Precast pile, combined pile and construction method

Abstract

The invention provides a precast pile, a combined pile and a construction method, and relates to the technical field of pile foundation construction.The precast pile comprises a first pile body, a second pile body and a third pile body, and the two ends, in the length direction, of the first pile body are the first end and the second end correspondingly; 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 flange ring is arranged on the outer side of the first pile body in a sleeving manner and is slidably connected with the first pile body in the length direction of the first pile body; the projection of the peripheral wall of the flange ring 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 present invention relates to the technical field of pile foundation construction, and in particular to a prefabricated pile, a combined pile and a construction method. Background Art

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

[0003] Under the existing construction process of implanted piles, there are two failure interfaces in the pile body under the vertical load, namely the interface S1 between the core pile 7 and the solidified soil 5 around the pile, and the interface S2 between the solidified soil 6 around the pile and the original soil 4 around the hole wall. Figure 1 As shown. According to the bearing capacity calculation formula, Q uk =u∑ξ si q sik l i +q pk A p Only by simultaneously increasing the limit friction resistance of the above two failure interfaces S1 and S2 can the single pile bearing capacity of the implanted pile be effectively improved.

[0004] In order to improve the single pile bearing capacity of the implanted pile, bamboo piles were developed on the basis of conventional pipe piles. They are a special-shaped pipe pile, see patent CN2611433Y. The bamboo pile has "bamboo nodes" protruding from the pile body at intervals, so it is also called bamboo pile. Unlike pipe piles, bamboo piles are difficult to cast on site. Although some literature points out that cast-in-place piles can also be made into a shape similar to bamboo piles, the bamboo piles formed by casting are significantly different from prefabricated bamboo piles in size, surface burrs and bearing performance due to the uncertainty of drilling technology and foundation construction conditions. The two cannot be confused. The technology of forming special-shaped piles similar to bamboo piles by casting has no reference and reference significance in the production and construction of prefabricated bamboo piles, and in addition to production tests in the industry, there have been no actual construction projects of cast-in-place bamboo piles. Prefabricated bamboo piles are very suitable for implantation construction. When traditional static pressure and hammering methods are applied to bamboo piles, the soil squeezing effect is very prominent. When the implantation method is used, the diameter of the drill hole is larger than the bamboo part, so the bamboo pile can be sent into the foundation in a "non-soil squeezing" manner. After the bamboo pile is completed and combined with the pile surrounding solidified soil 5, the pile surrounding solidified soil 5 not only contacts the pile body, but also contacts the surface of the bamboo, effectively increasing the peak shear stress of the interface S1. Compared with ordinary prefabricated piles of the same diameter, the interface S1 between the pile surrounding solidified soil 5 and the core pile 6 is less likely to be damaged.

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

[0006] In addition, in soft soil areas, in order to improve the single pile bearing capacity of cylindrical prefabricated piles that are pressed or hammered, bamboo piles that are pressed or hammered are developed. The ultimate bearing capacity of bamboo piles can reach about 1.23 times that of cylindrical pipe piles with the same outer diameter by pressing or hammering. However, when bamboo piles are pressed or hammered, the bamboo sections of the bamboo piles squeeze the soil, causing the soil and the pile body to be vacant. The soil backfills between adjacent bamboo sections over a long period of time, which takes more than 28 days, much longer than the soil backfill period (7 days) of cylindrical prefabricated piles. The long construction period leads to increased construction costs. Therefore, it is necessary to solve the problem of the long soil backfill period of bamboo piles in pressing or hammering construction. Summary of the invention

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

[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 arranged at intervals along the length direction of the first pile body; and

[0011] A flange ring, sleeved on the outer side of the first pile body and slidably connected to the first pile body along the length direction of the first pile body;

[0012] The outer peripheral wall of the flange ring 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 prefabricated pile of the present application has the following advantages: when the prefabricated pile is implanted in a borehole, the flange ring squeezes the cement soil on the lower side of the flange ring in the borehole to force part of the cement soil into the soil gap around 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 of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the prefabricated pile is implanted. In addition, the cement soil around the first thickened protrusion is squeezed by the flange ring, and the density increases, and the interaction force between the first thickened protrusion and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the prefabricated pile and the solidified soil around the pile, and further improving the bearing capacity of the single pile after the prefabricated pile is implanted. Because the outer wall of the flange ring 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, when the precast pile is pressed or hammered, the flange ring 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 enabling the combined pile using the precast pile to reach the designed bearing capacity more quickly.

[0014] In a preferred embodiment, the projection of the first thickened protrusion along the length direction of the first pile body is at least partially located outside the projection of the inner peripheral wall of the flange ring along the length direction of the first pile body;

[0015] When the prefabricated pile is placed in the drilled hole and / or after being placed in the drilled hole, the inner circumferential wall of the drilled hole is projected along the length direction of the first pile body around the outer side of the first pile body and the first thickened protrusion combination projected along the length direction of the first pile body, and the flange ring is projected along the length direction of the first pile body to completely cover the inner circumferential wall of the drilled hole along the length direction of the first pile body, and the flange ring can move downward along the length direction of the first pile body to squeeze the soil around the drilled hole and / or solidify the slurry.

[0016] In a preferred embodiment, the flange ring is located on the upper side or the lower side of the plurality of first thickened protrusions, and the flange ring is an integrally formed annular metal plate.

[0017] In a preferred embodiment, the flange ring is located on the upper side of the plurality of first thickened protrusions, and the distance between the first end and the first thickened protrusion close to the first end is 3 meters to 6 meters.

[0018] In a preferred embodiment, the flange ring is located on the lower side of the first thickened protrusion, and the flange ring includes two or more arc-shaped metal plates that can be spliced ​​together to form a ring. The two or more arc-shaped metal plates can be openably mounted on the first pile body, and the ends of two adjacent arc-shaped metal plates can be locked with each other.

[0019] In a preferred embodiment, the adjacent ends of the two or more arc-shaped metal plates are both detachably fixedly connected by bolts, or one of the adjacent ends of the two or more arc-shaped metal plates is detachably fixedly connected by bolts, and the others are hinged.

[0020] In a preferred embodiment, the inner circumferential wall of the flange ring and the outer circumferential wall of the first pile body are in contact with each other.

[0021] In a preferred embodiment, at least one end of the flange ring is provided with a guide structure, and the inner side wall of the guide structure is slidably abutted against the outer peripheral wall of the first pile body.

[0022] In a preferred embodiment, the guide structure is arranged in an annular shape, the inner circumferential wall of the guide structure is in contact with the outer circumferential wall of the first pile body, and the end of the guide structure facing away from the flange ring is provided with a guide slope adapted to the end of the first thickened protrusion.

[0023] In a preferred embodiment, the first thickened protrusion and the flange ring 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 flange ring 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.

[0024] In a preferred embodiment, the first pile body is arranged in a hollow round pile, and the plurality of the first thickened protrusions are arranged in a bamboo-joint shape along the length direction of the first pile body. The flange ring is arranged in a circular ring shape. The first thickened protrusion, the flange ring and the first pile body are coaxially arranged. The outer diameter of the first pile body is 350 mm to 750 mm, the outer diameter of the flange ring is 90 mm to 200 mm larger than the outer diameter of the first pile body, the outer diameter of the first thickened protrusion is 50 mm to 150 mm larger than the outer diameter of the first pile body, and the outer diameter of the flange ring is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion.

[0025] In a second aspect, the present application provides a combined pile, comprising:

[0026] A top precast pile consisting of a precast pile as described above; and

[0027] at least one bottom precast pile connected to the lower end of the top precast pile;

[0028] The bottom prefabricated pile includes a second pile body extending vertically, and 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.

[0029] Compared with the prior art, the composite pile for static drilling and rooting in the present application has the following advantages: when the prefabricated pile is implanted in the borehole, the flange ring squeezes the cement soil on the lower side of the flange ring in the borehole to force part of the cement soil into the soil gap around 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 of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted. In addition, the cement soil on the lower side of the flange ring is squeezed by the flange ring, and the density increases, and the force between the first thickened protrusion, the concrete pile and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, and further improving the bearing capacity of the single pile after the composite pile is implanted. Because the outer wall of the flange ring is projected along the length direction of the first pile body around the outside of the projection of the first thickened protrusion along the length direction of the first pile body, during the precast pile hugging or hammering construction, the flange ring 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 between the soil and the second pile body of the bottom precast pile, further improving the ultimate bearing capacity of the combined pile during hugging or hammering construction.

[0030] In a preferred embodiment, the bottom precast pile also includes a plurality of second thickened protrusions fixed around the outer peripheral wall of the second pile body, the second thickened protrusions are prefabricated integrally with the second pile body, and the plurality of second thickened protrusions are 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 overlaps with the projection of the outer peripheral wall of the second thickened protrusion along the length direction of the first pile body.

[0031] In a preferred embodiment, the second pile body and the first pile body are both arranged in the form of hollow round piles, a plurality of the first thickened protrusions are arranged in a bamboo-joint shape along the length direction of the second pile body, the flange ring is arranged in a circular ring shape, the first thickened protrusion, the flange ring, the second pile body and the first pile body are arranged coaxially, and a plurality of the second thickened protrusions are arranged in a bamboo-joint shape along the length direction of the second pile body.

[0032] In a preferred embodiment, the bottom precast piles are tubular structures with an inner cavity, and a blocking structure for at least partially blocking the inner cavity is fixed to at least one of the bottom precast piles; or at least one of the bottom precast piles is a solid structure.

[0033] In a preferred embodiment, the blocking structure is an end sealing plate arranged at the end of the bottom precast pile.

[0034] In a third aspect, the present application provides a construction method using the above-mentioned composite pile, comprising the following steps:

[0035] S1. Drilling hole setting: the drilling hole size is designed according to the cross-sectional size of the first pile body of the precast pile, the orthographic projection of the inner circumference wall of the drilled hole in the horizontal plane surrounds the outer side of the orthographic projection of the first pile body and the first thickened protrusion combination in the horizontal plane, and the orthographic projection of the inner circumference wall of the drilled hole in the horizontal plane is completely covered by the orthographic projection of the flange ring in the horizontal plane;

[0036] S2, drilling construction: drilling according to the drilling settings;

[0037] S3, grouting bottom and part precast piles: comprising injecting solidified grout into the borehole and placing at least one of the bottom precast piles into the borehole;

[0038] S4, top precast pile planting: the precast pile is placed on the upper end of the bottom precast pile at the uppermost end, and the precast pile is pressed into the borehole. During and / or after the precast pile is placed into the borehole, the soil around the borehole wall and / or the solidified slurry are squeezed by pressing down the flange ring.

[0039] Compared with the prior art, the composite pile construction method of the present application has the following advantages: a precast pile is used as the top precast pile of the composite pile. When the precast pile is implanted into the borehole, the lower end face of the flange ring forms a closed cavity with the outer peripheral wall of the first pile body and the side wall of the borehole, and squeezes the cement soil on the lower side of the flange ring in the borehole to increase the pressure on the lower side of the lower end face of the flange ring in the borehole, and the cement soil enters the gap of the soil body around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted. In addition, the cement soil on the lower side of the flange ring is squeezed by the flange ring, and the density increases, and the force between the first thickened protrusion, the precast pile and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, and further improving the bearing capacity of the single pile after the composite pile is implanted.

[0040] In a preferred embodiment, in step S3, the grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the precast pile is completely pressed into the borehole, or before the flange ring contacts the first thickened protrusion on the uppermost side of the precast pile, the liquid surface of the solidifying slurry is squeezed to contact the flange ring.

[0041] In a preferred embodiment, the flange ring is located on the upper side of the plurality of first thickened protrusions, and the distance between the uppermost first thickened protrusion of the precast pile and the first end is 3 meters to 6 meters;

[0042] Step S4 also includes, after placing the prefabricated pile into the borehole, driving the flange ring to slide downward along the length direction of the first pile body to squeeze the soil around the borehole wall and / or the solidified slurry.

[0043] In a preferred embodiment, the flange ring is located at the lower side of the first thickened protrusion, and the flange ring includes two or more arc-shaped metal plates that can be spliced ​​to each other to form a ring, and the two or more arc-shaped metal plates can be openably sleeved on the first pile body, and the ends of two adjacent arc-shaped metal plates can be locked with each other;

[0044] Step S4 also includes, before the precast pile is placed in the borehole or during the process of the precast pile being placed in the borehole, sleeveing ​​a flange ring on the first pile body at the lower side of a first thickened protrusion, and during the process of the precast pile being placed in the borehole, the first thickened protrusion presses down the flange ring to squeeze the soil around the borehole wall and / or the solidified slurry.

[0045] In a preferred embodiment, step S2 further comprises expanding the bottom of the borehole, wherein the expanded borehole cavity portion accommodates more than four second thickened protrusions at the bottom of the first section of bottom precast piles inserted into the borehole.

[0046] In a preferred embodiment, the depth of the expanded bottom is greater than or equal to 2.1 meters and less than or equal to 4.5 meters, preferably greater than or equal to 2.4 meters and less than or equal to 2.8 meters.

[0047] In a preferred embodiment, the four or more second thickened protrusions are each provided with a through channel, and the through channel penetrates the second thickened protrusion along the length direction of the second pile body.

[0048] In a preferred embodiment, the second thickened protrusion is provided with two or more through channels evenly distributed along the circumferential direction, and / or at least one of the through channels is a through hole or a notch.

[0049] In a fourth aspect, the present application provides a construction method using the above-mentioned combined piles, comprising the following steps:

[0050] S1. Planting of bottom prefabricated piles: comprising hammering or pressing at least one of the bottom prefabricated piles into the soil;

[0051] S2. Planting the top precast pile: placing the precast pile on the upper end of the bottom precast pile at the uppermost end, and hammering or pressing the precast pile into the soil. During and / or after the precast pile is placed into the soil, the surrounding soil of the precast pile and / or the bottom precast pile is squeezed by pressing down the flange ring.

[0052] Compared with the prior art, the composite pile construction method of the present application has the following advantages: precast piles are used as the top precast piles of the composite piles. Since the outer peripheral wall of the flange ring is projected along the length direction of the first pile body around the outer side of the first thickened protrusion projected along the length direction of the first pile body, when the precast piles are pressed or hammered, the flange ring presses the soil downward, thereby forcing the soil to enter the space between adjacent first thickened protrusions, accelerating the soil backtracking and shortening the soil backtracking cycle, while increasing the pile side friction between the soil and the second pile body of the bottom precast pile, further improving the ultimate bearing capacity of the composite pile during pressing or hammering construction.

[0053] In a preferred embodiment, the flange ring is located on the upper side of the plurality of first thickened protrusions, and the distance between the uppermost first thickened protrusion of the precast pile and the first end is 3 meters to 6 meters;

[0054] Step S2 also includes, after placing the precast pile into the soil, driving the flange ring to slide downward along the length direction of the first pile body to squeeze the soil around the precast pile and / or the bottom precast pile.

[0055] In a preferred embodiment, the flange ring is located at the lower side of the first thickened protrusion, and the flange ring includes two or more arc-shaped metal plates that can be spliced ​​to each other to form a ring, and the two or more arc-shaped metal plates can be openably sleeved on the first pile body, and the ends of two adjacent arc-shaped metal plates can be locked with each other;

[0056] Step S2 also includes, before the precast pile is placed into the soil, during the process of placing the precast pile into the soil, sleeve the flange ring on the first pile body at the lower side of a first thickened protrusion, and during the process of placing the precast pile into the soil, the first thickened protrusion presses down the flange ring to squeeze the surrounding soil of the precast pile and / or the bottom precast pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a bearing capacity analysis diagram of the implantation construction in the prior art;

[0058] Figure 2 The structure of the prefabricated pile in Example 1 of the present application is shown in FIG. Figure 1 ;

[0059] Figure 3 The structure of the prefabricated pile in Example 1 of the present application is shown in FIG. Figure 2 ;

[0060] Figure 4 This is a schematic diagram of the structure of the flange ring of Example 1 of the present application;

[0061] Figure 5 This is a schematic diagram of the structure of the combined pile in Example 2 of the present application. Figure 1 ;

[0062] Figure 6 This is a schematic diagram of the structure of the combined pile in Example 2 of the present application. Figure 2 ;

[0063] Figure 7 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 flange ring to squeeze the cement soil;

[0064] Figure 8 The construction process of the combined pile in Example 3 of this application Figure 1 ;

[0065] Fig. 9 The construction process of the combined pile in Example 3 of this application Figure 2 ;

[0066] Fig.10 The construction process of the combined pile in Example 3 of this application Figure 3 ;

[0067] Fig.11 This is a flow chart of the construction of combined piles in Example 4 of the present application;

[0068] Fig.12 for Fig.11 Enlarged view of part A in the middle;

[0069] Fig.13 for Fig.11 Enlarged view of part B in the middle.

[0070] Description of reference numerals:

[0071] 1. Precast pile; 10. First pile body; 10', First end; 10", Second end; 11, First thickened protrusion; 12, Flange ring; 120, Arc-shaped metal plate; 121, Bolt; 122, Guide structure; 123, Guide slope; 2. Bottom precast pile; 20, Second pile body; 21, Second thickened protrusion; 211, Through passage; 3, End sealing plate; 4, Original soil around the hole wall; 40, Evacuated gap; 5, Solidified soil around the pile; 6, Core pile; 7, Casing; 8, Clamp. DETAILED DESCRIPTION

[0072] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0073] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0074] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0075] The following is combined with Figure 2 to Figure 13 The present application is further described in detail with specific embodiments.

[0076] Example 1

[0077] See also Figure 2 to Figure 4 As shown, an embodiment of the present application discloses a prefabricated pile.

[0078] See also Figure 2 The prefabricated pile of the present embodiment comprises a first pile body 10, a plurality of first thickened protrusions 11 and a flange ring 12. The first pile body 10 is prefabricated integrally with concrete. The first pile body 10 can be a pipe pile or a solid pile. In the present embodiment, the first pile body 10 is introduced by taking a pipe pile as an example. The two ends of the first pile body 10 along the length direction are respectively a first end 10' and a second end 10", and the plurality of first thickened protrusions 11 are all 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 ring, or can be composed of a plurality of block-shaped protrusions distributed at intervals in the circumferential direction, 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 vertical extension of the first pile body 10 is taken as an example, that is, the length direction of the first pile body 10 is arranged vertically, the first end 10 ′ is the uppermost end of the first pile body 10 , and the second end 10 ″ is the lowermost end of the first pile body 10 .

[0079] According to the implantation method, before the prefabricated pile 1 is implanted into the foundation, it needs to go through the process of drilling, bottom expansion, mixing and grouting, and finally realize the foundation structure of "core pile - solidified soil around the pile - original soil around the hole wall". Due to the effect of the first thickened protrusion 11, the contact surface of the interface S1 between the core pile and the solidified soil around the pile is increased, the force direction becomes more, and the peak shear stress of the interface is improved; however, due to market competition considerations, without changing the diameter of the first pile body 10 or the borehole diameter during implantation, the interface S2 between the solidified soil around the pile and the original soil around the hole wall is not improved compared with ordinary prefabricated piles of the same diameter, which is a key factor limiting the bearing capacity of a single pile of a special-shaped pile with alternating thickness along the length direction constructed by the implantation method. Therefore, in order to further improve the bearing capacity of a single pile of an implanted pile, it is necessary to solve the problem of how to improve the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall.

[0080] In this embodiment, the flange ring 12 is sleeved on the outside of the first pile body 10. 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 flange ring 12 is projected along the length direction of the first pile body 10 around the outside of the first thickened protrusion 11 projected along the length direction of the first pile body 10, and the first thickened protrusion 11 projected along the length direction of the first pile body 10 is at least partially located outside the inner peripheral wall of the flange ring 12 projected along the length direction of the first pile body 10.

[0081] According to the implantation method, when the prefabricated pile 1 is implanted into the borehole, since the outer peripheral wall of the flange ring 12 is projected along the length direction of the first pile body 10 to surround the outer side of the first thickened protrusion 11 along the length direction of the first pile body 10, and the first thickened protrusion 11 is projected along the length direction of the first pile body 10 at least partially located outside the inner peripheral wall of the flange ring 12 along the length direction of the first pile body 10, during the downward implantation process, the lower end face of the flange ring 12 squeezes the cement soil on the lower side of the flange ring 12 in the borehole, and the cement soil diffuses to the soil around the borehole by increasing the pressure, and part of the cement soil enters the soil gap 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.

[0082] The flange ring 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 flange ring 12, the density increases, and the interaction force between the first thickened protrusion 11 and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the precast pile 1 and the solidified soil around the pile, and further improving the single pile bearing capacity of the precast pile 1 after implantation.

[0083] During the downward implantation process, the squeezing effect of the lower end of the flange ring 12 on the cement soil below the flange ring 12 in the borehole is affected by the physical properties of the flange ring 12. In order to improve the squeezing effect of the lower end of the flange ring 12 on the lower cement soil during the construction process, preferably, in some examples, the projection of the flange ring 12 along the length direction of the first pile body 10 completely covers the projection of the inner peripheral wall of the borehole along the length direction of the first pile body 10.

[0084] According to the implantation method, when the prefabricated pile 1 is implanted in the drill hole, the inner peripheral wall of the drill hole is projected along the length direction of the first pile body 10 around the outer side of the first pile body 10 and the first thickened protrusion 11 combination projected along the length direction of the first pile body 10, and the implantation action can be completed by relying on the weight of the prefabricated pile 1 and the pile holding and pressing down of the pile driver. In these examples, the projection of the flange ring 12 along the length direction of the first pile body 10 completely covers the projection of the inner peripheral wall of the drill hole along the length direction of the first pile body 10, which means that when the flange ring 12 is to be implanted in the drill hole, additional pressure from the pile driver is required.

[0085] In these examples, when the precast pile 1 is implanted in the borehole, especially when the flange ring 12 enters the borehole, the lower end surface of the flange ring 12 forms a closed cavity with the outer peripheral wall of the first pile body 10 and the side wall of the borehole.

[0086] In these examples, as the prefabricated pile 1 and the flange ring 12 descend, the flange ring 12 gradually increases the pressure in the closed cavity, driving the cement soil to diffuse to the soil around the hole wall. Because it is a closed cavity, the squeezing effect is significant, and the cement soil can more effectively enter the gaps in the soil around the hole wall to improve the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increase the boundary friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improve the single pile bearing capacity after the prefabricated pile 1 is implanted. Different from the natural diffusion between cement soil and the original soil around the hole wall in the ordinary implantation construction method, in this example, since the projection of the flange ring 12 along the length direction of the first pile body 10 completely covers the projection of the inner wall of the borehole along the length direction of the first pile body 10, when the flange ring 12 enters the borehole, the closed cavity formed can significantly enhance the squeezing effect of the lower end of the flange ring 12 on the lower cement soil, and the cement soil can actively diffuse to the soil around the hole wall with the help of the soil gaps, and the boundary friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall is significantly enhanced.

[0087] Preferably, the first pile body 10 is arranged in a hollow round pile, a plurality of first thickened protrusions 11 are arranged in a bamboo-joint shape along the length direction of the first pile body 10, the flange ring 12 is arranged in a circular ring shape, and the first pile body 10, the first thickened protrusions 11 and the flange ring 12 are arranged coaxially. For example, in order to make the flange ring 12 projected along the length direction of the first pile body 10 completely cover the inner circumferential wall of the borehole projected along the length direction of the first pile body 10, the outer diameter of the flange ring 12 is set to be 0 to 50 mm larger than the borehole diameter.

[0088] Optionally, the outer diameter of the first pile body 10 is 350 mm to 750 mm, the outer diameter of the flange ring 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 flange ring 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 flange ring 12 on the cement soil under the flange ring 12 in the borehole is affected by the size characteristics of the flange ring 12 and the first thickened protrusion 11. Preferably, the outer diameter of the flange ring 12 is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion 11.

[0089] See also Figure 2 In some examples, the flange ring 12 is located on the upper side or the lower side of all the first thickened protrusions 11, and the flange ring 12 is slidably connected to the first pile body 10 along the length direction of the first pile body 10. Specifically, the flange ring 12 is an integrally formed annular metal plate, and the inner diameter of the flange ring 12 is slightly larger than the outer diameter of the first pile body 10, that is, the inner diameter of the flange ring 12 is 0-5 mm larger than the outer diameter of the first pile body 10, so that when the flange ring 12 is sleeved on the first pile body 10, it can slide relative to the first pile body 10 along the length direction of the first pile body 10.

[0090] When the flange ring 12 is located on the upper side of all the first thickened protrusions 11, after the precast pile 1 is implanted into the borehole, the flange ring 12 is sleeved on the first pile body 10, and the flange ring 12 is driven by a tool (such as a pile driver) to move downward along the length direction of the first pile body 10, thereby squeezing the soil on the inner peripheral wall of the borehole and the solidified slurry in the borehole, until the lower end of the flange ring 12 abuts against the first thickened protrusion 11 on the uppermost side of the precast pile 1. When the flange ring 12 is located on the lower side of all the first thickened protrusions 11, during the process of implanting the precast pile 1 into the borehole, the flange ring 12 moves upward relative to the first pile body 10 under the action of the soil on the inner peripheral wall of the borehole, until the upper end of the flange ring 12 abuts against the first thickened protrusion 11 on the lowermost side of the precast pile 1, and then the flange ring 12 is implanted into the borehole together with the precast pile 1, squeezing the soil on the inner peripheral wall of the borehole and the solidified slurry in the borehole.

[0091] Preferably, the flange ring 12 is located on the upper side of all the first thickened protrusions 11, and the distance between the first end 10' of the first pile body 10 and the uppermost first thickened protrusion 11 of the precast pile 1 is 3 meters to 6 meters. The flange ring 12 is driven by a tool (such as a pile driver) to squeeze the soil on the inner wall of the borehole and the solidified slurry in the borehole until the lower end of the flange ring 12 abuts against the upper end of the first thickened protrusion 11. In this way, the pressure in the borehole can be controlled according to the construction environment and design requirements to balance the pile planting efficiency and the squeezing effect on the cement soil, and the applicability is strong.

[0092] See also Figure 3 and Figure 4 In some examples, the flange ring 12 is located at the lower side of a first thickened protrusion 11, and the flange ring 12 includes two or more arc-shaped metal plates 120 that can be spliced ​​together to form a ring. The two or more arc-shaped metal plates 120 can be openably sleeved on the first pile body 10, and the ends of two adjacent arc-shaped metal plates 120 can be locked with each other.

[0093] Optionally, the adjacent ends of the two or more arc-shaped metal plates 120 are detachably fixedly connected by bolts 13. During assembly, the two or more arc-shaped metal plates 120 are firstly arranged on the first pile body 10 at the lower side of the first thickened protrusion 11, the two or more arc-shaped metal plates 120 are spliced ​​to each other in a ring shape, and then the ends of the two adjacent arc-shaped metal plates 120 are fixedly connected by bolts 13.

[0094] Optionally, one of the adjacent ends of the two or more arc-shaped metal plates 120 is detachably fixedly connected by a bolt 13, and the others are hinged. Figure 4 , taking the flange ring 12 including two arc-shaped metal plates 120 as an example, one end of the two arc-shaped metal plates 120 is connected by a hinge, so that the other end of the two arc-shaped metal plates 120 can be opened to sleeve the flange ring 12 on the first pile body 10 on the lower side of the first thickened protrusion 11, and then the other end of the two arc-shaped metal plates 120 is fixed by bolts 13.

[0095] Before the precast pile 1 is implanted into the borehole or during the process of the precast pile 1 being implanted into the borehole, the flange ring 12 is sleeved on the first pile body 10 at the lower side of a first thickened protrusion 11; during the process of the precast pile 1 being implanted into the borehole, the flange ring 12 moves upward relative to the first pile body 10 under the action of the soil on the inner wall of the borehole until the upper end of the flange ring 12 abuts against the corresponding first thickened protrusion 11, and then the first thickened protrusion 11 presses down the flange ring 12, driving the flange ring 12 to be implanted into the borehole together with the precast pile 1, squeezing the soil on the inner wall of the borehole and the solidified slurry in the borehole.

[0096] See also Figure 4In some examples, at least one end of the flange ring 12 is provided with a guide structure 122, and the inner side wall of the guide structure 122 is slidably abutted against the outer peripheral wall of the first pile body 10, so that the flange ring 12 and the first pile body 10 remain coaxial and are not easily offset. Specifically, the guide structure 122 is arranged in an annular shape, and the inner peripheral wall of the guide structure 122 and the outer peripheral wall of the first pile body 10 are in contact with each other to guide the flange ring 12 to move along the length direction of the first pile body 10, and are not easily tilted or offset. When the flange ring 12 is located on the upper side of all the first thickened protrusions 11, the guide structure 122 is located at the lower end of the flange ring 12; when the flange ring 12 is located on the lower side of a first thickened protrusion 11, the guide structure 122 is located at the upper end of the flange ring 12. Guide structures 122 may also be provided at both ends of the flange ring 12 to increase the contact area between the flange ring 12 and the first pile body 10 , further improve the coaxiality between the flange ring 12 and the first pile body 10 , and the stability of the flange ring 12 when sliding along the length direction of the first pile body 10 .

[0097] Furthermore, a guiding bevel 123 is provided at the end of the guiding structure 122 facing away from the flange ring 12, and the guiding bevel 123 is matched with the end of the first thickened protrusion 11, so that when the guiding structure 122 abuts against the end of the first thickened protrusion 11, the guiding structure 122 and the flange ring 12 are both coaxially arranged with the first pile body 10, thereby improving the squeezing effect of the flange ring 12 on the soil and the solidified slurry on the inner wall of the borehole, and at the same time, the radial forces applied to the flange ring 12 by the inner wall of the borehole offset each other, so that the precast pile 1 is not easy to be planted off-center during implantation.

[0098] In addition, when the flange ring 12 is composed of two or more arc-shaped metal plates 120 , the guide structures 122 are divided and arranged corresponding to the number of the arc-shaped metal plates 120 , so as to facilitate the installation of the flange ring 12 on the first pile body 10 .

[0099] In addition, the first pile body 10 can also be set with a cross-sectional outer contour of a regular polygon, such as a square, and the first thickened protrusion 11 and the flange ring 12 can both be set in a circular ring shape, and can also be set in a regular polygon ring shape corresponding to the cross-sectional outer contour of the first pile body 10. When the first thickened protrusion 11 and the flange ring 12 are regular polygon ring shapes corresponding to the cross-sectional outer contour of the first pile body 10, the first thickened protrusion 11 and the flange ring 12 are parallel and surround the outside of the first pile body 10. However, it should be noted that no matter what shape is set, in order to ensure the extrusion effect of the flange ring 12 on the cement soil in the hole, and to improve the extrusion effect by using a closed cavity, the projection of the flange ring 12 along the length direction of the first pile body 10 completely covers the projection of the inner peripheral wall of the borehole along the length direction of the first pile body 10.

[0100] 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, or after the precast pile 1 is implanted into the borehole, the flange ring 12 is pressed downward, and the lower end face of the flange ring 12 continuously squeezes the cement soil in the lower borehole to increase the pressure in the borehole below the lower end face of the flange ring 12, thereby causing the cement soil to diffuse into the soil body around the borehole, and the cement soil ions enter the soil body voids, thereby increasing the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the precast pile is implanted; in addition, the density of the cement soil increases after being squeezed by the flange ring 12, which can increase the force between the first thickened protrusion 11 below the flange ring 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.

[0101] In addition, the precast pile 1 can also be used for holding or hammering construction. As the precast pile 1 is continuously implanted into the soil, or after the precast pile 1 is implanted into the soil, the flange ring 12 is pressed down, and the lower end surface of the flange ring 12 continuously squeezes the surrounding soil, driving the soil around the precast pile 1 to fill the space between adjacent first thickened protrusions 11, thereby forcing the soil to enter the space between adjacent first thickened protrusions 11, accelerating the soil backtracking, and shortening the soil backtracking cycle.

[0102] Example 2

[0103] See also Figure 5 to Figure 7 As shown, an embodiment of the present application discloses a combined pile.

[0104] See also Figure 5 The composite pile of this embodiment includes a top precast pile and at least one bottom precast pile 2 connected to the lower end of the top precast pile. The top precast pile 1 is composed of the precast pile 1 described in Example 1, and the precast pile 1 includes a first pile body 10, a plurality of first thickened protrusions 11 and a flange ring 12. The first pile body 10 is a pipe pile and is precast as a whole from concrete. The first pile body 10 extends vertically, and a plurality of first thickened protrusions 11 are fixed on the outer peripheral wall of the first pile body 10. The plurality of first thickened protrusions 11 are arranged in a bamboo-like shape along the length direction of the first pile body 10. The inner peripheral wall of the borehole is projected along the length direction of the first pile body 10 around the outer side of the projection of the first pile body 10 and the first thickened protrusion 11 combination along the length direction of the first pile body 10. The flange ring 12 is sleeved on the first pile body 10, and the projection of the flange ring 12 along the length direction of the first pile body 10 completely covers the projection of the inner peripheral wall of the borehole along the length direction of the first pile body 10. The flange ring 12 may be located on the upper side or the lower side of all the first thickened protrusions 11 , or may be located on the lower side of a first thickened protrusion 11 . For details, please refer to the relevant records in Embodiment 1, which will not be described again here.

[0105] In some examples, the bottom precast pile 2 includes a second pile body 20, which extends vertically and is integrally precast from concrete, and the projection of the outer peripheral wall of the second pile body 20 along the length direction of the first pile body 10 completely overlaps with the projection of the outer peripheral wall of the first pile body 10 along the length direction of the first pile body 10. Optionally, both the first pile body 10 and the second pile body 20 can be provided as hollow circular piles, or as pipe piles with a cross-sectional outer contour being a regular polygon, or as solid piles, which can be selected according to construction needs.

[0106] When the prefabricated pile 1 is implanted in the borehole, the lower end face of the flange ring 12 is used to squeeze the cement soil in the borehole below the flange ring 12 to increase the pressure in the borehole below the lower end face of the flange ring 12, so that the cement soil diffuses to the soil around the borehole, and the cement soil ions enter the soil gaps, thereby increasing the bonding strength between the solidified soil around the pile and the original soil around the hole wall, achieving an increase in 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. In addition, the force between the cement soil in the borehole after being squeezed and the first thickened protrusion 11, the first pile body 10 and the second pile body 20 increases, and the boundary friction resistance of the interface S1 between this part of the pile body of the composite pile and the solidified soil around the pile increases, further improving the bearing capacity of the single pile after the composite pile is implanted.

[0107] In some examples, the bottom precast pile 2 includes a second pile body 20 and a plurality of second thickened protrusions 21. The second pile body 20 extends vertically and is prefabricated integrally with concrete, the second thickened protrusions 21 are prefabricated integrally with the second pile body 20, the plurality of second thickened protrusions 21 are evenly distributed along the length direction of the second pile body 20, and the projection of the outer peripheral wall of the second thickened protrusion 21 along the length direction of the first pile body 10 coincides with the projection of the outer peripheral wall of the first thickened protrusion 11 along the length direction of the first pile body 10.

[0108] Preferably, the first pile body 10 and the second pile body 20 are both arranged as hollow round piles, the plurality of first thickened protrusions 11 are arranged in a bamboo-like shape along the length direction of the first pile body 10 , and the plurality of second thickened protrusions 21 are arranged in a bamboo-like shape along the length direction of the second pile body 20 .

[0109] Optionally, the first pile body 10 and the second pile body 20 may both be provided as hollow square piles, or may both be provided as solid square piles or solid round piles, which may be selected according to construction requirements.

[0110] Due to the effect of the second thickened protrusion 21, the contact area of ​​the interface S1 between the composite pile and the cement soil is increased, the force direction becomes more, the interface peak stress is increased, and the boundary friction resistance of the interface S1 between this part of the composite pile body and the solidified soil around the pile is increased, further improving the single pile bearing capacity of the composite pile after implantation.

[0111] In other examples, the multiple bottom precast piles 2 can also be a combination of pipe piles and special-shaped piles with alternating thickness along the length direction, that is, the bottom precast piles 2 at the lowest end are special-shaped piles with alternating thickness along the length direction, such as bamboo piles, and multiple cylindrical pipe piles or a combination of bamboo piles and cylindrical pipe piles are connected between the bottom bamboo pile and the top precast piles. The specific configuration can be selected according to the actual construction environment and construction requirements.

[0112] See also Figure 7 In some examples, the bottom precast pile 2 is a tubular structure with an inner cavity, such as a hollow round pile or a hollow square pile. A plugging structure that at least partially blocks the inner cavity of the bottom precast pile 2 is fixed on at least one bottom precast pile 2 to adjust the pressure in the borehole below the flange ring 12 and control the squeezing effect on the cement soil in the borehole. The plugging structure is an end sealing plate 3 arranged at the end of the bottom precast pile. The end sealing plate 3 is welded and fixed to the end of one of the bottom precast piles 2. The end sealing plate 3 is provided with a pressure regulating hole that passes through from top to bottom. The pressure regulating hole is connected to the inner hole 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 to adjust the pressure in the borehole below the flange ring 12 and control the squeezing effect on the cement soil in the borehole. Under the same conditions, the closer the position of the end sealing plate 3 is to the bottom of the borehole, the more cement soil there is between the outer peripheral wall of the first pile body 10, the outer peripheral wall of the second pile body 20 and the side wall of the borehole, and the greater the pressure in the borehole below the flange ring 12. The height of the end sealing plate 3 can be adjusted according to the impact of the pile foundation construction on the surrounding environment.

[0113] Optionally, the sealing structure can be replaced by setting one of the bottom precast piles 2 as a solid pile to adjust the amount of cement slurry entering the bottom precast pile 2, adjust the pressure in the borehole under the flange ring 12, and control the squeezing effect on the cement soil in the borehole.

[0114] In summary, the working principle of the combined pile of the above embodiment is as follows: the drilling size is designed according to the cross-sectional size of the first pile body 10 of the precast pile 1, the inner circumferential wall of the drilling hole is projected on the horizontal plane around the outer side of the projection of the combination of the first pile body 10 and the first thickened protrusion 11 on the horizontal plane, and the inner circumferential wall of the drilling hole is completely covered by the projection of the flange ring 12 on the horizontal plane; the drilling rig is in place and the hole is drilled to the designed depth; a certain volume of solidifying slurry is injected into the pile end; a certain volume of solidifying slurry is injected into the part above the pile end, and after mixing with the soil in the hole, a state between liquid and solid is formed; the bottom precast pile 2 is implanted into the borehole in sections in sequence by relying on its own weight and pile pressing force; the precast pile 1 is welded to the upper end of the uppermost bottom precast pile 2, and the precast pile 1 is pressed into the borehole, as the precast pile 1 is continuously implanted into the borehole, or After the prefabricated pile 1 is implanted in the borehole, the flange ring 12 is pressed downward, and the lower end surface of the flange ring 12 continuously squeezes the cement soil in the lower borehole to increase the pressure in the borehole below the lower end surface of the flange ring 12, thereby causing the cement soil to diffuse into the soil around the borehole, and the cement soil ions enter the soil gaps, thereby increasing the bonding strength between the solidified soil around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, and improving the bearing capacity of the single pile after the composite pile is implanted; in addition, the density of the cement soil increases after being squeezed by the flange ring 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 flange ring 12 and the cement soil, thereby increasing the limit friction resistance of the interface S1 between the composite pile and the solidified soil around the pile, and thereby improving the bearing capacity of the single pile after the composite pile is implanted.

[0115] In addition, the composite pile as described above can also be used for holding and pressing or hammering construction to solve the problem that when the bamboo pile is held and pressed or hammered, the bamboo joints of the bamboo pile squeeze out the soil, causing the soil and the pile body to be vacated, and the soil backfills to the adjacent bamboo joints for a long period of time. Because the outer peripheral wall of the flange ring 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, during the process of the prefabricated pile 1 being held and pressed or hammered into the soil, or after the prefabricated pile 1 is implanted into the soil, the flange ring 12 is pressed down to drive the flange ring 12 to squeeze the soil, forcing the soil to backfill into the space between the adjacent first thickened protrusions 11, accelerating the soil backfilling, shortening the soil backfilling period, and enabling the composite pile to reach the designed bearing capacity faster. 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 flange ring 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 bottom precast pile 2 can be more tightly combined, thereby further improving the single pile bearing capacity of the combined pile.

[0116] Example 3

[0117] The present application embodiment discloses a construction method using the combined piles described in Example 2, comprising the following steps:

[0118] S1, drilling setting: the drilling size is designed according to the cross-sectional size of the first pile body 10 of the precast pile 1, the inner peripheral wall of the drilling hole is projected on the horizontal plane around the outer side of the first pile body 10 and the first thickened protrusion 11 combination on the horizontal plane, and the inner peripheral wall of the drilling hole is completely covered by the flange ring 12 on the horizontal plane.

[0119] S2. Drilling construction: Drill holes according to the drilling settings; see Figure 8 In (a), drilling to the designed depth;

[0120] S3, grouting and planting of bottom precast piles 2: including injecting solidified grout into the borehole and placing at least one bottom precast pile 2 into the borehole; see Figure 8 In steps (b) to (c), a certain volume of solidifying slurry is first injected into the pile end, and then a certain volume of solidifying slurry is injected into the part above the pile end, and after mixing with the soil in the borehole, a state between liquid and solid is formed, and then at least one bottom prefabricated pile 2 is sequentially placed into the borehole in sections by relying on its own weight and pile pressure;

[0121] S4, top precast pile planting: the precast pile 1 is placed on the upper end of the uppermost bottom precast pile 2, and the precast pile 1 is pressed into the borehole. During and / or after the precast pile 1 is placed into the borehole, the soil and / or solidified slurry around the borehole are squeezed by pressing down the flange ring 12, see Figure 8 Middle (d)~(e).

[0122] When the precast pile 1 is implanted in the borehole, since the orthographic projection of the flange ring 12 on the horizontal plane completely covers the orthographic projection of the inner wall of the borehole on the horizontal plane, during the process of and / or after the precast pile 1 is placed in the borehole, the flange ring 12 is pressed down to drive the lower end face of the flange ring 12 to squeeze the cement soil on the lower side of the flange ring 12 in the borehole, and the pressure is increased to make the cement soil diffuse to the soil around the borehole, and part of the cement soil enters the soil gap around the hole wall, thereby improving the bonding strength between the solidified soil around the pile and the original soil of the hole wall, and improving the limit friction resistance of the interface S2 between the solidified soil around the pile and the original soil around the hole wall, thereby improving the bearing capacity of the single pile after the composite pile is implanted.

[0123] Furthermore, in step S3, grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the precast pile 1 is completely pressed into the borehole, or before the flange ring 12 contacts the first thickened protrusion 11 on the uppermost side of the precast pile 1, the liquid surface of the solidifying slurry is squeezed to contact with the flange ring 12.

[0124] Furthermore, the projection of the first thickened protrusion 11 along the length direction of the first pile body 10 is at least partially located outside the projection of the inner peripheral wall of the flange ring 12 along the length direction of the first pile body 10, so that the cement soil of the flange ring 12 is not easy to pass through the gap between the flange ring 12 and the first pile body 10, so as to better realize the flange ring 12 to squeeze the cement soil under the flange ring 12 in the borehole. The flange ring 12 can also be blocked and positioned by the first thickened protrusion 11 to control the degree of squeezing the cement soil in the borehole.

[0125] In some examples, the flange ring 12 is located on the upper side of the plurality of first thickened protrusions 11, that is, the flange ring 12 is located on the upper side of all the first thickened protrusions 11, and the distance between the uppermost first thickened protrusion 11 of the precast pile 1 and the first end 10' is 3 meters to 6 meters; step S4 also includes, after the precast pile 1 is pressed into the borehole, driving the flange ring 12 to slide downward along the length direction of the first pile body 10 to squeeze the soil and / or solidified slurry around the borehole wall, see Figure 8 (d)~(e).

[0126] By driving the flange ring 12 to squeeze the soil on the inner wall of the borehole and the solidified slurry in the borehole through a tool (such as a pile driver), the pressure in the borehole can be controlled according to the construction environment and design requirements to balance the pile planting efficiency and the squeezing effect on the cement soil, which has strong applicability. In addition, the difficulty of implanting the first pile body 10 of the prefabricated pile 1 into the borehole can be reduced.

[0127] In some examples, the flange ring 12 is located at the lower side of a first thickened protrusion 11, and the flange ring 12 includes two or more arc-shaped metal plates 120 that can be spliced ​​to each other in a ring shape. The two or more arc-shaped metal plates 120 can be openably sleeved on the first pile body 10, and the ends of two adjacent arc-shaped metal plates 120 can be locked with each other; step S4 also includes, before the precast pile 1 is pressed into the borehole or during the precast pile 1 is pressed into the borehole, sleeve the flange ring 12 on the first pile body 10 at the lower side of a first thickened protrusion 11, and during the process of placing the precast pile 1 into the borehole, the first thickened protrusion 11 presses down the flange ring 12 to squeeze the soil and / or solidified slurry around the borehole wall, see Fig. 9 (d)~(e).

[0128] More than two arc-shaped metal plates 120 can be openably sleeved on the first pile body 10, so that the flange ring 12 can be conveniently installed on the first pile body 10 on the lower side of any first thickened protrusion 11. The flange ring 12 can squeeze the soil around the borehole and the cement soil in the borehole during the process of implanting the prefabricated pile 1 into the borehole, without the need for additional tools to drive the flange ring 12 to move downward along the length direction of the first pile body 10, which makes the operation simpler.

[0129] In some examples, step S2 further includes expanding the bottom of the borehole, wherein the expanded borehole cavity portion accommodates at least four second thickened protrusions 21 at the bottom of a section of the bottom precast pile 2 first placed in the borehole, see Fig.10 (a)~(e).

[0130] The second thickened protrusions 21 of the lower section of the first precast pile 2 inserted into the borehole are arranged more densely, which can further improve the bearing capacity of the lower end of the composite pile, thereby improving the vertical bearing capacity of the single pile after the composite pile is implanted.

[0131] Furthermore, the depth of the bottom expansion is greater than or equal to 2.1 meters and less than or equal to 4.5 meters, preferably greater than or equal to 2.4 meters and less than or equal to 2.8 meters. The ratio of the bottom expansion diameter to the borehole diameter is between 1.2 and 1.6, preferably between 1.45 and 1.55.

[0132] Further, the four or more second thickened protrusions 21 are each provided with a through channel 211, and the through channel 211 penetrates the second thickened protrusion 21 along the length direction of the second pile body 20. Specifically, the second thickened protrusion 21 is provided with two or more through channels 211 evenly distributed along the circumferential direction, and / or at least one through channel 211 is a through hole or a notch.

[0133] The strength of the solidifying slurry injected into the pile end is greater than the strength of the solidifying slurry above the pile end. The bottom precast pile 2 is implanted in the expanded bottom. The through channel 211 guides part of the solidifying slurry at the pile end to move upward, thereby reducing the diffusion of the solidifying slurry at the pile end to the outer peripheral wall of the expanded bottom, so as to increase the strength of the solidifying slurry above the pile end, thereby increasing the boundary friction resistance of the interface S1 between the bottom precast pile 2 and the solidified soil around the pile, and further improving the single pile bearing capacity after the composite pile is implanted. In addition, the through channel 211 can also reduce the resistance of the bottom precast pile 2 when implanted into the expanded bottom, and improve the implantation efficiency of the composite pile.

[0134] Furthermore, in step S3, the amount of solidifying slurry injected is the bottom expansion volume. By expanding the bottom of the borehole, the amount of solidifying slurry injected can be increased, and the second thickened protrusions 21 of the lower section of the first bottom prefabricated pile 2 placed in the borehole are arranged more densely, which can further improve the bearing capacity of the lower end of the composite pile, thereby improving the vertical bearing capacity of the single pile after the composite pile is implanted.

[0135] Furthermore, in step S3, the planting of the bottom precast pile 2 also includes that one of the bottom precast piles 2 is a solid pile, or the bottom precast piles 2 are all hollow piles, an end sealing plate 3 is welded at the end of one of the bottom precast piles 2, the outer peripheral wall of the end sealing plate 3 along the length direction of the first pile body 10 is completely overlapped with the outer peripheral wall of the second pile body 20 along the length direction of the first pile body 10, and the end sealing plate 3 is provided with a pressure regulating hole that passes through from top to bottom, the pressure regulating hole is connected to the inner hole of the second pile body 20, and the diameter of the pressure regulating hole is smaller than the inner diameter of the second pile body 20, so as to prevent cement soil from passing through the pressure regulating hole from bottom to top. The end sealing plate 3 or the solid pile is used as a blocking structure to adjust the volume of cement soil entering the bottom precast pile 2, and then adjust the extrusion effect of the flange ring 12 of the precast pile 1 on the cement soil in the borehole. In addition, when the bottom precast pile 2 is a hollow pile, a plugging structure can also be set in the inner hole of the bottom precast pile 2 to adjust the squeezing effect of the flange ring 12 of the precast pile 1 on the cement soil in the borehole.

[0136] Example 4

[0137] See also Figure 11 to Figure 13 The present application embodiment discloses a construction method using the combined piles described in Example 2, comprising the following steps:

[0138] S1, implanting the bottom precast pile 2: comprising implanting at least one bottom precast pile 2 into the soil by hammering or pressing;

[0139] S2. Top precast pile implantation: The precast pile 1 is placed on the upper end of the uppermost bottom precast pile 2 and fixed, and the precast pile 1 is implanted into the soil by hammering or pressing. During and / or after the precast pile 1 is implanted into the soil, the surrounding soil of the precast pile 1 and / or the bottom precast pile 2 is squeezed by pressing down the flange ring 12.

[0140] In some examples, the flange ring 12 is located on the upper side of multiple first thickened protrusions 11, that is, the flange ring 12 is located on the upper side of all the first thickened protrusions 11, and the distance between the uppermost first thickened protrusion 11 of the precast pile 1 and the first end 10' is 3 meters to 6 meters; step S2 also includes, after the precast pile 1 is implanted into the soil, driving the flange ring 12 to slide downward along the length direction of the first pile body 10, squeezing the surrounding soil of the precast pile 1 and / or the bottom precast pile 2 until the lower end of the flange ring 12 abuts against the upper end of the uppermost first thickened protrusion 11.

[0141] After the prefabricated pile 1 is implanted into the soil, the flange ring 12 is sleeved on the first pile body 10 on the upper side of all the first thickened protrusions 11, and then the sleeve 7 is sleeved on the first pile body 10 on the upper side of all the first thickened protrusions 11. The lower end of the sleeve 7 abuts against the upper end of the flange ring 12, and the sleeve 7 is clamped by the clamp 8 to press the flange ring 12 into the soil.

[0142] In some examples, the flange ring 12 is located on the lower side of a first thickened protrusion 11, and the flange ring 12 includes more than two arc-shaped metal plates 120 that can be spliced ​​to each other in a ring shape. The more than two arc-shaped metal plates 120 can be openably sleeved on the first pile body 10, and the ends of two adjacent arc-shaped metal plates 120 can be locked with each other; step S2 also includes, before the precast pile 1 is placed into the soil or during the process of the precast pile 1 being placed into the soil, sleeve the flange ring 12 on the first pile body 10 on the lower side of a first thickened protrusion 11, and during the process of the precast pile 1 being placed into the soil, the first thickened protrusion 11 presses down the flange ring 12 to squeeze the surrounding soil of the precast pile 1 and / or the bottom precast pile 2.

[0143] Before the precast pile 1 is implanted into the soil or during the process of the precast pile 1 being implanted into the soil, the flange ring 12 is sleeved on the first pile body 10 at the lower side of a first thickened protrusion 11. The flange ring 12 moves upward relative to the first pile body 10 under the action of the soil until the upper end of the flange ring 12 abuts against the corresponding first thickened protrusion 11. Then, the flange ring 12 is implanted into the borehole together with the precast pile 1 to squeeze the surrounding soil of the precast pile 1 and / or the bottom precast pile 2.

[0144] See also Fig.11 and Fig.12 When the bottom precast pile 2 is hammered or pressed into the soil, the second thickened protrusion 11 of the precast pile 2 will break the soil to form a pile hole. The bottom precast pile 2 will form a gap 40 with the original soil 4 of the hole wall of the pile hole near the second thickened protrusion 21. It is difficult to backfill the gap 40 with the soil backtracking, resulting in a relatively long backtracking wall of the original soil 4 of the hole wall of the pile hole after the bamboo pile is hammered or pressed. Fig.11 and Fig.13 Because the outer peripheral wall of the flange ring 12 is projected along the length direction of the first pile body 10 around the outside of the projection of the first thickened protrusion 11 along the length direction of the first pile body, during the process of the precast pile 1 being pressed or hammered into the soil, the flange ring 12 squeezes the original soil 4 of the hole wall of the pile hole downward, forcing the original soil 4 of the hole wall to be backfilled into the vacated gap 40 near the first thickened protrusion 11, accelerating the backtracking of the original soil 4 of the hole wall, shortening the soil backtracking cycle, and enabling the composite pile to reach the designed bearing capacity faster. After the original soil 4 of the hole wall is backfilled into the vacated gap 40 near the first thickened protrusion 11, the precast pile 1 is continuously implanted downward, and the flange ring 12 continues to squeeze the soil downward, which can make the soil and the first pile body 10 of the precast pile 1 and the second pile body 20 of the bottom precast pile 2 more closely combined, thereby further improving the single pile bearing capacity of the composite pile.

[0145] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0146] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0147] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A prefabricated pile, characterized in that: include: A first pile body (10), wherein two ends of the first pile body (10) along the length direction are respectively a first end (10') and a second end (10"); A plurality of first thickened protrusions (11) fixed on the outer peripheral wall of the first pile body (10) and arranged at intervals along the length direction of the first pile body (10); and A flange ring (12) is sleeved on the outside of the first pile body (10) and is slidably connected to the first pile body (10) along the length direction of the first pile body (10); The outer peripheral wall of the flange ring (12) is projected along the length direction of the first pile body (10) to surround the outer side of the first thickened protrusion (11) projected along the length direction of the first pile body (10).

2. The prefabricated pile according to claim 1, characterized in that: The first thickened protrusion (11) is at least partially located outside the projection of the inner peripheral wall of the flange ring (12) along the length direction of the first pile body (10); When the prefabricated pile (1) is placed in a borehole and / or after the prefabricated pile (1) is placed in the borehole, the inner peripheral wall of the borehole is projected along the length direction of the first pile body (10) around the outer side of the first pile body (10) and the first thickened protrusion (11) combination projected along the length direction of the first pile body (10), and the flange ring (12) is projected along the length direction of the first pile body (10) to completely cover the inner peripheral wall of the borehole projected along the length direction of the first pile body (10), and the flange ring (12) can move downward along the length direction of the first pile body (10) to squeeze the soil and / or solidified slurry around the borehole.

3. The prefabricated pile according to claim 1 or 2, characterized in that: The flange ring (12) is located on the upper side or the lower side of the plurality of first thickened protrusions (11), and the flange ring (12) is an integrally formed annular metal plate.

4. The prefabricated pile according to claim 3, characterized in that: The flange ring (12) is located on the upper side of the plurality of first thickened protrusions (11), and the distance between the first end (10') and the first thickened protrusion (11) close to the first end (10') is 3 meters to 6 meters.

5. The prefabricated pile according to claim 1 or 2, characterized in that: The flange ring (12) is located at the lower side of the first thickened protrusion (11), and the flange ring (12) includes two or more arc-shaped metal plates (120) that can be spliced ​​to each other to form a ring. The two or more arc-shaped metal plates (120) can be openably sleeved on the first pile body (10), and the ends of two adjacent arc-shaped metal plates (120) can be locked with each other.

6. The prefabricated pile according to claim 5, characterized in that: The adjacent ends of the two or more arc-shaped metal plates (120) are both detachably fixedly connected by bolts (121), or one of the adjacent ends of the two or more arc-shaped metal plates (120) is detachably fixedly connected by bolts (121), and the other is hinged.

7. The prefabricated pile according to any one of claims 1 or 2, characterized in that: The inner peripheral wall of the flange ring (12) and the outer peripheral wall of the first pile body (10) are in contact with each other.

8. The prefabricated pile according to any one of claims 1 or 2, characterized in that: At least one end of the flange ring (12) is provided with a guide structure (122), and the inner side wall of the guide structure (122) is slidably abutted against the outer peripheral wall of the first pile body (10).

9. The prefabricated pile according to claim 8, characterized in that: The guide structure (122) is arranged in an annular shape, the inner peripheral wall of the guide structure (122) is in contact with the outer peripheral wall of the first pile body (10), and the end of the guide structure (122) facing away from the flange ring (12) is provided with a guide inclined surface (123) adapted to the end of the first thickened protrusion (11).

10. The prefabricated pile according to any one of claims 1 or 2 or 4 or 6 or 9, characterized in that: The first thickened protrusion (11) and the flange ring (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 flange ring (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.

11. The prefabricated pile according to any one of claims 1 or 2 or 4 or 6 or 9, characterized in that: The first pile body (10) is arranged in the shape of a hollow round pile, a plurality of the first thickened protrusions (11) are arranged in the shape of bamboo joints along the length direction of the first pile body (10), the flange ring (12) is arranged in the shape of a circular ring, the first thickened protrusion (11), the flange ring (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 flange ring (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 flange ring (12) is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion (11).

12. A composite pile, characterized in that: include: A top precast pile consisting of a precast pile (1) as claimed in any one of claims 1 to 11; as well as At least one bottom precast pile (2) connected to the lower end of the top precast pile (1); The bottom prefabricated pile (2) comprises a second pile body (20) extending vertically, wherein the projection of the outer peripheral wall of the second pile body (20) along the length direction of the first pile body (10) completely overlaps with the projection of the first pile body (10) along the length direction of the first pile body (10).

13. The combined pile according to claim 12, characterized in that: The bottom prefabricated pile (2) further comprises a plurality of second thickened protrusions (21) fixedly encircling the outer peripheral wall of the second pile body (20); the second thickened protrusions (21) are integrally prefabricated with the second pile body (20); the plurality of second thickened protrusions (21) are arranged at intervals along the length direction of the second pile body (20); the outer peripheral wall of the first thickened protrusion (11) projected along the length direction of the first pile body (10) completely overlaps with the outer peripheral wall of the second thickened protrusion (21) projected along the length direction of the first pile body (10).

14. The combined pile according to claim 13, characterized in that: The second pile body (20) and the first pile body (10) are both arranged in the form of hollow round piles, a plurality of the first thickened protrusions (11) are arranged in the form of bamboo joints along the length direction of the second pile body (20), the flange ring (12) is arranged in the form of a circular ring, the first thickened protrusion (11), the flange ring (12), the second pile body (20) and the first pile body (10) are arranged coaxially, and a plurality of the second thickened protrusions (21) are arranged in the form of bamboo joints along the length direction of the second pile body (20).

15. The combined pile according to any one of claims 12 to 14, characterized in that: The bottom precast pile (2) is a tubular structure with an inner cavity, and a blocking structure for at least partially blocking the inner cavity is fixed on at least one of the bottom precast piles (2); or at least one of the bottom precast piles (2) is a solid structure.

16. The combined pile according to claim 15, characterized in that: The blocking structure is an end sealing plate (3) arranged at the end of the bottom prefabricated pile (2).

17. A construction method using the composite pile according to claim 12, characterized in that: The steps include: S1. Drilling hole setting: the drilling hole size is designed according to the cross-sectional size of the first pile body (10) of the precast pile (1), the inner peripheral wall of the drilling hole is projected on the horizontal plane around the outer side of the first pile body (10) and the first thickened protrusion (11) combination on the horizontal plane, and the inner peripheral wall of the drilling hole is completely covered by the flange ring (12) on the horizontal plane. S2, drilling construction: drilling according to the drilling settings; S3, grouting and planting of bottom prefabricated piles (2): comprising injecting solidified grout into the borehole and placing at least one of the bottom prefabricated piles (2) into the borehole; S4, top precast pile planting: the precast pile (1) is placed on the upper end of the bottom precast pile (2) at the uppermost end, and the precast pile (1) is pressed into the borehole. During the process of placing the precast pile (1) into the borehole and / or after the precast pile (1) is placed into the borehole, the soil around the borehole wall and / or the solidified slurry are squeezed by pressing down the flange ring (12).

18. The construction method according to claim 17, characterized in that: In step S3, the grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the precast pile (1) is completely pressed into the borehole, or before the flange ring (12) contacts the uppermost first thickened protrusion (11), the liquid surface of the solidifying slurry is squeezed to contact the flange ring (12).

19. The construction method according to claim 18, characterized in that: The flange ring (12) is located on the upper side of the plurality of first thickened protrusions (11), and the distance between the uppermost first thickened protrusion (11) of the precast pile (1) and the first end (10') is 3 meters to 6 meters; Step S4 also includes, after placing the prefabricated pile (1) into the borehole, driving the flange ring (12) to slide downward along the length direction of the first pile body (10) to squeeze the soil around the borehole wall and / or the solidified slurry.

20. The construction method according to claim 18, characterized in that: The flange ring (12) is located at the lower side of the first thickened protrusion (11), and the flange ring (12) includes two or more arc-shaped metal plates (120) that can be spliced ​​to each other to form a ring shape. The two or more arc-shaped metal plates (120) can be openably sleeved on the first pile body (10), and the ends of two adjacent arc-shaped metal plates (120) can be locked with each other; Step S4 also includes: before the precast pile (1) is placed in the borehole or during the process of the precast pile (1) being placed in the borehole, the flange ring (12) is sleeved on the first pile body (10) at the lower side of a first thickened protrusion (11); during the process of the precast pile (1) being placed in the borehole, the first thickened protrusion (11) presses down the flange ring (12) to squeeze the soil and / or solidified slurry on the surrounding wall of the borehole.

21. The construction method according to any one of claims 17 to 20, characterized in that: Step S2 also includes expanding the bottom of the borehole, wherein the expanded borehole cavity portion accommodates more than four second thickened protrusions (21) at the bottom of the first section of the bottom precast pile (2) placed in the borehole.

22. The construction method according to claim 21, characterized in that: The depth of the expanded bottom is greater than or equal to 2.1 meters and less than or equal to 4.5 meters, preferably greater than or equal to 2.4 meters and less than or equal to 2.8 meters.

23. The construction method according to claim 21, characterized in that: The four or more second thickened protrusions (21) are each provided with a through channel (211), and the through channel (211) penetrates the second thickened protrusion (21) along the length direction of the second pile body (20).

24. The construction method according to claim 23, characterized in that: The second thickened protrusion (21) is provided with two or more through channels (211) evenly distributed along the circumferential direction, and / or at least one of the through channels (211) is a through hole or a notch.

25. A construction method using the composite pile according to claim 12, characterized in that: The steps include: S1. Planting of bottom prefabricated piles (2): comprising hammering or pressing at least one of the bottom prefabricated piles (2) into the soil; S2, top prefabricated pile planting: the prefabricated pile (1) is placed on the upper end of the bottom prefabricated pile (2) at the uppermost end, and the prefabricated pile (1) is hammered or pressed into the soil. During the process of the prefabricated pile (1) being placed into the soil and / or after being placed into the soil, the surrounding soil of the prefabricated pile (1) and / or the bottom prefabricated pile (2) is squeezed by pressing down the flange ring (12).

26. The construction method according to claim 25, characterized in that: The flange ring (12) is located on the upper side of the plurality of first thickened protrusions (11), and the distance between the uppermost first thickened protrusion (11) of the precast pile (1) and the first end (10') is 3 meters to 6 meters; Step S2 also includes, after the precast pile (1) is placed in the soil, driving the flange ring (12) to slide downward along the length direction of the first pile body (10) to squeeze the soil around the precast pile (1) and / or the bottom precast pile (2).

27. The construction method according to claim 25, characterized in that: The flange ring (12) is located at the lower side of the first thickened protrusion (11), and the flange ring (12) includes two or more arc-shaped metal plates (120) that can be spliced ​​to each other to form a ring shape. The two or more arc-shaped metal plates (120) can be openably sleeved on the first pile body (10), and the ends of two adjacent arc-shaped metal plates (120) can be locked with each other; Step S2 also includes, before the precast pile (1) is placed in the soil or during the process of the precast pile (1) being placed in the soil, sleeve-mounting a flange ring (12) on the first pile body (10) at the lower side of a first thickened protrusion (11); during the process of the precast pile (1) being placed in the soil, the first thickened protrusion (11) presses down the flange ring (12) to squeeze the soil around the precast pile (1) and / or the bottom precast pile (2).

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