Combined pile construction method

Abstract

The invention provides a combined pile construction method, and relates to the technical field of pile foundation construction, and the combined pile construction method comprises the following steps: S1, drill hole setting: the orthographic projection of the inner peripheral wall of a drill hole on the horizontal plane surrounds the outer side of the orthographic projection of a first pile body and / or a second pile body on the horizontal plane, a first protruding part surrounds the first pile body, and a second protruding part surrounds the second pile body; the orthographic projection of the inner peripheral wall of the drill hole on the horizontal plane is completely covered by the orthographic projection of the first protruding part on the horizontal plane; s2, drilling construction is conducted, specifically, drilling is conducted according to the drilling setting; s3, grouting and second precast pile planting are conducted, specifically, curing slurry is injected into the drilled hole, and at least one second precast pile is placed into the drilled hole; and S4, the first precast pile is planted, specifically, the first precast pile is placed at the upper end of the second precast pile at the uppermost end, the first precast pile is pressed into the drill hole, and in the process of placing the first precast pile into the drill hole and / or after the first precast pile is placed into the drill hole, a soil body and / or solidified slurry on the peripheral wall of the drill hole are / is extruded through a first protruding part. By the adoption of the combined pile construction method, after construction is completed, the bearing capacity of the combined pile can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation construction, and in particular to a combined pile 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. Summary of the invention

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

[0007] A combined pile construction method comprises the following steps:

[0008] S1. Drilling setting: the drilling size is designed according to the cross-sectional size of the first pile body of the first precast pile and / or the second pile body of the second precast pile, the inner peripheral wall of the drilled hole is projected on the horizontal plane around the outer side of the first pile body and / or the second pile body, the first pile body is surrounded by a first protrusion, and the inner peripheral wall of the drilled hole is completely covered by the first protrusion in the horizontal plane;

[0009] S2, drilling construction: drilling according to the drilling settings;

[0010] S3, grouting and second precast pile planting: comprising injecting solidified grout into the borehole and placing at least one of the second precast piles into the borehole;

[0011] S4, first precast pile planting: placing the first precast pile on the upper end of the second precast pile at the uppermost end, and pressing the first precast pile into the borehole, during and / or after the first precast pile is placed into the borehole, squeezing the soil around the borehole wall and / or the solidified slurry through the first protrusion.

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

[0013] In a preferred embodiment, the first prefabricated pile further comprises a plurality of first thickened protrusions, which are 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 the orthographic projection of the first thickened protrusions on the horizontal plane is at least partially located outside the orthographic projection of the inner peripheral wall of the first protruding portion on the horizontal plane;

[0014] In step S3, the grouting is to inject a certain volume of solidified slurry into the borehole, so that before the first precast pile is completely pressed into the borehole, or before the first protrusion contacts the uppermost first thickened protrusion, the liquid surface of the solidified slurry is squeezed to contact the first protrusion.

[0015] In a preferred embodiment, the orthographic projection of the outer wall of the second pile body on the horizontal plane completely overlaps with the orthographic projection of the first pile body on the horizontal plane, and the second prefabricated pile further includes a plurality of second thickened protrusions, which are circumferentially fixed on the outer wall of the second pile body, and the orthographic projection of the outer wall of the first thickened protrusion on the horizontal plane completely overlaps with the orthographic projection of the outer wall of the second thickened protrusion on the horizontal plane.

[0016] In a preferred embodiment, the first protrusion is located on the upper side of the plurality of first thickened protrusions and is slidably connected to the first pile body along the length direction of the first pile body, the first protrusion is an integrally formed annular metal plate, and the distance between the first thickened protrusion on the uppermost side of the first precast pile and the upper end of the first precast pile is 3 meters to 6 meters;

[0017] Step S4 also includes, after placing the first precast pile into the borehole, driving the first protrusion 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.

[0018] In a preferred embodiment, the first protrusion is located at the lower side of the first thickened protrusion, and the first protrusion 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;

[0019] Step S4 also includes, before the first precast pile is placed in the borehole or during the process of the first precast pile being placed in the borehole, sleeved the first protrusion on the first pile body at the lower side of a first thickened protrusion, and during the process of the first precast pile being placed in the borehole, the first thickened protrusion presses down the first protrusion to squeeze the soil around the borehole wall and / or the solidified slurry.

[0020] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as a whole, the outer peripheral wall of the lower end plate of the first prefabricated pile surrounds the outer side of the first thickened protrusion on the horizontal plane, and the portion of the lower end plate of the first prefabricated pile extending out of the first pile body forms the first protrusion;

[0021] Step S4 also includes that, during the process of placing the first precast pile into the borehole, the first pile body drives the first protrusion to squeeze the soil around the borehole wall and / or the solidified slurry.

[0022] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as a whole, the first protrusion is an annular flange made of metal material, and the inner ring edge of the annular flange is welded and fixed to the outer edge of the lower end of the first prefabricated pile;

[0023] Step S4 also includes, before the first precast pile is placed in the borehole, welding and fixing the two ends of the first protrusion to the lower end of the first precast pile and the upper end of the second precast pile respectively; during the process of placing the first precast pile in the borehole, the first precast pile drives the first protrusion to squeeze the soil around the borehole wall and / or the solidified slurry.

[0024] In a preferred embodiment, the inner edge of the annular flange is aligned with the outer edge of the lower end of the first precast pile and the outer edge of the upper end of the second precast pile, or the inner edge of the annular flange is embedded between the lower end of the first precast pile and the upper end of the second precast pile.

[0025] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as a whole, the first protrusion is an annular flange made of metal material, and the annular flange is fixed to the lower end of the first prefabricated pile by bolts or mortise and tenon structures;

[0026] Step S4 also includes that before the first precast pile is placed in the borehole, the two ends of the first protrusion are fixed to the lower end of the first precast pile and the upper end of the second precast pile by bolts and / or mortise and tenon structures and welding respectively; during the process of placing the first precast pile in the borehole, the first precast pile drives the first protrusion to squeeze the soil around the borehole wall and / or the solidified slurry.

[0027] In a preferred embodiment, the first protrusion is prefabricated integrally with the first pile body and the first thickened protrusion;

[0028] Step S4 also includes that, during the process of placing the first precast pile into the borehole, the first pile body drives the first protrusion to squeeze the soil around the borehole wall and / or the solidified slurry.

[0029] In a preferred embodiment, the first pile body and the first thickened protrusion are prefabricated as a whole, the first protrusion comprises two or more arc-shaped protrusions which can be spliced ​​to each other to form a circular ring, and the arc-shaped protrusions are welded and fixed or detachably fixed to the first pile body;

[0030] Step S4 also includes fixing the first protrusion on the first pile body during or before the first precast pile is placed in the drilled hole, and during the process of the first precast pile being placed in the drilled hole, the first pile body drives the first protrusion to squeeze the soil around the drilled hole and / or the solidified slurry.

[0031] In a preferred embodiment, a groove is provided on the inner peripheral wall of the arc-shaped protrusion, and when the arc-shaped protrusion is fixed on the first thickened protrusion, the outer peripheral wall of the first thickened protrusion and the inner side wall of the groove fit each other to limit the axial position of the arc-shaped protrusion.

[0032] In a preferred embodiment, the arc-shaped protrusion is prefabricated from concrete, and a first embedded steel part extending in a circumferential direction is pre-embedded in at least one of the two ends of the inner circumferential wall of the arc-shaped protrusion along the length direction of the first pile body, and a second embedded steel part extending in a circumferential direction and corresponding to the first embedded steel part is pre-embedded on the first pile body, and the first embedded steel part is correspondingly welded to the second embedded steel part.

[0033] In a preferred embodiment, the arc-shaped protrusion is prefabricated from concrete, and is provided with a through hole extending radially, the through hole passing through the inner and outer circumferential walls of the arc-shaped protrusion, and a bolt hole is provided on the outer circumferential wall of the first thickened protrusion, and the bolt hole is equipped with an expansion bolt passing through the through hole to fix the arc-shaped protrusion to the first thickened protrusion.

[0034] In a preferred embodiment, the second prefabricated pile is a tubular structure having an inner cavity;

[0035] Step S3 also includes: fixing a blocking structure for at least partially blocking the inner cavity on at least one of the second precast piles; or at least one of the second precast piles is a solid structure.

[0036] In a preferred embodiment, the blocking structure is an end sealing plate provided at the end of the second precast pile.

[0037] In a preferred embodiment, the first pile body is arranged as a hollow round pile, the end sealing plate is arranged in a circular ring or disc shape, the outer diameter of the end sealing plate is not less than the inner diameter of the first pile body and not greater than the outer diameter of the first pile body, the thickness of the end sealing plate is 3 mm to 5 mm, and the yield strength of the end sealing plate is 200 MPa to 400 MPa.

[0038] In a preferred embodiment, step S2 further comprises expanding the bottom of the borehole, wherein the expanded borehole cavity partially accommodates four or more second thickened protrusions at the bottom of the second precast pile section first inserted into the borehole.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 first protrusion is arranged in a circular ring shape, the first thickened protrusion, the first protrusion 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 first protrusion 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 first protrusion is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion.

[0043] In a preferred embodiment, the first thickened protrusion and the first protruding portion are both parallel and surround the outer side of the first pile body, and the distance from the outer edge of the projection of the first thickened protrusion along the length direction of the first pile body to the outer edge of the projection of the first protruding portion 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.

[0044] In a preferred embodiment, the first pile body is arranged in a hollow round pile, the first protrusion is arranged in a circular ring shape, and the first protrusion and the first pile body are arranged coaxially;

[0045] The thickness of the first protrusion is 20 mm to 30 mm, the yield strength of the first protrusion is 200 MPa to 400 MPa, the inner diameter of the first protrusion is equal to the outer diameter of the first pile body, and the difference between the outer diameter of the first protrusion and the diameter of the borehole is not less than 50 mm and not more than 150 mm.

[0046] In a preferred embodiment, the first pile body is arranged in a hollow round pile, the first protrusion is arranged in a circular ring shape, and the first protrusion and the first pile body are arranged coaxially;

[0047] When the compression stroke of the first protrusion is greater than 6 meters, the difference between the outer diameter of the first protrusion and the diameter of the drill hole is equal to 50 mm; when the compression stroke of the first protrusion is not greater than 6 meters, the difference between the outer diameter of the first protrusion and the diameter of the drill hole is not less than 100 mm and not greater than 150 mm.

[0048] In a preferred embodiment, the compression stroke of the first protrusion is defined as L1, the total pile length of the combined pile is L, and 0.5≥L1 / L≥0.06. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a bearing capacity analysis diagram of the implantation construction in the prior art;

[0050] Figure 2 The construction process of the combined pile in the embodiment of the present application Figure 1 ;

[0051] Figure 3 It is a full cross-sectional schematic diagram of the first protrusion welded to the first pile body in the embodiment of the present application;

[0052] Figure 4 for Figure 3 A partial schematic diagram of the connection between the first protruding portion, the first pile body and the first thickened protrusion;

[0053] Figure 5It is a full cross-sectional schematic diagram of the first protrusion of the embodiment of the present application being detachably fixed to the first pile body;

[0054] Figure 6 This is a schematic structural diagram of a combined pile in which the first protrusion of the embodiment of the present application is formed by the lower end plate of the first precast pile;

[0055] Figure 7 This is a schematic diagram of the structure in which the first protrusion of the embodiment of the present application is welded between the first precast pile and the second precast pile;

[0056] Figure 8 This is a schematic structural diagram of an embodiment of the present application in which the first protrusion is located at the lower side of a first thickened protrusion;

[0057] Fig. 9 This is a schematic structural diagram of the first protrusion of an embodiment of the present application including two or more arc-shaped metal plates;

[0058] Fig.10 The construction process of the combined pile in the embodiment of the present application Figure 2 ;

[0059] Fig.11 This is a schematic structural diagram of a combined pile when the first protrusion of the embodiment of the present application is located on the upper side of all the first thickened protrusions;

[0060] Fig.12 The construction process of the combined pile in the embodiment of the present application Figure 3 ;

[0061] Fig.13 The construction process of the combined pile in the embodiment of the present application Figure 4 ;

[0062] Fig.14 It is a structural schematic diagram of the composite pile of the embodiment of the present application in which the pressure is adjusted by the end sealing plate.

[0063] Description of reference numerals:

[0064] 1. First precast pile; 10. First pile body; 11. First protrusion; 110. Arc-shaped metal plate; 111. Guide structure; 112. Guide slope; 113. Arc-shaped protrusion; 114. First conical surface; 115. Cylinder; 116. Second conical surface; 117. Groove; 118. First embedded steel part; 119. Through hole; 12. First thickened protrusion; 121. Bolt hole; 13. Second embedded steel part; 14. Expansion bolt; 15. Second protrusion; 151. Pressure relief channel; 2. Second precast pile; 20. Second pile body; 21. Second thickened protrusion; 211. Through channel; 3. End sealing plate; 4. Original soil around the hole wall; 5. Solidified soil around the pile; 6. Core pile. DETAILED DESCRIPTION

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The following is combined with Figure 2 to Figure 14 The present application is further described in detail with specific embodiments.

[0069] See also Figure 2 The present application discloses a method for constructing a combined pile, comprising the following steps:

[0070] S1. Drilling arrangement: the drilling size is designed according to the cross-sectional size of the first pile body 10 of the first precast pile 1 and / or the second pile body 20 of the second precast pile 2, the inner peripheral wall of the drilled hole surrounds the outer side of the first pile body 10 and / or the second pile body 20 in the horizontal plane, the first pile body 10 is surrounded by the first protruding portion 11, and the inner peripheral wall of the drilled hole in the horizontal plane is completely covered by the first protruding portion 11 in the horizontal plane;

[0071] S2. Drilling construction: Drill holes according to the drilling settings, see Figure 2 In (a), drilling to the designed depth;

[0072] S3, grouting and planting of second precast piles 2: including injecting solidified grout into the borehole and placing at least one second precast pile 2 into the borehole; see Figure 2In 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 being mixed with the soil in the borehole, a state between liquid and solid is formed, and then at least one second precast pile 2 is sequentially placed into the borehole in sections by relying on its own weight and pile pressure force;

[0073] S4, planting the first precast pile 1: placing the first precast pile 1 on the upper end of the second precast pile 2 at the uppermost end, and pressing the first precast pile 1 into the borehole. During the process of placing the first precast pile 1 into the borehole, the soil and / or solidified slurry around the borehole are squeezed by the first protruding portion 11. Figure 2 Middle (d)~(e).

[0074] Among them, the combined pile includes a first precast pile 1 and at least one second precast pile 2 connected to the lower end of the first precast pile 1, the first precast pile 1 includes a first pile body 10, the second precast pile 2 includes a second pile body 20, the first pile body 10 and the second pile body 20 are both precast from concrete, the first pile body 10 and the second pile body 20 can both be pipe piles or solid piles. In this embodiment, the first pile body 10 and the second pile body 20 are introduced using pipe piles as an example.

[0075] When the first precast pile 1 is implanted into the borehole, especially when the first protrusion 11 enters the borehole, since the projection of the first protrusion 11 on the horizontal plane completely covers the projection of the inner peripheral wall of the borehole on the horizontal plane, the lower end surface of the first protrusion 11 forms a closed cavity with the outer peripheral wall of the first pile body 10 and the side wall of the borehole. As the first precast pile 1 descends, the first protrusion 11 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 extrusion 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 pile surrounding solidified soil 5 and the original soil of the hole wall, increase the boundary friction resistance of the interface S2 between the pile surrounding solidified soil 5 and the original soil 4 around the hole wall, and improve the bearing capacity of the single pile after the composite pile is implanted. Different from the natural diffusion between cement soil and the original soil 4 around the hole wall in the ordinary implantation construction method, in this example, since the horizontal projection of the first protrusion 11 completely covers the horizontal projection of the inner wall of the borehole, when the first protrusion 11 enters the borehole, the closed cavity formed can significantly enhance the squeezing effect of the lower end of the first protrusion 11 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 5 around the pile and the original soil 4 around the hole wall is significantly enhanced.

[0076] According to the implantation method, when the first precast pile 1 is implanted into the borehole, the orthographic projection of the inner circumference of the borehole in the horizontal plane surrounds the outer side of the orthographic projection of the first pile body 10 in the horizontal plane, and the implantation action can be completed by relying on the weight of the first precast pile 1 and the pile holding and pressing down of the pile driver. In these examples, the orthographic projection of the first protrusion 11 in the horizontal plane completely covers the orthographic projection of the inner circumference of the borehole in the horizontal plane, which means that when the first protrusion 11 is to be implanted into the borehole, additional pressure from the pile driver is required.

[0077] Furthermore, the first precast pile 1 further includes a plurality of first thickened protrusions 12, which are fixed on the outer peripheral wall of the first pile body 10 and are arranged at intervals along the length direction of the first pile body 10, and the orthographic projection of the first thickened protrusions 12 in the horizontal plane is at least partially located outside the orthographic projection of the inner peripheral wall of the first protruding portion 11 in the horizontal plane, and the orthographic projection of the outer peripheral wall of the drilled hole in the horizontal plane surrounds the outer side of the orthographic projection of the first thickened protrusion 12 and the first pile body 10 in the horizontal plane. The orthographic projection of the outer peripheral wall of the second pile body 20 in the horizontal plane completely overlaps with the orthographic projection of the outer peripheral wall of the first pile body 10 in the horizontal plane, and the second precast pile 2 further includes a plurality of second thickened protrusions 21, which are fixed on the outer peripheral wall of the second pile body 20, and the orthographic projection of the outer peripheral wall of the first thickened protrusion 12 in the horizontal plane completely overlaps with the orthographic projection of the outer peripheral wall of the second thickened protrusion 21 in the horizontal plane. The first thickened protrusion 12 and the second thickened protrusion 21 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 protrusion 12 and the first pile body 10 are combined to form a special-shaped pile with alternating thickness along the length direction, and the second thickened protrusion 21 and the second pile body 20 are combined to form a special-shaped pile with alternating thickness along the length direction, such as a bamboo pile, a special-shaped square pile with alternating thickness along the length direction, etc.

[0078] Due to the action of the first thickened protrusion 12 and the second thickened protrusion 21, the contact surface of the interface S1 between the core pile 6 and the pile surrounding solidified soil 5 increases, the force direction becomes more, and the peak shear stress of the interface is improved. The first protrusion 11 completely covers the horizontal projection of the inner peripheral wall of the borehole in the horizontal plane, so that during the downward implantation process, the cement soil around the first thickened protrusion 12 and the second thickened protrusion 21 is squeezed by the first protrusion 11, the density increases, and the action force between the first thickened protrusion 12 and the second thickened protrusion 21 and the surrounding cement soil increases, thereby increasing the limit friction resistance of the interface S1 between the first precast pile 1, the second precast pile 2 and the pile surrounding solidified soil 5, and further improving the single pile bearing capacity after the composite pile is implanted.

[0079] Preferably, the first pile body 10 and the second pile body 20 are both arranged in a cylindrical pipe pile, a plurality of first thickened protrusions 12 are arranged in a bamboo-like shape along the length direction of the first pile body 10, a plurality of second thickened protrusions 21 are arranged in a bamboo-like shape along the length direction of the second pile body 20, the first protrusion 11 is arranged in a circular ring shape, and the first pile body 10, the second pile body 20, the first thickened protrusion 12, the second thickened protrusion 21 and the first protrusion 11 are arranged coaxially. Optionally, the outer diameter of the first pile body 10 is 350 mm to 750 mm, the outer diameter of the first protrusion 11 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 12 is 50 mm to 150 mm larger than the outer diameter of the first pile body 10, and the outer diameter of the first protrusion 11 is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion 12.

[0080] In order to make the orthographic projection of the first protrusion 11 in the horizontal plane completely cover the orthographic projection of the inner wall of the borehole in the horizontal plane, the outer diameter of the first protrusion 11 is set to be 50 mm to 150 mm larger than the borehole diameter. The outer diameter of the first protrusion 11 can be adjusted according to the compression stroke of the first protrusion 11. The outer diameter of the first protrusion 11 and the compression stroke of the first protrusion 11 are comprehensively considered to achieve the required extrusion effect, so as to increase the limit friction resistance of the interface S2 between the solidified soil 5 around the pile and the original soil 4 around the hole wall, and to increase the limit friction resistance of the interface S1 between the composite pile and the solidified soil 5 around the pile, thereby improving the bearing capacity of the single pile after the composite pile is implanted. The compression stroke of the first protrusion 11 is the distance the first protrusion 11 moves downward after entering the borehole.

[0081] Preferably, when the compression stroke of the first protrusion 11 is greater than 6 meters, the difference between the outer diameter of the first protrusion 11 and the diameter of the drilled hole is equal to 50 mm; when the compression stroke of the first protrusion 11 is not greater than 6 meters, the difference between the outer diameter of the first protrusion 11 and the diameter of the drilled hole is not less than 100 mm and not greater than 150 mm.

[0082] Furthermore, the compression stroke of the first protrusion 11 is defined as L1, the total pile length of the combined pile is L, 0.5≥L1 / L≥0.06, so as to ensure that the soil around the borehole wall and / or the solidified slurry is squeezed by the first protrusion 11 to increase the limit friction resistance of the interface S2 between the solidified soil 5 around the pile and the original soil 4 around the hole wall, and to increase the limit friction resistance of the interface S1 between the combined pile and the solidified soil 5 around the pile, thereby improving the bearing capacity of the single pile after the combined pile is implanted.

[0083] For some examples, see Figure 2 The first protruding portion 11, the first thickened protrusion 12 and the first pile body 10 are prefabricated as a whole;

[0084] Step S4 also includes that during the process of placing the first precast pile 1 into the borehole, the first pile body 10 drives the first protruding portion 11 to squeeze the soil around the borehole wall and / or the solidified slurry.

[0085] The first pile body 10, the first thickened protrusion 12 and the first protruding portion 11 are prefabricated by centrifugal molding using a steel mold. In this way, no subsequent assembly is required, and the production process is simple to operate. However, demolding is difficult during demolding, which is particularly prominent for bamboo piles with protrusions on the outer wall. The industry has developed different types of molds to improve the yield rate.

[0086] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11 .

[0087] Before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11. The first precast pile 1 is continuously implanted, and the first pile body 10 can be used to drive the first protrusion 11 to squeeze the solidifying slurry on the lower side of the first protrusion 11 in the borehole. By increasing the pressure, the cement soil diffuses to the soil around the borehole, and part of the cement soil enters the soil gaps around the hole wall, thereby improving the bonding strength between the solidified soil 5 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 5 around the pile and the original soil 4 around the hole wall, thereby improving the bearing capacity of the single pile after the composite pile is implanted.

[0088] Furthermore, the first protrusion 11 includes a first conical surface 114, a cylindrical surface 115 and a second conical surface 116 which are sequentially connected from top to bottom, wherein the upper end of the first conical surface 114 and the lower end of the second conical surface 116 are both connected to the first pile body 10, the cylindrical surface 115 extends vertically and surrounds the outer side of the first pile body 10, the diameter of the first conical surface 114 gradually increases from top to bottom, and the diameter of the second conical surface 116 gradually decreases from top to bottom, so as to facilitate demolding when the first pile body 10 and the first protrusion 11 are prefabricated as a whole.

[0089] Preferably, the angle between the first conical surface 114 of the first protruding portion 11 and the horizontal plane is set to be 45°, and the angle between the second conical surface 116 of the first protruding portion 11 and the vertical direction is greater than 45° and less than 90°. The above arrangement makes the upper and lower end surfaces of the first protruding portion 11 no longer symmetrical. From a local point of view, there is a stress difference between the upper and lower end surfaces of the first protruding portion 11, but from the perspective of the entire pile body, this part of the stress difference can just weaken or offset the problem of uneven stress distribution caused by the size and position factors of the first protruding portion 11 to a certain extent, thereby improving the yield rate. At the same time, the angle between the second conical surface 116 of the first protruding portion 11 and the horizontal plane is reduced, so that when the first prefabricated pile 1 is implanted, the extrusion of the first protruding portion 11 can act as much as possible on the cement soil under the first protruding portion 11 in the borehole, thereby improving the extrusion effect of the first protruding portion 11 on the cement soil under the first protruding portion 11 in the borehole.

[0090] For some examples, see Figure 3 The first pile body 10 and the first thickened protrusion 12 are prefabricated as a whole, and the first protrusion 11 includes two or more circular arc protrusions 113 that can be spliced ​​to each other, and the arc protrusion 113 is welded and fixed or detachably fixed to the first pile body 10;

[0091] Step S4 also includes fixing the first protrusion 11 on the first pile body 10 during or before the first precast pile 1 is placed in the drilled hole. During the first precast pile 1 is placed in the drilled hole, the first pile body 10 drives the first protrusion 11 to squeeze the soil around the drilled hole and / or the solidified slurry.

[0092] Compared with the integral prefabrication of the first protrusion 11 and the first pile body 10, the first prefabricated pile 1 can be the same as the existing bamboo pile during the centrifugal prefabrication stage by welding or detachable fixing, and the existing production mold and production operation can remain unchanged. The stress distribution of the entire first prefabricated pile 1 is uniform, and the pile body is not prone to collapse during demoulding, which can effectively reduce the adverse effect of the first protrusion 11 on the stress distribution of the pile body during the centrifugal forming stage.

[0093] In addition, there are multiple options for the form of the lower end surface of the first protrusion 11. Preferably, the first protrusion 11 includes a first conical surface 114, a cylindrical surface 115 and a second conical surface 116 connected in sequence from top to bottom. The cylindrical surface 115 extends vertically and surrounds the outer side of the first pile body 10. The end of the upper end of the first conical surface 114 is connected to the first pile body 10, and the end of the lower end of the first conical surface 114 is connected to the cylindrical surface 115; the end of the upper end of the second conical surface 116 is connected to the first pile body 10, and the end of the lower end of the second conical surface 116 is connected to the cylindrical surface 115. The diameter of the first conical surface 114 gradually increases from top to bottom, and the diameter of the second conical surface 116 gradually increases from top to bottom. The second conical surface 116 cooperates with the first pile body 10 to form an annular concave cavity with an opening facing downward. When the first precast pile 1 is implanted, the second conical surface 116 of the first protrusion 11 guides the cement soil to gather toward the first pile body 10, thereby reducing the cement soil from the lower side of the first protrusion 11 to the upper side of the first protrusion 11 overflowing. At the same time, the force of the second conical surface 116 of the first protrusion 11 can completely act on the cement soil in the borehole, further improving the squeezing effect of the first protrusion 11 on the cement soil in the borehole.

[0094] Furthermore, the inner peripheral wall of the arc-shaped protrusion 113 has a groove 117 adapted to the first thickened protrusion 12, and the groove 117 is located in the middle of the inner peripheral wall of the arc-shaped protrusion 113. When the arc-shaped protrusion 113 is fixed on the first pile body 10, the outer peripheral wall of the first thickened protrusion 12 and the inner side wall of the groove 117 of the arc-shaped protrusion 113 fit each other, and the arc-shaped protrusion 113 is axially limited, so as to improve the firmness of the connection between the arc-shaped protrusion 113 and the first pile body 10, so that when the first prefabricated pile 1 is implanted in the drilled hole, the arc-shaped protrusion 113 is not easy to move relative to the first pile body 10 in the axial direction.

[0095] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11 .

[0096] Alternatively, see Figure 4 , the first protrusion 11 is welded and fixed on the first pile body 10. Specifically, at least one of the two ends of the arc-shaped protrusion 113 is pre-embedded with a first embedded steel part 118, and the first embedded steel part 118 can be an arc-shaped steel part, or can be composed of a plurality of arc-shaped steel sheets uniformly arranged along the circumference of the arc-shaped protrusion 113. In this example, the first embedded steel part 118 is a plurality of arc-shaped steel sheets uniformly arranged along the circumference of the arc-shaped protrusion 113, and the inner diameter of the arc-shaped steel sheet is equal to the inner diameter of the arc-shaped protrusion 113. Specifically, the arc-shaped steel sheet is embedded in a specific position of the steel mold in advance during production, and is prefabricated and formed integrally with the arc-shaped protrusion 113.

[0097] The first pile body 10 is pre-embedded with a second embedded steel part 13, which may be an annular steel part or may be composed of a plurality of arc-shaped steel sheets evenly arranged along the circumference of the first pile body 10. In this example, the second embedded steel part 13 corresponds to the first embedded steel part 118 and is arranged as a plurality of arc-shaped steel sheets evenly arranged along the circumference of the first pile body 10, and the outer diameter of the arc-shaped steel sheet is equal to the outer diameter of the first pile body 10. Specifically, the arc-shaped steel sheet is embedded in a specific position of the steel mold in advance during production, and then centrifugal prefabrication is performed. The first embedded steel part 118 is welded to the second embedded steel part 13 to fix the arc-shaped protrusion 113 to the first pile body 10.

[0098] To ensure the firmness of the connection, preferably, first embedded steel parts 118 are embedded at both ends of the arc-shaped protrusion 113, the upper end surface of the upper first embedded steel part 118 is not lower than the upper end of the first protrusion 11, and the lower end surface of the lower first embedded steel part 118 is not higher than the lower end of the first protrusion 11. Two second embedded steel parts 13 are provided corresponding to the first embedded steel parts 118, the two second embedded steel parts 13 are respectively located on both sides of a first thickened protrusion 12, and the two first embedded steel parts 118 are respectively welded to the two second embedded steel parts 13.

[0099] Through the welding forming method, the applicable scenarios can be well expanded. Due to different construction environments, the physical properties of the foundation are also different. By adjusting the size specifications of the first protrusion 11, a balance can be achieved between improving the extrusion effect and controlling the soil extrusion effect.

[0100] Alternatively, see Figure 5 , the first protrusion 11 and the first pile body 10 are both detachably fixed. Specifically, the first thickened protrusion 12 is provided with a bolt hole 121 extending in the radial direction, and the arc-shaped protrusion 113 is provided with a through hole 119 corresponding to the bolt hole 121. After the arc-shaped protrusion 113 abuts against the outer side of the first thickened protrusion 12, the expandable end of the expansion bolt 14 is inserted into the bolt hole 121 through the through hole 119, and the nut of the expansion bolt 14 is rotated to fix the two arc-shaped protrusions 113 on the first thickened protrusion 12. In order to ensure the extrusion effect, preferably, the first protrusion 11 is detachably fixed to the outer side of the first thickened protrusion 12 on the side of the first pile body 10 closest to the cap.

[0101] In this example, since the relatively large-sized first protrusion 11 is avoided during production, the first pile body 10 and the first thickened protrusion 12 can be demoulded relatively easily. On this basis, there are more choices for the shape of the first protrusion 11. At the same time, since the embedded parts such as the second embedded steel part 13 and the first embedded steel part 118 are avoided during production, the first pile body 10 and the first thickened protrusion 12 can be prefabricated as a whole relatively easily, and the first protrusion 11 can also be prefabricated separately relatively easily. Moreover, the first protrusion 11 is connected to the first thickened protrusion 12 by the expansion bolt 14, which makes assembly easier.

[0102] For some examples, see Figure 6 The first pile body 10 and the first thickened protrusion 12 are prefabricated as a whole, the outer peripheral wall of the lower end plate of the first prefabricated pile 1 surrounds the outer side of the first thickened protrusion 12 on the horizontal plane, and the part of the lower end plate of the first prefabricated pile 1 extending out of the first pile body 10 forms a first protrusion 11; the thickness of the first protrusion 11 is 20 mm to 30 mm, the yield strength of the first protrusion 11 is 200 MPa to 400 MPa, and the inner diameter of the first protrusion 11 is equal to the outer diameter of the first pile body 10.

[0103] Step S4 also includes that during the process of placing the first precast pile 1 into the borehole, the first pile body 10 drives the first protruding portion 11 to squeeze the soil around the borehole wall and / or the solidified slurry.

[0104] When the first prefabricated pile 1 is prefabricated in one piece, a standard end plate is connected to one end of the steel cage of the first pile body 10, and the outer diameter of the standard end plate is equal to the outer diameter of the first pile body 10. A larger end plate is connected to the other end of the steel cage of the first pile body 10, and the outer diameter of the larger end plate is greater than the outer diameter of the first pile body 10.

[0105] Since the first protrusion 11 of relatively large size is avoided during production, the first pile body 10 and the first thickened protrusion 12 can be demoulded relatively easily without the need for subsequent assembly. On this basis, the shape of the first protrusion 11 can also have more choices.

[0106] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11 .

[0107] For some examples, see Figure 7The first pile body 10 and the first thickened protrusion 12 are prefabricated as a whole, the first protrusion 11 is a metal annular flange, the inner ring edge of the annular flange is welded and fixed to the outer edge of the lower end of the first prefabricated pile 1, the thickness of the annular flange is 20 mm to 30 mm, and the yield strength of the annular flange is 200 MPa to 400 MPa;

[0108] Step S4 also includes that before the first precast pile 1 is placed into the borehole, the two ends of the first protrusion 11 are respectively welded and fixed to the lower end of the first precast pile 1 and the upper end of the second precast pile 2. During the process of placing the first precast pile 1 into the borehole, the first precast pile 1 drives the first protrusion 11 to squeeze the soil around the borehole wall and / or the solidified slurry.

[0109] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11 .

[0110] See also Figure 7 (a), optionally, the inner ring size of the annular flange is smaller than the outer ring size of the first precast pile 1. During construction, the lower end of the annular flange is first abutted against the upper end of the second precast pile 2, the annular flange is welded and fixed to the upper end of the second precast pile 2, and then the first precast pile 1 is abutted against the upper end of the annular flange, and finally the annular flange is welded and fixed to the lower end of the first precast pile 1.

[0111] See also Figure 7 (b), optionally, the inner ring edge of the annular flange can be aligned with the outer edge of the lower end plate of the first precast pile 1, that is, the annular flange can be mounted on the end plates at the lower end of the first precast pile 1 and the upper end of the second precast pile 2, and the inner ring edge of the annular flange fits with the outer edge of the lower end plate of the first precast pile 1 and the outer edge of the upper end plate of the second precast pile 2. During construction, the annular flange is first mounted on the upper end of the second precast pile 2, and then the first precast pile 1 is abutted against the upper end of the second precast pile 2, and then the annular flange is simultaneously mounted on the lower end plate of the first precast pile 1 and the upper end plate of the second precast pile 2, and finally the annular flange is welded and fixed to the lower end plate of the first precast pile 1 and the upper end plate of the second precast pile 2.

[0112] In this example, since the first protrusion 11 of relatively large size is avoided during production, the first prefabricated pile 1 can be the same as the existing bamboo pile during the centrifugal prefabrication molding stage, the existing production mold and production operation can remain unchanged, the stress distribution of the entire first prefabricated pile 1 is uniform, and the pile body is not prone to collapse during demoulding, which can effectively reduce the adverse effects of the first protrusion 11 on the stress distribution of the pile body during the centrifugal molding stage. On this basis, there are also more choices for the shape of the first protrusion 11.

[0113] In some examples, the first pile body 10 and the first thickened protrusion 12 are prefabricated as a whole, the first protrusion 11 is an annular flange made of metal, the annular flange is fixed to the lower end of the first prefabricated pile 1 by bolts or mortise and tenon structures, the thickness of the annular flange is 20 mm to 30 mm, and the yield strength of the annular flange is 200 MPa to 400 MPa;

[0114] Step S4 also includes that before the first precast pile 1 is placed in the borehole, the two ends of the first protrusion 11 are fixed to the lower end of the first precast pile 1 and the upper end of the second precast pile 2 by bolts and / or mortise and tenon structures and welding respectively. During the process of placing the first precast pile 1 in the borehole, the first precast pile 1 drives the first protrusion 11 to squeeze the soil around the borehole wall and / or the solidified slurry.

[0115] The annular flange can be first fixed to the upper end of the second precast pile 2 by bolts, and then the lower end of the first precast pile 1 can be abutted against the annular flange, and the lower end annular flange of the first precast pile 1 can be fixedly connected by welding or mortise and tenon structure, and finally the first precast pile 1 can be implanted into the drilled hole.

[0116] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11 .

[0117] For some examples, see Figure 8 and Fig. 9 The first protrusion 11 is located at the lower side of a first thickened protrusion 12. The first protrusion 11 includes two or more arc-shaped metal plates 110 that can be spliced ​​to each other in a ring shape. The two or more arc-shaped metal plates 110 can be openably sleeved on the first pile body 10. The ends of two adjacent arc-shaped metal plates 110 can be locked with each other. The thickness of the arc-shaped metal plate 110 is 20 mm to 30 mm, and the yield strength of the arc-shaped metal plate 110 is 200 MPa to 400 MPa.

[0118] Step S4 also includes: before or during the first precast pile 1 is placed in the borehole, sleeve the first protrusion 11 on the first pile body 10 at the lower side of a first thickened protrusion 12; during the first precast pile 1 is placed in the borehole, the first thickened protrusion 12 presses down the first protrusion 11 to squeeze the soil and / or solidified slurry around the borehole wall, see Fig.10 (d)~(e).

[0119] More than two arc-shaped metal plates 110 can be openably sleeved on the first pile body 10, so that the first protrusion 11 can be installed on the first pile body 10 at the lower side of any first thickened protrusion 12. The first protrusion 11 can squeeze the soil around the borehole and the cement soil in the borehole during the process of implanting the first precast pile 1 into the borehole, without the need for additional tools to drive the first protrusion 11 to move downward along the length direction of the first pile body 10, which makes the operation simpler.

[0120] Furthermore, in step S3 , grouting is to inject a certain volume of solidifying slurry into the borehole, so that before the first precast pile 1 is completely pressed into the borehole, the liquid surface of the solidifying slurry is squeezed to contact with the first protrusion 11 .

[0121] Optionally, the adjacent ends of the two or more arc-shaped metal plates 110 are detachably fixedly connected by bolts. During assembly, the two or more arc-shaped metal plates 110 are firstly arranged around the first pile body 10 on the lower side of the first thickened protrusion 12, the two or more arc-shaped metal plates 110 are spliced ​​to form a ring, and then the ends of the two adjacent arc-shaped metal plates 110 are fixedly connected by bolts.

[0122] Optionally, one of the adjacent ends of the two or more arc-shaped metal plates 110 is detachably fixedly connected by a bolt, and the others are hinged. Fig. 9 , taking the example that the first protrusion 11 includes two arc-shaped metal plates 110, one end of the two arc-shaped metal plates 110 is connected by a hinge, so that the other end of the two arc-shaped metal plates 110 can be opened to sleeve the first protrusion 11 on the first pile body 10 on the lower side of a first thickened protrusion 12, and then fix the other end of the two arc-shaped metal plates 110 by bolts.

[0123] Furthermore, the orthographic projection of the first thickened protrusion 12 on the horizontal plane is at least partially located outside the orthographic projection of the inner peripheral wall of the first protrusion 11 on the horizontal plane, so that the cement soil of the first protrusion 11 is not easy to pass through the gap between the first protrusion 11 and the first pile body 10, so as to better realize the first protrusion 11 to squeeze the cement soil under the first protrusion 11 in the borehole. Preferably, the orthographic projection of the first thickened protrusion 12 on the horizontal plane is completely located outside the orthographic projection of the inner peripheral wall of the first protrusion 11 on the horizontal plane, that is, the inner peripheral wall of the first protrusion 11 and the outer peripheral wall of the first pile body 10 are mutually attached, and the first protrusion 11 is slidably connected to the first pile body 10 along the length direction of the first pile body 10.

[0124] Before the first precast pile 1 is implanted into the borehole or during the process of implanting the first precast pile 1 into the borehole, the first protrusion 11 is sleeved on the first pile body 10 at the lower side of a first thickened protrusion 12; during the process of implanting the first precast pile 1 into the borehole, the first protrusion 11 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 first protrusion 11 abuts against the corresponding first thickened protrusion 12, and then the first thickened protrusion 12 presses down on the first protrusion 11, driving the first protrusion 11 to be implanted into the borehole together with the first precast pile 1, squeezing the soil on the inner wall of the borehole and the solidified slurry in the borehole.

[0125] For some examples, see Fig.11 and Fig.12 , the first protrusion 11 is located on the upper side of the plurality of first thickened protrusions 12, that is, the first protrusion 11 is located on the upper side of all the first thickened protrusions 12, the first protrusion 11 is slidably connected to the first pile body 10 along the length direction of the first pile body 10, and the distance between the uppermost first thickened protrusion 12 of the first precast pile 1 and the upper end of the first precast pile 1 is 3 meters to 6 meters; the first protrusion 11 is an integrally formed annular metal plate, the thickness of the annular metal plate is 20 mm to 30 mm, and the yield strength of the annular metal plate is 200 MPa to 400 MPa;

[0126] Step S4 also includes, after the first precast pile 1 is pressed into the borehole, driving the first protrusion 11 to move downward along the length direction of the first pile body 10 to squeeze the soil and / or solidified slurry around the borehole, see Fig.12 (d)~(e).

[0127] By driving the first protrusion 11 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 first prefabricated pile 1 into the borehole can be reduced.

[0128] Furthermore, the orthographic projection of the first thickened protrusion 12 on the horizontal plane is at least partially located outside the orthographic projection of the inner peripheral wall of the first protruding portion 11 on the horizontal plane, so that the cement soil of the first protruding portion 11 is not easy to pass through the gap between the first protruding portion 11 and the first pile body 10, so as to better realize the first protruding portion 11 to squeeze the cement soil under the first protruding portion 11 in the borehole. The first thickened protrusion 12 can also be used to block and position the first protruding portion 11 to control the degree of squeezing the cement soil in the borehole.

[0129] Furthermore, in step S3 , grouting is to inject a certain volume of solidified slurry into the borehole, so that before the first protrusion 11 contacts the uppermost first thickened protrusion 12 , the liquid surface of the solidified slurry is squeezed to contact the first protrusion 11 .

[0130] After the first protrusion 11 contacts the liquid surface of the solidifying slurry, the first protrusion 11 is driven to continue to move downward along the length direction of the first pile body 10, and the first protrusion 11 squeezes the solidifying slurry on the lower side of the first protrusion 11 in the borehole, thereby increasing the pressure so that the cement soil diffuses to the soil around the borehole, and part of the cement soil enters the soil gaps around the hole wall, thereby improving the bonding strength between the solidified soil 5 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 5 around the pile and the original soil 4 around the hole wall, thereby improving the single pile bearing capacity after the first precast pile 1 is implanted.

[0131] Further, see Fig. 9 and Fig.11 , at least one end of the first protrusion 11 is provided with a guide structure 111, and the inner side wall of the guide structure 111 is slidably abutted against the outer peripheral wall of the first pile body 10, so that the first protrusion 11 and the first pile body 10 remain coaxial and are not easily offset. Specifically, the guide structure 111 is arranged in an annular shape, and the inner peripheral wall of the guide structure 111 and the outer peripheral wall of the first pile body 10 are in contact with each other to guide the first protrusion 11 to move along the length direction of the first pile body 10, and are not easily tilted or offset. When the first protrusion 11 is located on the upper side of all the first thickened protrusions 12, the guide structure 111 is located at the lower end of the first protrusion 11; when the first protrusion 11 is located on the lower side of a first thickened protrusion 12, the guide structure 111 is located at the upper end of the first protrusion 11. Guide structures 111 may also be provided at both ends of the first protrusion 11 to increase the contact area between the first protrusion 11 and the first pile body 10 , further improve the coaxiality between the first protrusion 11 and the first pile body 10 , and the stability of the first protrusion 11 when sliding along the length direction of the first pile body 10 .

[0132] Furthermore, a guiding slope 112 is provided at the end of the guiding structure 111 facing away from the first protruding portion 11, and the guiding slope 112 is matched with the end of the first thickened protrusion 12, so that when the guiding structure 111 abuts against the end of the first thickened protrusion 12, the guiding structure 111 and the first protruding portion 11 are coaxially arranged with the first pile body 10, thereby improving the squeezing effect of the first protruding portion 11 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 first protruding portion 11 by the inner wall of the borehole offset each other, so that the precast pile is not easy to be planted off-center during implantation.

[0133] In addition, when the first protruding portion 11 is composed of two or more arc-shaped metal plates 110 , the guide structures 111 are divided and arranged corresponding to the number of the arc-shaped metal plates 110 , so as to facilitate the installation of the first protruding portion 11 on the first pile body 10 .

[0134] For some examples, see Fig.13Step S2 also 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 the second precast pile 2 first placed in the borehole, see Fig.13 (a)~(e).

[0135] The second thickened protrusions 21 of the lower section of the second precast pile 2 first 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.

[0136] 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.

[0137] 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.

[0138] 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 second precast pile 2 is implanted in the expanded bottom, and 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 second precast pile 2 and the solidified soil 5 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 when the second precast pile 2 is implanted in the expanded bottom, and improve the implantation efficiency of the composite pile.

[0139] 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 second precast pile 2 first 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.

[0140] For some examples, see Fig.14 , the second prefabricated pile 2 is a tubular structure with an inner cavity;

[0141] Step S3 also includes that a blocking structure for at least partially blocking the inner cavity is fixed on at least one of the second precast piles 2; or at least one of the second precast piles 2 is a solid structure.

[0142] Preferably, a blocking structure for at least partially blocking the inner cavity is fixed on at least one second precast pile 2, and the blocking structure is an end sealing plate 3, that is, an end sealing plate 3 is welded at the end of at least one second precast pile 2, and the end sealing plate 3 is arranged in a circular ring or disc shape, and the outer diameter of the end sealing plate 3 is not less than the inner diameter of the first pile body 10 and not greater than the outer diameter of the first pile body 10, and the thickness of the end sealing plate 3 is 3 mm to 5 mm, and the yield strength of the end sealing plate 3 is 200 MPa to 400 MPa. When the end sealing plate 3 is arranged in a circular ring shape, the inner hole of the end sealing plate 3 is connected with the inner hole of the second pile body 20, and the inner hole diameter of the end sealing plate 3 is smaller than the inner diameter of the second pile body 20, so as to prevent cement soil from passing through the inner hole of the end sealing plate 3 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 second precast pile 2, and then adjust the squeezing effect of the first protrusion 11 of the precast pile on the cement soil in the drilled hole.

[0143] In addition, when the second precast pile 2 is a hollow pile, a blocking structure can also be arranged in the inner hole of the second precast pile 2 to adjust the squeezing effect of the first protruding portion 11 of the precast pile on the cement soil in the borehole.

[0144] Furthermore, the first precast pile 1 also includes another second protrusion 15 that is fixed around the outer peripheral wall of the first pile body 10. The second protrusion 15 is located between the first protrusion 11 and the lower end of the first pile body 10. The second protrusion 15 can adopt a structure in which the first protrusion 11 and the first pile body 10 are prefabricated, or a structure in which the first protrusion 11 is prefabricated alone and then welded or detachably fixed to the first pile body 10.

[0145] When the projection of the outer peripheral wall of the first protrusion 11 along the length direction of the first pile body 10 completely overlaps with the projection of the outer peripheral wall of the second protrusion 15 along the length direction of the first pile body 10, and both the first protrusion 11 and the second protrusion 15 are solid rings, or the projection of the first protrusion 11 along the length direction of the first pile body 10 covers the projection of the second protrusion 15 along the length direction of the first pile body 10, and the projection of the outer peripheral wall of the second protrusion 15 along the length direction of the first pile body 10 is located outside the projection of the borehole along the length direction of the first pile body 10, the first protrusion 11 and the second protrusion 15 can separate the cement soil in the borehole into a closed cavity, which is formed by the first protrusion 11, the second protrusion 15, the outer peripheral wall of the first pile body 10, and the side wall of the borehole. As the first precast pile 1 is implanted, the cement soil on the lower side of the second protrusion 15 overflows into the closed cavity on the upper side of the second protrusion 15. Since it is a closed cavity, as the cement soil in the closed cavity increases, the pressure in the closed cavity continues to increase. Therefore, the squeezing effect on the cement soil in the cavity is significant during the construction process, and the cement soil can more effectively enter the soil gaps around the hole wall, thereby improving the bonding strength between the solidified soil 5 around the pile and the original soil of the hole wall, increasing the limit friction resistance of the interface S2 between the solidified soil 5 around the pile and the original soil 4 around the hole wall, and improving the bearing capacity of the single pile after the combined assembly is implanted.

[0146] When the outer diameter of the first protrusion 11 and the second protrusion 15 is larger than the borehole diameter, additional downward pressure is required to implant the prefabricated pile into the borehole. As mentioned above, a closed cavity is formed between the second protrusion 15, the outer peripheral wall of the first pile body 10 and the borehole wall. In this case, it may be difficult to push the pile downward when applying pressure. For this reason, see Figure 2 In some examples, at least one pressure relief channel 151 is provided on the second protruding portion 15 , and the pressure relief channel 151 penetrates the second protruding portion 15 along the length direction of the first pile body 10 .

[0147] Furthermore, the second protrusion 15 is provided with more than two pressure relief channels 151 evenly distributed along the circumferential direction. The pressure relief channels 151 can all be through holes or notches, or a combination of through holes and notches. Specifically, the combination can be set according to the degree of influence of the pile foundation construction environment on the surrounding environment. When the pressure relief channel 151 is a notch, the radial dimension of the pressure relief channel 151 is not less than 50 mm, and the arc length of a single pressure relief channel 151 is not greater than / the circumference of the borehole and not less than / the circumference of the borehole. When the pressure relief channel 151 is a notch, the projection of the outer peripheral wall of the first protrusion 11 along the length direction of the first pile body 10 partially overlaps the projection of the outer peripheral wall of the second protrusion 15 along the length direction of the first pile body 10; when the pressure relief channel 151 is a through hole, the projection of the outer peripheral wall of the first protrusion 11 along the length direction of the first pile body 10 completely overlaps the projection of the outer peripheral wall of the second protrusion 15 along the length direction of the first pile body 10.

[0148] 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.

[0149] 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.

[0150] 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 composite pile construction method, characterized in that: The steps include: S1. Drilling arrangement: the drilling size is designed according to the cross-sectional size of the first pile body (10) of the first precast pile (1) and / or the second pile body (20) of the second precast pile (2), the inner peripheral wall of the drilled hole surrounds the outer side of the first pile body (10) and / or the second pile body (20) in the horizontal plane, the first pile body (10) is surrounded by a first protruding portion (11), and the inner peripheral wall of the drilled hole in the horizontal plane is completely covered by the first protruding portion (11) in the horizontal plane; S2, drilling construction: drilling according to the drilling settings; S3, grouting and planting of the second precast pile (2): comprising injecting a solidifying grout into the borehole and placing at least one of the second precast piles (2) into the borehole; S4, planting the first precast pile (1): placing the first precast pile (1) on the upper end of the second precast pile (2) at the uppermost end, and pressing the first precast pile (1) into the borehole. During and / or after the first precast pile (1) is placed into the borehole, the soil around the borehole wall and / or the solidified slurry are squeezed by the first protrusion (11).

2. The combined pile construction method according to claim 1, characterized in that: The first prefabricated pile (1) further comprises a plurality of first thickened protrusions (12), the first thickened protrusions (12) being fixed on the outer peripheral wall of the first pile body (10) and being arranged at intervals along the length direction of the first pile body (10), the inner peripheral wall of the drilled hole being projected on the horizontal plane surrounding the outer side of the projected body of the first pile body (10) and the first thickened protrusions (12) on the horizontal plane, and the projected body of the first thickened protrusions (12) on the horizontal plane being at least partially located on the outer side of the projected body of the inner peripheral wall of the first protruding portion (11) on the horizontal plane; In step S3, the grouting is to inject a certain volume of solidified slurry into the borehole, so that before the first precast pile (1) is completely pressed into the borehole, or before the first protrusion (11) contacts the uppermost first thickened protrusion (12), the liquid surface of the solidified slurry is squeezed to contact the first protrusion (11).

3. The combined pile construction method according to claim 2, characterized in that: The orthographic projection of the outer wall of the second pile body (20) on the horizontal plane completely overlaps with the orthographic projection of the first pile body (10) on the horizontal plane. The second prefabricated pile (2) further comprises a plurality of second thickened protrusions (21). The second thickened protrusions (21) are fixed around the outer wall of the second pile body (20). The orthographic projection of the outer wall of the first thickened protrusion (12) on the horizontal plane completely overlaps with the orthographic projection of the outer wall of the second thickened protrusion (21) on the horizontal plane.

4. The combined pile construction method according to claim 2, characterized in that: The first protrusion (11) is located on the upper side of the plurality of first thickened protrusions (12) and is slidably connected to the first pile body (10) along the length direction of the first pile body (10); the first protrusion (11) is an integrally formed annular metal plate; the distance between the first thickened protrusion (12) on the uppermost side of the first precast pile (1) and the upper end of the first precast pile (1) is 3 meters to 6 meters; Step S4 also includes, after placing the first prefabricated pile (1) into the borehole, driving the first protrusion (11) 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.

5. The combined pile construction method according to claim 2, characterized in that: The first protrusion (11) is located at the lower side of the first thickened protrusion (12), and the first protrusion (11) includes two or more arc-shaped metal plates (110) that can be spliced ​​to each other to form a ring shape, and the two or more arc-shaped metal plates (110) can be openably sleeved on the first pile body (10), and the ends of two adjacent arc-shaped metal plates (110) can be locked with each other; Step S4 also includes: before the first precast pile (1) is placed in the drill hole or during the process of the first precast pile (1) being placed in the drill hole, the first protrusion (11) is sleeved on the first pile body (10) at the lower side of a first thickened protrusion (12); during the process of the first precast pile (1) being placed in the drill hole, the first thickened protrusion (12) presses down the first protrusion (11) to squeeze the soil around the drill hole wall and / or the solidified slurry.

6. The combined pile construction method according to claim 2, characterized in that: The first pile body (10) and the first thickened protrusion (12) are prefabricated as a whole, the outer peripheral wall of the lower end plate of the first prefabricated pile (1) surrounds the outer side of the first thickened protrusion (12) in the horizontal plane, and the part of the lower end plate of the first prefabricated pile (1) extending out of the first pile body (10) forms the first protrusion (11); Step S4 also includes that, during the process of placing the first prefabricated pile (1) into the borehole, the first pile body (10) drives the first protrusion (11) to squeeze the soil around the borehole wall and / or the solidified slurry.

7. The combined pile construction method according to claim 2, characterized in that: The first pile body (10) and the first thickened protrusion (12) are prefabricated as a whole, the first protrusion (11) is an annular flange made of metal material, and the inner ring edge of the annular flange is welded and fixed to the outer edge of the lower end of the first prefabricated pile (1); Step S4 also includes that, before the first precast pile (1) is placed into the borehole, the two ends of the first protrusion (11) are respectively welded and fixed to the lower end of the first precast pile (1) and the upper end of the second precast pile (2); during the process of placing the first precast pile (1) into the borehole, the first precast pile (1) drives the first protrusion (11) to squeeze the soil around the borehole wall and / or the solidified slurry.

8. The combined pile construction method according to claim 12, characterized in that: The inner ring edge of the annular flange is aligned with the outer edge of the lower end of the first precast pile (1) and the outer edge of the upper end of the second precast pile (2), or the inner ring edge of the annular flange is embedded between the lower end of the first precast pile (1) and the upper end of the second precast pile (2).

9. The combined pile construction method according to claim 2, characterized in that: The first pile body (10) and the first thickened protrusion (12) are prefabricated as a whole, the first protrusion (11) is an annular flange made of metal material, and the annular flange is fixed to the lower end of the first prefabricated pile (1) by bolts or mortise and tenon structures; Step S4 also includes that before the first precast pile (1) is placed in the borehole, the two ends of the first protrusion (11) are respectively fixed to the lower end of the first precast pile (1) and the upper end of the second precast pile (2) by bolts and / or mortise and tenon structures or welding; during the process of placing the first precast pile (1) in the borehole, the first precast pile (1) drives the first protrusion (11) to squeeze the soil around the borehole wall and / or the solidified slurry.

10. The combined pile construction method according to claim 2, characterized in that: The first protruding portion (11), the first pile body (10), and the first thickened protrusion (12) are prefabricated as a whole; Step S4 also includes that, during the process of placing the first prefabricated pile (1) into the borehole, the first pile body (10) drives the first protrusion (11) to squeeze the soil around the borehole wall and / or the solidified slurry.

11. The combined pile construction method according to claim 2, characterized in that: The first pile body (10) and the first thickened protrusion (12) are prefabricated as a whole, the first protrusion (11) comprises two or more circular arc-shaped protrusions (113) which can be spliced ​​to each other, and the arc-shaped protrusions (113) are welded or detachably fixed to the first pile body (10); Step S4 also includes fixing the first protrusion (11) to the first pile body (10) during or before the first precast pile (1) is placed in the borehole, and during the process of placing the first precast pile (1) in the borehole, the first pile body (10) drives the first protrusion (11) to squeeze the soil around the borehole wall and / or the solidified slurry.

12. The combined pile construction method according to claim 11, characterized in that: A groove (117) is provided on the inner peripheral wall of the arc-shaped protrusion (113); when the arc-shaped protrusion (113) is fixed on the first thickened protrusion (12), the outer peripheral wall of the first thickened protrusion (12) and the inner side wall of the groove (117) fit each other to limit the axial position of the arc-shaped protrusion (113).

13. The combined pile construction method according to claim 12, characterized in that: The arc-shaped protrusion (113) is prefabricated from concrete, and a first embedded steel part (118) extending in the circumferential direction is embedded in at least one of the two ends of the inner peripheral wall of the arc-shaped protrusion (113) along the length direction of the first pile body (10), and a second embedded steel part (13) extending in the circumferential direction and corresponding to the first embedded steel part (118) is embedded in the first pile body (10), and the first embedded steel part (118) is correspondingly welded to the second embedded steel part (13).

14. The combined pile construction method according to claim 12, characterized in that: The arc-shaped protrusion (113) is prefabricated from concrete, and is provided with a through hole (119) extending in the radial direction, and the through hole (119) passes through the inner and outer peripheral walls of the arc-shaped protrusion (113). A bolt hole (121) is provided on the outer peripheral wall of the first thickened protrusion (12), and an expansion bolt (14) passing through the through hole (119) is installed in the bolt hole (121) to fix the arc-shaped protrusion (113) to the first thickened protrusion (12).

15. The combined pile construction method according to any one of claims 1 to 14, characterized in that: The second prefabricated pile (2) is a tubular structure with an inner cavity; Step S3 also includes fixing a blocking structure for at least partially blocking the inner cavity on at least one of the second prefabricated piles (2); or at least one of the second prefabricated piles (2) is a solid structure.

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

17. The combined pile construction method according to claim 16, characterized in that: The first pile body (10) is arranged in the shape of a hollow round pile, the end sealing plate (3) is arranged in the shape of a circular ring or a circular disc, the outer diameter of the end sealing plate (3) is not less than the inner diameter of the first pile body (10) and not greater than the outer diameter of the first pile body (10), the thickness of the end sealing plate (3) is 3 mm to 5 mm, and the yield strength of the end sealing plate (3) is 200 MPa to 400 MPa.

18. The combined pile construction method according to any one of claims 3 to 14, 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 second precast pile (2) first inserted into the borehole.

19. The combined pile construction method according to claim 18, 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.

20. The combined pile construction method according to claim 18, 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).

21. The combined pile construction method according to claim 20, 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.

22. The combined pile construction method according to any one of claims 1 to 14, 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 (12) are arranged in the shape of bamboo joints along the length direction of the first pile body (10), the first protrusion (11) is arranged in the shape of a circular ring, the first thickened protrusion (12), the first protrusion (11) and the first pile body (10) are arranged coaxially, the outer diameter of the first pile body (10) is 350 mm to 750 mm, the outer diameter of the first protrusion (11) 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 (12) is 50 mm to 150 mm larger than the outer diameter of the first pile body (10), and the outer diameter of the first protrusion (11) is 40 mm to 150 mm larger than the outer diameter of the first thickened protrusion (12).

23. The combined pile construction method according to any one of claims 1 to 14, characterized in that: The first thickened protrusion (12) and the first protruding portion (11) 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 (12) along the length direction of the first pile body (10) to the outer edge of the projection of the first protruding portion (11) 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.

24. The combined pile construction method according to any one of claims 4 to 9, characterized in that: The first pile body (10) is arranged in the shape of a hollow round pile, the first protrusion (11) is arranged in the shape of a circular ring, and the first protrusion (11) and the first pile body (10) are arranged coaxially; The thickness of the first protrusion (11) is 20 mm to 30 mm, the yield strength of the first protrusion (11) is 200 MPa to 400 MPa, the inner diameter of the first protrusion (11) is equal to the outer diameter of the first pile body (10), and the difference between the outer diameter of the first protrusion (11) and the diameter of the borehole is not less than 50 mm and not more than 150 mm.

25. The combined pile construction method according to any one of claims 1 to 14, characterized in that: The first pile body (10) is arranged in the shape of a hollow round pile, the first protrusion (11) is arranged in the shape of a circular ring, and the first protrusion (11) and the first pile body (10) are arranged coaxially; When the compression stroke of the first protrusion (11) is greater than 6 meters, the difference between the outer diameter of the first protrusion (11) and the diameter of the drill hole is equal to 50 mm; when the compression stroke of the first protrusion (11) is not greater than 6 meters, the difference between the outer diameter of the first protrusion (11) and the diameter of the drill hole is not less than 100 mm and not greater than 150 mm.

26. The combined pile construction method according to any one of claims 1 to 14, characterized in that: The compression stroke of the first protrusion (11) is defined as L1, the total pile length of the combined pile is L, and 0.5≥L1 / L≥0.06.

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