the first pile body (10); the end of the first conical surface (122) facing the first end (10') and the end of the second conical surface (124) facing the second end (10") are both connected to the first pile body (10); the diameter of the first conical surface (122) gradually increases from the first end (10') to the second end (10") of the first pile body (10); and the diameter of the second conical surface (124) gradually decreases from the first end (10') to the second end (10") of the first pile body (10).

14. The prefabricated pile according to claim 13, characterized in that: The included angle between the second conical surface (124) and the first pile body (10) in the length direction is greater than 45° and less than 90°.

15. The prefabricated pile according to claim 1, characterized in that: The first pile body (10) and the first thickened protrusion (11) are prefabricated in one piece; The outer peripheral wall of the end plate of the first end (10') is projected along the length direction of the first pile body (10) to surround the outer side of the first thickened protrusion (11) projected along the length direction of the first pile body (10), and the part of the end plate of the first end (10') extending out of the first pile body (10) forms the first annular protrusion (12).

16. The prefabricated pile according to claim 1, characterized in that: The first pile body (10) and the first thickened protrusion (11) are prefabricated in one piece; The first annular protrusion (12) is arranged in an end plate shape, and a plurality of through holes (129') are arranged on the first annular protrusion (12) and are distributed at intervals. The through holes (129') penetrate the two end surfaces of the first annular protrusion (12) along the length direction of the first pile body (10). The end plate of the first end (10') of the first pile body (10) is provided with a threaded hole (19) corresponding to the through hole (129'), and a bolt (18) passing through the through hole (129') is installed in the threaded hole (19) to fix the first annular protrusion (12) to the first pile body (10).

17. The prefabricated pile according to claim 16, characterized in that The threaded hole (19) is an anchor hole of the end plate of the first end (10') of the first pile body (10), and the anchor hole is used for the heading to pass through from the first end (10') to the second end (10").

18. The precast pile according to any one of claims 1 to 12 or 14 to 17, characterized in that The length of the first pile body (10) is defined as L, the first end (10') is defined as a starting point, and the first annular protrusion (12) is located within the interval [0, L / 2] of the first pile body (10).

19. The prefabricated pile according to claim 18, characterized in that The first annular protrusion (12) is located within the interval [0, L / 4] of the first pile body (10).

20. The precast pile according to any one of claims 1 to 12 or 14 to 17, characterized in that The first thickened protrusion (11) and the first annular protrusion (12) are both parallel and surround the outer side of the first pile body (10), and the distance from the outer edge of the first thickened protrusion (11) projected along the length direction of the first pile body (10) to the outer edge of the first annular protrusion (12) projected along the length direction of the first pile body (10) is a fixed value, and the fixed value is not less than 40 mm and not more than 150 mm.

21. The precast pile according to any one of claims 1 to 5 or 7 to 12 or 14 to 17, characterized in that: The first pile body (10) is arranged in the shape of a hollow round pile, the first thickened protrusion (11) and the first annular protrusion (12) are arranged in the shape of a circular ring, the first thickened protrusion (11), the first annular protrusion (12) and the first pile body (10) are arranged coaxially, the outer diameter of the first annular protrusion (12) is 0 to 50 mm larger than the diameter of the drilled hole, and the outer diameter of the first thickened protrusion (11) is 40 to 100 mm smaller than the diameter of the drilled hole.

22. The precast pile according to any one of claims 1 to 5 or 7 to 12 or 14 to 17, characterized in that The first pile body (10) is arranged in the shape of a hollow round pile, the first thickened protrusion (11) and the first annular protrusion (12) are arranged in the shape of an annular ring, the first thickened protrusion (11), the first annular protrusion (12) and the first pile body (10) are arranged coaxially, the outer diameter of the first pile body (10) is 350 mm to 750 mm, the outer diameter of the first annular protrusion (12) is 90 mm to 200 mm larger than the outer diameter of the first pile body (10), the outer diameter of the first thickened protrusion (11) is 50 mm to 150 mm larger than the outer diameter of the first pile body (10), and the outer diameter of the first annular protrusion (12) is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion (11).

23. A composite pile, characterized in that: include: A top precast pile consisting of a precast pile (1) as claimed in any one of claims 1 to 22; as well as at least one bottom precast pile (2) connected to the lower end of the top precast pile; The bottom prefabricated pile (2) comprises a second pile body (20) extending vertically, wherein the projection of the outer peripheral wall of the second pile body (20) along the length direction of the first pile body (10) completely overlaps with the projection of the outer peripheral wall of the first pile body (10) along the length direction of the first pile body (10).

24. The composite pile according to claim 23, characterized in that: The bottom prefabricated pile (2) further comprises a plurality of second thickened protrusions (21) fixedly encircling the outer peripheral wall of the second pile body (20); the second thickened protrusions (21) are integrally prefabricated with the second pile body (20); the plurality of second thickened protrusions (21) are arranged at intervals along the length direction of the second pile body (20); the outer peripheral wall of the first annular protrusion (12) is projected along the length direction of the first pile body (10) to surround the outer side of the projection of the second pile body (20) and the second annular protrusion (21) combination along the length direction of the first pile body (10).

25. The composite pile according to claim 24, characterized in that: The second pile body (20) and the first pile body (10) are both arranged in the form of hollow round piles; the first thickened protrusion (11), the first annular protrusion (12) and the second thickened protrusion (21) are all arranged in the form of circular rings; the first thickened protrusion (11), the first annular protrusion (12), the second thickened protrusion (21), the second pile body (20) and the first pile body (10) are arranged coaxially; a plurality of the second thickened protrusions (21) are arranged in the form of bamboo joints along the length direction of the second pile body (20); and the outer diameter of the second annular protrusion (21) is equal to the outer diameter of the first thickened protrusion (11).

26. The composite pile according to claim 25, characterized in that The bottom precast pile (2) is a tubular structure with an inner cavity, and a blocking structure for at least partially blocking the inner cavity is fixed on at least one of the bottom precast piles (2); or at least one of the bottom precast piles (2) is a solid structure.

27. The composite pile according to claim 26, characterized in that: The blocking structure is an end sealing plate (3) arranged at the end of the bottom prefabricated pile (2).

28. The combined pile according to any one of claims 23 to 27, characterized in that: It also comprises a uniform cross-section pipe pile (4) connected to the upper end of the precast pile (1), the uniform cross-section pipe pile (4) extending vertically and being precast integrally from concrete, the outer peripheral wall of the uniform cross-section pipe pile (4) projected along the length direction of the first pile body (10) coincides with the outer peripheral wall of the first annular protrusion (12) projected along the length direction of the first pile body (10).

29. The composite pile according to claim 28, characterized in that The first annular protrusion (12) is arranged at the uppermost end of the first pile body (10) and is connected to the uniform cross-section pipe pile (4). The first annular protrusion (12) and the first pile body (10) are prefabricated as a whole. The upper end face, the outer peripheral face and the lower end face of the first annular protrusion (12) are sequentially connected from top to bottom. The upper end face of the first annular protrusion (12) extends from the outer peripheral face to the first pile body (10). The upper end face of the first annular protrusion (12) is coplanar with the upper end face of the first pile body (10). The outer peripheral face of the first annular protrusion (12) extends vertically and surrounds the outer side of the first pile body (10). The lower end face of the first annular protrusion (12) extends from the outer peripheral face to the first pile body (10). The lower end face of the first annular protrusion (12) is arranged in a conical surface. The diameter of the lower end face of the first annular protrusion (12) gradually decreases from top to bottom.

30. A prefabricated pile construction method, characterized in that: Use the prefabricated piles as described in any one of claims 1 to 22 or the combined piles as described in any one of claims 23 to 29.

31. A construction method using the composite pile according to any one of claims 23 to 29, characterized in that: The steps include: S1. Drilling hole setting: the drilling hole size is designed according to the cross-sectional size of the first pile body (10) of the prefabricated pile (1), the inner peripheral wall of the drilled hole is projected on the horizontal plane around the outer side of the first pile body (10) and the first thickened protrusion (11) combination on the horizontal plane, and the inner peripheral wall of the drilled hole is completely covered by the second annular protrusion (12) on the horizontal plane. S2, drilling construction: drilling according to the drilling settings; S3, planting and grouting of the bottom prefabricated pile (2): comprising placing at least one of the bottom prefabricated piles (2) into a borehole and injecting solidified slurry into the borehole; S4, top precast pile planting: the precast pile (1) is placed on the upper end of the bottom precast pile (2) mentioned at the uppermost end, and the precast pile (1) is pressed into the borehole, wherein the first annular protrusion (12) and the second annular protrusion (13) squeeze the soil around the borehole wall and / or the solidified slurry during the process of placing the precast pile (1) into the borehole.

32. The construction method according to claim 31, characterized in that: The grouting is to inject a certain volume of solidified slurry into the borehole, so that before the prefabricated pile (1) is completely pressed into the borehole, the liquid surface of the solidified slurry is squeezed to contact the second annular protrusion (13) or the first annular protrusion (12).

33. The construction method according to claim 31 or 32, characterized in that: The bottom 2.6m length range of a section of bottom prefabricated pile (2) first placed into the borehole has at least four second thickened protrusions (21) distributed.

34. The construction method according to claim 33, characterized in that: Step S2 also includes expanding the diameter of the borehole at the bottom, wherein the borehole cavity of the expanded diameter borehole accommodates at least four second thickened protrusions (21) at the bottom of the first section of the bottom precast pile (2) placed in the borehole.

35. The construction method according to claim 34, characterized in that: The depth of the expanded diameter borehole is greater than 2 m and less than 3 m, preferably greater than 2.4 m and less than 2.8 m.

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