A low-headroom bored pile construction system and method using a flexible steel cage

Abstract

The present invention provides a low-headroom bored pile construction system and method using a flexible steel cage, which uses the main bars, stirrups, pile end concrete counterweights and top rigid steel cage of the flexible steel cage. The main bars of the flexible steel cage use unbonded prestressed steel strands, and stirrups are wound around the outside of the main bars of the flexible steel cage to form a flexible steel cage. The pile end concrete counterweight is arranged at the bottom of the flexible steel cage, and a prefabricated top rigid steel cage is connected to the top design elevation of the flexible steel cage pile. After the flexible steel cage is lowered to the design elevation, the hole is cleaned and concrete is poured in the pile hole. After the foundation pit is excavated to expose the pile top concrete, the main bars of the flexible steel cage are tensioned and locked with anchors, and the main bars of the top rigid steel cage are anchored into the basement floor steel bars. The present invention has high construction efficiency, short time consumption, and low labor and material costs, and can solve the problem of pile foundation construction under low headroom and limited space conditions.

Description

Technical Field

[0001] The invention belongs to the field of cast-in-place pile construction, and in particular relates to a low-headroom bored cast-in-place pile construction system and method using a flexible steel cage. Background Art

[0002] In recent years, with the continuous promotion of the concept of urban renewal, urban development has gradually shifted from large-scale demolition and construction to organic renewal. At present, the repair, renovation and redevelopment of existing old buildings and historical buildings have become the main direction of urban renewal. The renovation of existing buildings often requires pile foundation construction inside the preserved building. Due to the height and space limitations of indoor construction, it is impossible to tie and hoist the complete steel cage into the hole. According to the traditional steel cage production method, only segmented tying, segmented hoisting, and segment-by-segment welding can be adopted. This construction method has obvious problems, namely low efficiency, long time consumption, and high labor and material costs.

[0003] Therefore, how to provide a high-altitude work safety control system and method for supporting the bull leg pressure situation that can solve the pile foundation construction problems under low clearance and limited space conditions has become a technical problem that needs to be further improved and optimized in the construction industry. Summary of the invention

[0004] The present invention aims to provide a low-headroom bored pile construction system and method using a flexible steel cage, which solves the problem of pile foundation construction under low-headroom and limited space conditions, and has the advantages of high construction efficiency, short construction time and low labor and material costs.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A low-headroom bored pile construction system using a flexible steel cage comprises: main bars of the flexible steel cage, stirrups, a pile end concrete counterweight and a top rigid steel cage, wherein the main bars of the flexible steel cage are made of unbonded prestressed steel strands, stirrups are wound around the outside of the main bars of the flexible steel cage, and the stirrups are connected to the main bars of the flexible steel cage by buckles to form a flexible steel cage; the main bars of the flexible steel cage are connected to the main bars of the pile end concrete counterweight, so that the pile end concrete counterweight is fixedly arranged at the bottom of the flexible steel cage, a prefabricated top rigid steel cage is connected at the design elevation position of the flexible steel cage pile top, the top rigid steel cage is coaxially arranged with the flexible steel cage, the top rigid steel cage is located inside the flexible steel cage, the flexible steel cage is lowered to the design elevation, the hole is cleaned and concrete is poured in the pile hole; after the foundation pit is excavated to expose the pile top concrete, the main bars of the flexible steel cage are tensioned and locked by anchors; the main bars of the top rigid steel cage are anchored into the steel bars of the basement floor slab, thereby completing the construction of the low-headroom bored pile.

[0007] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, stirrups are wound around the outside of the main reinforcement of the flexible steel cage by a stirrup conveying device, the stirrup conveying device includes a circular track, a stirrup retracting device, a slider seat, and a first motor, the stirrup retracting device includes a stirrup winch and a second motor, the stirrup retracting device is arranged on the slider seat, the stirrup winch is arranged horizontally, a roller is arranged at the bottom of the slider seat, a groove matching the roller is arranged on the circular track, the second motor is connected to the stirrup winch, the second motor realizes the retracting and releasing of the stirrups by driving the stirrup winch to rotate, the first motor is connected to the slider seat, the first motor can drive the slider seat to rotate around the pile hole along the circular track, the circular track is arranged on the ground outside the pile hole, the circular track is coaxially arranged with the pile hole, when the main reinforcement of the flexible steel cage moves downward, the stirrup retracting device rotates around the circular track while conveying the stirrups, so that the stirrups are spirally wound around the outside of the main reinforcement of the flexible steel cage.

[0008] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, after the foundation pit is excavated to expose the concrete on the pile top, an anchor is installed on the pile top to tension the unbonded prestressed steel strands in the pile. After a single unbonded prestressed steel strand is tensioned to 50% of the designed tensile strength, it is locked with an anchor.

[0009] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, the pile end concrete counterweight block includes a cylindrical concrete block, a plurality of main bars of the pile end concrete counterweight blocks are arranged in the cylindrical concrete block, the main bars of the plurality of pile end concrete counterweight blocks are parallel to the axial direction of the cylindrical concrete block, the main bars of the plurality of pile end concrete counterweight blocks are evenly arranged around the axis of the cylindrical concrete block, the main bars of the pile end concrete counterweight blocks are arranged in a one-to-one correspondence with the main bars of the flexible steel cage, and the main bars of the pile end concrete counterweight blocks are connected in a one-to-one correspondence with the main bars of the flexible steel cage, so that the main bars of the flexible steel cage are in place, thereby locking the relative positions between the main bars of the flexible steel cage.

[0010] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, a conical concrete block is also provided at the bottom of the cylindrical concrete block, the circular bottom surface of the conical concrete block is consistent in size with the circular bottom surface of the cylindrical concrete block and is coaxially fixedly connected, and the cone tip of the conical concrete block is arranged downward to facilitate the pile end concrete counterweight block to pull the flexible steel cage downward.

[0011] A low-headroom bored pile construction method using a flexible steel cage comprises the following steps:

[0012] Step 1, pile foundation drilling;

[0013] Step 2, prefabricate the pile end concrete counterweight;

[0014] Step 3, the main reinforcement of the flexible steel cage is connected to the main reinforcement of the pile end concrete counterweight, and the main reinforcement of the flexible steel cage is made of unbonded prestressed steel strands;

[0015] Step 4, placing a pile end concrete counterweight in the pile hole, and the pile end concrete counterweight pulls the main reinforcement of the flexible steel cage into the pile hole;

[0016] Step 5, winding stirrups around the outside of the main reinforcement of the flexible steel cage, and connecting the stirrups to the main reinforcement of the flexible steel cage with buckles;

[0017] Step 6, after the flexible steel cage is manufactured on site and lowered to the specified height, a prefabricated top rigid steel cage is connected to the designed elevation position of the pile top, the top rigid steel cage is coaxially arranged with the flexible steel cage, and the top rigid steel cage is located inside the flexible steel cage;

[0018] Step 7, continue to lower the flexible steel cage to the designed elevation;

[0019] Step 8, cleaning the hole and pouring concrete in the pile hole;

[0020] Step 9: After the foundation pit is excavated to expose the concrete on the top of the pile, the main reinforcement of the flexible steel cage is tensioned and locked with anchors;

[0021] Step 10: Anchor the main reinforcement of the top rigid reinforcement cage into the basement floor reinforcement to complete the construction.

[0022] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, after the foundation pit is excavated to expose the concrete on the pile top, an anchor is installed on the pile top to tension the unbonded prestressed steel strands in the pile. After a single unbonded prestressed steel strand is tensioned to 50% of the designed tensile strength, it is locked with an anchor.

[0023] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, stirrups are wound around the outside of the main reinforcement of the flexible steel cage by a stirrup conveying device, the stirrup conveying device includes a circular track, a stirrup retracting device, a slider seat, and a first motor, the stirrup retracting device includes a stirrup winch and a second motor, the stirrup retracting device is arranged on the slider seat, the stirrup winch is arranged horizontally, a roller is arranged at the bottom of the slider seat, a groove matching the roller is arranged on the circular track, the second motor is connected to the stirrup winch, the second motor realizes the retracting and releasing of the stirrups by driving the stirrup winch to rotate, the first motor is connected to the slider seat, the first motor can drive the slider seat to rotate around the pile hole along the circular track, the circular track is arranged on the ground outside the pile hole, the circular track is coaxially arranged with the pile hole, when the main reinforcement of the flexible steel cage moves downward, the stirrup retracting device rotates around the circular track while conveying the stirrups, so that the stirrups are spirally wound around the outside of the main reinforcement of the flexible steel cage.

[0024] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, the pile end concrete counterweight block includes a cylindrical concrete block, a plurality of main bars of the pile end concrete counterweight blocks are arranged in the cylindrical concrete block, the main bars of the plurality of pile end concrete counterweight blocks are parallel to the axial direction of the cylindrical concrete block, the main bars of the plurality of pile end concrete counterweight blocks are evenly arranged around the axis of the cylindrical concrete block, the main bars of the pile end concrete counterweight blocks are arranged in a one-to-one correspondence with the main bars of the flexible steel cage, the main bars of the pile end concrete counterweight blocks are connected in a one-to-one correspondence with the main bars of the flexible steel cage, so that the main bars of the flexible steel cage are in place, thereby locking the relative positions between the main bars of the flexible steel cage, a conical concrete block is also provided at the bottom of the cylindrical concrete block, the circular bottom surface of the conical concrete block is consistent in size with the circular bottom surface of the cylindrical concrete block and is coaxially fixedly connected, and the cone tip of the conical concrete block is arranged downward to facilitate the pile end concrete counterweight block to pull the flexible steel cage to move downward.

[0025] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, the length of the top rigid steel cage is not less than 4.0 / α, where α is the horizontal deformation coefficient of the pile foundation.

[0026] It can be seen from the technical solutions disclosed above that, compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] In summary, the present invention provides a low-headroom bored pile construction system and method using a flexible steel cage, which uses main bars, stirrups, pile end concrete counterweights and a top rigid steel cage of the flexible steel cage. The main bars of the flexible steel cage use unbonded prestressed steel strands, and stirrups are wound around the outside of the main bars of the flexible steel cage. The stirrups are connected to the main bars of the flexible steel cage by buckles to form a flexible steel cage; the main bars of the flexible steel cage are connected to the main bars of the pile end concrete counterweight, so that the pile end concrete counterweight is fixedly arranged at the bottom of the flexible steel cage, and a prefabricated top rigid steel cage is connected at the design elevation position of the flexible steel cage pile top. The top rigid steel cage is coaxially arranged with the flexible steel cage, and the top rigid steel cage is located inside the flexible steel cage. After the flexible steel cage is lowered to the design elevation, the hole is cleaned and concrete is poured in the pile hole; after the foundation pit is excavated to expose the pile top concrete, the main bars of the flexible steel cage are tensioned and locked with anchors; the main bars of the top rigid steel cage are anchored into the steel bars of the basement floor slab, thereby completing the construction of low-headroom bored piles. The present invention uses unbonded prestressed steel strands to replace the main bars in the traditional steel cage as the main bars of the flexible steel cage, fixes the stirrups to the outside of the main bars of the flexible steel cage by buckles, sets pile end concrete counterweights at the bottom of the flexible steel cage, and the pile end concrete counterweights can assist the flexible steel cage in sinking as counterweights. A prefabricated top rigid steel cage, i.e., an ordinary steel cage, is connected at the designed elevation position of the flexible steel cage pile top, and the top rigid steel cage is connected to the basement floor steel bar anchoring connection, so that the main bars of the pile body and the basement floor steel bar can be more conveniently connected quickly and firmly; after the concrete pouring in the pile hole is completed, the unbonded prestressed steel strands are tensioned to ensure that the main bars of the pile body are in a stressed state and improve the cross-sectional bending bearing capacity. Compared with the traditional steel cage manufacturing method, the present invention can solve the problem of pile foundation construction under low headroom and limited space conditions, and has high construction efficiency, short time consumption, and low labor and material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of the concrete counterweight at the pile end.

[0029] Figure 2 yes Figure 1 Top view of the .

[0030] Figure 3 It is a schematic diagram of the connection between the main reinforcement of the flexible steel cage and the main reinforcement of the concrete counterweight block at the pile end.

[0031] Figure 4 It is a schematic diagram of the structure of stirrup winding.

[0032] Figure 5 It is a structural schematic diagram of the stirrup conveying device.

[0033] Figure 6It is a schematic diagram of the assembly of the main reinforcement of the top rigid steel cage and the flexible steel cage.

[0034] In the figure: 1-main reinforcement of flexible steel cage, 2-stirrups, 3-pile end concrete counterweight, 31-cylindrical concrete block, 32-conical concrete block, 33-main reinforcement of pile end concrete counterweight, 4-top rigid steel cage, 5-pile hole, 7-mechanical joint, 8-circular track, 9-stirrup winch. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The technical content and features of the present invention will be described in detail below by combining the enumerated embodiments with the accompanying drawings. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. For the convenience of description, the "upper" and "lower" described below are consistent with the upper and lower directions of the accompanying drawings, but this cannot be a limitation of the technical solution of the present invention.

[0036] See also Figures 1 to 6 The present embodiment discloses a low-headroom bored pile construction system using a flexible steel cage, including a main steel bar 1 of the flexible steel cage, stirrups 2, a pile end concrete counterweight 3, and a top rigid steel cage 4. The main steel bar 1 of the flexible steel cage adopts unbonded prestressed steel strands, and the stirrups 2 are wound around the outside of the main steel bar 1 of the flexible steel cage. The stirrups 2 are connected to the main steel bar 1 of the flexible steel cage by buckles (not shown) to form a flexible steel cage; the main steel bar 1 of the flexible steel cage is connected to the main steel bar of the pile end concrete counterweight 3, so that the pile end concrete counterweight 3 is fixedly arranged on the flexible steel cage. At the bottom of the cage, a prefabricated top rigid steel cage 4 is connected at the design elevation of the flexible steel cage pile top. The top rigid steel cage 4 is coaxially arranged with the flexible steel cage. The top rigid steel cage 4 is located inside the flexible steel cage. After the flexible steel cage is lowered to the design elevation, the hole is cleaned and concrete is poured in the pile hole 5; after the foundation pit is excavated to expose the concrete on the pile top, the main reinforcement 1 of the flexible steel cage is tensioned and locked with an anchor; the main reinforcement of the top rigid steel cage 4 is anchored into the basement floor steel (not shown), thereby completing the construction of low-headroom bored piles.

[0037] The present invention uses unbonded prestressed steel strands to replace the main bars in the traditional steel cage as the main bars 1 of the flexible steel cage, fixes the stirrups 2 to the outside of the main bars 1 of the flexible steel cage by buckles, and sets a pile end concrete counterweight 3 at the bottom of the flexible steel cage. The pile end concrete counterweight 3 can assist the flexible steel cage in sinking as a counterweight. A prefabricated top rigid steel cage 4, i.e., a common steel cage, is connected at the design elevation position of the top of the flexible steel cage pile, and the top rigid steel cage 4 is connected to the basement floor steel bar anchoring connection, so that the main bars of the pile body and the basement floor steel bar can be more conveniently connected quickly and firmly; after the concrete pouring in the pile hole 5 is completed, the unbonded prestressed steel strands are tensioned to ensure that the main bars of the pile body are in a stressed state and improve the cross-sectional bending bearing capacity. Compared with the traditional steel cage manufacturing method, the present invention can solve the problem of pile foundation construction under low headroom and limited space conditions, and has high construction efficiency, short time consumption, and low labor and material costs.

[0038] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, the stirrups 2 can be wound around the outside of the flexible steel cage manually or by a stirrup conveying device, the stirrup conveying device includes a circular track 8, a stirrup retracting device (not shown), a slider seat (not shown), and a first motor (not shown), the stirrup retracting device includes a stirrup winch 9 and a second motor (not shown), the stirrup retracting device is arranged on the slider seat, the stirrup winch 9 is arranged horizontally, a roller (not shown) is provided at the bottom of the slider seat, and a roller is provided on the circular track 8. The second motor is connected to the stirrup winch 9, and the second motor realizes the retraction and release of the stirrup 2 by driving the stirrup winch 9 to rotate. The first motor is connected to the slider seat, and the first motor can drive the slider seat to rotate around the pile hole along the circular track 8. The circular track 8 is set on the ground outside the pile hole 5. The circular track 8 is coaxially arranged with the pile hole 5. When the main reinforcement 1 of the flexible steel cage moves downward, the stirrup retracting and releasing device rotates around the circular track 8 while conveying the stirrup 2, so that the stirrup 2 is spirally wound around the outside of the main reinforcement 1 of the flexible steel cage. The stirrup conveying device can automatically wrap the stirrup 2 around the outside of the main reinforcement 1 of the flexible steel cage, which improves the on-site production accuracy and efficiency of the flexible steel cage, effectively saves labor costs, and improves the automation level of low-headroom bored pile construction.

[0039] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, after the foundation pit is excavated to the point where the concrete on the pile top is exposed, an anchor is installed on the pile top to tension the unbonded prestressed steel strand in the pile, i.e., the main reinforcement 1 of the flexible steel cage. After a single unbonded prestressed steel strand is tensioned to 50% of the designed tensile strength, it is locked with an anchor to put the pile body in a prestressed state, thereby ensuring that the main reinforcement 1 of the flexible steel cage and the concrete of the pile body are stressed synergistically, thereby avoiding the situation where the main reinforcement 1 of the flexible steel cage is stressed lagging behind.

[0040] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, the main bars and stirrups 2 of the top rigid steel cage 4 are ribbed steel bars, the main bars of the top rigid steel cage 4 are staggered with the main bars 1 of the flexible steel cage, the main bars of the top rigid steel cage 4 are connected to the main bars 1 of the flexible steel cage by snap fasteners, and the main bars 1 of the flexible steel cage extend upward to the ground to facilitate prestressing and fixing of the main bars 1 of the flexible steel cage.

[0041] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, the length of the top rigid steel cage 4 is not less than 4.0 / α, where α is the horizontal deformation coefficient of the pile foundation, so as to improve the horizontal bearing capacity of the pile top.

[0042] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, lowering the flexible steel cage is achieved by lowering the main bars 1 of the flexible steel cage, and the main bars 1 of the flexible steel cage can be delivered manually or by respective winches or main bar winches driven by a motor. The main bars 1 of the flexible steel cage can be gathered in the pile hole 5 through a guide. The pile end concrete counterweight 3 includes a cylindrical concrete block 31, and a plurality of main bars 33 of the pile end concrete counterweights are arranged in the cylindrical concrete block 31. The main bars 33 of the pile end concrete counterweights are parallel to the axial direction of the cylindrical concrete block. The main bars 33 of the pile end concrete counterweights are evenly arranged around the axis of the cylindrical concrete block 31. The main bars 33 of the pile end concrete counterweights are arranged one-to-one with the main bars 1 of the flexible steel cage. The main bars 33 of the pile end concrete counterweights are connected one-to-one with the main bars 1 of the flexible steel cage, so that the main bars 1 of the flexible steel cage are in place, thereby locking the relative positions between the main bars 1 of the flexible steel cage. In this embodiment, the main reinforcement 33 of the pile end concrete counterweight is connected to the main reinforcement 1 of the flexible steel cage through a mechanical joint 7. A conical concrete block 32 is also provided at the bottom of the cylindrical concrete block 31. The circular bottom surface of the conical concrete block 32 is consistent in size with the circular bottom surface of the cylindrical concrete block 31 and is coaxially fixedly connected. The cone tip of the conical concrete block 32 is set downward to facilitate the pile end concrete counterweight 3 to pull the flexible steel cage to move downward.

[0043] Please continue reading Figures 1 to 6 This embodiment also discloses a low-headroom bored pile construction method using a flexible steel cage, comprising the following steps:

[0044] Step 1, pile foundation drilling;

[0045] Step 2, prefabricate pile end concrete counterweight block 3;

[0046] Step 3, the main reinforcement 1 of the flexible steel cage is connected to the main reinforcement of the pile end concrete counterweight 3, and the main reinforcement 1 of the flexible steel cage adopts unbonded prestressed steel strands;

[0047] Step 4, placing the pile end concrete counterweight 3 in the pile hole 5, and the pile end concrete counterweight 3 pulls the main reinforcement 1 of the flexible steel cage into the pile hole 5;

[0048] Step 5, winding stirrups 2 around the outside of the main reinforcement 1 of the flexible steel cage, and connecting the stirrups 2 to the main reinforcement 1 of the flexible steel cage with buckles;

[0049] Step 6, after the flexible steel cage is manufactured on site and lowered to the specified height, a prefabricated top rigid steel cage 4 is connected to the designed elevation position of the pile top, wherein the top rigid steel cage 4 is coaxially arranged with the flexible steel cage, and the top rigid steel cage 4 is located inside the flexible steel cage;

[0050] Step 7, continue to lower the flexible steel cage to the designed elevation;

[0051] Step 8, cleaning the hole and pouring concrete in the pile hole 5;

[0052] Step 9, after the foundation pit is excavated to expose the concrete on the pile top, the main reinforcement 1 of the flexible steel cage is tensioned and locked with an anchor;

[0053] Step 10, anchor the main reinforcement of the top rigid reinforcement cage 4 into the basement floor reinforcement to complete the construction.

[0054] The present invention uses unbonded prestressed steel strands to replace the main bars in the traditional steel cage as the main bars 1 of the flexible steel cage, fixes the stirrups 2 to the outside of the main bars 1 of the flexible steel cage by buckles, and sets a pile end concrete counterweight 3 at the bottom of the flexible steel cage. The pile end concrete counterweight 3 can assist the flexible steel cage in sinking as a counterweight. A prefabricated top rigid steel cage 4, i.e., a common steel cage, is connected at the design elevation position of the top of the flexible steel cage pile, and the top rigid steel cage 4 is connected to the basement floor steel bar anchoring connection, so that the main bars of the pile body and the basement floor steel bar can be more conveniently connected quickly and firmly; after the concrete pouring in the pile hole 5 is completed, the unbonded prestressed steel strands are tensioned to ensure that the main bars of the pile body are in a stressed state and improve the cross-sectional bending bearing capacity. Compared with the traditional steel cage manufacturing method, the present invention can solve the problem of pile foundation construction under low headroom and limited space conditions, and has high construction efficiency, short time consumption, and low labor and material costs.

[0055] Preferably, in the above-mentioned low-headroom bored pile construction method using a flexible steel cage, after the foundation pit is excavated to expose the concrete on the pile top, an anchor is installed on the pile top to tension the unbonded prestressed steel strands in the pile. After a single unbonded prestressed steel strand is tensioned to 50% of the designed tensile strength, it is locked with an anchor to put the pile body in a prestressed state, ensuring that the main reinforcement 1 of the flexible steel cage and the pile body concrete are stressed synergistically, thereby avoiding the situation where the main reinforcement 1 of the flexible steel cage is stressed lagging.

[0056] Preferably, in the above-mentioned low-headroom bored pile construction system using a flexible steel cage, lowering the flexible steel cage is achieved by lowering the main bars 1 of the flexible steel cage, and the main bars 1 of the flexible steel cage are transported by respective winches. The main bars 1 of the flexible steel cage can be gathered in the pile hole 5 through a guide. The pile end concrete counterweight 3 includes a cylindrical concrete block 31, in which a plurality of main bars 33 of the pile end concrete counterweight are arranged, the main bars 33 of the pile end concrete counterweight are parallel to the axial direction of the cylindrical concrete block 31, the main bars 33 of the pile end concrete counterweight are evenly arranged around the axis of the cylindrical concrete block 31, the main bars 33 of the pile end concrete counterweight are arranged one by one with the main bars 1 of the flexible steel cage, and the main bars 33 of the pile end concrete counterweight are connected one by one with the main bars 1 of the flexible steel cage, so that the main bars 1 of the flexible steel cage are in place, thereby locking the relative positions between the main bars 1 of the flexible steel cage. In this embodiment, the main reinforcement 33 of the pile end concrete counterweight is connected to the main reinforcement 1 of the flexible steel cage through a mechanical joint 7. A conical concrete block 32 is also provided at the bottom of the cylindrical concrete block 31. The circular bottom surface of the conical concrete block 32 is consistent in size with the circular bottom surface of the cylindrical concrete block 31 and is coaxially fixedly connected. The cone tip of the conical concrete block 32 is set downward to facilitate the pile end concrete counterweight 3 to pull the flexible steel cage to move downward.

[0057] Preferably, in the above-mentioned low-headroom bored pile construction method using a flexible steel cage, the stirrups 2 can be wound around the outside of the flexible steel cage manually or by a stirrup conveying device, the stirrup conveying device includes a circular track 8, a stirrup retracting device (not shown), a slider seat (not shown), and a first motor (not shown), the stirrup retracting device includes a stirrup winch 9 and a second motor (not shown), the stirrup retracting device is arranged on the slider seat, the stirrup winch 9 is arranged horizontally, a roller (not shown) is provided at the bottom of the slider seat, and a roller is provided on the circular track 8. The second motor is connected to the stirrup winch 9, and the second motor realizes the retraction and release of the stirrup 2 by driving the stirrup winch 9 to rotate. The first motor is connected to the slider seat, and the first motor can drive the slider seat to rotate around the pile hole along the circular track 8. The circular track 8 is set on the ground outside the pile hole 5. The circular track 8 is coaxially arranged with the pile hole 5. When the main reinforcement 1 of the flexible steel cage moves downward, the stirrup retracting and releasing device rotates around the circular track 8 while conveying the stirrup 2, so that the stirrup 2 is spirally wound around the outside of the main reinforcement 1 of the flexible steel cage. The stirrup conveying device can automatically wrap the stirrup 2 around the outside of the main reinforcement 1 of the flexible steel cage, which improves the on-site production accuracy and efficiency of the flexible steel cage, effectively saves labor costs, and improves the automation level of low-headroom bored pile construction. Preferably, in the above-mentioned low-headroom bored pile construction method using a flexible steel cage, the main bars and stirrups 2 of the top rigid steel cage 4 are ribbed steel bars, the main bars of the top rigid steel cage 4 are staggered with the main bars 1 of the flexible steel cage, the main bars of the top rigid steel cage 4 are connected to the main bars 1 of the flexible steel cage by snap buckles, and the main bars 1 of the flexible steel cage extend upward to the ground to facilitate prestressing and fixing of the main bars 1 of the flexible steel cage.

[0058] Preferably, in the above-mentioned low-headroom bored pile construction method using a flexible steel cage, the length of the top rigid steel cage 4 is not less than 4.0 / α, where α is the horizontal deformation coefficient of the pile foundation, so as to improve the horizontal bearing capacity of the pile top.

[0059] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A low-headroom bored pile construction method using a flexible steel cage, characterized in that: The steps include: Step 1, pile foundation drilling; Step 2, prefabricate a pile end concrete counterweight block, wherein the pile end concrete counterweight block comprises a cylindrical concrete block, wherein a plurality of main bars of the pile end concrete counterweight blocks are arranged in the cylindrical concrete block, wherein the main bars of the plurality of pile end concrete counterweight blocks are parallel to the axial direction of the cylindrical concrete block, wherein the main bars of the plurality of pile end concrete counterweight blocks are evenly arranged around the axis of the cylindrical concrete block, wherein a conical concrete block is further arranged at the bottom of the cylindrical concrete block, wherein the circular bottom surface of the conical concrete block is consistent in size with the circular bottom surface of the cylindrical concrete block and the conical concrete block is coaxially fixedly connected; Step 3, the main reinforcement of the flexible steel cage is connected to the main reinforcement of the pile end concrete counterweight, the main reinforcement of the flexible steel cage adopts unbonded prestressed steel strands, and the main reinforcement of the pile end concrete counterweight is connected to the main reinforcement of the flexible steel cage in a one-to-one correspondence, so that the main reinforcement of the flexible steel cage is in place, thereby locking the relative position between the main reinforcements of the flexible steel cage; Step 4, placing a pile end concrete counterweight block in the pile hole, the pile end concrete counterweight block pulls the main reinforcement of the flexible steel cage into the pile hole, and the cone tip of the conical concrete block is set downward to facilitate the pile end concrete counterweight block to pull the flexible steel cage to move downward; Step 5, winding stirrups around the outside of the main reinforcement of the flexible steel cage, and connecting the stirrups with the main reinforcement of the flexible steel cage by snap buckles, and winding stirrups around the outside of the main reinforcement of the flexible steel cage by a stirrup conveying device, the stirrup conveying device comprising a circular track, a stirrup retracting device, a slider seat, and a first motor, the stirrup retracting device comprising a stirrup winch and a second motor, the stirrup retracting device being arranged on the slider seat, the stirrup winch being arranged horizontally, a roller being arranged at the bottom of the slider seat, a groove matching the roller being arranged on the circular track, the second motor being connected to the stirrup winch, the second motor realizing the retracting and releasing of the stirrups by driving the stirrup winch to rotate, the first motor being connected to the slider seat, the first motor being able to drive the slider seat to rotate around the pile hole along the circular track, the circular track being arranged on the ground outside the pile hole, the circular track being arranged coaxially with the pile hole, and when the main reinforcement of the flexible steel cage moves downward, the stirrup retracting device rotates around the circular track while conveying stirrups, thereby spirally winding the stirrups around the outside of the main reinforcement of the flexible steel cage; Step 6, after the flexible steel cage is manufactured on site and lowered to the specified height, a prefabricated top rigid steel cage is connected to the designed elevation position of the pile top, the top rigid steel cage is coaxially arranged with the flexible steel cage, and the top rigid steel cage is located inside the flexible steel cage; Step 7, continue to lower the flexible steel cage to the designed elevation; Step 8, cleaning the hole and pouring concrete in the pile hole; Step 9: After the foundation pit is excavated to expose the concrete on the top of the pile, the main reinforcement of the flexible steel cage is tensioned and locked with anchors; Step 10: Anchor the main reinforcement of the top rigid reinforcement cage into the basement floor reinforcement to complete the construction.

2. The low-headroom bored pile construction method using a flexible steel cage as claimed in claim 1, characterized in that: After the foundation pit is excavated to the point where the concrete on the pile top is exposed, an anchor is installed on the pile top to tension the unbonded prestressed steel strands in the pile. After a single unbonded prestressed steel strand is tensioned to 50% of the designed tensile strength, it is locked with an anchor.

Images