A kind of extrusion composite pile and its construction method

Abstract

The application discloses an extrusion expansion composite pile and a construction method thereof. The extrusion expansion composite pile comprises a concrete outer pile and a prefabricated core pile, the outer pile surrounds the prefabricated core pile wholly or partially, at least one composite extrusion expansion pile section is arranged on the outer pile, the composite extrusion expansion pile section comprises reverse screw threads I which are continuously spirally wound on the outer pile body, a plurality of protrusions and a cylindrical concrete-soil mixed layer which wraps the outer pile body, the reverse screw threads I and the plurality of protrusions, the reverse screw threads I are superfluid concrete solidification bodies with screw shapes, the outer diameter formed by the reverse screw threads I is D2, the outer diameter formed by the cylindrical concrete-soil mixed layer is D3, D3>D2, and the reverse screw threads I and the cylindrical concrete-soil mixed layer are in a screw nut cooperation structure. The extrusion expansion composite pile can meet the requirements of firm combination between the outer pile and the prefabricated core pile, high pile end bearing capacity and no cement soil overflow during construction.

Description

Technical Field

[0001] This invention belongs to the field of building pile construction, and specifically relates to an extrusion-expanded composite pile and its construction method. Background Technology

[0002] Cement-soil composite piles account for a significant share of building pile foundations due to their advantages, including minimal soil displacement during pile formation, wide adaptability to geological conditions, and high bearing capacity. The construction of cement-soil composite piles typically involves on-site mixing to form the cement-soil pile. However, due to factors such as geological conditions, cement slurry ratio, mixing personnel, and equipment, achieving the theoretically required uniform mixing of cement and soil is often difficult. This results in a significant amount of sediment at the bottom of the hole. The end resistance of the cement-soil composite pile formed by pressing the precast core pile into the cement-soil is very low, and the pressing of the precast core pile causes a large amount of cement-soil to overflow, resulting in material waste and environmental pollution. Furthermore, the uneven bonding strength between the cement-soil and the precast core pile is low, sometimes failing to allow for synchronous displacement between the outer pile and the core pile in the composite pile, leading to the core pile penetrating the outer pile and reducing the bearing capacity of the composite pile. Summary of the Invention

[0003] To address the shortcomings of existing cement-soil composite piles, this invention proposes an extrusion-expansion composite pile that can achieve a strong bond between the outer pile and the precast core pile, high pile end bearing capacity, and no cement-soil overflow during construction, as well as a construction method for the foundation pile.

[0004] The technical solution adopted in this invention is: a composite extrusion pile, comprising a concrete outer pile and a precast core pile, wherein the outer pile surrounds the precast core pile entirely or partially at the same center, and the outer pile is provided with at least one composite extrusion pile segment, wherein the composite extrusion pile segment comprises a continuously spirally coiled reverse thread I and several protrusions on the outer pile body, and a columnar concrete-soil mixed layer that encloses the outer pile body, the reverse thread I and the several protrusions; wherein the reverse thread I is a superfluid concrete solid with a screw-shaped shape, and the outer diameter formed by the reverse thread I is D2, and the outer diameter formed by the columnar concrete-soil mixed layer is D3, then D3>D2, and the reverse thread I and the columnar concrete-soil mixed layer have a screw-nut mating structure.

[0005] Furthermore, in the aforementioned type of extrusion-expansion composite pile, the protrusion is a superfluid concrete solid or a mixture of superfluid concrete and soil solid.

[0006] Furthermore, in the aforementioned type of extrusion-expansion composite pile, the outer pile consists entirely of threaded pile segments, except for the composite extrusion-expansion pile segments. The threaded pile segments include reverse threads II continuously spirally coiled around the outer pile body.

[0007] Furthermore, in the aforementioned type of extrusion-expansion composite pile, the reverse screw thread II is a superfluid concrete solid with a screw-shaped appearance, and the reverse screw thread II has a screw-nut fit structure with the surrounding soil.

[0008] Furthermore, in the aforementioned type of extrusion-expansion composite pile, if the outer diameter formed by the reverse thread II is D1, then D2 ≥ D1.

[0009] Furthermore, in the aforementioned type of extrusion-expanded composite pile, the precast core pile is a precast concrete pile or a precast steel pile.

[0010] Furthermore, in the aforementioned type of extrusion-expanded composite pile, a precast drill tip or plug plate is provided at the bottom end of the precast core pile.

[0011] A construction method for an expanded-expanded composite pile includes the following steps:

[0012] 1) The spiral soil squeezing drill bit with an enlarged diameter body is connected to the output end of the pile driver power head through the spiral drill rod, and the concrete delivery pump is connected to the upper end of the main shaft of the pile driver power head through the concrete delivery pipe; In the spiral soil squeezing drill bit with an enlarged diameter body, when the enlarged diameter body is in the retracted state, the outer edge of the lower part of the enlarged diameter body protrudes beyond the maximum outer edge formed by the spiral blades in the spiral soil squeezing drill bit. Let the protrusion amount be Q, then 125mm≥Q≥20mm;

[0013] 2) The enlarged body of the spiral soil-displacing drill bit is in the retracted state, the drill tip is aligned with the pile hole position, and the verticality of the drill bit is adjusted.

[0014] 3) Start the pile driver. The pile driver power head drives the spiral soil squeezing drill bit to perform spiral soil squeezing drilling through the spiral drill rod. During the drilling process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms the first positive spiral groove in the soil of the pile hole wall. The soil coming up continuously fills the first positive spiral groove.

[0015] 4) Formation of composite extrusion-expanded pile segments:

[0016] 4.1) Continue drilling to the designed depth of the composite extrusion pile section. Keep the drill bit rotating. First, start the concrete delivery pump to inject super-fluid concrete into the inner cavity of the drill bit. Then, lift the spiral extrusion drill bit 200mm to 400mm. The super-fluid concrete injected will open the drill tip assembly and be injected into the bottom of the pile hole. The super-fluid concrete will be injected to a height of 800mm to 1200mm below the bottom of the drill bit.

[0017] 4.2) Fully open the outer edge of the lower part of the auger body of the auger soil squeezing drill bit, lift the rotating drill bit and press-fill superfluid concrete. During the lifting process, the lower end of the opened auger body forms a first reverse auger groove in the soil of the pile hole wall. The first reverse auger groove and the pile hole cavity are press-filled with superfluid concrete together. Lift the drill and press-fill until the top of the composite extrusion pile section is reached, then stop lifting and press-filling.

[0018] 4.3) Release the rotating drill bit downwards again. During the drilling process of squeezing concrete, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a second positive spiral groove in the soil of the pile hole wall. The second positive spiral groove is filled with the squeezed concrete. Drill to the design depth of the composite squeezed pile section and keep the drill bit rotating.

[0019] 4.4) Raise the rotating drill bit again and inject superfluid concrete. During the lifting process, the lower end of the expanded diameter body forms a second reverse spiral groove in the pile hole wall soil. The second reverse spiral groove and the pile hole cavity are injected with superfluid concrete together. Raise the drill and inject until the top of the composite extrusion pile section is reached. The superfluid concrete in the second reverse spiral groove forms reverse spiral thread I.

[0021] During repeated drilling and lifting grouting of the composite extrusion-expanded pile section, the expansion body cuts off the continuity of the spiral groove formed in the previous process when forming the next spiral groove. The expansion body squeezes and mixes the concrete and soil in the spiral groove formed in the previous process, and the concrete in the spiral groove formed in the previous process forms several protrusions on the outer pile body.

[0022] During the secondary drilling process, the lower part of the drill bit radially squeezes the concrete in the spiral groove and the hole wall of the composite extrusion pile section (120), forcing some of the concrete to squeeze into the surrounding soil and further squeezing the surrounding soil to form a columnar concrete-soil mixture layer.

[0023] During the secondary drilling process of the composite extrusion pile section, the compressed concrete pushes the soil on the spiral extrusion drill bit to move upward, compacting the soil remaining on the spiral extrusion drill bit.

[0024] 5) Formation of threaded pile segments

[0025] Retract the enlarged body of the spiral soil squeezing drill bit, continue to lift the rotating drill bit and pressurize it with superfluid concrete, lift the rotating drill bit to the surface outside the hole, during the lifting process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a third reverse spiral groove in the soil of the pile hole wall, the third reverse spiral groove and the pile hole cavity are pressurized with superfluid concrete to form a continuous reverse spiral thread II.

[0026] 6) After the outer pile is poured, the precast core pile is inserted into the outer pile.

[0027] Furthermore, the above construction method, steps 5) and 6) are further described as follows:

[0028] 5) Formation of threaded pile segment (130)

[0029] The enlarged body of the spiral soil-squeezing drill bit is retracted, and the rotating drill bit is continuously lifted and superfluid concrete is injected. During this lifting and injection process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a third reverse spiral groove in the soil of the pile hole wall. At the same time, the third reverse spiral groove formed is injected with superfluid concrete along with the pile hole cavity. After lifting and injection to a certain height from the ground surface outside the pile hole, the injection is stopped, and the rotating drill bit is continuously lifted to the ground surface outside the pile hole. During this lifting process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit continues to squeeze out a third reverse spiral groove in the soil of the pile hole wall, forming a third reverse spiral groove and a pile hole with an empty upper end.

[0030] 6) After the outer pile is poured, the precast core pile is inserted into the outer pile. During the process of inserting the precast core pile into the outer pile, the precast core pile squeezes the super-fluid concrete in the pile hole, squeezes and expands the surrounding soil, and squeezes the super-fluid concrete to flow into the empty third reverse spiral groove and pile hole at the top of the pile hole, filling the third reverse spiral groove and pile hole, and finally forming a continuous reverse spiral thread II.

[0031] Furthermore, in the above construction method, during the formation of the composite extrusion pile section in step 4), the enlarged body in the spiral extrusion drill bit is always in a retracted state.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention uses a spiral extrusion drill bit with an enlarged diameter body. When the enlarged diameter body is in the retracted state, its lower end protrudes from the maximum outer diameter profile of the drill bit. During pile construction, it can maximize the outer diameter of the extruded pile section and also meet the requirements for the formation of the outer pile of the threaded pile section.

[0034] 2. The expansion composite pile provided by this invention features a screw-tooth pile segment where the outer pile is connected to the surrounding soil in a screw-nut fit. This results in a high bonding force between the outer pile and the surrounding soil, which is beneficial for improving the bearing capacity of the composite pile. Simultaneously, the surrounding soil of the outer pile is compacted, further enhancing the bonding force between the outer pile and the surrounding soil.

[0035] 3. The expanded composite pile provided by this invention features an outer pile formed through multiple compaction processes, resulting in thorough compaction of the surrounding soil. The core concrete-compacted threaded pile segment is bonded to the outer concrete-soil mixture layer using a screw-nut fit, resulting in high strength. The bond between the compacted surrounding soil and the concrete-soil mixture layer is stronger than that between ordinary piles and soil, thus improving the bearing capacity of the composite pile. The protrusions on the outer pile also increase the bonding force between the outer pile and the concrete-soil mixture layer. This invention, with its expanded composite pile segment, is suitable for plastic to hard cohesive soils, silt, sand, gravelly soil, completely weathered rock, and strongly weathered rock layers.

[0036] 4. The extrusion-expanded composite pile provided by this invention has high end resistance. The end cross-section of the composite extrusion-expanded pile segment is large, and the soil at the bottom end is in a compacted state. In particular, the composite pile with multiple composite extrusion-expanded pile segments in the outer pile has even higher end resistance, which can fully utilize the end bearing potential of the foundation soil and achieve energy saving.

[0037] 5. The extrusion-expanded composite pile provided by this invention has a strong bond between the precast core pile and the concrete outer pile. The outer pile is made of super-fluid concrete, which is of reliable quality and has good uniformity of centralized mixing. The bond between the outer pile and the precast core pile is free of impurities and gaps. In particular, the precast core pile is constructed by post-pressing, which further compacts the concrete and increases the bonding force between the concrete outer pile and the precast pile (core pile).

[0038] 6. The extrusion-expansion composite pile provided by the present invention can have its precast core pile bottom constructed inside the concrete outer pile or through the concrete outer pile, which can meet the requirements of different bearing strata and soil layers.

[0039] 7. The extrusion-expanded composite pile provided by the present invention allows the amount of concrete poured into the outer pile to be estimated based on the volume of the core pile and the diameter and depth of the borehole, ensuring that the poured concrete does not overflow to the surface outside the hole when the core pile is driven in, thus avoiding waste.

[0040] 8. The extrusion-expansion composite pile provided by this invention, for pile foundations with negative skin friction in the near-surface soil layer, can avoid setting up external piles in the negative skin friction soil layer by reasonably controlling the amount of concrete poured into the external pile, which is conducive to improving the bearing capacity of the extrusion-expansion composite pile and reducing the pile construction cost.

[0041] 9. The extrusion-expanded composite pile provided by this invention is adaptable to a wide range of strata, which can expand the strata in which precast piles can be used, and is conducive to promoting the prefabricated development of pile foundations and achieving low carbon emission reduction.

[0042] 10. The expansion composite pile provided by the present invention has a pile hole formed by spiral extrusion drilling, which is a partial extrusion hole formation, with less residual soil discharge and less negative extrusion effect.

[0043] 11. The extrusion-expansion composite pile provided by this invention, under the influence of the reverse force of the soil at the pile hole position during extrusion drilling, has a much higher compaction of the soil between the spiral blades of the extrusion drill bit than that between the spiral blades of the non-extrusion drill bit. During the process of drilling the outer pile of the extrusion-expansion composite pile to form the extrusion-expansion pile section, the soil remaining between the spiral blades of the extrusion drill bit is further squeezed and compacted, which further strengthens the bonding force between the soil and the surface of the spiral blades and the core tube. During the process of stopping the pressure grouting and lifting the drilling tool, the soil between the spiral blades of the drill bit will not fall down, thus ensuring the quality of the concrete in the pile hole.

[0044] 12. The extrusion-expansion composite pile provided by the present invention adopts the post-pressing construction of precast core piles. First, it compacts the concrete outer pile body in the pile hole. Second, the soil around the outer pile is further compacted by the compressed concrete, thereby improving the bonding force between the soil around the outer pile and the outer pile.

[0045] 13. The extrusion-expansion composite pile provided by the present invention has a pile tip at the bottom of the core pile, which is conducive to the radial extrusion of concrete during the pressing of the core pile, and the soil around the outer pile has better compaction.

[0046] 14. In the extrusion-expansion composite pile provided by the present invention, when the core pile is a precast hollow pile and its bottom end is not sealed, some concrete will enter the inner cavity of the core pile during the pressing process, which improves the strength of the core pile body. Attached Figure Description

[0047] Figure 1 This is a structural schematic diagram of the first type of extrusion-expansion composite pile.

[0048] Figure 2 This is a structural schematic diagram of the second type of extrusion-expansion composite pile.

[0049] Figure 3 This is a structural schematic diagram of the third type of extrusion-expansion composite pile.

[0050] Figure 4 This is a structural diagram of the fourth type of extrusion-expanded composite pile.

[0051] Figure 5 This is a front view schematic diagram of a spiral soil-displacing drill bit.

[0052] Figure 6 This is a cross-sectional schematic diagram of a spiral soil-displacing drill bit (with the enlarger body retracted and the drill tip assembly closed).

[0053] Figure 7 This is a cross-sectional schematic diagram of a spiral soil-displacing drill bit (with the enlarged body open and the drill tip assembly in the open state).

[0054] Figure 8 This is a schematic front view (sectional view) of the expanded diameter body.

[0055] Figure 9 yes Figure 7 A top-down view.

[0056] Figure 10 This is a schematic diagram of the construction process.

[0057] Figure 11 This is a schematic diagram of the construction process.

[0058] Figure 12 This is a schematic diagram of the construction process.

[0059] Figure 13This is a schematic diagram of the construction process. Detailed Implementation

[0060] Example 1: An extruded and expanded composite pile and its construction method

[0061] (I) Structure of Expansion-Expanded Composite Piles

[0062] An extrusion-expanded composite pile includes a concrete outer pile (100) and a precast core pile (200), wherein the outer pile (100) surrounds the precast core pile (200) entirely or partially at the center.

[0063] At least one composite extrusion pile segment (120) is provided on the outer pile (100), and all other piles on the outer pile (100) except for the composite extrusion pile segment (120) are threaded pile segments (130). The composite extrusion pile segment (120) is suitable for plastic to hard cohesive soil, silt, sand, gravelly soil, completely weathered rock, strongly weathered rock and other soil and rock layers.

[0064] like Figure 1 The first type of extrusion-expanded composite pile is shown. A composite extrusion-expanded pile section (120) is provided on the outer pile (100) and is located at the bottom of the pile. The upper end of the composite extrusion-expanded pile section (120) is a threaded pile section (130). The outer pile (100) completely surrounds the precast core pile (200) at the same center.

[0065] like Figure 2 The second type of extrusion-expanded composite pile is shown. A composite extrusion-expanded pile section (120) is provided on the outer pile (100) and is located at the bottom of the pile. The upper end of the composite extrusion-expanded pile section (120) is a threaded pile section (130). The outer pile (100) surrounds the precast core pile (200) at the same center.

[0066] like Figure 3 The third type of extrusion-expanded composite pile is shown. The outer pile (100) is provided with two composite extrusion-expanded pile segments (120) and are respectively set at the bottom and middle of the pile. There are threaded pile segments (130) at the upper end of the composite extrusion-expanded pile segment (120) and between the two composite extrusion-expanded pile segments (120). The outer pile (100) surrounds the precast core pile (200) at the center.

[0067] like Figure 4 The fourth type of extrusion-expanded composite pile is shown. A composite extrusion-expanded pile section (120) is provided on the outer pile (100) and is located in the middle of the pile. The upper and lower ends of the composite extrusion-expanded pile section (120) are threaded pile sections (130). The outer pile (100) completely surrounds the precast core pile (200) at the same center.

[0068] The composite extrusion pile segment (120) includes a reverse thread I (121) and several protrusions (122) continuously spirally wound around the outer pile body (110), and a columnar concrete-soil mixture layer (123) enclosing the outer pile body (110), the reverse thread I (121), and the several protrusions (122). The reverse thread I (121) is a superfluid concrete solid with a screw-like shape. Let the outer diameter formed by the reverse thread I (121) be D2, and the outer diameter formed by the columnar concrete-soil mixture layer (123) be D3, then D3 > D2. The reverse thread I (121) and the columnar concrete-soil mixture layer (123) have a screw-nut fit structure. The reverse thread I (121), the several protrusions (122), and the concrete-soil mixture layer (123) are an integral structure.

[0069] The protrusion (122) is a superfluid concrete solid or a mixture of superfluid concrete and soil solid.

[0070] The threaded pile segment (130) includes a reverse thread II (131) that is continuously spirally wound on the outer pile body (110).

[0071] Reverse thread II (131) is a superfluid concrete solid with a screw-shaped appearance. Reverse thread II (131) and the surrounding soil have a screw and nut fit structure.

[0072] Let the outer diameter formed by the reverse thread II (131) be D1, then D2 > D1.

[0073] The precast core pile (200) is a precast concrete pile, but precast steel piles can also be used.

[0074] The bottom end of the precast core pile (200) is provided with a precast drill tip or a plug plate.

[0075] Let the outer diameter or diagonal length of the precast core pile be d, and the outer diameter of the outer pile body (110) be D. Then we have: 400mm≥Dd≥100mm, 250mm≥D1-D≥40mm.

[0076] (II) Construction Method of Expansion-Expanded Composite Piles

[0077] This embodiment uses, as follows: Figures 5-9 The spiral soil-dispatch drill bit with an enlarged diameter body shown has the following structure:

[0078] The spiral soil-displacing drill bit includes a connector (1), a hollow hydraulic cylinder (2), a connecting plate (3), spiral blades (4), a core tube (5), a drill tip assembly (6), an enlarged body (7), and a concrete grouting pipe (8). The connector (1) is fixed as a whole with the core tube (5) at the same center. The spiral blade (4) is spirally wound around its outer surface. The concrete pouring pipe (8) passes through the inner cavity of the core tube (5) at the same center. Its upper end is fixed with the connector (1) and its lower end is fixed with the lower end of the core tube (5). The drill tip assembly (6) is hinged to the inner stop of the ear plate at the lower end of the core tube (5) by a pin. The drill tip assembly (6) can rotate around the pin to close or open the bottom outlet of the concrete pouring pipe. The maximum angle β when the drill tip assembly (6) is open is ≤45°. The right side of the upper part of the expansion body (7) is hinged to the hinge seat on the wall of the core tube (5) through the shaft I (7-1). The core tube (5) wall and the spiral blade (4) corresponding to the lower part of the expansion body (7) are provided with openings that allow the expansion body (7) to rotate through. (7) The upper left side is hinged to the lower end of the connecting plate (3) via shaft II (7-2). The upper end of the connecting plate (3) is hinged to the lower end of the piston rod of the hollow cylinder (2) via shaft III (3-1). The cylinder body of the hollow cylinder (2) is fixed on the inner wall of the core tube (5). The concrete grouting pipe (8) passes through the piston rod of the hollow cylinder (2) and the upper middle cavity of the expansion body (7). The movement of the piston rod of the hollow cylinder (2) at the two extreme positions above and below drives the lower part of the expansion body (7) to rotate around shaft I (7-1) via the connecting plate (3), thereby realizing the retraction and opening of the lower part of the expansion body (7). When the lower part of the expansion body (7) is in the retracted state, the outer edge of the lower part of the expansion body is outside the outer edge of the drill bit diameter, and the protrusion is Q. Then 125mm≥Q≥20mm.

[0079] This invention employs a hollow hydraulic cylinder in the expansion body of a spiral soil squeezing drill bit, which is set in an annular cavity formed by the core tube and the concrete grouting pipe. The cylinder is well sealed, ensuring safe use and smooth concrete grouting. When the expansion body is in the retracted state, its lower end protrudes beyond the outer diameter of the drill bit. During pile construction, the outer diameter of the expanded pile segment can be maximized using a single cylinder stroke, while also satisfying the formation of the outer pile of the threaded pile segment.

[0080] Construction methods for expanded-expanded composite piles, such as Figure 10-13 As shown, it includes the following steps:

[0081] 1) Connect the spiral drilling bit with an expanding body to the output end of the pile driver's power head via the spiral drill rod. Connect the concrete pump to the upper end of the pile driver's power head spindle via the concrete delivery pipe. Verify that the pile driver and its accessories meet normal construction requirements before commencing construction.

[0082] 2) The enlarged body of the auger soil-displacing drill bit is in the retracted state, the drill tip is aligned with the pile hole position, and the verticality of the drill bit is adjusted to meet the requirements;

[0083] 3) Start the pile driver. The pile driver's power head drives the spiral soil squeezing drill bit through the spiral drill rod to perform spiral soil squeezing drilling. The soil at the pile hole is directly subjected to the radial downward squeezing force of the spiral soil squeezing drill bit. For soil with high compressibility, most of the soil is squeezed into the pile hole wall. For soil with low compressibility, a small part of the soil is squeezed into the pile hole wall. The soil that is not squeezed into the pile hole wall is transported from bottom to top along the upper surface of the spiral blade of the drill bit by squeezing and peeling, and continues to be carried up to the standard spiral drill rod until it reaches the ground surface outside the hole, forming residual soil. During the drilling process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms the first positive spiral groove in the soil of the pile hole wall. The soil carried up continuously fills the first positive spiral groove.

[0084] 4) Formation of the composite extrusion-expanded pile segment (120):

[0085] 4.1) Continue drilling to the design depth of the composite extrusion pile section (120). Keep the drill bit rotating. First, start the concrete delivery pump to inject super-fluid concrete into the inner cavity of the drill bit. Then, lift the spiral extrusion drill bit 200mm to 400mm. The super-fluid concrete injected opens the drill tip assembly and is injected into the bottom of the pile hole. The concrete interface in the pile hole continues to move upward to a height of 800mm to 1200mm above the bottom of the drill bit.

[0086] 4.2) Start the hydraulic control system, supply oil to the upper cavity of the hollow cylinder inside the drill bit, and move the piston rod down to the limit stroke to fully open the outer edge of the lower part of the spiral extrusion drill bit, lift the rotating drill bit and press-fill superfluid concrete. During the lifting process, the lower end of the opened extrusion body forms the first reverse spiral groove in the soil of the pile hole wall. The first reverse spiral groove and the pile hole cavity are press-filled with superfluid concrete together. Lift the drill and press-fill until the composite extrusion pile section (120) is at its top height, and stop lifting and press-filling.

[0087] 4.3) Release the rotating drill bit downwards. The drill tip assembly, which is drilling downwards, closes the concrete pouring outlet under the action of the pressure concrete below. During the drilling process of the spiral extrusion drill bit into the concrete in the pile hole, the lower part of the drill bit radially extrudes the concrete, forcing some of the concrete to squeeze into the surrounding soil and further extruding the surrounding soil and compacting the surrounding soil. During the drilling process of the extruded concrete, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a second positive spiral groove in the soil of the pile hole wall. The second positive spiral groove is filled with the extruded concrete. At the same time, the super-fluid concrete that is extruded in the pile hole also extrudes the looser soil between the spiral blades of the drill bit and moves it upwards, and compacts the denser soil between the spiral blades of the drill bit, increasing the bonding force between the soil and the spiral blades of the drill bit and the outer surface of the core tube. Drill to the design depth of the composite extrusion pile section (120) and keep the drill bit rotating.

[0088] 4.4) Raise the rotating drill bit again and inject superfluid concrete. During the lifting process, the injected concrete opens the drill tip assembly. The lower end of the expanded diameter body squeezes and mixes the concrete and soil within its protruding height range. The squeezed concrete enters the soil and compacts the surrounding soil. The lower end of the expanded diameter body forms a second reverse spiral groove in the soil of the pile hole wall. The second reverse spiral groove and the pile hole cavity are injected with superfluid concrete together. Raise the drill and inject until the composite extrusion pile section (120) reaches its top height. Stop lifting and injecting to form a composite extrusion pile section with a core of concrete and a concrete-soil mixed layer on the outside. The core and the outside are connected by a screw and nut type, and the soil around the outer mixed layer is compacted. The second reverse spiral groove and the superfluid concrete inside form a reverse spiral I (121).

[0089] During repeated drilling and lifting, the expansion body cuts off the continuity of the spiral groove formed in the previous process when forming the next spiral groove. The expansion body squeezes and mixes the concrete and soil in the spiral groove formed in the previous process. The concrete in the spiral groove formed in the previous process forms several protrusions (122) on the outer pile body (110).

[0090] During the secondary drilling process, the lower part of the drill bit radially squeezes the concrete in the spiral groove and the hole wall, forcing some of the concrete to squeeze into the surrounding soil and further squeezing the surrounding soil to form a columnar concrete-soil mixture layer (123).

[0091] During the secondary drilling process, the compressed concrete pushes the soil on the spiral extrusion drill bit to move upward and compacts the soil remaining on the spiral extrusion drill bit.

[0092] 5) Formation of threaded pile segment (130)

[0093] The enlarged body of the spiral extrusion drill bit is retrieved, and the rotating drill bit is continuously lifted and superfluid concrete is injected. During this lifting and injection process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a third reverse spiral groove in the soil of the pile hole wall. At the same time, the third reverse spiral groove formed together with the pile hole cavity is injected with superfluid concrete. After lifting and injection to a certain height from the ground surface outside the pile hole, the injection is stopped, forming the lower part of the reverse spiral thread II (131). At the same time, the rotating drill bit is continuously lifted to the ground surface outside the pile hole. During this lifting process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit continues to squeeze out a third reverse spiral groove in the soil of the pile hole wall, forming a third reverse spiral groove and a pile hole with an empty upper end.

[0094] Because the grouting stops after the drill reaches a certain height from the ground surface outside the pile hole, the super-fluid concrete at the lower end is squeezed upward and pressed into the empty third reverse spiral groove and pile hole by the subsequent pressing of precast core piles. This can prevent concrete from overflowing the pile hole and causing waste.

[0095] 6) Insert precast core piles

[0096] After the outer pile (100) is poured, the precast core pile (200) is inserted into the outer pile. During the insertion of the precast core pile (200) into the outer pile (100), the precast core pile (200) squeezes the superfluid concrete in the pile hole, expands the surrounding soil, and squeezes the superfluid concrete to flow into the empty third reverse spiral groove at the upper end of the pile hole and the pile hole, filling the third reverse spiral groove and the pile hole, forming the upper part of the reverse thread II (131), and finally forming a continuous reverse thread II (131). This completes the process. Figure 13 The outer pile (100) shown in the middle k is provided with a composite extrusion pile section (120) and is located at the bottom of the pile. The upper end of the composite extrusion pile section (120) is a threaded pile section (130).

[0097] Of course, it can also be made as needed, such as Figure 13 As shown in (n), a composite extrusion pile section (120) is provided on the outer pile (100) and is located in the middle of the pile. The upper and lower ends of the composite extrusion pile section (120) are threaded pile sections (130), and the near-surface pile section of the extrusion composite pile does not have an outer pile (100), but only a precast core pile (200).

[0098] Of course, it can also be made as needed, such as Figure 13 As shown in the middle (m), the outer pile (100) is provided with two composite extrusion pile segments (120) and is respectively set at the bottom of the pile and the middle of the pile. The upper end of the composite extrusion pile segment (120) and the two composite extrusion pile segments (120) are all threaded pile segments (130). The near-surface pile segment of the extrusion composite pile does not have an outer pile (100), but only a precast core pile (200).

[0099] Example 2: An extrusion-expanded composite pile and its construction method

[0100] (I) Structure of Expansion-Expanded Composite Piles

[0101] Everything else is the same as in Example 1, except that D2 = D1.

[0102] (II) Construction Method of Expansion-Expanded Composite Piles

[0103] The structure and construction method of the spiral soil squeezing drill bit are the same as those in Example 1. The difference is that in the process of forming the composite extrusion and expansion pile segment (120) in step 4) of the construction method, the expansion body of the spiral soil squeezing drill bit is always in a retracted state. That is, in the construction process of the overall extrusion and expansion composite pile, the expansion body is always in a retracted state and does not open.

Claims

1. A type of extrusion-expanded composite pile, comprising a concrete outer pile (100) and a precast core pile (200), wherein the outer pile (100) concentrically surrounds all or part of the precast core pile (200), characterized in that, At least one composite extrusion pile section (120) is provided on the outer pile (100). The composite extrusion pile section (120) includes a reverse screw thread I (121) and several protrusions (122) continuously spirally coiled on the outer pile body (110) and a columnar concrete-soil mixture layer (123) that encloses the outer pile body (110), the reverse screw thread I (121) and the several protrusions (122). The reverse screw thread I (121) is a superfluid concrete solid in the shape of a screw. Let the outer diameter formed by the reverse screw thread I (121) be D2 and the outer diameter formed by the columnar concrete-soil mixture layer (123) be D3. Then D3 > D2. The reverse screw thread I (121) and the columnar concrete-soil mixture layer (123) have a screw and nut matching structure.

2. The extrusion-expansion composite pile according to claim 1, characterized in that, The protrusion (122) is a superfluid concrete solid or a mixture of superfluid concrete and soil solid.

3. The extrusion-expansion composite pile according to claim 1, characterized in that, Except for the composite extrusion pile segment (120), all the outer piles (100) are threaded pile segments (130), and the threaded pile segments (130) include reverse threads II (131) that are continuously spirally coiled on the outer pile body (110).

4. The extrusion-expansion composite pile according to claim 3, characterized in that, Reverse thread II (131) is a superfluid concrete solid with a screw-shaped appearance. Reverse thread II (131) and the surrounding soil have a screw and nut fit structure.

5. The extrusion-expansion composite pile according to claim 3, characterized in that, Let the outer diameter formed by the reverse thread II (131) be D1, then D2≥D1.

6. The extrusion-expansion composite pile according to claim 1, characterized in that, The precast core pile (200) is a precast concrete pile or a precast steel pile.

7. The extrusion-expansion composite pile according to claim 6, characterized in that, The bottom end of the precast core pile (200) is provided with a precast drill tip or a plug plate.

8. A construction method for an expanded-expansion composite pile according to any one of claims 3-7, characterized in that, The construction method includes the following steps: 1) The spiral soil squeezing drill bit with an enlarged diameter body is connected to the output end of the pile driver power head through the spiral drill rod, and the concrete delivery pump is connected to the upper end of the main shaft of the pile driver power head through the concrete delivery pipe; In the spiral soil squeezing drill bit with an enlarged diameter body, when the enlarged diameter body is in the retracted state, the outer edge of the lower part of the enlarged diameter body protrudes beyond the maximum outer edge formed by the spiral blades in the spiral soil squeezing drill bit. Let the protrusion amount be Q, then 125mm≥Q≥20mm; 2) The enlarged body of the spiral soil-displacing drill bit is in the retracted state, the drill tip is aligned with the pile hole position, and the verticality of the drill bit is adjusted. 3) Start the pile driver. The pile driver power head drives the spiral soil squeezing drill bit to perform spiral soil squeezing drilling through the spiral drill rod. During the drilling process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms the first positive spiral groove in the soil of the pile hole wall. The soil coming up continuously fills the first positive spiral groove. 4) Formation of the composite extrusion-expanded pile segment (120): 4.1) Continue drilling to the design depth of the composite extrusion pile section (120). Keep the drill bit rotating. First, start the concrete delivery pump to inject super-fluid concrete into the inner cavity of the drill bit. Then, lift the spiral extrusion drill bit 200mm to 400mm. The super-fluid concrete injected will open the drill tip assembly and be injected into the bottom of the pile hole. The super-fluid concrete will be injected to a height of 800mm to 1200mm below the bottom of the drill bit. 4.2) Fully open the outer edge of the lower part of the enlarged body of the spiral soil squeezing drill bit, lift the rotating drill bit and press-fill superfluid concrete. During the lifting process, the lower end of the enlarged body forms the first reverse spiral groove in the soil of the pile hole wall. The first reverse spiral groove and the pile hole cavity are press-filled with superfluid concrete together. Lift the drill and press-fill until the top of the composite extrusion pile section (120) is reached, then stop lifting and press-filling. 4.3) Release the rotating drill bit downwards again. During the drilling process of squeezing concrete, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a second positive spiral groove in the soil of the pile hole wall. The second positive spiral groove is filled with the squeezed concrete. Drill to the design depth of the composite squeezed pile section (120) and keep the drill bit rotating. 4.4) The rotating drill bit is lifted again and superfluid concrete is injected. During the lifting process, the lower end of the expanded diameter body forms a second reverse spiral groove in the soil of the pile hole wall. The second reverse spiral groove and the pile hole cavity are injected with superfluid concrete together. The drill bit is lifted and injected until the composite extrusion pile section (120) is at its top height. The superfluid concrete in the second reverse spiral groove forms reverse screw thread I (121). During repeated drilling and lifting grouting of the composite extrusion pile section (120), the expansion body cuts off the continuity of the spiral groove formed in the previous process when forming the next spiral groove. The expansion body squeezes and mixes the concrete and soil in the spiral groove formed in the previous process. The concrete in the spiral groove formed in the previous process forms several protrusions (122) on the outer pile body (110). During the secondary drilling process, the lower part of the drill bit radially squeezes the concrete in the spiral groove and the hole wall, forcing some of the concrete to squeeze into the surrounding soil and further squeezing the surrounding soil to form a columnar concrete-soil mixture layer (123). During the secondary drilling process, the compressed concrete pushes the soil on the spiral extrusion drill bit to move upward and compacts the soil remaining on the spiral extrusion drill bit. 5) Formation of threaded pile segment (130) The enlarged body of the spiral soil squeezing drill bit is retrieved, the rotating drill bit is lifted and superfluid concrete is injected, the rotating drill bit is lifted to the surface outside the hole, during the lifting process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a third reverse spiral groove in the soil of the pile hole wall, the third reverse spiral groove and the pile hole cavity are injected with superfluid concrete together to form a continuous reverse spiral thread II (131). 6) After the outer pile (100) is poured, the precast core pile (200) is inserted into the outer pile.

9. The construction method according to claim 8, characterized in that, Steps 5) and 6) are as follows: 5) Formation of threaded pile segment (130) The enlarged body of the spiral soil-squeezing drill bit is retracted, and the rotating drill bit is continuously lifted and superfluid concrete is injected. During this lifting and injection process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit forms a third reverse spiral groove in the soil of the pile hole wall. At the same time, the third reverse spiral groove formed is injected with superfluid concrete along with the pile hole cavity. After lifting and injection to a certain height from the ground surface outside the pile hole, the injection is stopped, and the rotating drill bit is continuously lifted to the ground surface outside the pile hole. During this lifting process, the part of the enlarged body on the drill bit that protrudes from the maximum outer edge of the drill bit continues to squeeze out a third reverse spiral groove in the soil of the pile hole wall, forming a third reverse spiral groove and a pile hole with an empty upper end. 6) After the outer pile (100) is poured, the precast core pile (200) is inserted into the outer pile. During the process of inserting the precast core pile (200) into the outer pile (100), the precast core pile (200) squeezes the superfluid concrete in the pile hole, squeezes and expands the surrounding soil, and squeezes the superfluid concrete to flow into the empty third reverse spiral groove and pile hole at the top of the pile hole, filling the third reverse spiral groove and pile hole, and finally forming a continuous reverse spiral thread II (131).

10. The construction method according to claim 8 or 9, characterized in that, Step 4) During the formation of the composite extrusion pile segment (120), the enlarged body in the spiral extrusion drill bit is always in a retracted state.

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