Precast pile and composite pile

Abstract

The utility model provides a precast pile and a combined pile, and relates to the technical field of pile foundation construction, the precast pile comprises: a first pile body, the two ends of the first pile body along the length direction are respectively a first end and a second end; 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; the projection of the peripheral wall of the first annular protrusion in the length direction of the first pile body surrounds the outer side of the projection of the first thickened protrusion 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 utility model relates to the technical field of pile foundation construction, in particular to a prefabricated pile and a combined pile. Background Art

[0002] With the increasing density of urban buildings, pile foundation construction in a growing number of new construction and renovation projects is increasingly demanding the reduction or even elimination of soil extrusion impacts on the surrounding environment. This has driven the development of embedded pile technology. Early applications of embedded pile technology were in my country's coastal soft soil areas. After drilling, embedded pile construction involves mixing and liquefying the soil within the hole before driving the pile into the ground. This process causes the liquid level within the hole to rise and partially drain, eliminating soil extrusion. Therefore, the embedded pile method is well-suited for soft soil foundations.

[0003] Under the existing construction process of the pile, there are two failure interfaces 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 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. This is a special-shaped pipe pile, see patent CN2611433Y. The bamboo pile body has "bamboo nodes" protruding from the pile body surface at intervals, so it is also called a bamboo pile. Unlike pipe piles, bamboo piles are difficult to cast on site. Although some literature indicates that cast-in-place piles can also be made into shapes similar to bamboo piles, whether it is the drilling technology or the uncertainty of foundation construction conditions, the bamboo piles formed by casting are significantly different from prefabricated bamboo piles in size, surface burrs and bearing performance. 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. In addition, except for production tests in the industry, there have been no actual construction projects of cast-in-place bamboo piles. Prefabricated bamboo piles are well-suited for implantation. Traditional static pressure and hammering methods significantly expel soil when applied to bamboo piles. However, with implantation, the drilled hole diameter is larger than the bamboo joint, allowing the pile to be inserted into the foundation without extrusion. After the completed bamboo pile is combined with the surrounding soil 6, the soil contacts not only the pile body but also the surface of the bamboo joint, effectively increasing the peak shear stress at interface S1. Compared to conventional prefabricated piles of the same diameter, the interface S1 between the surrounding soil 6 and the core pile 7 is less susceptible to damage.

[0005] However, under the implantation method of construction, the interface S2 between the solidified soil around the pile and the undisturbed soil around the hole wall has not been improved compared to ordinary precast piles of the same diameter, and has now become a limiting factor in the bearing capacity of single bamboo piles constructed by the implantation method. Although increasing the pile diameter can improve the bearing capacity, the amount of concrete used will inevitably increase significantly with the increase in pile diameter, and the transportation, construction difficulty and curing time of the bamboo piles 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 bearing capacity of single piles of implanted piles, it is necessary to solve the problem of how to increase the boundary friction between the solidified soil around the pile and the undisturbed soil around the hole wall.

[0006] Furthermore, in soft soil areas, bamboo-jointed piles, which are installed by compression or hammering, have been developed to improve the bearing capacity of single cylindrical precast piles. Using these methods, the ultimate bearing capacity of bamboo-jointed piles can reach approximately 1.23 times that of cylindrical pipe piles of the same outer diameter. However, during these methods, the bamboo-jointed piles' joints displace the soil, creating a void between the soil and the pile body. The soil backfilling process between adjacent joints takes a long time, over 28 days, far longer than the soil backfill period (7 days) for cylindrical precast piles installed by compression or hammering. This long construction period increases construction costs. Therefore, it is necessary to address the long soil backfill period associated with bamboo-jointed piles installed by compression or hammering. Utility Model Content

[0007] The technical problem to be solved by this application is how to increase the boundary friction resistance between the solidified soil around the pile and the original soil around the hole wall, and how to shorten at least one of the backtracking cycles of the bamboo pile holding pressure or hammering construction soil. In view of this, this application provides a prefabricated pile and a combined pile.

[0008] In a first aspect, a prefabricated pile comprises:

[0009] 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;

[0010] a plurality of first thickened protrusions fixed to the outer peripheral wall of the first pile body and spaced apart along the length direction of the first pile body; and

[0011] a first annular protrusion, circumferentially fixed to the first pile body, at least one of the first thickened protrusions being located between the first annular protrusion and the second end;

[0012] The outer peripheral wall of the first annular protrusion is projected along the length direction of the first pile body and surrounds the outer side of the first thickened protrusion projected along the length direction of the first pile body.

[0013] Compared with the prior art, the precast pile of the present application has the following advantages: When the precast pile is inserted into the drilled hole, the first annular protrusion squeezes the cement soil below the annular protrusion in the drilled hole, forcing some of the cement soil into the voids in the soil surrounding the hole wall, thereby increasing the bonding strength between the solidified soil around the pile and the original soil around the hole wall, increasing the boundary friction resistance at 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 inserted. In addition, the cement soil around the first thickened protrusion is squeezed by the first annular protrusion, increasing its density, and increasing the interaction force between the first thickened protrusion and the surrounding cement soil, thereby increasing the boundary friction resistance at the interface S1 between the precast pile and the solidified soil around the pile, further improving the bearing capacity of the single pile after the precast pile is inserted. Because the outer wall of the first annular protrusion is projected along the length direction of the first pile body around the outside of the first thickened protrusion projected along the length direction of the first pile body, when the precast pile is pressed or hammered, the first annular protrusion squeezes the soil downward, thereby forcing the soil to enter the space between adjacent first thickened protrusions, accelerating the soil backflow, shortening the soil backflow cycle, and enabling the combined pile using the precast pile to reach the designed bearing capacity more quickly.

[0014] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as one piece;

[0015] The first annular protrusion is an annular flange made of metal, and the inner ring edge of the annular flange is welded and fixed to the outer edge of the first end of the precast pile.

[0016] In a preferred embodiment, at least a portion of the surface of the annular flange facing the second end forms an undercut conical surface.

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

[0018] The first annular protrusion is an annular flange made of metal, and a plurality of spaced-apart through-holes are provided on the annular flange. The through-holes pass through the two end surfaces of the annular flange along the length direction of the first pile body. The end plate at the first end of the first pile body is provided with threaded holes corresponding to the through-holes, and bolts passing through the through-holes are assembled in the threaded holes to fix the annular flange to the first pile body.

[0019] In a preferred embodiment, the threaded hole is an anchoring hole of an end plate at the first end of the first pile body, and the anchoring hole is used for a heading to pass through from the first end to the second end.

[0020] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as one piece;

[0021] 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 along the length direction of the first pile body. The first annular protrusion is an annular flange formed by the portion of the end plate at the first end extending out of the first pile body.

[0022] In a preferred embodiment, the precast pile further comprises at least one second annular protrusion fixed around the circumferential wall of the first pile body, the second annular protrusion being 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 covering 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 being located outside the projection of the drilled hole into which the precast pile is implanted 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.

[0023] In a preferred embodiment, at least one pressure relief channel is provided on the second annular protrusion, and the pressure relief channel passes through the second annular protrusion along the length direction of the first pile body;

[0024] And / or, at least one first thickened protrusion is provided between the first annular protrusion and the second annular protrusion.

[0025] 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.

[0026] In a preferred embodiment, the first pile body is provided as a hollow round pile, and the plurality of first thickened protrusions are provided in a bamboo-like shape along the length direction of the first pile body;

[0027] The second annular protrusion and the first annular protrusion are both arranged in an annular shape, the first thickened protrusion, the second annular protrusion, the first annular protrusion and the first pile body are arranged coaxially, and the second annular protrusion and the first pile body are prefabricated as a whole.

[0028] In a preferred embodiment, the first pile body is provided as a hollow round pile, and the plurality of first thickened protrusions are provided in a bamboo-like shape along the length direction of the first pile body;

[0029] The second annular protrusion and the first annular protrusion are both arranged in a circular ring shape, the first thickened protrusion, the second annular protrusion, the first annular protrusion and the first pile body are coaxially arranged, the second annular protrusion includes two or more 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.

[0030] In a preferred embodiment, a groove is provided on the inner peripheral wall of the arc-shaped protrusion. 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 together to limit the axial position of the arc-shaped protrusion.

[0031] In a preferred embodiment, the arc-shaped protrusion is prefabricated from concrete, and a first embedded steel part extending circumferentially is pre-embedded in at least one of the two ends of the inner peripheral wall of the arc-shaped protrusion along the length direction of the first pile body, and a second embedded steel part extending circumferentially 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.

[0032] In a preferred embodiment, a plurality of first steel bars, first connecting bars and radial bars are pre-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 are evenly distributed along the length direction of the first steel bar, and the radial bars extend radially along the arc-shaped protrusion;

[0033] 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 end 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 both sides of the axial direction of the first thickened protrusion.

[0034] 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 side walls of the arc-shaped protrusion, and a bolt hole is provided on the outer peripheral 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.

[0035] In a preferred embodiment, the second annular protrusion includes a first conical surface, a first cylindrical surface, and a second conical surface connected in sequence from the first end to the second end of the first pile body, the first 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, and 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 concave cavity with an opening facing the second end.

[0036] In a preferred embodiment, the second annular protrusion includes a third conical surface, a second cylindrical surface, and a fourth conical surface sequentially connected from the first end to the second end of the first pile body, the second 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 third conical surface facing the first end and the end of the fourth conical surface facing the second end are both connected to the first pile body, the diameter of the third conical surface gradually increases from the first end to the second end of the first pile body, and the diameter of the fourth conical surface gradually decreases from the first end to the second end of the first pile body.

[0037] In a preferred embodiment, the included angle between the fourth conical surface and the length direction of the first pile body is greater than 45° and less than 90°.

[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 projection of the first thickened protrusion along the length direction of the first pile body to the outer edge of the projection of the first annular protrusion 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 both arranged in a circular ring shape, the first thickened protrusion, the first annular protrusion and the first pile body are coaxially arranged, 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.

[0040] In a second aspect, the present application provides a combined pile, comprising:

[0041] Precast piles as described above; and

[0042] at least one end-connected precast pile connected to the first end and / or the second end of the precast pile;

[0043] The prefabricated pile includes a second pile body extending vertically, wherein a projection of an outer peripheral wall of the second pile body along the length direction of the first pile body completely overlaps with a projection of the first pile body along the length direction of the first pile body.

[0044] Compared with the prior art, the present invention provides a composite pile for static drilling and rooting, which has the following advantages: When the prefabricated pile is inserted into the drilled hole, the first annular protrusion squeezes the cement soil below the first annular protrusion in the drilled hole, forcing some of the cement soil into the soil voids surrounding the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil around the hole wall, increasing the limit friction resistance at 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 inserted. In addition, the cement soil below the first annular protrusion is squeezed by the first annular protrusion, increasing its density, and increasing the interaction force between the first thickened protrusion, the concrete pile, and the surrounding cement soil, thereby increasing the limit friction resistance at the interface S1 between the composite pile and the solidified soil around the pile, further improving the bearing capacity of the single pile after the composite pile is inserted. Because the outer wall of the first annular protrusion is projected along the length direction of the first pile body around the outside of the first thickened protrusion projected along the length direction of the first pile body, during the precast pile holding and pressing or hammering construction, the first annular protrusion squeezes the soil downward, thereby forcing the soil to enter the space between adjacent first thickened protrusions, accelerating the soil backtracking, shortening the soil backtracking cycle, and at the same time increasing the pile side friction resistance between the soil and the second pile body of the terminated precast pile, further improving the ultimate bearing capacity of the combined pile during holding and pressing or hammering construction.

[0045] In a preferred embodiment, the at least one terminal precast pile is connected to the first end of the precast pile, the first annular protrusion is an annular flange made of metal, and the two ends of the annular flange are respectively welded and fixed to the first end of the precast pile and one end of the terminal precast pile.

[0046] In a preferred embodiment, the inner edge of the annular flange is aligned with the outer edge of the first end of the precast pile and the outer edge of one end of the terminal precast pile, or the inner edge of the annular flange is embedded between the first end of the precast pile and one end of the terminal precast pile.

[0047] In a preferred embodiment, the length of the combined pile is defined as L, and the first annular protrusion is located within the interval [0, 2 / L] of the combined pile, with the upper end of the combined pile as the starting point.

[0048] In a preferred embodiment, the precast pile further comprises a plurality of second thickened protrusions fixed around the outer peripheral wall of the second pile body, the second thickened protrusions being prefabricated integrally with the second pile body, the plurality of second thickened protrusions being arranged at intervals along the length direction of the second pile body, and the projection of the outer peripheral wall of the first thickened protrusion along the length direction of the first pile body completely overlapping with the projection of the outer peripheral wall of the second thickened protrusion along the length direction of the first pile body.

[0049] In a preferred embodiment, the second pile body and the first pile body are both hollow circular piles, the first annular protrusion is arranged in a circular ring shape, and multiple first thickened protrusions are arranged in a bamboo-like shape along the length direction of the second pile body, and the first thickened protrusion, the first annular protrusion, the second pile body and the first pile body are coaxially arranged.

[0050] In a preferred embodiment, the bottom precast piles are tubular structures having 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.

[0051] In a preferred embodiment, the blocking structure is an end blocking plate provided at the end of the bottom precast pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a bearing capacity analysis diagram for the implantation method in the prior art;

[0053] Figure 2 This is a structural schematic diagram of Example 1 of the present application in which the first annular protrusion is integrally prefabricated on the upper end of the first pile body;

[0054] Figure 3 The QS curves of the prefabricated piles, pipe piles and bamboo piles in Example 1 of the present application are compared;

[0055] Figure 4 This is a structural diagram of the first annular protrusion welded and fixed to the upper end of the first pile body in Example 1 of the present application;

[0056] Figure 5 This is a structural diagram of the first annular protrusion bolt fixed to the upper end of the first pile body in Example 1 of the present application;

[0057] Figure 6 This is an exploded schematic diagram of the first annular protrusion bolt fixed to the upper end of the first pile body in Example 1 of the present application;

[0058] Figure 7 for Figure 6 Enlarged view of part A in the middle;

[0059] Figure 8This is a schematic structural diagram of the second annular protrusion in Example 1 of the present application being integrally prefabricated on the first pile body;

[0060] Figure 9 This is a structural diagram of the second annular protrusion being welded and fixed to the first pile body in Example 1 of the present application;

[0061] Figure 10 for Figure 9 A partial enlarged view of the second annular protrusion being welded and fixed to the first pile body;

[0062] Figure 11 This is a schematic structural diagram of the second annular protrusion in Example 1 of the present application being detachably fixed to the first pile body;

[0063] Figure 12 This is a structural diagram of a combined pile according to Example 2 of the present application;

[0064] Figure 13 This is a structural diagram of a first annular protrusion welded and fixed between a first pile body and a second pile body in Example 2 of the present application;

[0065] Figure 14 This is a structural schematic diagram of the composite pile of Example 2 of the present application, in which the end sealing plate adjusts the squeezing effect of the first annular protrusion on the cement soil.

[0066] Description of reference numerals:

[0067] 1. Precast pile; 10. First pile body; 10', first end; 10", second end; 11. First thickened protrusion; 111. Bolt hole; 112. Expansion bolt; 12. First annular protrusion; 121. Through hole; 13. Threaded hole; 14. Bolt; 15. Second annular protrusion; 151. Pressure relief channel; 152. Arc-shaped protrusion; 1521. Groove; 1522. First embedded steel member; 1523. First reinforcement bar; 1524. First connecting bar; 152 5. Radial reinforcement; 1526. Through hole; 1527. Third conical surface; 1528. Second cylindrical surface; 1529. Fourth conical surface; 1527'. First conical surface; 1528'. First cylindrical surface; 1529'. Second conical surface; 16. Second embedded steel part; 17. Second steel bar; 171. Second connecting reinforcement; 2. End precast pile; 20. Second pile body; 21. Second thickened protrusion; 3. End sealing plate; 5. Original soil around the hole wall; 6. Solidified soil around the pile; 7. Core pile. DETAILED DESCRIPTION

[0068] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0069] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0070] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "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," and "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.

[0071] The following is combined with Figures 2 to 12 The present application is further described in detail with specific embodiments.

[0072] Example 1

[0073] See also Figures 2 to 10 As shown, an embodiment of the present application discloses a prefabricated pile.

[0074] See also Figure 2 The prefabricated pile of this embodiment 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 prefabricated in one piece from concrete. The first pile body 10 can be a tubular pile or a solid pile. In this embodiment, the first pile body 10 is introduced by taking a tubular 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 the plurality of first thickened protrusions 11 are located between the first end 10' and the second end 10". 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. The first thickened protrusions 11 can be a circumferentially closed continuous annular shape, or can be composed of a plurality of circumferentially spaced block-shaped protrusions. 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 of the first pile body 10, such as a bamboo pile, a special-shaped square pile with alternating thickness along the length direction, etc. In this embodiment, the first pile body 10 is extended vertically 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 .

[0075] According to the implantation method, before the precast pile 1 is implanted into the foundation, it needs to go through the processes 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 diverse, 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 precast piles of the same diameter. This is a key factor that limits the bearing capacity of a single pile with alternating thickness along the length direction of the special-shaped pile constructed by the implantation method. Therefore, in order to further improve the bearing capacity of a single pile of the 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.

[0076] In this embodiment, the first annular protrusion 12 is fixed around the first pile body 10, and the 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 the 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.

[0077] 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 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 on the lower side of the first annular protrusion 12 in the borehole, forcing the cement soil to diffuse to the soil around the borehole, 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 boundary 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.

[0078] 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, further improving the single pile bearing capacity of the precast pile 1 after implantation.

[0079] During the downward implantation process, the effect of the lower end of the first annular protrusion 12 squeezing the cement soil below the first annular protrusion 12 in the borehole is affected by the physical properties of the first annular protrusion 12. To improve the squeezing effect of the lower end of the first annular protrusion 12 on the cement soil below during construction, 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 circumferential wall of the borehole along the length direction of the first pile body 10.

[0080] Preferably, the first annular protrusion 12 is located above all the first thickened protrusions 11, and all 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 drilled hole below it, but cannot squeeze the cement soil above it. Therefore, all the first thickened protrusions 11 are located below the first annular protrusion 12, so that the cement soil around all the first thickened protrusions 11 can be squeezed, thereby improving the overall bearing capacity of the precast pile 1 after implantation.

[0081] Preferably, the first pile body 10 is configured as a hollow circular pile, the plurality of first thickened protrusions 11 are configured in a bamboo-like shape along the length of the first pile body 10, the first annular protrusion 12 is configured in a circular ring shape, and the first pile body 10, the first thickened protrusion 11, and the first annular protrusion 12 are configured coaxially. In order to ensure that the first annular protrusion 12 completely covers the inner circumferential wall of the borehole along the length of the first pile body 10, the outer diameter of the first annular protrusion 12 is configured to be 0 to 50 mm larger than the borehole diameter. According to preliminary test pile experimental data, once the outer diameter of the first annular protrusion 12 exceeds the borehole diameter by more than 50 mm, the additional static pressure load required during construction is excessively large, greatly increasing the difficulty of construction. Furthermore, during the maintenance period after the test pile construction is completed, monitoring of the surrounding soil indicates that the soil squeezing effect is too significant, making it particularly unsuitable for soft soil foundations. 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, and the outer diameter of the first annular protrusion 12 was 550mm, 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 bottom expansion was not performed. The single pile bearing capacity comparison chart of the test pile, bamboo pile and pipe pile was obtained, as shown below. Figure 3As shown in Table 1, the concrete usage for the test piles increased by no more than 2.4% compared to conventional 450mm / 500mm bamboo piles. The pile bearing capacity increased by 28.57%, and no soil extrusion occurred around the piles after the curing period. Considering factors such as construction difficulty, implantability, and raw material cost, the test piles offer a competitive advantage over similarly sized and larger bamboo piles on the market.

[0082] Table 1 Comparison of 450mm / 500mm / 550mm test piles and 450mm / 500mm bamboo piles

[0083] Pile type Pile size Bamboo size Single pile concrete consumption 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

[0084] In addition to the above-mentioned test pile, 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, and 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. The outer diameter of the first annular protrusion 12 is larger than the outer diameter of the first thickened protrusion 11. 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 drilled hole is affected by the dimensional characteristics of the first annular protrusion 12 and the first thickened protrusion 11. Preferably, 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.

[0085] See also Figure 2 In 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 first annular protrusion 12 is an annular flange formed by 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. Specifically, when the precast pile 1 is prefabricated in one piece, a standard end plate is connected to one end of the reinforcement 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. A larger end plate is connected to the other end of the reinforcement 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.

[0086] The first annular protrusion 12 is formed by the end plate of the first end 10' of the prefabricated pile 1, which avoids the need to prefabricate the first annular protrusion 12 of a relatively large size during production, and avoids the problem of uneven stress distribution caused by prefabricating the first annular protrusion 12 of a large size. The first pile body 10 and the first thickened protrusion 11 can be demoulded relatively easily.

[0087] Reference Figure 4In some examples, the first annular protrusion 12 is an annular flange made of metal, such as an annular flange made of steel, and the inner annular edge of the annular flange is welded and fixed to the outer edge of the first end 10' of the precast pile 1. Specifically, the inner annular edge of the annular flange can be aligned with the outer edge of the end plate of the first end 10' of the precast pile 1, so that the annular flange is sleeved on the end plate of the first end 10', and then the annular flange is welded and fixed to the end plate of the first end 10' of the precast pile 1. In addition, the inner annular size of the annular flange can also be smaller than the outer annular size of the precast pile 1, one end of the annular flange abuts the first end 10' of the precast pile 1, and then the annular flange is welded and fixed to the end plate of the first end 10' of the precast pile 1.

[0088] Since the use of a relatively large end plate at one end of the precast pile 1 is avoided during production, the centrifugal prefabrication molding stage can be the same as that of existing bamboo piles, and the existing production molds and production operations can remain unchanged. The stress distribution of the entire precast pile 1 is uniform, and the pile body is less likely to collapse during demolding. During construction, the first annular protrusion 12 is welded to the first end 10' of the first pile body 10. The first annular protrusion 12 can be installed after the first end 10' of the precast pile 1 passes through the pile clamp box, avoiding interference between the first annular protrusion 12 and the pile clamp box. There is no need to modify the pile clamp box, thereby reducing the construction cost of the precast pile 1.

[0089] Furthermore, at least a portion of the surface of the annular flange facing the second end forms an inverted conical surface. In this way, when the precast pile 1 is implanted, the lower end surface of the annular flange guides the cement soil to gather toward the first pile body 10, thereby reducing the cement soil from the lower side of the annular flange to the upper side of the annular flange. At the same time, the force of the lower end surface of the annular flange can fully act on the cement soil in the drilled hole, further improving the squeezing effect of the annular flange on the cement soil in the drilled hole.

[0090] See also Figure 5 In some examples, the first annular protrusion 12 is an annular flange made of metal. The first annular protrusion 12 is provided with a plurality of spaced-apart through-holes 121. The through-holes 121 pass through the upper and lower end surfaces of the first annular protrusion 12. Correspondingly, a threaded hole 13 is provided on the end plate of the first end 10' of the first pile body 10. The stud of the bolt 14 passes through the through-hole 121 and is threadedly connected to the threaded hole 13 to fix the first annular protrusion 12 to the first end 10' of the first pile body 10.

[0091] Since the use of a relatively large end plate at one end of the precast pile 1 is avoided during production, the centrifugal prefabrication molding stage can be the same as the existing bamboo pile, and the existing production mold and production operation can remain unchanged. The stress distribution of the entire precast pile 1 is uniform, and the pile body is not prone to collapse during demoulding. During construction, the first annular protrusion 12 is detachably fixed to the first end 10' of the first pile body 10 by bolts 14. The first annular protrusion 12 can be installed after the first end 10' of the precast pile 1 passes through the pile clamp box, avoiding interference between the first annular protrusion 12 and the pile clamp box, and thus eliminating the need to modify the pile clamp box, thereby reducing the construction cost of the precast pile 1. At the same time, it is convenient to disassemble and recycle the first annular protrusion 12 before the foundation construction after excavation, further reducing the construction cost of the precast pile 1.

[0092] See also Figure 6 and Figure 7 Furthermore, 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, which is a threaded hole 13, so as to be connected with the tensioning bolt, so as to facilitate the tensioning of the steel cage; the threaded hole 13 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 13 is larger than the diameter of the swaging head, so that the swaging head can pass through the threaded hole 13 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 long strip-shaped rib hole 131, which 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 131 extends along the circumference of the end plate of the first end 10'. One end of the rib hole 131 is connected to the anchor hole, and the width of the rib hole 131 is larger than the diameter of the main reinforcement and smaller than the diameter of the swaging 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 131. The rib hole is a stepped hole. The rib hole includes a large diameter hole 132 and a small diameter hole 133. The opening of the large diameter hole 132 is set away from the first pile body 10, and the opening of the small diameter hole 133 is set toward the first pile body 10. The diameter of the large diameter hole 132 is larger than the diameter of the small diameter hole 133. The diameter of the large diameter hole 132 is larger than the diameter of the upsetting head, and the diameter of the small diameter hole 133 is larger than the main rib The diameter of the main reinforcement is smaller than that of the pier head, and the upsetting head can be clamped into the large-diameter hole 132. When the main reinforcement is assembled with the end plate at the first end 10', the upsetting head passes through the threaded hole 13 in the direction from the second end 10" to the first end 10'. Then, the end plate at the first end 10' is rotated, and the main reinforcement moves to the other end of the reinforcement hole 131. The end plate at 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 into the large-diameter hole 132.

[0093] 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 14 , without the need to additionally process the threaded hole 13 on the end plate, thus simplifying the processing steps and reducing the production cost of the prefabricated pile 1 .

[0094] See also Figure 8 In some examples, the precast pile 1 further includes at least one second annular protrusion 15 fixed around the outer peripheral wall of the first pile body 10, and the second annular protrusion 15 is located between the first annular protrusion 12 and the second end 10". The number of the second annular protrusion 15 can be one or more. When there are more than two second annular protrusions 15, the two or more second annular protrusions 15 are spaced apart along the length direction of the first pile body 10.

[0095] When the first annular protrusion 12 is projected along the length direction of the first pile body 10 and covers the second annular protrusion 15 projected along the length direction of the first pile body 10, due to the action of the second annular protrusion 15, 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 15 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.

[0096] When the outer peripheral wall of the first annular protrusion 12 projected along the length direction of the first pile body 10 completely overlaps with the outer peripheral wall of the second annular protrusion 15 projected along the length direction of the first pile body 10 and both the first annular protrusion 12 and the second annular protrusion 15 are solid rings, or when the first annular protrusion 12 projected along the length direction of the first pile body 10 covers the second annular protrusion 15 projected along the length direction of the first pile body 10 and the outer peripheral wall of the second annular protrusion 15 projected along the length direction of the first pile body 10 is located outside the borehole projected along the length direction of the first pile body 10, the first annular protrusion 12 and the second annular protrusion 15 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 15, 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 15 overflows into the closed cavity on the upper side of the second annular protrusion 15. 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 boundary 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.

[0097] Furthermore, at least one first thickened protrusion 11 is provided between the first annular protrusion 12 and the second annular protrusion 15 to fully utilize the pressurizing and compacting effect of the first annular protrusion 12 on the cement soil below the first annular protrusion 12 in the borehole. The cement soil squeezed by the first annular protrusion 12 and the first thickened protrusion 11 between the first annular protrusion 12 and the second annular protrusion 15 increase the force acting on the cement soil. This increases the boundary friction resistance at the interface S1 between this portion of the precast pile 1 and the solidified soil surrounding the pile, thereby further improving the bearing capacity of the single precast pile 1 after implantation.

[0098] In addition, since the drilling hole in the implantation method is different from the conventional lead hole, the pile body may deviate during the implantation process after grouting is completed due to the actual construction environment. The first annular protrusion 12 and the second annular protrusion 15 are arranged in conjunction with each other. When the precast pile 1 is implanted in the drilled hole, the first annular protrusion 12 completely covers the inner peripheral wall of the drilled hole along the length direction of the first pile body 10, the outer peripheral wall of the first annular protrusion 12 at least partially overlaps the second annular protrusion 15 along the length direction of the first pile body 10, or the first annular protrusion 12 covers the second annular protrusion 15 along the length direction of the first pile body 10, and the outer peripheral wall of the second annular protrusion 15 along the length direction of the first pile body 10 is located outside the drilled hole along the length direction of the first pile body 10. This can improve the coaxiality of the precast pile 1 and the drilled hole, solving the technical problem of the precast pile 1 being deviated due to the construction environment when using the implantation method.

[0099] See also Figure 8 Optionally, in some examples, the first pile body 10 is arranged as a hollow round pile, and multiple 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 15 are both arranged in a circular ring shape. The outer diameters of the first annular protrusion 12 and the second annular protrusion 15 are equal, and the first thickened protrusion 11, the first annular protrusion 12, the second annular protrusion 15 and the first pile body 10 are coaxially arranged.

[0100] The first pile body 10, the first thickened protrusion 11, and the second annular protrusion 15 are prefabricated and centrifugally formed as a single unit using a steel mold. This production process eliminates the need for subsequent assembly and simplifies the production process. The second annular protrusion 15 includes a third conical surface 1527, a second cylindrical surface 1528, and a fourth conical surface 1529, which are sequentially connected from top to bottom. The upper end of the third conical surface 1527 and the lower end of the fourth conical surface 1529 are both connected to the first pile body 10. The second cylindrical surface 1528 extends vertically and surrounds the outer side of the first pile body 10. The diameter of the third conical surface 1527 gradually increases from top to bottom, while the diameter of the fourth conical surface 1528 gradually decreases from top to bottom, so as to facilitate demolding when the first pile body 10 and the second annular protrusion 15 are prefabricated as a single unit.

[0101] When using steel molds to produce precast piles 1, centrifugal one-piece molding can easily lead to demolding difficulties. This problem is particularly prominent for bamboo piles with protrusions on the outer peripheral wall. 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 section of a conventional bamboo pile, while the outer peripheral wall of the second annular protrusion 15 is projected along the length of the first pile body 10 and surrounds the outer side of the first thickened protrusion 11 along the length of the first pile body 10. That is, the outer diameter of the second annular protrusion 15 is larger than the outer diameter of the first thickened protrusion 11, which changes the stress distribution in the entire precast pile 1, which brings new challenges to demolding.

[0102] To address the aforementioned technical issue of demolding difficulties, the angle between the third tapered surface 1527 of the second annular protrusion 15 and the horizontal plane is set at 45°, and the angle between the fourth tapered surface 1529 of the second annular protrusion 15 and the vertical plane is set at a value greater than 45° and less than 90°. This arrangement results in the upper and lower end surfaces of the second annular protrusion 15 becoming asymmetrical. While a stress difference may occur locally, this stress difference, viewed from the entire pile body, can mitigate or offset the uneven stress distribution caused by the size and position of the second annular protrusion 15, thereby improving the yield rate. Furthermore, the reduced angle between the fourth tapered surface 1529 of the second annular protrusion 15 and the horizontal plane ensures that, during the implantation of the precast pile 1, the compression of the second annular protrusion 15 is directed primarily to the cement soil beneath the second annular protrusion 15 within the borehole, thereby enhancing the compression effect of the second annular protrusion 15 on the cement soil beneath the second annular protrusion 15 within the borehole.

[0103] Usually when preparing bamboo piles, the bamboo protrusions should be symmetrical up and down to adjust the stress distribution, such as Figure 8 As shown, the first thickened protrusion 11 is conventional with symmetrical upper and lower end surfaces. However, when the second annular protrusion 15 surrounds the outside of the first pile body 10 and is larger than the first thickened protrusion 11, uneven stress distribution occurs across the entire pile body 10. In this case, configuring the second annular protrusion 15 with asymmetrical upper and lower end surfaces can reduce or offset this uneven stress distribution and resolve the technical issue of demoulding difficulty.

[0104] See also Figure 9 and Figure 10In other examples, in order to solve the problem of difficulty in demoulding caused by the above-mentioned uneven stress distribution and expand the applicable scenarios of the precast pile 1, the first pile body 10 and the first thickened protrusion 11 are prefabricated as a whole, and the second annular protrusion 15 is welded and fixed or detachably fixed to the first pile body 10. Preferably, the second annular protrusion 15 includes two or more arc-shaped protrusions 152 that can be spliced ​​together to form a circular ring. The arc-shaped protrusion 152 is prefabricated from concrete, which is convenient for mass production, not easily corroded, low in cost, and long in service life. In this way, in the centrifugal prefabrication molding stage, it can be the same as the existing bamboo pile, and the existing production mold and production operation can remain unchanged. The stress distribution of the entire precast pile 1 is uniform, and the pile body is not prone to collapse during demoulding. The adverse effect of the second annular protrusion 15 on the stress distribution of the pile body during the centrifugal molding stage can be effectively reduced.

[0105] Since the second annular protrusion 15 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. On this basis, the shape and size of the second annular protrusion 15 can also have more choices. Figure 9 Preferably, the second annular protrusion 15 includes a first conical surface 1527', a first cylindrical surface 1528' and a second conical surface 1529' connected in sequence from top to bottom, the first cylindrical surface 1528' extends vertically and surrounds the outer side of the first pile body 10, the upper end of the first conical surface 1527' is connected to the first pile body 10, and the lower end of the first conical surface 1527' is connected to the first cylindrical surface 1528'; the upper end of the second conical surface 1529' is connected to the first pile body 10, and the lower end of the second conical surface 1529' is connected to the first cylindrical surface 1528', the diameter of the first conical surface 1527' gradually increases from top to bottom, and the diameter of the second conical surface 1529' gradually increases from top to bottom, and the second conical surface 1529' 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 1529' of the second annular protrusion 15 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 second annular protrusion 15 to the upper side of the second annular protrusion 15. At the same time, the force of the second conical surface 1529' of the second annular protrusion 15 can fully act on the cement soil in the drilled hole, further enhancing the squeezing effect of the second annular protrusion 15 on the cement soil in the drilled hole.

[0106] In addition, the lower surface of the arc-shaped protrusion 152 can also be set horizontally. With this setting, the force of the lower end surface of the second annular protrusion 15 can be kept vertically downward as much as possible when the precast pile 1 is implanted, so that it can fully act on the cement soil in the borehole, further improving the squeezing effect of the second annular protrusion 15 on the cement soil in the borehole.

[0107] See also Figure 10Furthermore, the inner circumferential wall of the arcuate protrusion 152 has a groove 1521 that matches the first thickened protrusion 11. The groove 1521 is located in the middle of the inner circumferential wall of the arcuate protrusion 152. When the arcuate protrusion 152 is fixed to the first pile body 10, the outer circumferential wall of the first thickened protrusion 11 and the inner side wall of the groove 1521 of the arcuate protrusion 152 fit together, axially limiting the arcuate protrusion 152 and improving the secure connection between the arcuate protrusion 152 and the first pile body 10. When the precast pile 1 is implanted in the drilled hole, the arcuate protrusion 152 is unlikely to move axially relative to the first pile body 10.

[0108] Optionally, the second annular protrusion 15 is welded and fixed to the first pile body 10. Specifically, a first embedded steel member 1522 is pre-embedded at at least one of the ends of the arc-shaped protrusion 152. The first embedded steel member 1522 can be a curved steel component or can be composed of a plurality of curved steel sheets evenly arranged along the circumference of the arc-shaped protrusion 152. In this example, the first embedded steel member 1522 is a plurality of curved steel sheets evenly arranged along the circumference of the arc-shaped protrusion 152, and the inner diameter of the curved steel sheet is equal to the inner diameter of the arc-shaped protrusion 152. Specifically, the curved steel sheet is embedded in a specific position of the steel mold in advance during production, and is prefabricated integrally with the arc-shaped protrusion 152.

[0109] A second embedded steel member 16 is pre-embedded in the first pile body 10. The second embedded steel member 16 can be an annular steel member or comprised of a plurality of arcuate steel sheets evenly spaced along the circumference of the first pile body 10. In this example, the second embedded steel member 16 corresponds to the first embedded steel member 1522 and is configured as a plurality of arcuate steel sheets evenly spaced along the circumference of the first pile body 10. The outer diameter of the arcuate steel sheets is equal to the outer diameter of the first pile body 10. Specifically, during production, the arcuate steel sheets are pre-embedded in specific locations in the steel mold and then centrifugally preformed. The first embedded steel member 1522 is welded to the second embedded steel member 16 to secure the arcuate protrusion 152 to the first pile body 10.

[0110] To ensure a secure connection, preferably, first embedded steel members 1522 are embedded at both ends of the arc-shaped protrusion 152. The upper end surface of the upper first embedded steel member 1522 is no lower than the upper end of the second annular protrusion 15, and the lower end surface of the lower first embedded steel member 1522 is no higher than the lower end of the second annular protrusion 15. Two second embedded steel members 16 are provided corresponding to the first embedded steel members 1522. The two second embedded steel members 16 are located on either side of a first thickened protrusion 10, and the two first embedded steel members 1522 are welded to the two second embedded steel members 16, respectively.

[0111] Furthermore, a plurality of first steel bars 1523, first connecting ribs 1524 and radial ribs 1525 are embedded in the arc-shaped protrusion 152. The first steel bar 1523 extends along the axial direction of the arc-shaped protrusion 152, and the plurality of first steel bars 1523 are evenly arranged along the circumference of the arc-shaped protrusion 152; two first connecting ribs 1524 are connected to one first steel bar 1523 respectively, and one end of the two first connecting ribs 1524 are respectively connected to the two ends of the first steel bar 1523, the first connecting rib 1524 at the upper end is parallel to the upper end surface of the arc-shaped protrusion 152, and the other end of the first connecting rib 1524 at the upper end is welded and fixed to the upper first embedded steel part 1522; the first connecting rib 1524 at the lower end is parallel to the lower end surface of the arc-shaped protrusion 152, and the other end of the first connecting rib 1524 at the lower end is welded and fixed to the lower first embedded steel part 1522. The first steel bar 1523 and the first connecting rib 1524 are completely embedded in the arc-shaped protrusion 152, providing a stronger bond with the arc-shaped protrusion 152. The connection between the first embedded steel member 1522 and the first connecting rib 1524 further strengthens the connection between the first embedded steel member 1522 and the arc-shaped protrusion 152. Several radial ribs 1525 are welded to the first steel bar 1523. These ribs extend radially along the arc-shaped protrusion 152 and are evenly distributed along the length of the first steel bar 1523. The first steel bar 1523 and the radial ribs 1525 cooperate to form the framework of the arc-shaped protrusion 152, strengthening its structure and improving its load-bearing capacity. This prevents the arc-shaped protrusion 152 from cracking or damage when the precast pile 1 is implanted in the drilled hole.

[0112] Furthermore, a plurality of second steel bars 17 and second connecting bars 171 are pre-embedded in the first pile body 10. The second steel bars 17 extend vertically and are evenly distributed along the circumference of the first pile body 10. The second steel bars 17 are fixed to the prestressed main bars 18 of the first pile body 10 by means of hoops 181. Two second connecting bars 171 are connected to one second steel bar 17, one end of each second connecting bar 171 is connected to the two ends of the second steel bar 17, the other end of the upper second connecting bar 171 is welded to the upper second embedded steel member 16, and the other end of the lower second connecting bar 171 is welded to the lower second embedded steel member 16. The second steel bar 17 and the second connecting bar 171 are completely embedded in the first pile body 10, and the bonding force with the first pile body 10 is stronger. The second embedded steel part 16 is connected to the second connecting bar 171, so that the second embedded steel part 16 is more firmly connected to the first pile body 10, and it is convenient to fix the second embedded steel part 16 on the prestressed main bar 18 of the steel cage for fixation and positioning before embedding.

[0113] Compared with the integral prefabrication of the second annular protrusion 15 and the first pile body 10, the application scenarios can be well expanded by welding. Due to different construction environments, the physical properties of the foundation are also different. By adjusting the size of the second annular protrusion 15, the extrusion effect can be improved. For example, second annular protrusions 15 of different sizes (two or more arc-shaped protrusions 152 spliced ​​together) are welded and fixed to the second embedded steel part 16 of the first pile body 10. Usually, when the foundation contains a soil layer of sand, gravel, pebbles and larger stones, drilling is more difficult and the hole wall is easily disturbed by external forces. At this time, it is suitable to use a smaller-sized second annular protrusion 15 to extrude the cement soil; when the foundation contains a soil layer with more clay and silt, there are fewer gaps in the soil layer and it is more difficult for the cement soil to penetrate. At this time, it is suitable to use a larger-sized second annular protrusion 15 to extrude the cement soil.

[0114] See also Figure 11 Optionally, the second annular protrusion 15 is detachably fixed to the first pile body 10. Specifically, a radially extending bolt hole 111 is formed on the first thickened protrusion 11, and a through hole 1526 corresponding to the bolt hole 111 is formed on the arc-shaped protrusion 152. After the arc-shaped protrusion 152 abuts against the outer side of the first thickened protrusion 11, the expandable end of the expansion bolt 112 is inserted into the bolt hole 111 through the through hole 1526, and the nut of the expansion bolt 112 is rotated to fix the two arc-shaped protrusions 152 to the first thickened protrusion 11.

[0115] In this example, since the relatively large second annular protrusion 15 is not prefabricated during production, the first pile body 10 and the first thickened protrusion 11 can be demolded relatively easily. On this basis, there are also more options for the shape of the second annular protrusion 15. Furthermore, since the second embedded steel part 16 and the first embedded steel part 1522 are not prefabricated during production, the first pile body 10 and the first thickened protrusion 11 can be prefabricated as a single piece relatively easily, and the second annular protrusion 15 can also be prefabricated separately relatively easily. Furthermore, the second annular protrusion 15 is connected to the first thickened protrusion 11 via expansion bolts 112, making assembly even simpler.

[0116] When the outer diameters of the first annular protrusion 12 and the second annular protrusion 15 are larger than the borehole diameter, additional downward pressure is required to implant the prefabricated pile 1 into the borehole. As previously mentioned, a closed cavity is formed between the outer circumferential wall of the second annular protrusion 15, the first pile body 10, and the borehole wall. In this case, applying downward pressure to implant the pile may cause difficulty. For this reason, see Figure 8In some examples, at least one pressure relief channel 151 is provided on the second annular protrusion 15, and the pressure relief channel 151 passes through the second annular protrusion 15 along the length direction of the first pile body 10. Furthermore, the second annular protrusion 15 is provided with two or more pressure relief channels 151 evenly distributed along the circumference. The pressure relief channels 151 can all be through holes or notches, or a combination of through holes and notches. The specific combination can be set according to the degree of impact of the pile foundation construction environment on the surrounding environment. When the pressure relief channel 151 is a notch, the radial dimension of the pressure relief channel 151 is not less than 50 mm, and the arc length of a single pressure relief channel 151 is not greater than 1 / 15 of the drilled hole circumference and not less than 1 / 20 of the drilled hole circumference. When the pressure relief channel 151 is a notch, the outer peripheral wall of the first annular protrusion 12 is partially overlapped with the outer peripheral wall of the second annular protrusion 15 along the length direction of the first pile body 10; when the pressure relief channel 151 is a through hole, the outer peripheral wall of the first annular protrusion 12 is completely overlapped with the outer peripheral wall of the second annular protrusion 15 along the length direction of the first pile body 10.

[0117] As the first pile body 10 is lowered, a portion of the cement soil can be transferred to the upper end of the second annular protrusion 15 through the pressure relief channel 151, thereby reducing the pressure load on the lower end surface of the second annular protrusion 15 to a certain extent. This facilitates pressure control and achieves a balance between reducing the holding pressure applied during the installation of the precast pile 1 and improving the squeezing effect. Whether the second annular protrusion 15 is provided with a pressure relief channel 151, as well as the number and size of the pressure relief channels 151, can be determined based on the degree of impact of the pile foundation construction environment on the surrounding environment. Furthermore, in this example, the second annular protrusion 15 with the pressure relief channel 151 is preferably formed by prefabricating the first pile body 10 and the first thickened protrusion 11 integrally, then welding or bolting the second annular protrusion 15 together. Simultaneously, the lower end surface of the second annular protrusion 15 is positioned horizontally or concavely. During the installation of the precast pile, the force acting on the lower end surface of the second annular protrusion 15 can be maintained vertically downward as much as possible, thereby fully acting on the cement soil in the borehole and further enhancing the squeezing effect of the second annular protrusion 15 on the cement soil in the borehole. This method selects different sizes and shapes of second annular protrusions 15 with pressure relief channels 151 and installs them on the first pile body 10 of the prefabricated pile 1 according to the actual situation of the soil layer, the soil squeezing conditions during construction and the squeezing effect of cement soil. This can effectively balance the pile planting effect and the squeezing effect on cement soil, while taking into account the operational complexity of construction and production preparation.

[0118] 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 15 continuously squeeze 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 and the lower end face of the second annular protrusion 15, thereby causing the cement soil to diffuse into the soil around the borehole, and the cement soil ions enter the soil voids, 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 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 15, which can increase the interaction 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.

[0119] To enhance the compression effect on cement soil, improve the yield rate during production, and reduce the complexity of manufacturing operations, the above embodiment also specifically designs the shapes of the upper and lower end surfaces of the second annular protrusion 15. The stress difference formed between the upper and lower end surfaces reduces or offsets the uneven stress distribution caused by the size of the second annular protrusion 15. Furthermore, the first pile body 10 and the first thickened protrusion 11 are prefabricated as a single piece, and the second annular protrusion 15 is fixed to the mold by welding or bolts to avoid the difficulty of demolding caused by the uneven stress distribution.

[0120] Taking into account the complexity of construction operations, the complexity of preparation operations 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 fix the second annular protrusion 15 by welding or bolting to form a second annular protrusion 15 with a pressure relief channel 151, thereby controlling the complexity of construction and preparation operations to a minimum and balancing the pile planting efficiency and the squeezing effect on cement soil.

[0121] Example 2

[0122] See also Figures 12 to 14 As shown, an embodiment of the present application discloses a combined pile.

[0123] See also Figure 12The composite pile of this embodiment includes a precast pile 1 and at least one end-connected precast pile 2. 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 tubular pile precast integrally from concrete. The first pile body 10 extends vertically. The plurality of first thickened protrusions 11 are fixed to the outer peripheral wall of the first pile body 10. The plurality of first thickened protrusions 11 are spaced apart along the length of the first pile body 10. The inner peripheral wall of the drilled hole, projected along the length of the first pile body 10, surrounds the outer side of the combination of the first pile body 10 and the first thickened protrusions 11, projected along the length of the first pile body 10. The first annular protrusion 12 is fixed around the first pile body 10. The first annular protrusion 12 is located above the at least one first thickened protrusion 11. The first annular protrusion 12, projected along the length of the first pile body 10, completely covers the inner peripheral wall of the drilled hole, projected along the length of the first pile body 10. The first annular protrusion 12 can be directly formed by the portion of the first end 10' extending out of the first pile body 10, or can be bolted or welded to the end plate of the first end 10' of the first pile body 10 in the form of an end plate. For details, please refer to the relevant description in Example 1 and will not be repeated here.

[0124] In this embodiment, at least one end-connected precast pile 2 is connected to the first end 10 ′ and / or the second end 10 ″ of the precast pile 1 , and the connection can be adjusted according to the construction requirements and the construction environment.

[0125] Preferably, at least one terminal precast pile 2 is connected to the first end 10' of the precast pile 1, and the first annular protrusion 12 is an annular flange made of metal material, and the two ends of the annular flange are respectively welded and fixed to the first end 10' of the precast pile 1 and the lower end of the terminal precast pile 2.

[0126] See also Figure 13 (a) Optionally, the inner ring size of the annular flange is smaller than the outer ring size of the precast pile 1. During construction, the lower end of the annular flange is first abutted against the upper side of the first end 10' of the precast pile 1, and the annular flange is welded and fixed to the first end 10' of the precast pile 1. The terminal precast pile 2 is then abutted against the upper end of the annular flange, and finally the annular flange is welded and fixed to the lower end of the terminal precast pile 2.

[0127] See also Figure 13(b) Optionally, the inner edge of the annular flange may be aligned with the outer edge of the end plate at the first end 10' of the precast pile 1, that is, the annular flange may be sleeved onto the first end 10' of the precast pile 1 and the end plate of the terminating precast pile 2, and the inner edge of the annular flange may be in contact with the outer edge of the end plate at the first end 10' of the precast pile 1 and the outer edge of the end plate of the terminating precast pile 2. During construction, the annular flange is first sleeved onto the end plate at the first end 10', and then the terminating precast pile 2 is brought into contact with the first end 10' of the precast pile 1. The annular flange is then simultaneously sleeved onto the end plate at the first end 10' and the end plate at the upper end of the terminating precast pile 2. Finally, the annular flange is welded and fixed to the end plate at the first end 10' of the precast pile 1.

[0128] At least one end prefabricated pile 2 is connected to the upper end of the prefabricated pile 1, so that the first annular protrusion 12 increases the squeezing stroke of the cement soil on the lower side of the first annular protrusion 12 in the borehole, forcing the cement soil to diffuse better to the soil around the borehole, further increasing the cement soil ions entering the soil voids 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 boundary 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.

[0129] Preferably, the length of the composite pile is defined as L, with the upper end of the composite pile as the starting point, and the first annular protrusion 12 located within the interval [0, 2 / L] of the composite pile. This increases the extrusion stroke of the first annular protrusion 12 on the cement soil below the first annular protrusion 12 in the borehole, increases the cement soil ions entering the soil voids around the hole wall, and thereby improves the bonding strength between the solidified soil around the pile and the undisturbed soil around the hole wall, and increases the limit friction resistance of the interface S2 between the solidified soil around the pile and the undisturbed soil around the hole wall, thereby improving the bearing capacity of the composite pile after implantation. At the same time, the cement soil around all first thickened protrusions 11 and most of the second thickened protrusions 21 is squeezed by the first annular protrusion 12, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, further improving the bearing capacity of the composite pile after implantation.

[0130] In some examples, the terminated precast pile 2 includes a second pile body 20, which extends vertically and is integrally precast from concrete. The outer peripheral wall of the second pile body 20, projected along the length of the first pile body 10, completely overlaps with the outer peripheral wall of the first pile body 10, projected along the length of the first pile body 10. Optionally, both the first pile body 10 and the second pile body 20 can be configured as hollow circular piles, as tubular piles with a regular polygonal cross-sectional profile, or as solid piles, the specific selection of which can be made based on construction needs.

[0131] When the precast 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, thereby increasing the pressure in the borehole below the lower end surface of the first annular protrusion 12, thereby causing the cement soil to diffuse into the soil surrounding the borehole, and some cement soil ions to enter the soil voids, 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 interaction 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 S1 at the interface between this part of the composite pile body and the solidified soil around the pile increases, further improving the bearing capacity of the single pile after the composite pile is implanted.

[0132] In some examples, the terminal 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 precast integrally with concrete. The second thickened protrusions 21 are precast integrally with the second pile body 20. The plurality of second thickened protrusions 21 are evenly distributed along the length of the second pile body 20. The outer peripheral walls of the second thickened protrusions 21 projected along the length of the first pile body 10 coincide with the outer peripheral walls of the first thickened protrusions 11 projected along the length of the first pile body 10. Optionally, both the first pile body 10 and the second pile body 20 can be configured as hollow round piles, hollow square piles, solid square piles, or solid round piles, depending on construction requirements.

[0133] Due to the action of the second thickened protrusion 21, the contact surface 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.

[0134] In other examples, the plurality of terminated precast piles 2 may also be a combination of pipe piles and special-shaped piles with alternating thickness along the length direction, that is, the terminated precast pile 2 at the lowest end is a special-shaped pile with alternating thickness along the length direction, such as a bamboo pile, and a plurality of cylindrical pipe piles or a combination of bamboo piles and cylindrical pipe piles are connected between the bamboo pile at the lowest end and the precast pile 1. The specific configuration can be selected according to the actual construction environment and construction requirements.

[0135] See also Figure 14In some examples, the terminal precast pile 2 is a tubular structure with an inner cavity, such as a hollow round pile or a hollow square pile. A sealing structure is fixed to at least one terminal precast pile 2 to at least partially block the inner cavity of the terminal precast pile 2, thereby adjusting the pressure in the borehole below the first annular protrusion 12 and controlling the squeezing effect on the cement soil in the borehole. The sealing structure is an end sealing plate 3 disposed at the end of the bottom precast pile. The end sealing plate 3 is welded and fixed to the end of one of the terminal precast piles 2. The end sealing plate 3 is provided with a pressure regulating hole extending vertically therethrough. The pressure regulating hole is connected to the inner cavity of the second pile body 20. The diameter of the pressure regulating hole is smaller than the inner diameter of the second pile body 20. The pressure regulating hole is used to prevent cement slurry from passing through the pressure regulating hole while allowing air to pass through the pressure regulating hole, thereby adjusting the pressure in the borehole below the first annular protrusion 12 and controlling the squeezing effect of the first annular protrusion 12 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 better the squeezing effect of the first annular protrusion 12 on the cement soil on the lower side of the first annular protrusion 12 in the borehole. The height of the end sealing plate 3 can be adjusted according to the impact of the pile foundation construction on the surrounding environment.

[0136] In addition, the sealing structure can be replaced by setting one of the terminal precast piles 2 as a solid pile to adjust the amount of cement slurry entering the terminal precast pile 2, adjust the pressure in the borehole below the first annular protrusion 12, and control the squeezing effect on the cement soil in the borehole.

[0137] In summary, the working principle of the combined piles in the above embodiment is as follows: 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 terminated precast piles 2 and the precast piles 1 are sequentially placed into the borehole in sections by relying on their own weight and pile pressing force, and the precast pile 1 is connected to the upper end of the uppermost terminated precast pile 2, or connected to the middle of at least two terminated precast piles 2, or connected to the lower end of at least one terminated precast pile 2; when the precast pile 1 is implanted into the borehole, as the precast pile 1 is continuously implanted into the borehole, the lower end surface of the first annular protrusion 12 continuously squeezes the lower side The cement soil in the borehole is squeezed by the first annular protrusion 12, so that the cement soil diffuses into the soil around the borehole, and some cement soil ions enter the soil voids, 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 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 thus improving the bearing capacity of the single pile after the composite pile is implanted.

[0138] The composite pile described above can also be used in crimping or hammering construction to solve the problem that during crimping or hammering of bamboo piles, the bamboo sections of the bamboo pile squeeze out the soil, causing the soil to be vacant from the pile body, and the soil has to be backfilled into the space between adjacent bamboo sections over a long period of time. Because the outer peripheral wall of the first annular protrusion 12, projected along the length direction of the first pile body 10, surrounds the outer side of the first thickened protrusion 11 projected along the length direction of the first pile body, during the crimping or hammering process of the precast pile 1 into the soil, the first annular protrusion 12 squeezes the soil downward, forcing the soil to backfill into the space between adjacent first thickened protrusions 11, accelerating the soil backfilling and shortening the soil backfilling period, so that the composite pile can reach the designed bearing capacity more quickly. After the soil is backfilled into the space between the adjacent first thickened protrusions 11, the precast pile 1 is continuously implanted downward, and the first annular protrusion 12 continues to squeeze the soil downward, so that the soil and the first pile body 10 of the precast pile 1 and the second pile body 20 of the terminal precast pile 2 can be more tightly combined, thereby further improving the single pile bearing capacity of the composite pile.

[0139] 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 accompanying 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.

[0140] 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" 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 can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0141] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection 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), which 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 A first annular protrusion (12) is fixed around 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''); The outer peripheral wall of the first annular protrusion (12) is projected along the length direction of the first pile body (10) around the outer side of the first thickened protrusion (11) projected along the length direction of the first pile body (10).

2. The precast pile according to claim 1, characterized in that: The first pile body (10) and the first thickened protrusion (11) are prefabricated as a whole; The first annular protrusion (12) is an annular flange made of metal, and the inner ring edge of the annular flange is welded and fixed to the outer edge of the first end (10') of the prefabricated pile (1).

3. The precast pile according to claim 2, characterized in that: At least a portion of the surface of the annular flange facing the second end (10") forms an undercut conical surface.

4. The precast pile according to claim 1, characterized in that: The first pile body (10) and the first thickened protrusion (11) are prefabricated as a whole; The first annular protrusion (12) is an annular flange made of metal. A plurality of spaced-apart through-holes (121) are provided on the annular flange. The through-holes (121) penetrate both end surfaces of the annular flange along the length direction of the first pile body (10). A threaded hole (13) corresponding to the through-hole (121) is provided on the end plate of the first end (10') of the first pile body (10). Bolts (14) passing through the through-hole (121) are installed in the threaded hole (13) to fix the annular flange to the first pile body (10).

5. The prefabricated pile according to claim 4, characterized in that: The threaded hole (13) is an anchoring hole of the end plate of the first end (10') of the first pile body (10), and the anchoring hole is used for a heading to pass through from the first end (10') to the second end (10'').

6. The precast pile according to claim 1, characterized in that: The first pile body (10) and the first thickened protrusion (11) are prefabricated as a whole; 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) around the outer side of the first thickened protrusion (11) projected along the length direction of the first pile body (10), and the first annular protrusion (12) is an annular flange formed by the portion of the end plate of the first end (10') extending out of the first pile body (10).

7. The prefabricated pile according to any one of claims 1 to 6, characterized in that: The precast pile (1) further comprises at least one second annular protrusion (15) fixed around the outer peripheral wall of the first pile body (10), the second annular protrusion (15) being located between the first annular protrusion (12) and the second end (10''), the first annular protrusion (12) projected along the length direction of the first pile body (10) covering the second annular protrusion (15) projected along the length direction of the first pile body (10), and the outer peripheral wall of the second annular protrusion (15) projected along the length direction of the first pile body (10) being located outside the borehole into which the precast pile (1) is implanted, projected along the length direction of the first pile body (10), or the outer peripheral wall of the first annular protrusion (12) projected along the length direction of the first pile body (10) at least partially overlaps the outer peripheral wall of the second annular protrusion (15) projected along the length direction of the first pile body (10).

8. The prefabricated pile according to claim 7, characterized in that: At least one pressure relief channel (151) is provided on the second annular protrusion (15), and the pressure relief channel (151) passes through the second annular protrusion (15) along the length direction of the first pile body (10); And / or, at least one first thickened protrusion (11) is provided between the first annular protrusion (12) and the second annular protrusion (15).

9. The prefabricated pile according to claim 8, characterized in that The second annular protrusion (15) is provided with two or more pressure relief channels (151) spaced apart along the circumferential direction, and / or at least one of the pressure relief channels (151) is a through hole or a notch.

10. The prefabricated pile according to claim 7, characterized in that: The first pile body (10) is arranged in the form of a hollow circular pile, and a plurality of the first thickened protrusions (11) are arranged in the form of bamboo joints along the length direction of the first pile body (10); The second annular protrusion (15) and the first annular protrusion (12) are both arranged in a circular ring shape, the first thickened protrusion (11), the second annular protrusion (15), the first annular protrusion (12) and the first pile body (10) are arranged coaxially, and the second annular protrusion (15) and the first pile body (10) are prefabricated as a whole.

11. The prefabricated pile according to claim 7, characterized in that: The first pile body (10) is arranged in the form of a hollow circular pile, and a plurality of the first thickened protrusions (11) are arranged in the form of bamboo joints along the length direction of the first pile body (10); The second annular protrusion (15) and the first annular protrusion (12) are both arranged in an annular shape; the first thickened protrusion (11), the second annular protrusion (15), the first annular protrusion (12) and the first pile body (10) are arranged coaxially; the second annular protrusion (15) includes two or more arc-shaped protrusions (152) that can be spliced ​​together to form an annular shape; the arc-shaped protrusions (152) are welded or detachably fixed to the first pile body (10).

12. The prefabricated pile according to claim 11, characterized in that A groove (1521) is provided on the inner peripheral wall of the arc-shaped protrusion (152). When the arc-shaped protrusion (152) 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 (1521) fit together to limit the axial position of the arc-shaped protrusion (152).

13. The prefabricated pile according to claim 11 or 12, characterized in that: The arc-shaped protrusion (152) is prefabricated from concrete. A first embedded steel part (1522) extending in a circumferential direction is embedded in at least one of the two ends of the inner peripheral wall of the arc-shaped protrusion (152) along the length direction of the first pile body (10). A second embedded steel part (16) extending in a circumferential direction and corresponding to the first embedded steel part (1522) is embedded in the first pile body (10). The first embedded steel part (1522) is correspondingly welded to the second embedded steel part (16).

14. The prefabricated pile according to claim 13, characterized in that A plurality of first steel bars (1523), first connecting bars (1524) and radial bars (1525) are pre-embedded in the arc-shaped protrusion (152); the plurality of first steel bars (1523) are evenly arranged along the circumference of the arc-shaped protrusion (152); the first steel bars (1523) extend along the axial direction of the arc-shaped protrusion (152); one end of two first connecting bars (1524) are respectively connected to the two ends of one first steel bar (1523); the other ends of the two first connecting bars (1524) are respectively welded and fixed to the two first embedded steel parts (1522); the plurality of radial bars (1525) are all connected to the first steel bar (1523) and evenly distributed along the length direction of the first steel bar (1523); the radial bars (1525) extend radially along the arc-shaped protrusion (152); The first pile body (10) is pre-embedded with a plurality of second steel bars (17) and second connecting bars (171). The plurality of second steel bars (17) are evenly distributed along the circumference of the first pile body (10) and fixed to the prestressed main bars of the first pile body (10). The second steel bars (17) are arranged corresponding to the first thickened protrusion (11). One end of two second connecting bars (171) are respectively connected to the two ends of one second steel bar (17), and the other ends of the two second connecting bars (171) are respectively welded and fixed to the two second embedded steel parts (16) on both axial sides of the first thickened protrusion (11).

15. The prefabricated pile according to claim 11 or 12, characterized in that: The arc-shaped protrusion (152) is prefabricated from concrete, and a through hole (1526) extending in the radial direction is provided on the arc-shaped protrusion (152), and the through hole (1526) passes through the inner and outer side walls of the arc-shaped protrusion (152). A bolt hole (111) is provided on the outer peripheral wall of the first thickened protrusion (11), and an expansion bolt (112) passing through the through hole (1526) is assembled in the bolt hole (111) to fix the arc-shaped protrusion (152) to the first thickened protrusion (11).

16. The precast pile according to claim 11, characterized in that The second annular protrusion (15) includes a first conical surface (1527'), a first cylindrical surface (1528') and a second conical surface (1529') which are connected in sequence from the first end (10') to the second end (10'') of the first pile body (10), wherein the first cylindrical surface (1528') 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 (1527') facing the first end (10') is connected to the first pile body (10), and the end of the second conical surface (1529') facing the first end (10') is connected to the first pile body (10), and the second conical surface (1529') cooperates with the first pile body (10) to form an annular concave cavity with an opening facing the second end (10'').

17. The prefabricated pile according to claim 10 or 11, characterized in that: The second annular protrusion (15) includes a third conical surface (1527), a second cylindrical surface (1528) and a fourth conical surface (1529) which are connected in sequence from the first end (10') to the second end (10'') of the first pile body (10); the second cylindrical surface (1528) 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 third conical surface (1527) facing the first end (10') and the end of the fourth conical surface (1529) facing the second end (10'') are both connected to the first pile body (10); the diameter of the third conical surface (1527) gradually increases from the first end (10') to the second end (10'') of the first pile body (10); and the diameter of the fourth conical surface (1529) gradually decreases from the first end (10') to the second end (10'') of the first pile body (10).

18. The prefabricated pile according to claim 17, characterized in that The included angle between the fourth conical surface (1529) and the length direction of the first pile body (10) is greater than 45° and less than 90°.

19. The prefabricated pile according to any one of claims 1 to 3 or 6, 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 projection of the first thickened protrusion (11) along the length direction of the first pile body (10) to the outer edge of the projection of the first annular protrusion (12) 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.

20. The prefabricated pile according to any one of claims 1 to 3 or 6, characterized in that: The first pile body (10) is arranged in the shape of a hollow circular pile, the first thickened protrusion (11) and the first annular protrusion (12) are both arranged in an annular shape, 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).

21. A composite pile, characterized in that: include: The prefabricated pile (1) according to claim 1; as well as At least one end-connected prefabricated pile (2) connected to the first end (10') and / or the second end (10'') of the prefabricated pile (1); The prefabricated pile (1) 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 first pile body (10) along the length direction of the first pile body (10).

22. The composite pile according to claim 21, characterized in that: The at least one end prefabricated pile (2) is connected to the first end (10') of the prefabricated pile (1), the first annular protrusion (12) is an annular flange made of metal, and the two ends of the annular flange are respectively welded and fixed to the first end (10') of the prefabricated pile (1) and one end of the end prefabricated pile (2).

23. The composite pile according to claim 22, characterized in that: The inner ring edge of the annular flange is aligned with the outer edge of the first end (10') of the precast pile (1) and the outer edge of one end of the terminal precast pile (2), or the inner ring edge of the annular flange is embedded between the first end (10') of the precast pile (1) and one end of the terminal precast pile (2).

24. The composite pile according to claim 21, characterized in that The length of the combined pile is defined as L, and the upper end of the combined pile is taken as the starting point, and the first annular protrusion (12) is located within the interval [0, 2 / L] of the combined pile.

25. The composite pile according to claim 21, characterized in that The prefabricated pile (1) further comprises a plurality of second thickened protrusions (21) fixed around the outer peripheral wall of the second pile body (20), the second thickened protrusions (21) and the second pile body (20) being prefabricated integrally, the plurality of second thickened protrusions (21) being arranged at intervals along the length direction of the second pile body (20), and the outer peripheral wall of the first thickened protrusion (11) projected along the length direction of the first pile body (10) completely overlapping with the outer peripheral wall of the second thickened protrusion (21) projected along the length direction of the first pile body (10).

26. The composite pile according to any one of claims 21 to 25, characterized in that: The second pile body (20) and the first pile body (10) are both arranged in the form of hollow circular piles, a plurality of the first thickened protrusions (11) are arranged in a bamboo-like shape along the length direction of the second pile body (20), the first annular protrusion (12) is arranged in a circular ring shape, and the first thickened protrusion (11), the first annular protrusion (12), the second pile body (20) and the first pile body (10) are arranged coaxially.

27. The composite pile according to any one of claims 21 to 25, characterized in that: The termination prefabricated pile (2) is a tubular structure having an inner cavity, and a blocking structure for at least partially blocking the inner cavity is fixed on at least one of the termination prefabricated piles (2); or at least one of the termination prefabricated piles (2) is a solid structure.

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

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