A cast-in-place pile with a conical pile section with an enlarged diameter, a drill bit for pile construction, and a pile construction method

Abstract

The invention relates to a cast-in-place pile with an enlarged diameter conical pile section, a drill bit for pile formation, and a pile construction method. The cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile and a conical pile bottom. The outer edge of the main column cast-in-place pile is provided with a plurality of sections of an enlarged diameter conical pile section with an integral structure. The enlarged diameter conical pile section comprises one or two types of an enlarged diameter conical screw thread pile section and an enlarged diameter conical composite compact pile section. The structure of the enlarged diameter conical screw thread pile section is that an integral screw thread I is provided on the outer edge of the main column cast-in-place pile, and the outer edge of the integral screw thread I constitutes a cone. The structure of the enlarged diameter conical composite compact pile section is that an integral structure is provided on the outer edge of the main column cast-in-place pile, and the upper part is a composite compact column pile section and the lower part is a composite compact cone pile section. The outer edges of the composite compact column pile section and the composite compact cone pile section are wrapped with a composite compact reinforcement layer. The cast-in-place pile created by the invention has high bearing capacity, energy saving and environmental protection.

Description

Technical Field

[0001] The invention belongs to the field of foundation pile construction of building construction, and specifically relates to a cast-in-place pile with a conical pile section with an enlarged diameter, a drill bit for pile formation, and a pile formation method. Background Art

[0002] Among the building pile foundations, cast-in-place concrete piles have a wide range of applicable geological conditions. The pile diameter and pile length can be determined by the requirements of engineering geology and pile bearing capacity. Most of them are rotary bored piles and long spiral bored piles. They have the advantages of good pile quality, high construction efficiency, and high bearing capacity. However, due to the simple type of the pile, the stress between the pile and the soil is not fully exerted, resulting in a low bearing capacity. At the same time, a large amount of residual soil is discharged, which is not environmentally friendly. Summary of the invention

[0003] In view of the above problems, one of the purposes of the present invention is to provide a new pile type with high bearing capacity, energy saving and environmental protection - a cast-in-place pile with a conical pile section with an enlarged diameter.

[0004] A second object of the invention is to provide a drill bit for forming cast-in-place piles with a conical pile section having an enlarged diameter.

[0005] The third purpose of the invention is to provide a method for constructing a cast-in-place pile with a conical pile section with an enlarged diameter.

[0006] The technical solution adopted by the invention is: a cast-in-place pile with an enlarged diameter conical pile section, comprising a main column cast-in-place pile, the bottom end of the main column cast-in-place pile is a conical pile bottom, and the outer edge of the main column cast-in-place pile is provided with a plurality of sections of enlarged diameter conical pile sections with an integral structure, the enlarged diameter conical pile sections include one or two types of enlarged diameter conical screw thread pile sections and enlarged diameter conical complex compacted pile sections; the structure of the enlarged diameter conical screw thread pile section is that a screw thread I with an integral structure, spirally coiled around the outer edge of the main column cast-in-place pile, and gradually increasing in outer diameter from bottom to top is provided on the outer edge of the main column cast-in-place pile, The outer edge of the integral screw thread I constitutes a cone, and the cross-section of the screw thread I is a trapezoidal structure; the structure of the expanded diameter cone-shaped composite compaction pile section is that an upper portion of an integrated structure is formed on the outer edge of the main columnar cast-in-place pile, which is a composite compaction column pile section and a lower portion is a composite compaction cone pile section, the outer edge of the composite compaction cone pile section constitutes a cone, and the outer edges of the composite compaction column pile section and the composite compaction cone pile section are wrapped with a composite compaction reinforcement layer.

[0007] Furthermore, the above-mentioned cast-in-place pile with an enlarged diameter conical pile section has a plurality of sections of enlarged diameter cylindrical screw-thread pile sections with an integral structure formed on the outer edge of the main cylindrical cast-in-place pile. The structure of the enlarged diameter cylindrical screw-thread pile sections is that an integral structure of screw thread II is formed on the outer edge of the main cylindrical cast-in-place pile and is spirally coiled around the outer edge of the main cylindrical cast-in-place pile, and the outer edge of the integral screw thread II constitutes a columnar body.

[0008] Furthermore, in the above-mentioned cast-in-place pile with an enlarged diameter conical pile section, the diameter of the main column cast-in-place pile is d, the outer diameter of the enlarged diameter cylindrical screw pile section is D, the outer diameter of the composite compacted column pile section is D1, the maximum outer diameter of the composite compacted reinforced layer is D4, the outer diameter of the smallest end of the enlarged diameter conical screw pile section is D2, the outer diameter of the largest end is D3, the pitch of screw thread I is T1, and the pitch of screw thread II is T2, then: d=400-800mm, D>d, D1>d, D3>D2>d, D4>D1, D / T2=1.1-1.5; the pitch T1 of the enlarged diameter conical screw pile section increases with the increase of the outer diameter of the screw thread, and the ratio of the diameter formed by the outer edge of screw thread I at any point in the enlarged diameter conical screw pile section around the center of the main column cast-in-place pile to the pitch T1 between the upper and lower adjacent screw threads I (201) is between 1.1 and 1.5.

[0009] Furthermore, in the above-mentioned cast-in-place pile with an enlarged diameter tapered pile section, the structure of thread I and thread II is that the thread height is h, the thread outer thickness is b1, and the inner thickness is b2, then: h = 50-200mm, b1 = 50-80mm, b2 = 100-200mm.

[0010] A drill bit for forming a cast-in-place pile with an enlarged diameter conical pile section, comprising a joint, a spiral column soil squeezing blade, a column core tube, a cone core tube, a spiral cone soil squeezing blade and a drill tip gate, and is provided with a cylinder device, an enlarged diameter slider device, a fixed seat, a cylinder ear plate, shaft I, shaft II and shaft III; the fixed seat is installed at the connection between the column core tube and the cone core tube, and penetrates the column core tube, the cone core tube and the spiral column soil squeezing blade; the cylinder device is placed in the inner cavity of the column core tube, and the cylinder device includes a main Oil cylinder, protective tube I, auxiliary oil cylinder, protective tube II and push rod, the extended end of the piston rod of the main oil cylinder is fixed to the cylinder sleeve end of the auxiliary oil cylinder, the extended end of the piston rod of the auxiliary oil cylinder is fixed to one end of the push rod, one end of the protective tube I is fixed to the outer wall of the cylinder sleeve of the auxiliary oil cylinder, and the other end is movably sealed with the outer diameter of the cylinder sleeve of the main oil cylinder; one end of the protective tube II is fixed to the outer wall of the cylinder sleeve of the auxiliary oil cylinder, and the other end is movably sealed with the outer diameter of the push rod; the exposed end of the push rod is provided with a connecting ear seat I; the exposed end of the main oil cylinder is provided with a connecting ear seat II; The diameter-expanding slider device is fixed as a whole by a sleeve, a slider and a connecting plate. The sleeve is installed in a fixed seat through shaft III and rotates around shaft III. The cylinder ear plate is fixed on the inner wall of the column core tube. One end of the cylinder device is hinged to the cylinder ear plate through the connecting ear seat II and shaft I. The other end of the cylinder device is hinged through the connecting ear seat I, shaft II and the connecting plate of the diameter-expanding slider device. The slider is driven to rotate around shaft III through the telescopic movement of the cylinder device. The working end of the slider is a trapezoidal structure.

[0011] Furthermore, the above-mentioned bored pile drill bit with an enlarged diameter conical pile section, the joint, the column core tube and the cone core tube are concentrically fixed into one body, and the inner cavity forms a channel for concrete to pass through, the spiral column soil squeezing blades are spirally wound and fixed on the outer edges of the joint and the column core tube, the spiral cone soil squeezing blades are spirally wound and fixed on the outer edge of the cone core tube, the upper end faces of the spiral cone soil squeezing blades are correspondingly connected to the lower end faces of the spiral column soil squeezing blades, and the lower ends of the spiral cone soil squeezing blades are provided with cutting teeth.

[0012] Furthermore, in the above-mentioned bored pile drill with an enlarged diameter conical pile section, the drill tip door is installed on the lower end surface of the conical core tube, and the drill tip door is movably connected to the lower end of the conical core tube by a pin. The drill tip door rotates downward around the pin through a maximum angle δ, 35°≤δ≤45°, to open the drill bit outlet to the maximum opening, and the drill tip door rotates upward around the pin to the lower end surface of the conical core tube to close the drill bit outlet.

[0013] Furthermore, in the above-mentioned bored pile drill bit with an enlarged diameter conical pile section, the joint, spiral cylindrical soil-extruding blades and cylindrical core tube constitute the cylindrical structure part of the drill bit device, and its outer edge is a cylinder; the conical core tube, spiral cone soil-extruding blades and drill tip gate constitute the conical structure part of the drill bit device, and its outer edge is a cone.

[0014] A method for constructing a cast-in-place pile with a conical pile section with an enlarged diameter, using the drill bit, comprises the following steps:

[0015] 1) The drill bit joint is used to assemble the soil squeezing drill rod with the spiral soil squeezing pile driver and the concrete pumping device, the oil cylinder device is connected to the hydraulic control system, the slider of the drill bit expansion slider device is in a retracted state, and the pile driver is aligned with the pile position;

[0016] 2) Start the pile driver, the power head drives the drill bit to rotate through the soil-squeezing drill rod, and drills slowly at first. After the hole position is confirmed, drill normally. The drill bit squeezes the rock and soil at the pile hole position into a small-diameter cone hole. As the drill bit moves downward, the small-diameter cone hole is squeezed and expanded into a large-diameter cone hole until the foundation pile hole diameter is reached. The soil is squeezed and drilled until the designed hole depth is reached, and the rotation continues for 2 to 3 minutes in situ to fully squeeze the rock and soil at the bottom and wall of the foundation pile hole;

[0017] 3) While lifting the drill bit and drill rod and pumping concrete, follow the construction sequence from the bottom of the pile to the top section by section to complete the construction of each pile section:

[0018] 3.1) Main column cast-in-place pile and conical pile bottom

[0019] First, the drill bit at the bottom of the pile hole is pumped with concrete to the bottom of the drill bit cavity, and then the drill bit and drill rod rotating in the drilling direction are lifted, the drill lifting speed is kept matching with the pump pressure injection volume, the drill is lifted and pressure injection is performed until the column pile hole diameter is reached, and the injection construction of the conical pile bottom is completed; the drill is continued to be lifted and pressure injection is performed to the column pile hole to the design height of the main column cast-in-place pile top, and the injection construction of the main column cast-in-place pile is completed. During this process, the slider of the drill bit internal diameter expansion slider device is in a fully retracted state;

[0020] 3.2) Expanded diameter cylindrical screw thread pile section

[0021] During the process of lifting the drill to cast the main column cast-in-place pile section, when it is necessary to set the enlarged diameter cylindrical body screw thread pile section, the hydraulic control system is used to first drive the auxiliary cylinder piston rod in the cylinder device to fully extend, and then drive the main cylinder piston rod in the cylinder device to extend. According to the designed height of the screw thread of the enlarged diameter cylindrical body screw thread pile section, a fixed extension amount of the main cylinder piston rod is determined to push and control the extension amount of the slider in the enlarged diameter slider device, and the drilling direction of the drill bit and the drill rod is rotated by one turn, and the screw pitch is lifted upward. At the same time, matching with the pump pressure pouring, the spiral screw thread groove squeezed out by the slider in the pile hole wall is poured with concrete together with the pile hole, and it is lifted and poured to the designed height to complete the pouring construction of the enlarged diameter cylindrical body screw thread pile section;

[0022] 3.3) Expanded diameter cone-shaped compacted pile segment

[0023] During the process of lifting the drill to cast the main column cast-in-place pile section, when it is necessary to set the expanded diameter cone body re-extruded pile section, the main column cast-in-place pile that has been cast is rotated downward again to squeeze the concrete in the pile hole and drill, and the rock and soil hole wall of the pile is squeezed and expanded by the squeezed concrete, and a re-extruded and dense reinforcement layer is formed in the hole wall after the squeezing and expansion. A small part of the concrete in the pile hole is squeezed into the re-extruded and dense reinforcement layer, and most of it remains in the rock and soil hole cavity that has been squeezed and expanded. The drilling is carried out until the designed depth of the expanded diameter cone body re-extruded pile section, and then the concrete is pumped to the bottom of the drill bit inner cavity, and then the drilling tool rotating in the drilling direction is lifted, and the matching degree of the lifting drill speed and the pumping pressure injection volume is maintained. The newly injected concrete and the concrete remaining in the squeezed and expanded rock and soil hole cavity are integrated, and the drill is lifted and pressure-injected to the designed elevation to complete the pouring construction of the expanded diameter cone body re-extruded pile section. During this process, the slider of the expansion slider device in the drill bit is in a fully retracted state;

[0024] 3.4) Expanded diameter tapered thread pile section

[0025] During the process of lifting the drill to cast the main column cast-in-place pile section, when it is necessary to set the enlarged diameter conical screw thread pile section, the hydraulic control system is used to first drive the piston rod of the auxiliary cylinder in the cylinder device to fully extend, drive the slider in the enlarged diameter slider device to partially extend, and then drive the piston rod of the main cylinder in the cylinder device to extend at a uniform speed to match the length of the enlarged diameter conical screw thread pile section with the total amount of uniform extension of the main cylinder piston rod, and rotate the drilling direction of the drill bit and the drill rod by one turn, lift one pitch upward, and match the pump pressure pouring at the same time, the slider squeezes out a gradually deepening spiral screw thread groove in the pile hole wall, and pours concrete together with the pile hole, lifts and pours to the designed height, and completes the pouring construction of the enlarged diameter conical screw thread pile section;

[0026] 4) Place the prefabricated steel cage or prefabricated parts into the poured pile hole to form a pile.

[0027] The beneficial effects of the present invention are:

[0028] 1. The cast-in-place pile with an expanded diameter cone pile section created by the present invention has a strong bearing capacity. The single-squeezing pile hole is formed by squeezing the soil with a cone-shaped drill bit. The soil is squeezed fully, and the standard value of the ultimate side resistance of the rock and soil layer of the pile hole wall is improved. The bottom of the single-squeezing cone pile has a wedge-shaped squeezing and expansion effect, and the end bearing capacity is good; the double-squeezing column pile section and the double-squeezing cone pile section The outer double-squeezing reinforcement layer increases the side resistance surface area of ​​the pile section on the one hand, and on the other hand, the double-squeezing reinforcement layer changes the sliding surface of the pile section under stress damage. The action between pile (concrete) and soil is changed into action between soil and soil, so that the bearing capacity is improved. At the same time, the composite compaction reinforcement layer outside the composite compaction cone pile section effectively increases the geometric size of the cone, and the wedge-shaped extrusion effect is enhanced. Within the specified pitch range of the enlarged diameter cylindrical screw thread pile section, the outer contour surface of the screw thread is the failure interface, and the side resistance value of the pile section is the friction force (shear resistance of the soil) value of the soil-soil interface. Under the condition of meeting the high bearing capacity, the cost between the screw threads of the pile section is reasonably reduced. The enlarged diameter conical screw thread pile section is a combination of the advantages of the enlarged diameter cylindrical screw thread pile section and the composite compaction cone pile section. The failure sliding surface is the outer contour of the screw thread, which is reflected on the soil-soil interface. The failure interface is conical and has a wedge-shaped extrusion effect, and the bearing capacity of the pile section will be higher.

[0029] 2. The cast-in-place pile with an expanded diameter cone pile section created by the present invention is suitable for different soil properties, and the corresponding pile sections are designed and implemented, with high efficiency. According to different rock and soil layers, the pile type with different pile section combinations is selected and designed to give full play to the stress effect between the pile and the soil, improve the bearing capacity of the pile, and reduce the cost of pile construction. Soft soil layers such as clay, silt, and sand are suitable for expanded diameter cylindrical screw-tooth pile sections and expanded diameter cone screw-tooth pile sections, especially soft soil layers with gradually increasing compressibility of rock and soil from bottom to top, which are more suitable for expanded diameter cone screw-tooth pile sections; dense gravel sand, garden gravel, angular gravel, crushed stone, pebbles, fully weathered rock and other harder rock and soil layers are suitable for expanded diameter cone re-compacted pile sections; hard rock and soil layers such as strongly weathered rock and moderately weathered rock are suitable for the conical pile bottom of one-time soil extrusion and the main columnar pile section of one-time soil extrusion.

[0030] 3. The cast-in-place pile with the expanded diameter cone-shaped pile section created by the present invention is energy-saving and environmentally friendly, and has good pile quality reliability. There is no mud, vibration, or noise during construction, and less residual soil is discharged. The pile can be formed by a single machine operation, and the operation is simple, the controllability is strong, and the efficiency is high.

[0031] 4. The drill bit for pile formation with an expanded diameter conical pile section created by the present invention has a simple structure and good rationality. The cone structure of the drill bit squeezes soil (including concrete) to form holes reasonably, squeezes soil (including concrete) fully, and has good penetration ability. The bottom of the pile formed by the first squeeze, the double squeeze pile section and the lower part of the double squeeze reinforcement layer are all cone-shaped, with a wedge-shaped squeezing and expansion effect, which is conducive to the improvement of bearing capacity; the expansion slider device for squeezing the screw groove is set at the lower end of the drill bit column structure part, and is also under the drill bit buried depth interface when pouring concrete, which is conducive to the pouring of concrete in the screw groove, avoiding the adverse effects of groundwater, and also meeting the smoothness of the concrete channel in the inner cavity of the drill bit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic structural diagram of a drill bit for forming a bored pile with a conical pile section having an enlarged diameter.

[0033] Figure 2 The present invention is a side view of a drill bit for forming a bored pile with a conical pile section having an enlarged diameter (with the slider retracted).

[0034] Figure 3 The present invention is a side view of a drill bit for forming a cast-in-place pile with a conical pile section having an enlarged diameter (with a slider partially extended).

[0035] Figure 4 The present invention is a side view of a drill bit for forming a cast-in-place pile with a conical pile section having an enlarged diameter (the slider is in a fully extended state).

[0036] Figure 5 It is a structural schematic diagram of the oil cylinder device created by the present invention.

[0037] Figure 6 It is a schematic diagram of the first structure of a cast-in-place pile with a conical pile section with an enlarged diameter created by the present invention.

[0038] Figure 7 It is a second structural schematic diagram of a cast-in-place pile with a conical pile section with an enlarged diameter created by the present invention.

[0039] Figure 8 It is a third structural schematic diagram of a cast-in-place pile with a conical pile section with an enlarged diameter created by the present invention.

[0040] Fig. 9 It is a fourth structural schematic diagram of a cast-in-place pile with a conical pile section with an enlarged diameter created by the present invention.

[0041] Fig.10 It is a fifth structural schematic diagram of the cast-in-place pile with a conical pile section with an enlarged diameter created by the present invention.

[0042] Fig.11It is a sixth structural schematic diagram of a cast-in-place pile with a conical pile section with an enlarged diameter created by the present invention.

[0043] Fig.12 It is a schematic diagram of the wedge-shaped squeezing and expansion effect of a cone.

[0044] Fig.13 The present invention provides a pile construction drawing for a cast-in-place pile with a conical pile section with an enlarged diameter. DETAILED DESCRIPTION

[0045] Example 1

[0046] like Figure 1-Figure 5 As shown, a drill bit for bored piles with an enlarged diameter conical pile section comprises a joint (1), a spiral cylindrical soil-squeezing blade (2), a cylindrical core tube (3), a conical core tube (4), a spiral conical soil-squeezing blade (5), a drill tip door (6), a cylinder device (7), an enlarged diameter slider device (8), a fixing seat (9), a cylinder ear plate (10), a shaft I (11), a shaft II (12) and a shaft III (13).

[0047] The joint (1), the column core tube (3) and the cone core tube (4) are coaxially fixed in sequence to form an integral body, and the inner cavity thereof forms a passage through which concrete can pass. The spiral column soil squeezing blade (2) is spirally wound and fixed on the outer edges of the joint (1) and the column core tube (3), and the spiral cone soil squeezing blade (5) is spirally wound and fixed on the outer edge of the cone core tube (4). The upper end surface of the spiral cone soil squeezing blade (5) is correspondingly connected to the lower end surface of the spiral column soil squeezing blade (2), and the lower end of the spiral cone soil squeezing blade (5) is provided with a cutting tooth (5-1).

[0048] The drill tip door (6) is installed on the lower end surface of the cone core tube (4), and is movably connected to the lower end of the cone core tube (4) through a pin (6-1). The drill tip door (6) rotates downward around the pin (6-1) to a maximum angle δ, 35°≤δ≤45°, to open the drill bit discharge port to the maximum opening, and the drill tip door (6) rotates upward around the pin (6-1) to the lower end surface of the cone core tube (4), to close the drill bit discharge port.

[0049] The joint (1), the spiral cylindrical soil squeezing blades (2) and the cylindrical core tube (3) constitute the cylindrical structure of the drill bit, the outer edge of which is cylindrical and bears the functions of auxiliary soil squeezing and diameter maintenance; the cone core tube (4), the spiral cone soil squeezing blades (5) and the drill tip gate (6) constitute the cone structure of the drill bit device, the outer edge of which is a cone and bears the main soil squeezing function.

[0050] like Figure 5As shown, the oil cylinder device (7) includes a main oil cylinder (7-1), a protective tube I (7-2), a secondary oil cylinder (7-3), a protective tube II (7-4) and a push rod (7-5). The extended end of the piston rod (7-1A) of the main oil cylinder is fixed to the cylinder sleeve end of the secondary oil cylinder (7-3), and the extended end of the piston rod (7-3A) of the secondary oil cylinder is fixed to one end of the push rod (7-5). One end of the protective tube I (7-2) is fixed to the outer wall of the cylinder sleeve of the secondary oil cylinder (7-3), and the other end is movably sealed with the outer diameter of the cylinder sleeve of the main oil cylinder (7-1). One end of the protective tube II (7-4) is fixed to the outer wall of the cylinder sleeve of the secondary oil cylinder (7-3), and the other end is movably sealed with the outer diameter of the push rod (7-5). The exposed end of the push rod (7-5) is provided with a connecting ear seat I (7-5A). The exposed end of the main oil cylinder (7-1) is provided with a connecting ear seat II (7-1B).

[0051] The fixing seat (9) is installed at the connection between the column core tube (3) and the cone core tube (4), and penetrates the column core tube (3), the cone core tube (4) and the spiral column soil squeezing blade (2). The oil cylinder device (7) is placed in the inner cavity of the column core tube (3). The expansion slider device (8) is fixed into one body by a sleeve (8-1), a slider (8-2) and a connecting plate (8-3). The sleeve (8-1) The oil cylinder lug plate (10) is fixed on the inner wall of the column core tube (3) through the shaft III (13), and one end of the oil cylinder device (7) is hinged to the oil cylinder lug plate (10) through the connecting lug seat II (7-1B) and the shaft I (11), and the other end of the oil cylinder device (7) is hinged to the connecting lug seat I (7-5A), the shaft II (12) and the connecting plate (8-3) of the diameter-expanding slider device (8). The slider (8-2) is driven to rotate around the shaft III (13) through the expansion and contraction of the oil cylinder device (7); the working end of the slider (8-2) is a trapezoidal structure, which corresponds to the trapezoidal structure of the cross-section of the screw thread I (201) and the screw thread II (401) of the cast-in-place pile with the expanded diameter cone pile section.

[0052] Working principle of the bored pile drill with an enlarged diameter conical pile section:

[0053] When drilling a hole, first close the drill outlet, and at the same time, the piston rod of the main oil cylinder and the piston rod of the auxiliary oil cylinder are all in the retracted state, and the slider 8-2 is in the fixed seat 9, as shown in FIG. Figure 2 shown.

[0054] When the drill is lifted and the concrete is pumped to form an enlarged diameter cylindrical screw-thread pile section, the hydraulic control system is first used to supply oil to the rodless chamber of the auxiliary oil cylinder 7-3 to drive the piston rod 7-3A of the auxiliary oil cylinder to fully extend, and then the rodless chamber of the main oil cylinder 7-1 is supplied with oil. The extension amount of the piston rod 7-1A of the main oil cylinder is determined according to the designed height of the screw thread of the enlarged diameter cylindrical screw-thread pile section. The extension of the piston rods of the two oil cylinders pushes the connecting plate 8-3 to rotate downward, driving the slider 8-2 to rotate outward. Figure 4 As shown, the extended slide block 8-2 is rotated and lifted upward along with the drill bit in the drilling direction, and squeezes the rock and soil on the wall of the column pile hole into a spiral thread groove.

[0055] When the drill is lifted and concrete is pumped to form a tapered pile segment with an enlarged diameter, the hydraulic control system is used to supply oil to the rodless chamber of the auxiliary oil cylinder 7-3, driving the piston rod 7-3A of the auxiliary oil cylinder to fully extend, and the sliding block 8-2 is driven to rotate outward by pushing the connecting plate 8-3 downward, until the maximum diameter formed by the outermost edge of the sliding block 8-2 around the center of the drill bit reaches the outer diameter of the drill bit column structure. Figure 3 As shown, or slightly exceeds the outer diameter of the drill bit column structure. Then, the hydraulic control system is used to adjust and determine the oil supply speed of the rodless chamber of the main oil cylinder 7-1 according to the rotation speed, lifting speed of the drill bit and the length of the expanded diameter conical body screw thread pile section to meet the matching degree between the length of the expanded diameter conical body screw thread pile section and the rotation extension amount of the slider 8-2, so as to realize the uniform extension of the main oil cylinder piston rod 7-1A, push the connecting plate 8-3 to rotate downward, and drive the slider 8-2 to rotate outward at a uniform speed, so as to realize that the slider 8-2 forms a gradually deepening spiral screw thread groove in the rock and soil of the pile hole wall until the maximum screw thread outer diameter is reached, and the construction of the expanded diameter conical body threaded pile section is completed.

[0056] The cone structure of the drill bit takes on the main extrusion function during the drilling process of squeezing soil into pile holes and re-squeezing and compacting concrete. The rock and soil at the pile hole or the concrete in the pile hole is directly subjected to the radial downward rotational extrusion force of the cone structure. When drilling for squeezing soil into holes, the squeezed rock and soil are forced to move radially downward to compact the rock and soil on the pile hole wall; when drilling for re-squeezing and compacting concrete, the bottom surface of the drill tip is subjected to the upward force of the pressure concrete in the pile hole. As the drill bit moves downward during drilling, it rotates around the pin in the direction of closing the outlet until the drill bit outlet is closed, blocking the mutual flow of concrete inside and outside the drill tool. The concrete squeezed by the drill bit acts as a medium, transmitting force to the adjacent hole wall rock and soil, squeezing and expanding the rock and soil aperture again, forming an enlarged rock and soil hole wall. At the same time, part of the concrete will be squeezed into the rock and soil hole wall to form a mixture layer of concrete and soil, that is, a re-squeezing and compacting reinforcement layer. After the cone structure of the drill bit squeezes soil or concrete to the designed depth, the outer contour of the formed rock and soil bottom hole or the lower part of the composite compaction reinforcement layer is a cone structure, which is similar to the outer contour of the cone structure of the drill bit.

[0057] Example 2

[0058] (I) A cast-in-place pile with an enlarged diameter conical pile section

[0059] A cast-in-place pile with an enlarged diameter conical pile section comprises a main columnar cast-in-place pile (100), wherein the bottom end of the main columnar cast-in-place pile (100) is a conical pile bottom (101).

[0060] A plurality of integrally structured expanded diameter conical pile segments are formed on the outer edge of the main columnar cast-in-place pile (100), wherein the expanded diameter conical pile segments include one or both of an expanded diameter conical screw thread pile segment (200) and an expanded diameter conical composite compacted pile segment (300).

[0061] The structure of the enlarged diameter conical screw thread pile section (200) is that a screw thread I (201) with an integral structure, spirally coiled around the outer edge of the main column cast-in-place pile (100), and gradually increasing in outer diameter from bottom to top is formed on the outer edge of the main column cast-in-place pile (100), the outer edge of the integral screw thread I (201) forms a cone, and the cross section of the screw thread I (201) is a trapezoidal structure. The diameter of the outer edge of the screw thread I gradually increases from bottom to top around the pile center. The outer edge surface of the enlarged diameter conical screw thread pile section is a cone, and the small diameter of the cone is at the lower end.

[0062] The structure of the expanded diameter conical body re-extruded pile segment (300) is that the outer edge of the main column cast-in-place pile (100) is provided with an integrated structure of an upper re-extruded column pile segment (301) and a lower re-extruded cone pile segment (302), the outer edge of the re-extruded cone pile segment (302) forms a cone, and the outer edges of the re-extruded column pile segment (301) and the re-extruded cone pile segment (302) are wrapped with a re-extruded reinforcement layer (303). The re-extruded reinforcement layer (303) is a mixture of concrete and soil formed by the squeezed concrete entering the rock and soil, and wraps the re-extruded pile segment inside, and its outer edge shape is similar to that of the re-extruded pile segment, with the lower part being a cone and the upper part being a column.

[0063] Furthermore, in the above-mentioned cast-in-place pile with an enlarged diameter conical pile section, a plurality of sections of enlarged diameter cylindrical screw-thread pile sections (400) of an integral structure are provided on the outer edge of the main cylindrical cast-in-place pile (100).

[0064] The structure of the enlarged diameter cylindrical screw thread pile section (400) is that a screw thread II (401) of an integral structure and spirally coiled around the outer edge of the main cylindrical cast-in-place pile (100) is formed on the outer edge of the main cylindrical cast-in-place pile (100), and the outer edge of the integral screw thread II (401) constitutes a cylindrical body.

[0065] Furthermore, in the above-mentioned cast-in-place pile with an enlarged diameter conical pile section, the diameter of the main column cast-in-place pile (100) is d, the outer diameter of the enlarged diameter column screw pile section (400) is D, the outer diameter of the double-extruded column pile section (301) is D1, the maximum outer diameter of the double-extruded reinforcement layer (303) is D4, the outer diameter of the smallest end of the enlarged diameter conical screw pile section (200) is D2, and the outer diameter of the largest end is D3, the pitch of the screw thread I (201) is T1, and the pitch of the screw thread II (401) is T2, then: d = 400-800 mm, D>d, D1>d, D3>D2>d, D4>D1, D / T2=1.1-1.5; the pitch T1 of the enlarged diameter conical screw thread pile section (200) increases with the increase of the outer diameter of the screw thread, and the ratio of the diameter formed by the outer edge of the screw thread I (201) at any point in the enlarged diameter conical screw thread pile section (200) around the center of the main column cast-in-place pile (100) to the pitch T1 between the upper and lower adjacent screw threads I (201) is satisfied to be between 1.1-1.5.

[0066] Furthermore, in the above-mentioned cast-in-place pile with an enlarged diameter tapered pile section, the structure of the thread I (201) and the thread II (401) is that the thread height is h, the outer thickness of the thread is b1, and the inner thickness is b2, then: h = 50-200mm, b1 = 50-80mm, b2 = 100-200mm.

[0067] Preferably, in one embodiment, Figure 6 As shown, a cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile (100), the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), and the conical pile bottom (101) is provided with an enlarged diameter conical body multi-extruded pile section (300), an enlarged diameter columnar body screw-thread pile section (400), an enlarged diameter conical body multi-extruded pile section (300) of an integral structure in sequence on the outer edge of the main column cast-in-place pile (100), and the top end is an enlarged diameter columnar body screw-thread pile section (400).

[0068] Preferably, in one embodiment, Figure 7 As shown, a cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile (100), the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), upward from the conical pile bottom (101) on the outer edge of the main column cast-in-place pile (100) there are sequentially provided an enlarged diameter conical re-extruded pile section (300) and an enlarged diameter columnar screw thread pile section (400) of an integral structure, and the top end is an enlarged diameter conical re-extruded pile section (300).

[0069] Preferably, in one embodiment, Figure 8As shown, a cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile (100), the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), and an enlarged diameter conical body composite compaction pile section (300) of an integral structure is formed on the conical pile bottom (101). An enlarged diameter columnar body screw thread pile section (400) of an integral structure is provided on the outer edge of the middle part of the main column cast-in-place pile (100) upward from the conical pile bottom (101).

[0070] Preferably, in one embodiment, Fig. 9 As shown, a cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile (100), the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), upward from the conical pile bottom (101) on the outer edge of the main column cast-in-place pile (100) are sequentially provided with an enlarged diameter conical body multi-extruded pile section (300), an enlarged diameter conical body screw-thread pile section (200), an enlarged diameter conical body multi-extruded pile section (300) of an integral structure, and the top end is an enlarged diameter columnar body screw-thread pile section (400).

[0071] Preferably, in one embodiment, Fig.10 As shown, a cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile (100), the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), and the conical pile bottom (101) is provided with an enlarged diameter conical screw thread pile section (200) of an integral structure on the outer edge of the main column cast-in-place pile (100) in sequence, and the top end is the enlarged diameter conical screw thread pile section (200).

[0072] Preferably, in one embodiment, Fig.11 As shown, a cast-in-place pile with an enlarged diameter conical pile section comprises a main column cast-in-place pile (100), the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), and an enlarged diameter conical body re-extruded pile section (300) with an integral structure is formed on the conical pile bottom (101). The conical pile bottom (101) is provided with an enlarged diameter conical body re-extruded pile section (300) with an integral structure and an enlarged diameter conical body screw thread pile section (200) on the outer edge of the middle part of the main column cast-in-place pile (100).

[0073] (II) Construction method of cast-in-place piles with expanded diameter conical pile sections

[0074] 1) The drill bit joint (1) is assembled with a soil squeezing drill rod, a spiral soil squeezing pile driver and a concrete pumping device, the oil cylinder device (7) is connected to a hydraulic control system, the slider (8-2) of the drill bit expansion slider device (8) is in a retracted state, and the pile driver is aligned with the pile position.

[0075] 2) Start the pile driver. The power head drives the drill bit to rotate through the soil-extruding drill rod. Drill slowly first, and then drill normally after the hole position is confirmed. The drill bit first squeezes the rock and soil at the pile hole position into a small-diameter cone hole. As the drill bit moves downward, the small-diameter cone hole is squeezed and expanded into a large-diameter cone hole until the foundation pile hole diameter is reached. The soil is squeezed and drilled until the designed hole depth is reached. Continue to rotate in place for 2 to 3 minutes to fully squeeze the rock and soil at the bottom and wall of the foundation pile hole. Fig.13 (a).

[0076] 3) While lifting the drill bit and drill rod and pumping concrete, follow the construction sequence from the bottom of the pile to the top section by section to complete the construction of each pile section:

[0077] 3.1) Main column cast-in-place pile (100) and conical pile bottom (101) at the bottom

[0078] First, concrete is pumped into the drill bit at the bottom of the pile hole to the bottom of the drill bit inner cavity, then the drill bit and the drill rod rotating in the drilling direction are lifted, the drill lifting speed is kept matching with the pump pressure injection amount, the drill is lifted and pressure injection is performed until the column pile hole diameter is reached, and the injection construction of the conical pile bottom (101) is completed; the drill is continued to be lifted and pressure injection is performed into the column pile hole to the top design height of the main column cast-in-place pile (100), and the injection construction of the main column cast-in-place pile (100) is completed. During this process, the slider of the drill bit inner diameter expansion slider device is in a fully retracted state, such as Fig.13 (b).

[0079] 3.2) Enlarged diameter cylindrical screw thread pile section (400)

[0080] During the process of drilling and pouring the main columnar cast-in-place pile (100) pile section, when it is necessary to set the enlarged diameter cylindrical body screw thread pile section (400), the hydraulic control system is used to first drive the auxiliary cylinder piston rod in the cylinder device to fully extend, and then drive the main cylinder piston rod in the cylinder device to extend. According to the designed depth of the thread of the enlarged diameter cylindrical body screw thread pile section, a fixed extension amount of the main cylinder piston rod is determined to push and control the extension amount of the slider in the enlarged diameter slider device, and the drilling direction of the drill bit and the drill rod is rotated by one turn, and the screw pitch is raised upward. At the same time, matching with the pump pressure pouring, the spiral groove squeezed by the slider in the pile hole wall is poured with concrete together with the pile hole, and the pile hole is lifted and poured to the designed height, thereby completing the pouring construction of the enlarged diameter cylindrical body screw thread pile section (400). Fig.13 (c).

[0081] 3.3) Expanded diameter cone-shaped compacted pile section (300)

[0082] During the process of drilling and pouring the main columnar cast-in-place pile (100), when it is necessary to set the expanded diameter conical body re-compacting pile section (300), the main columnar cast-in-place pile (100) that has been poured is rotated downward again to squeeze the concrete in the pile hole and drill. The squeezed concrete squeezes and expands the rock and soil hole wall of the pile, and a re-compacting and compacting reinforcement layer is formed in the hole wall after squeezing and expanding. A small part of the concrete in the pile hole is squeezed into the re-compacting and compacting reinforcement layer, and most of it remains in the squeezed and expanded rock and soil hole cavity. The drilling is continued until the designed depth of the expanded diameter conical body re-compacting and compacting pile section (300), and then the concrete is pumped and poured to the bottom of the drill bit inner cavity, and then the drilling tool rotating in the drilling direction is lifted, and the matching degree of the drilling speed and the pumping and pouring volume is maintained. The newly poured concrete and the concrete remaining in the squeezed and expanded rock and soil hole cavity are integrated. The drill is lifted and pressure poured until the designed elevation, and the pouring construction of the expanded diameter conical body re-compacting and compacting pile section (300) is completed. Fig.13 As shown in (d), (e), (f) and (g), during this process, the slider of the drill bit internal diameter expansion slider device is in a fully retracted state.

[0083] 3.4) Expanded diameter conical screw thread pile section (200)

[0084] During the process of drilling and pouring the main columnar cast-in-place pile (100), when it is necessary to set the enlarged diameter conical screw thread pile section (200), the hydraulic control system is used to first drive the piston rod of the auxiliary cylinder in the cylinder device to fully extend, drive the slider in the enlarged diameter slider device to partially extend, and then drive the piston rod of the main cylinder in the cylinder device to extend at a uniform speed, so that the length of the enlarged diameter conical screw thread pile section matches the total amount of uniform extension of the piston rod of the main cylinder, and the drilling direction of the drill bit and the drill rod is rotated by one turn, and the screw pitch is raised upward. At the same time, the slider is matched with the pump pressure pouring, and the slider squeezes a gradually deepening spiral groove in the pile hole wall to pour concrete together with the pile hole, and the pile hole is lifted and poured to the designed height, thereby completing the pouring construction of the enlarged diameter conical screw thread pile section (200). Fig.13 (h).

[0085] The pouring of the bored pile with a cone is carried out by pouring from the bottom of the pile upwards in sections, meeting the structural requirements of each section of the designed foundation pile. After the pile hole is formed, the drill bit is always kept in the effective burial depth of the concrete in the pile hole during the process of lifting the drill, pouring and re-compacting drilling, and a certain amount of concrete is kept in the inner cavity of the drill tool, thereby ensuring the quality of the pile. The expansion slider device is set at the upper end of the drill bit cone structure, that is, at the maximum outer edge of the bottom of the drill bit. When lifting the drill and pouring, it is in the effective burial depth of the pressurized concrete in the pile hole. The spiral groove squeezed out by the slider in the pile hole wall is immediately filled with pressurized concrete, and is pressurized together with the main columnar pile hole to ensure the strength between the screw thread and the main columnar pile body.

[0086] 4) Place the prefabricated steel cage or prefabricated parts into the poured pile hole to form a pile. Fig.13 (i).

[0087] (III) Bearing mechanism of piles

[0088] The conical pile bottom (101) and the main column cast-in-place pile (100) are both formed by squeezing soil once by a drill bit to form a hole, and concrete is poured by pump pressure when the drill is lifted. The main column cast-in-place pile formed by squeezing soil once has a stress-damaged sliding surface on the outer surface of the main column cast-in-place pile, that is, on the concrete pile-soil interface. The side resistance of this pile section is the friction between the outer surface of the concrete pile and the soil around the pile. Because the soil around the pile is squeezed and compacted, the standard value of the ultimate side resistance of the soil around the pile is improved, and the pile side bearing capacity is enhanced. The pile bottom is a conical structure, and the surrounding soil is also squeezed and compacted, which has a wedge-shaped squeezing and expansion effect, and can effectively improve the bearing capacity of the pile bottom.

[0089] The enlarged diameter cylindrical screw pile section is formed by re-extruding a spiral screw groove in the compacted cylindrical hole wall rock and soil, and pumping concrete together with the once squeezed soil pile hole. The pile section is damaged along the outer contour of the screw. This screw outer contour surface is composed of the outer surface of the concrete screw and the soil, which accounts for a small proportion. The stress-damaged sliding surface is mainly reflected on the soil-soil interface. The side resistance of the pile section is the friction of the soil-soil interface (the shear resistance of the soil), which is higher than the side resistance of the pile-soil interface. According to the calculation formula of Bellum and the research results of relevant experts, the friction of the soil-soil interface is 1.3-1.6 times the side resistance of the pile-soil interface.

[0090] The expanded diameter cone-shaped re-compacted pile section is a pile section formed by a single extrusion of soil, which is then expanded and pressed again (or expanded and pressed multiple times). A drill bit is used to utilize the concrete in the pile hole as a medium to squeeze and expand the rock and soil hole wall. During the squeezing process, part of the concrete is squeezed into the rock and soil wall after the diameter is expanded to form a mixture layer of concrete and soil, namely, a composite compaction and reinforcement layer. In this layer, the concrete content is higher near the center of the pile hole and lower on the far side. Most of the squeezed concrete remains in the inner cavity of the squeezed and expanded rock and soil hole wall. Controlled by the outer structure of the drill bit, the contour of the squeezed and expanded rock and soil hole is similar to the outer shape of the drill bit, namely, the upper part is cylindrical and the lower part is conical. The drill is lifted and concrete is pumped again. The newly poured concrete is integrated with the concrete remaining in the inner cavity of the expanded hole wall to form an expanded conical composite compaction pile section with a cone at the lower part and a column at the upper part. The outer contour of the composite compaction and reinforcement layer is similar to the outer contours of the composite compaction column pile section and the composite compaction cone pile section, and wraps the composite compaction column pile section and the composite compaction cone pile section. Due to the high bonding strength between the composite compaction reinforcement layer and the concrete pile body in the composite compaction column pile segment and the composite compaction cone pile segment, the stress-damaging interface of the pile segment will occur on the outer contour surface of the composite compaction reinforcement layer. The composition of the near outer contour surface in the composite compaction reinforcement layer is a small amount of concrete in the re-compacted rock and soil, and the soil occupies the vast majority. Therefore, the stress-damaging sliding surface of the pile segment is mainly reflected on the soil-soil interface, and the side resistance of the pile segment is the friction force of the soil-soil interface (shear resistance of the soil); at the same time, the rock and soil outside the composite compaction reinforcement layer are further compacted, laying the foundation for further improvement of the bearing capacity; the outer wrapped composite compaction reinforcement layer of the composite compaction cone pile segment is in the shape of a cone, which effectively increases the effective volume of the composite compaction cone, and the wedge-shaped expansion effect is significant.

[0091] The enlarged diameter conical screw-thread pile section is an advantageous combination of the enlarged diameter cylindrical screw-thread pile section and the conical pile section. The pile section is destroyed along the outer contour of the screw thread when subjected to force, and the failure sliding surface is reflected on the soil-soil interface. The failure interface is conical and has a wedge-shaped squeezing effect, which can further improve the bearing capacity.

[0092] The wedge-shaped expansion effect of the cone is as follows Fig.12 As shown in the figure, when the building (structure) applies force P to the cone of the pile body, the direction of force P is changed on the outer surface of the cone, and it is decomposed into the normal force P1 and the tangential force P2 on the outer surface of the cone. P1 radially squeezes the rock and soil around the outer surface of the cone to further compact the rock and soil. The effect of P2 is overcome by the friction force of the soil-soil interface on the cone surface (the surface of the first soil squeezing cone is the pile-soil interface). The cone reduces the vertical effect of force P, and the pile settlement is reduced. A large number of studies, tests and applications by professionals at home and abroad have given an empirical calculation formula for the lateral resistance of the cone pile segment (wedge pile):

[0093] P n =∑U i li (f i cosα+t i sinα)

[0094] Where P n —Allowable value of the side resistance of the conical pile segment (kN); U i —the circumference of the pile at the middle of the pile section in the i-th soil layer (m); i —The length of the pile section in the i-th soil layer (m); f i —Friction force of piles with equal cross-section in the i-th soil layer (kPa); t i —Normal pressure exerted by the ith soil layer on the conical side surface (kPa); α—cone angle of the conical pile section.

[0095] From the above formula, we can see that U i 、f i The value is taken according to the sliding surface of the cone pile segment under stress. For the double compaction cone in the double compaction pile segment, it is calculated according to the surface of its double compaction reinforcement layer. One is the geometric size U i Increased, and secondly, f i The friction force value is calculated based on the soil-soil interface, which is higher than that calculated based on the pile-soil interface. For the expanded diameter cone thread pile section, it is calculated based on the outer contour surface of the thread. i According to the friction value of the soil-soil interface, the cost of pile materials (materials between screw threads) is saved under the condition of ensuring high load of the pile. The rock and soil around the bottom of the first extrusion cone pile and the double extrusion reinforcement layer outside the double extrusion cone are all squeezed and compacted, especially the rock and soil around the double extrusion reinforcement layer outside the double extrusion cone is squeezed again or multiple times, t i It can be concluded that the cast-in-place pile with an enlarged diameter cone is a high-bearing capacity, energy-saving and environmentally friendly pile type.

Claims

1. A cast-in-place pile with an enlarged diameter conical pile section, comprising a main column cast-in-place pile (100), wherein the bottom end of the main column cast-in-place pile (100) is a conical pile bottom (101), characterized in that: The outer edge of the main column cast-in-place pile (100) is provided with a plurality of integrally structured expanded diameter conical pile segments, the expanded diameter conical pile segments comprising one or both of an expanded diameter conical screw thread pile segment (200) and an expanded diameter conical composite compacted pile segment (300); the structure of the expanded diameter conical screw thread pile segment (200) is that an integrally structured screw thread I (201) is formed on the outer edge of the main column cast-in-place pile (100), spirally wound around the outer edge of the main column cast-in-place pile (100), and the outer diameter gradually increases from bottom to top, the outer edge of the integral screw thread I (201) forms a cone, and the cross section of the screw thread I (201) is trapezoidal. The structure of the expanded diameter conical body composite compaction pile segment (300) is that the outer edge of the main column cast-in-place pile (100) is provided with an integrated structure, the upper part is a composite compaction column pile segment (301) and the lower part is a composite compaction cone pile segment (302), the outer edge of the composite compaction cone pile segment (302) forms a cone, the outer edges of the composite compaction column pile segment (301) and the composite compaction cone pile segment (302) are wrapped with a composite compaction reinforcement layer (303), and the composite compaction reinforcement layer (303) is a mixture layer of concrete and soil; the force exerted by the soil surrounding the cone in the expanded diameter conical body pile segment on the cone is the shear resistance of the soil on the surface of the cone.

2. A cast-in-place pile with a conical pile section with an enlarged diameter according to claim 1, characterized in that: A plurality of sections of enlarged diameter cylindrical body screw thread pile sections (400) are formed on the outer edge of the main columnar cast-in-place pile (100). The structure of the enlarged diameter cylindrical body screw thread pile sections (400) is that an integrally structured screw thread II (401) is formed on the outer edge of the main columnar cast-in-place pile (100) and is spirally wound around the outer edge of the main columnar cast-in-place pile (100). The outer edge of the integral screw thread II (401) constitutes a columnar body.

3. A cast-in-place pile with a conical pile section with an enlarged diameter according to claim 2, characterized in that: Assuming that the diameter of the main column cast-in-place pile (100) is d, the outer diameter of the expanded diameter column screw thread pile section (400) is D, the outer diameter of the double-extruded column pile section (301) is D1, the maximum outer diameter of the double-extruded reinforced layer (303) is D4, the outer diameter of the smallest end of the expanded diameter conical screw thread pile section (200) is D2, the outer diameter of the largest end is D3, the pitch of the screw thread I (201) is T1, and the pitch of the screw thread II (401) is T2, then: d = 400-800 mm, D>d, D1>d, D3>D2>d, D4>D1, D / T2 = 1.1-1 .5; the pitch T1 of the enlarged diameter conical screw thread pile section (200) increases with the increase of the outer diameter of the screw thread, and the ratio of the diameter formed by the outer edge of the screw thread I (201) at any point in the enlarged diameter conical screw thread pile section (200) around the center of the main column cast-in-place pile (100) to the pitch T1 between the upper and lower adjacent screw threads I (201) is between 1.1 and 1.

5.

4. A cast-in-place pile with a conical pile section with an enlarged diameter according to claim 2, characterized in that: The structure of thread Ⅰ (201) and thread Ⅱ (401) is that the thread height is h, the outer thickness of the thread is b1, and the inner thickness is b2, then: h = 50 ~ 200mm, b1 = 50 ~ 80mm, b2 = 100 ~ 200mm.

5. A drill bit for bored piles with an enlarged diameter conical pile section, comprising a joint (1), a spiral cylindrical soil-squeezing blade (2), a cylindrical core tube (3), a conical core tube (4), a spiral conical soil-squeezing blade (5) and a drill tip gate (6), characterized in that: The invention is provided with an oil cylinder device (7), an expansion slide block device (8), a fixing seat (9), an oil cylinder ear plate (10), an axis I (11), an axis II (12) and an axis III (13); the fixing seat (9) is installed at the connection between the column core tube (3) and the cone core tube (4), and penetrates the column core tube (3), the cone core tube (4) and the spiral column soil squeezing blade (2); the oil cylinder device (7) is arranged in the inner cavity of the column core tube (3), and the oil cylinder device (7) comprises a main oil cylinder (7-1), a protective tube I (7-2), auxiliary oil cylinder (7-3), protective tube II (7-4) and push rod (7-5), the extended end of the piston rod (7-1A) of the main oil cylinder is fixed to the cylinder sleeve end of the auxiliary oil cylinder (7-3), the extended end of the piston rod (7-3A) of the auxiliary oil cylinder is fixed to one end of the push rod (7-5), one end of the protective tube I (7-2) is fixed to the outer wall of the cylinder sleeve of the auxiliary oil cylinder (7-3), and the other end is movably sealed with the outer diameter of the cylinder sleeve of the main oil cylinder (7-1); one end of the protective tube II (7-4) is fixed to the auxiliary oil cylinder (7-3) is on the outer wall of the cylinder sleeve, and the other end is movably sealed with the outer diameter of the push rod (7-5); the exposed end of the push rod (7-5) is provided with a connecting ear seat I (7-5A); the exposed end of the main oil cylinder (7-1) is provided with a connecting ear seat II (7-1B); the diameter expansion slider device (8) is fixed as a whole by the sleeve (8-1), the slider (8-2) and the connecting plate (8-3); the sleeve (8-1) is installed in the fixed seat (9) through the shaft III (13) and rotates around the shaft III (13), and the cylinder ear plate (10) is fixed on the inner wall of the column core tube (3); one end of the cylinder device (7) is hinged to the cylinder ear plate (10) through the connecting ear seat II (7-1B) and the shaft I (11); the other end of the cylinder device (7) is hinged to the connecting ear seat I (7-5A), the shaft II (12) and the connecting plate (8-3) of the diameter expansion slider device (8); the slider (8-2) is driven to rotate around the shaft III (13) through the expansion and contraction of the cylinder device (7); the working end of the slider (8-2) is a trapezoidal structure.

6. A drill bit for bored piles with a conical pile section with an enlarged diameter according to claim 5, characterized in that: The joint (1), the column core tube (3) and the cone core tube (4) are fixed together concentrically in sequence, and their inner cavities form a passage for concrete to pass through. The spiral column soil squeezing blades (2) are spirally wound and fixed on the outer edges of the joint (1) and the column core tube (3). The spiral cone soil squeezing blades (5) are spirally wound and fixed on the outer edge of the cone core tube (4). The upper end surface of the spiral cone soil squeezing blades (5) is connected to the lower end surface of the spiral column soil squeezing blades (2) in correspondence, and the lower end of the spiral cone soil squeezing blades (5) is provided with cutting teeth (5-1).

7. A drill bit for bored piles with a conical pile section with an enlarged diameter according to claim 5, characterized in that: The drill tip door (6) is installed on the lower end surface of the cone core tube (4), and is movably connected to the lower end of the cone core tube (4) through a pin (6-1). The drill tip door (6) rotates downward around the pin (6-1) to a maximum angle δ, 35°≤δ≤45°, to open the drill bit discharge port to the maximum opening, and the drill tip door (6) rotates upward around the pin (6-1) to the lower end surface of the cone core tube (4), to close the drill bit discharge port.

8. A drill bit for bored piles with a conical pile section with an enlarged diameter according to claim 5, characterized in that: The joint (1), the spiral column soil squeezing blades (2) and the column core tube (3) constitute the column structure part of the drill bit device, the outer edge of which is a column; the cone core tube (4), the spiral cone soil squeezing blades (5) and the drill tip gate (6) constitute the cone structure part of the drill bit device, the outer edge of which is a cone.

9. A method for constructing a cast-in-place pile with a conical pile section with an enlarged diameter, characterized in that: Using the drill bit according to any one of claims 5 to 8 comprises the following steps: 1) The drill bit joint (1) is assembled with the soil squeezing drill rod, the spiral soil squeezing pile driver and the concrete pumping device, the oil cylinder device (7) is connected to the hydraulic control system, the slider (8-2) of the drill bit expansion slider device (8) is in a retracted state, and the pile driver is aligned with the pile position; 2) Start the pile driver, the power head drives the drill bit to rotate through the soil-squeezing drill rod, and drills slowly at first. After the hole position is confirmed, drill normally. The drill bit squeezes the rock and soil at the pile hole position into a small-diameter cone hole. As the drill bit moves downward, the small-diameter cone hole is squeezed and expanded into a large-diameter cone hole until the foundation pile hole diameter is reached. The soil is squeezed and drilled until the designed hole depth is reached, and the rotation continues for 2 to 3 minutes in situ to fully squeeze the rock and soil at the bottom and wall of the foundation pile hole; 3) While lifting the drill bit and drill rod and pumping concrete, follow the construction sequence from the bottom of the pile to the top section by section to complete the construction of each pile section: 3.1) The main columnar cast-in-place pile (100) and the conical pile bottom (101) at the bottom are first pumped with concrete to the bottom of the drill bit inner cavity at the bottom of the pile hole, and then the drill bit and the drill rod rotating in the drilling direction are lifted, and the matching degree between the lifting speed of the drill and the pumping amount is maintained. The drill is lifted and pumped until the column pile hole diameter is reached, and the pouring construction of the conical pile bottom (101) is completed; the drill is continued to be lifted and pumped to the column pile hole to the designed height of the top of the main columnar cast-in-place pile (100), and the pouring construction of the main columnar cast-in-place pile (100) is completed. During this process, the slider of the slider device of the drill bit inner diameter expansion is in a fully retracted state; 3.2) During the process of drilling and pouring the main column cast-in-place pile (100) segment, when the enlarged diameter cylindrical screw-thread pile segment (400) needs to be set, the hydraulic control system is used to first drive the piston rod of the auxiliary oil cylinder in the oil cylinder device to fully extend, and then drive the piston rod of the main oil cylinder in the oil cylinder device to extend. According to the designed height of the thread of the enlarged diameter cylindrical screw-thread pile segment, a fixed extension amount of the piston rod of the main oil cylinder is determined to push and control the extension amount of the slider in the enlarged diameter slider device, and the drilling direction of the drill bit and the drill rod is rotated by one turn, and the thread pitch is raised upward. At the same time, matching with the pump pressure pouring, the spiral thread groove squeezed by the slider in the pile hole wall is poured with concrete together with the pile hole, and the pile hole is lifted and poured to the designed height, completing the pouring construction of the enlarged diameter cylindrical screw-thread pile segment (400); 3.3) Expanded diameter cone body re-compacting pile section (300) During the process of drilling and pouring the main column cast-in-place pile (100), when it is necessary to set the expanded diameter cone body re-compacting pile section (300), the main column cast-in-place pile (100) that has been poured is rotated downward again to squeeze the concrete in the pile hole and drill into it. The squeezed concrete squeezes and expands the pile rock and soil hole wall, and a re-compacting reinforcement layer is formed in the hole wall after squeezing and expansion. A small part of the concrete in the pile hole is squeezed into the re-compacting reinforcement layer, and most of it remains in the squeezed concrete. Drilling into the expanded rock and soil cavity until the designed depth of the expanded diameter cone body re-dense pile section (300), then pumping concrete to the bottom of the drill bit cavity, then lifting the drill tool rotating in the drilling direction, keeping the matching degree between the lifting speed of the drill and the pumping amount, the newly poured concrete and the concrete remaining in the squeezed and expanded rock and soil cavity are integrated, the drill is lifted and pumped to the designed elevation, and the pouring construction of the expanded diameter cone body re-dense pile section (300) is completed. During this process, the slider of the expanded diameter slider device in the drill bit is in a fully retracted state; 3.4) During the process of drilling and pouring the main columnar cast-in-place pile (100) pile section, when the enlarged diameter conical screw thread pile section (200) needs to be set, the hydraulic control system is used to first drive the piston rod of the auxiliary oil cylinder in the oil cylinder device to fully extend, drive the slider in the enlarged diameter slider device to partially extend, and then drive the piston rod of the main oil cylinder in the oil cylinder device to extend at a uniform speed, so that the length of the enlarged diameter conical screw thread pile section matches the total amount of uniform extension of the main oil cylinder piston rod, and the drilling direction of the drill bit and the drill rod is rotated by one turn, and the screw pitch is lifted upward. At the same time, the slider is matched with the pump pressure pouring, and the slider squeezes a gradually deepening spiral screw thread groove in the pile hole wall to pour concrete together with the pile hole, and the pile hole is lifted and poured to the designed height, completing the pouring construction of the enlarged diameter conical screw thread pile section (200); 4) Place the prefabricated steel cage or prefabricated parts into the poured pile hole to form a pile.

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