Cast-in-place pile construction method

Abstract

Disclosed in the present invention is a cast-in-place pile construction method, comprising: burying a steel casing; performing impacting to create holes, in which when the hole-forming depth is above the bottom of the steel casing, a hammering height is set to be 1-2 m, when the hole-forming depth reaches the bottom of the steel casing, a hammering height is reduced to 0.4-0.6 m, and when the hole-forming depth reaches a position 3-4 m below the bottom of the steel casing, the hammering height is increased to 2-3.5 m; mounting and placing a steel reinforcement cage by connecting the steel reinforcement cage to the steel casing and fixing the steel reinforcement cage in the center of the steel casing; mounting a guide pipe, wherein a support structure is provided at the bottom of the guide pipe, the support structure is used to support the guide pipe, and a gap of 30-50 cm is reserved between the bottom of the guide pipe and the bottom of a pile hole; manufacturing a pile body by pouring concrete into the pile hole through the guide pipe so as to manufacture the pile body, wherein when the concrete is poured, the gap between the bottom of the guide pipe and the bottom of the pile hole is filled with the concrete, and the depth of the buried concrete at the lower end of the guide pipe is greater than 1.0 m; and treating a pile head. The present invention can improve the construction quality of a cast-in-place pile.

Description

Cast-in-place pile construction method Technical Field

[0001] The present invention relates to the technical field of building construction, in particular to a cast-in-place pile construction method. Background Art

[0002] Bored piles, as a construction method for cast-in-place piles, have the advantages of high bearing capacity and reliable construction quality and are currently widely used in construction and bridge engineering. Currently, the construction steps of bored piles mainly include impact drilling, installation and placement of the reinforcement cage, and pile body production. However, existing construction methods still have defects in the quality of impact drilling, the positioning of the reinforcement cage, and the quality of the pile body. As a result, the construction quality of the cast-in-place piles still needs to be improved.

[0003] Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] An object of the present invention is to provide a cast-in-place pile construction method, which can improve the quality of impact hole formation, improve the positioning accuracy of the reinforcement cage and the quality of the pile body, and ultimately improve the construction quality of the cast-in-place pile.

[0006] In order to achieve these objects and other advantages according to the present invention, a method for constructing a cast-in-place pile is provided, comprising the following steps:

[0007] Step (1) burying the steel casing: burying the steel casing at the location where the pile is to be formed;

[0008] Step (2) impact drilling: using a pile driver to impact drill holes inside the casing, when the drilling depth is above the bottom of the steel casing, the hammering height is set to 1-2m, when the drilling depth reaches the bottom of the steel casing, the hammering height is reduced to 0.4-0.6m, when the drilling depth reaches 3-4m below the bottom of the steel casing, the hammering height is increased to 2-3.5m; when the punching reaches the designed height, the hammering height is adjusted to 50-100cm and repeated impacts are performed to disturb the pile bottom sediment of the formed pile hole;

[0009] Step (3) installing and placing the steel cage: using a crane to hoist the steel cage into the pile hole, connecting the steel cage to the steel casing, fixing the steel cage in the center of the steel casing, and ensuring that the lower end of the steel cage does not contact the bottom of the pile hole;

[0010] Step (4) installing the conduit: placing the conduit inside the steel casing, with a support structure provided at the bottom of the conduit for supporting the conduit, and leaving a gap of 30-50 cm between the bottom of the conduit and the bottom of the pile hole;

[0011] Step (5) making the pile body: pouring concrete into the pile hole through the conduit to make the pile body, when pouring concrete, the concrete fills the gap between the bottom of the conduit and the bottom of the pile hole, and the depth of the lower end of the conduit buried in the concrete is greater than 1.0m;

[0012] Step (6) treating the pile head: when pouring concrete, continue pouring 1.5 m of concrete after seeing fresh concrete, then stop pouring, and vibrate with a vibrating rod until the top of the pile head is not loose;

[0013] Step (7) is to pull out the catheter.

[0014] Preferably, in the cast-in-place pile construction method, in the step (2), when punching in a soft soil layer, a mixture of clay blocks and small stones is filled into the formed pile hole portion after each 1-2 punches, with each filling height being 10-20 cm, and then punching is continued; when punching in a bedrock layer, the hammering height is 3-4 m; if the rock surface of the bedrock layer is inclined, a mixture of clay blocks and small stones is added to the formed pile hole portion, with a filling height of 30-50 cm, and then punching is continued, with a hammering height of 0.4-0.6 m, and when the bedrock layer forms a plane, the hammering height is adjusted to 1-2 m.

[0015] Preferably, in the cast-in-place pile construction method, in the step (2), when the impact hole is formed, slag is discharged every 1-2 impacts, and the mud used for slag discharge is made of bentonite or loess, the specific gravity of the mud is 1.05-1.15, the viscosity is 18-45s, the sand content is less than 6%, and the pH value is 7-9; in the step (3), after the steel cage is installed and placed, the pile hole is cleaned twice using the mud until the sediment thickness at the bottom of the pile hole is less than 5 cm.

[0016] Preferably, in the cast-in-place pile construction method, a group of connecting hooks are provided in the middle of the inner wall of the steel casing, the group of connecting hooks are evenly distributed relative to the cross-section of the steel casing, and the connecting hooks are bent in the direction; the steel cage has a transverse reinforcement hoop extending along the cross-section of the steel cage; when the steel cage is hoisted into the pile hole using a crane, the transverse reinforcement hoop is hung on the group of connecting hooks.

[0017] Preferably, in the cast-in-place pile construction method, the upper end of the steel cage is connected to a ring-shaped connecting frame, and the inner wall of the upper end of the steel casing is connected to a group of connecting steel bars. After the steel cage is hoisted into the pile hole using a crane, the ring-shaped connecting frame and the group of connecting steel bars are welded together.

[0018] Preferably, in the cast-in-place pile construction method, the annular connection frame includes at least two circles of annular connection hoops and a plurality of radial reinforcement ribs, each radial reinforcement rib is connected to the at least two circles of annular connection hoops in sequence, the plurality of radial reinforcement ribs are evenly distributed relative to each annular connection hoop, one of the annular connection hoops is an inner ring connection hoop, and the other annular connection hoop is an outer ring connection hoop; in step (3), after using a crane to hoist the steel cage into the pile hole, the annular connection frame is first sleeved on the outside of the upper end of the steel cage, and then the inner ring connection hoop is welded to the upper end of the steel cage, and the outer ring connection hoop is connected to a group of connecting steel bars of the steel casing.

[0019] Preferably, in the cast-in-place pile construction method, the support structure includes four legs, an upper support ring and a lower support ring, the upper ends of the four legs are connected to the bottom of the conduit and are evenly distributed relative to the conduit, the upper support ring is sleeved on the outside of the four legs and fixedly connected to the upper ends of the four legs, the lower support ring is sleeved on the outside of the four legs and fixedly connected to the lower ends of the four legs, the diameter of the upper support ring is smaller than the diameter of the lower support ring, and the diameter of the lower support ring is 1-2 cm smaller than the inner diameter of the steel cage.

[0020] The present invention has at least the following beneficial effects:

[0021] The embodiment of the present invention provides a cast-in-place pile construction method, comprising the following steps: step (1) burying a steel casing: burying the steel casing at a location where a pile is to be formed; step (2) impact drilling: using a pile driver to impact drill holes inside the casing, when the drilling depth is above the bottom of the steel casing, the hammering height is set to 1-2m, when the drilling depth reaches the bottom of the steel casing, the hammering height is reduced to 0.4-0.6m, when the drilling depth reaches 3-4m below the bottom of the steel casing, the hammering height is increased to 2-3.5m; when the punching reaches the designed height, the hammering height is adjusted to 50-100cm and repeated impacts are performed to disturb the pile bottom sediment of the formed pile hole; step (3) installing and placing a steel cage: using a crane to hoist the steel cage into the pile hole, connecting the steel cage to the steel casing, and placing the steel cage The invention relates to a pile body, wherein the pile body is fixed in the center position of the steel casing, and the lower end of the steel cage is not in contact with the bottom of the pile hole; step (4) installing the conduit: placing the conduit inside the steel casing, and a supporting structure is provided at the bottom of the conduit, the supporting structure is used to support the conduit, and a gap of 30-50 cm is reserved between the bottom of the conduit and the bottom of the pile hole; step (5) making the pile body: pouring concrete into the pile hole through the conduit to make the pile body, and when pouring concrete, the concrete fills the gap between the bottom of the conduit and the bottom of the pile hole, and the depth of the lower end of the conduit buried in the concrete is greater than 1.0 m; step (6) processing the pile head: when pouring concrete, continue pouring 1.5 m of concrete after seeing fresh concrete, and then stop pouring, and use a vibrating rod to vibrate until the top of the pile head is not loose; step (7) pulling out the conduit. The present invention sets the hammer height according to the different depths of the soil layer during the impact hole forming process, so as to improve the density of the soil layer at different depths, thereby improving the stability and quality of the formed pile hole, and fixes the steel cage and the steel casing to solve the problem that the steel cage is easy to shift in the subsequent construction process. At the same time, the process of installing the guide tube and making the pile body is improved to avoid the mixing of concrete and mud to form mud inclusions, thereby finally improving the construction quality of the grouting.

[0022] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a flow chart of a cast-in-place pile construction method according to an embodiment of the present invention;

[0024] FIG2 is a schematic structural diagram of a cast-in-place pile after the conduit is installed according to an embodiment of the present invention;

[0025] FIG3 is a schematic structural diagram of an annular connection frame according to an embodiment of the present invention;

[0026] FIG4 is a schematic structural diagram of a support structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0028] As shown in Figures 1 to 4, an embodiment of the present invention provides a cast-in-place pile construction method, comprising the following steps:

[0029] Step (1) burying the steel casing 1: burying the steel casing 1 at the location where the pile is to be formed.

[0030] Step (2) impact drilling: use a pile driver to impact drill holes inside the casing. When the drilling depth is above the bottom of the steel casing 1, the hammer height is set to 1-2m. When the drilling depth reaches the bottom of the steel casing 1, the hammer height is reduced to 0.4-0.6m. When the drilling depth reaches 3-4m below the bottom of the steel casing 1, the hammer height is increased to 2-3.5m. When the punching reaches the designed height, the hammer height is adjusted to 50-100cm and repeated impacts are performed to disturb the pile bottom sediment of the formed pile hole.

[0031] Step (3) Installing and placing the steel cage 2: Use a crane to hoist the steel cage 2 into the pile hole, connect the steel cage 2 to the steel casing 1, fix the steel cage 2 in the center position of the steel casing 1, and make the lower end of the steel cage 2 not contact the bottom of the pile hole.

[0032] Step (4) Installing the conduit 3: The conduit 3 is placed inside the steel casing 1. A support structure 6 is provided at the bottom of the conduit 3. The support structure 6 is used to support the conduit 3 and leave a gap of 30-50 cm between the bottom of the conduit 3 and the bottom of the pile hole.

[0033] Step (5) making the pile body: pouring concrete into the pile hole through the conduit 3 to make the pile body, when pouring concrete, the concrete fills the gap between the bottom of the conduit 3 and the bottom of the pile hole, and the depth of the lower end of the conduit 3 buried in the concrete is greater than 1.0m.

[0034] Step (6) treating the pile head: when pouring concrete, continue pouring 1.5 m of concrete after seeing fresh concrete, then stop pouring, and vibrate with a vibrating rod until the top of the pile head is not loose.

[0035] Step (7) pulls out the catheter 3.

[0036] During the construction process, as the depth of the pile driver entering the soil layer varies, the situation near the pile hole also changes. If a uniform hammering height is used, the quality of the pile hole will be affected, resulting in the collapse of the pile hole or the instability of the soil layer around the pile hole, thereby affecting the final pile quality. The present invention accurately sets the hammering height as the soil layer depth (i.e., the hole depth) changes. When the hole depth is above the bottom of the steel casing 1, the hammering height is set to 1-2m. When the hole depth reaches the bottom of the steel casing 1, the hammering height is reduced to 0.4-0.6m. When the hole depth reaches 3-4m below the bottom of the steel casing 1, the hammering height is increased to 2-3.5m. The hammering height is first reduced and then increased, which can improve the density of the soil layer near the bottom of the steel casing 1 and improve the stability of the area near the bottom of the bored pile formed by the construction. When the design height is reached, the hammering height is adjusted to 50-100cm, and repeated impacts are performed to peel off the sediment from the soil layer at the bottom of the pile hole by shaking the bottom of the pile hole, so as to facilitate the emptying operation.

[0037] Furthermore, during the process of installing the steel cage 2, after the steel cage 2 is hoisted into the pile hole, the steel cage 2 is connected to the steel casing 1, thereby fixing the steel cage 2 in the center position of the steel casing 1 to prevent the steel cage 2 from shifting in the steel casing 1. At the same time, through the above-mentioned fixation, the lower end of the steel cage 2 is prevented from contacting the bottom of the pile hole, and the deformation of the steel cage 2 is avoided, thereby improving the stability of the cast-in-place pile.

[0038] Furthermore, when installing the conduit 3 and constructing the pile body, a support structure 6 is used to support the conduit 3, leaving a certain gap between the conduit 3 and the bottom of the pile hole to ensure that concrete can overflow from the bottom of the conduit 3. Furthermore, when pouring concrete, the concrete fills the gap between the bottom of the conduit 3 and the bottom of the pile hole, and the lower end of the conduit 3 is buried in the concrete to a depth of more than 1.0 m. This prevents the concrete from mixing with the mud inside the pile hole, which would cause mud inclusion, thereby improving the construction quality of the cast-in-place pile.

[0039] To sum up, the present invention sets the hammer height according to the different depths of the soil layer during the impact hole forming process to improve the compaction degree of the soil layer at different depths, thereby improving the stability and quality of the formed pile hole, and fixes the steel cage 2 to the steel casing 1 to solve the problem that the steel cage 2 is easily displaced during the subsequent construction process. At the same time, the process of installing the guide tube 3 and making the pile body is improved to avoid the mixing of concrete and mud to form mud inclusions, thereby ultimately improving the construction quality of the grouting device.

[0040] In a preferred embodiment, in the cast-in-place pile construction method, in the step (2), when punching holes in a soft soil layer, a mixture of clay blocks and small stones is filled into the formed pile hole portion after each 1-2 punches, with each filling height being 10-20 cm, and then punching is continued; when punching holes in a bedrock layer, the hammering height is 3-4 m; if the rock surface of the bedrock layer is inclined, a mixture of clay blocks and small stones is added to the formed pile hole portion, with a filling height of 30-50 cm, and then punching is continued, with a hammering height of 0.4-0.6 m, and after the bedrock layer forms a plane, the hammering height is adjusted to 1-2 m.

[0041] Among them, when encountering a soft soil layer, a mixture of clay blocks and small stones of a certain height is thrown into the pile hole every few impacts. During the impact process, the clay blocks and small stones are mixed into the surrounding soil layer to enhance the strength and stability of the soil layer around the pile hole formed by the impact. When encountering a bedrock layer, the hammering height is increased and the hammering frequency is reduced to effectively crush the bedrock layer. However, if the rock surface of the bedrock layer is inclined, a mixture of clay blocks and small stones can be thrown into the pile hole, using the clay blocks and small stones as a buffer, and hammering is performed at a lower hammering height to gradually flatten the inclined part of the bedrock layer, and then return to the normal hammering height. This measure will avoid the problem of skewed pile holes caused by continuous hammering on an inclined rock surface.

[0042] In a preferred embodiment, in the cast-in-place pile construction method, in the step (2), when impacting the hole, slag is discharged every 1-2 impacts, and the mud used for slag discharge is made of bentonite or loess, the specific gravity of the mud is 1.05-1.15, the viscosity is 18-45s, the sand content is less than 6%, and the pH value is 7-9; in the step (3), after the steel cage 2 is installed and placed, the pile hole is cleaned twice using the mud until the sediment thickness at the bottom of the pile hole is less than 5 cm.

[0043] During impact drilling, timely slag removal is essential to prevent sediment from affecting the impact on the pile hole and the quality of the hole. This invention utilizes a slurry formulated with bentonite or loess, and selects the slurry ratio, viscosity, sand content, and pH value. These parameters allow for effective slurry removal from the pile hole. Slurry with excessively low or high viscosity will hinder sediment removal.

[0044] After the reinforcement cage 2 is placed, the pile hole needs to be cleaned for a second time using mud to prevent sediment from being deposited at the bottom of the pile hole and affecting the pouring of concrete.

[0045] In a preferred embodiment, in the cast-in-place pile construction method, a group of connecting hooks 4 are provided in the middle of the inner wall of the steel casing 1, and the group of connecting hooks 4 are evenly distributed relative to the cross-section of the steel casing 1, and the connecting hooks 4 are bent in the direction; the steel cage 2 has a transverse reinforcement hoop extending along the cross-section of the steel cage 2; when the steel cage 2 is hoisted into the inside of the pile hole using a crane, the transverse reinforcement hoop is hung on the group of connecting hooks 4.

[0046] During the process of placing the steel cage 2 below, the connecting hooks 4 and the transverse reinforcing hoops originally on the steel cage 2 are first used to determine the center position of the steel cage 2 in the steel casing 1, and to prevent the bottom of the steel cage 2 from contacting the bottom of the pile hole and deforming. Specifically, the steel cage 2 itself is provided with transverse reinforcing hoops at regular intervals. Therefore, a set of connecting hooks 4 is pre-processed in the middle of the steel casing 1. When the steel cage 2 is placed downward, the transverse reinforcing hoops in the middle of the steel cage 2 can be directly hung on this set of connecting hooks 4, confining the steel cage 2 to the middle of the steel casing 1, thereby limiting the position of the steel cage 2. Moreover, using the connecting hooks 4 and the transverse reinforcing hoops of the steel cage 2 itself to limit the steel cage 2 can achieve rapid positioning of the position below the steel cage 2, simplifying the construction process and reducing processing costs.

[0047] In a preferred embodiment, in the cast-in-place pile construction method, the upper end of the steel cage 2 is connected to a ring-shaped connecting frame 5, and the inner wall of the upper end of the steel casing 1 is connected to a group of connecting steel bars 10. After the steel cage 2 is hoisted into the pile hole using a crane, the ring-shaped connecting frame 5 and the group of connecting steel bars 10 are welded together.

[0048] In order to further determine the position of the steel cage 2 and avoid displacement of the steel cage 2, an annular connecting frame 5 is added, and a group of connecting steel bars 10 are set inside the upper end of the steel casing 1. The annular connecting frame 5 and the connecting steel bars 10 are welded together to fix the steel cage 2 to the steel casing 1, and ensure that the steel cage 2 does not deviate from the center position of the steel casing 1 during the concrete pouring process and does not sink to the bottom.

[0049] In a preferred embodiment, in the cast-in-place pile construction method, the annular connecting frame 5 includes at least two circles of annular connecting hoops and multiple radial reinforcing ribs 9, each radial reinforcing rib 9 is connected to the at least two circles of annular connecting hoops in sequence, and the multiple radial reinforcing ribs 9 are evenly distributed relative to each annular connecting hoop, one of the annular connecting hoops is an inner ring connecting hoop 7, and the other annular connecting hoop is an outer ring connecting hoop 8; in step (3), after using a crane to hoist the steel cage 2 into the pile hole, the annular connecting frame 5 is first sleeved on the outside of the upper end of the steel cage 2, and then the inner ring connecting hoop 7 is welded to the upper end of the steel cage 2, and the outer ring connecting hoop 8 is connected to a group of connecting steel bars 10 of the steel casing 2.

[0050] The annular connecting frame 5 is used to connect the steel cage 2 and the steel casing 1, so its strength must be paid attention to. The annular connecting frame 5 includes at least two rings of connecting hoops and a plurality of radial reinforcing ribs 9. Each radial reinforcing rib 9 connects at least two rings of connecting hoops into a whole. The annular connecting frame 5 can be used as an auxiliary device, that is, the steel cage 2 can be made separately. After the steel cage 2 is hung in place using the connecting hook 4, the annular connecting frame 5 and the connecting steel bars 10 of the steel casing 1 are welded together to achieve a fixed connection between the steel cage 2 and the steel casing 1. Such a design can improve the flexibility of the processing of the steel cage 2, and the implementation method is simple and the construction cost is low.

[0051] In a preferred embodiment, in the cast-in-place pile construction method, the support structure 6 includes four legs 11, an upper support ring 12 and a lower support ring 13. The upper ends of the four legs 11 are connected to the bottom of the conduit 3 and are evenly distributed relative to the conduit 3. The upper support ring 12 is arranged on the outside of the four legs 11 and is fixedly connected to the upper ends of the four legs 11. The lower support ring 13 is sleeved on the outside of the four legs 11 and is fixedly connected to the lower ends of the four legs 11. The diameter of the upper support ring 12 is smaller than the diameter of the lower support ring 13, and the diameter of the lower support ring 13 is 1-2 cm smaller than the inner diameter of the steel cage 2.

[0052] To ensure that the conduit 3 maintains the designed distance from the bottom of the pile hole after sinking, an auxiliary support structure 6 is installed at the lower end of the conduit 3. The support structure 6 must have sufficient stability and must leave space to ensure that concrete can overflow from the bottom of the conduit 3. The support structure 6 includes four legs and two upper and lower support rings. The diameter of the upper support ring is smaller than the diameter of the lower support ring, so that the support structure 6 forms a trumpet shape to provide sufficiently stable support for the conduit 3. The diameter of the lower support ring is 1-2 cm smaller than the inner diameter of the steel cage 2 to reduce the displacement of the conduit 3 inside the steel cage 2 and ensure that concrete overflows evenly from the bottom of the conduit 3 to the outside of the conduit 3, thereby filling the steel cage 2 and the surrounding space at a relatively uniform rate.

[0053] In summary, the embodiment of the present invention provides a cast-in-place pile construction method, comprising the following steps: step (1) burying steel casing: burying the steel casing at the location where the pile is to be formed; step (2) impact drilling: using a pile driver to impact drill holes inside the casing, when the drilling depth is above the bottom of the steel casing, the hammering height is set to 1-2m, when the drilling depth reaches the bottom of the steel casing, the hammering height is reduced to 0.4-0.6m, when the drilling depth reaches 3-4m below the bottom of the steel casing, the hammering height is increased to 2-3.5m; when the punching reaches the designed height, the hammering height is adjusted to 50-100cm and repeated impacts are performed to disturb the pile bottom sediment of the formed pile hole; step (3) installing and placing a steel cage: using a crane to hoist the steel cage into the pile hole, connecting the steel cage to the steel casing, and placing the steel cage. The reinforcement cage is fixed at the center position of the steel casing, and the lower end of the reinforcement cage is not in contact with the bottom of the pile hole; step (4) installing the conduit: placing the conduit inside the steel casing, and a support structure is provided at the bottom of the conduit, the support structure is used to support the conduit, and a gap of 30-50 cm is reserved between the bottom of the conduit and the bottom of the pile hole; step (5) making the pile body: pouring concrete into the pile hole through the conduit to make the pile body, when pouring concrete, the concrete is filled in the gap between the bottom of the conduit and the bottom of the pile hole, and the depth of the lower end of the conduit buried in the concrete is greater than 1.0 m; step (6) processing the pile head: when pouring concrete, continue pouring 1.5 m of concrete after seeing fresh concrete, and then stop pouring, and use a vibrating rod to vibrate until the top of the pile head is not loose; step (7) pulling out the conduit. The present invention sets the hammer height according to the different depths of the soil layer during the impact hole forming process, so as to improve the density of the soil layer at different depths, thereby improving the stability and quality of the formed pile hole, and fixes the steel cage and the steel casing to solve the problem that the steel cage is easy to shift in the subsequent construction process. At the same time, the process of installing the guide tube and making the pile body is improved to avoid the mixing of concrete and mud to form mud inclusions, thereby finally improving the construction quality of the grouting.

[0054] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the present invention. Further modifications will be readily apparent to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims

1. A method for constructing a cast-in-place pile, characterized in that: The following steps are involved: Step (1) burying the steel casing: burying the steel casing at the location where the pile is to be formed; Step (2) impact drilling: a pile driver is used to impact drill holes inside the casing. When the drilling depth is above the bottom of the steel casing, the hammering height is set to 1-2 m. When the drilling depth reaches the bottom of the steel casing, the hammering height is reduced to 0.4-0.6 m. When the drilling depth reaches 3-4 m below the bottom of the steel casing, the hammering height is increased to 2-3.5 m. When the punching reaches the designed height, the hammering height is adjusted to 50-100 cm and repeatedly impacted to disturb the pile bottom sediment of the formed pile hole. Step (3) installing and placing the steel cage: using a crane to hoist the steel cage into the pile hole, connecting the steel cage to the steel casing, fixing the steel cage at the center of the steel casing, and making the lower end of the steel cage not contact the bottom of the pile hole; Step (4) installing the conduit: placing the conduit inside the steel casing, with a support structure provided at the bottom of the conduit, the support structure being used to support the conduit, and leaving a gap of 30-50 cm between the bottom of the conduit and the bottom of the pile hole; Step (5) making a pile body: pouring concrete into the pile hole through the conduit to make the pile body, when pouring concrete, the concrete fills the gap between the bottom of the conduit and the bottom of the pile hole, and the depth of the lower end of the conduit buried in the concrete is greater than 1.0m; Step (6) treating the pile head: when pouring concrete, continue pouring 1.5 m of concrete after seeing fresh concrete, then stop pouring, and vibrate with a vibrating rod until the top of the pile head is not loose; Step (7) is to pull out the catheter.

2. The cast-in-place pile construction method according to claim 1, characterized in that: In the step (2), when punching holes in a soft soil layer, a mixture of clay blocks and small stones is filled into the formed pile hole portion after each 1-2 impacts, with each filling height being 10-20 cm, and then the punching is continued; when punching holes in a bedrock layer, the hammering height is 3-4 m; if the rock surface of the bedrock layer is inclined, a mixture of clay blocks and small stones is added into the formed pile hole portion, with the filling height being 30-50 cm, and then the punching is continued, with the hammering height being 0.4-0.6 m, and when the bedrock layer forms a plane, the hammering height is adjusted to 1-2 m.

3. The cast-in-place pile construction method according to claim 2, characterized in that: In the step (2), when the impact hole is formed, slag is discharged every 1-2 impacts, and the mud used for slag discharge is made of bentonite or loess, and the specific gravity of the mud is 1.05-1.15, the viscosity is 18-45s, the sand content is less than 6%, and the pH value is 7-9; in the step (3), after the installation and placement of the steel cage, the pile hole is cleaned twice with the mud until the sediment thickness at the bottom of the pile hole is less than 5 cm.

4. The cast-in-place pile construction method according to claim 1, characterized in that: A group of connecting hooks is arranged in the middle of the inner wall of the steel casing, and the group of connecting hooks are evenly distributed relative to the cross-section of the steel casing, and the connecting hooks are bent toward each other; the steel cage has a transverse reinforcement hoop extending along the cross-section of the steel cage; when the steel cage is hoisted into the pile hole by a crane, the transverse reinforcement hoop is hung on the group of connecting hooks.

5. The cast-in-place pile construction method according to claim 4, characterized in that: The upper end of the steel cage is connected to an annular connecting frame, and the inner wall of the upper end of the steel casing is connected to a group of connecting steel bars. After the steel cage is hoisted into the pile hole by a crane, the annular connecting frame is welded to the group of connecting steel bars.

6. The cast-in-place pile construction method according to claim 5, characterized in that: The annular connection frame includes at least two circles of annular connection hoops and a plurality of radial reinforcement ribs, each radial reinforcement rib is connected to the at least two circles of annular connection hoops in sequence, and the plurality of radial reinforcement ribs are evenly distributed relative to each annular connection hoop, wherein one annular connection hoop is an inner ring connection hoop, and the other annular connection hoop is an outer ring connection hoop; in step (3), after the steel cage is hoisted into the pile hole by a crane, the annular connection frame is first sleeved on the outer side of the upper end of the steel cage, and then the inner ring connection hoop is welded to the upper end of the steel cage, and the outer ring connection hoop is connected to a group of connecting steel bars of the steel casing.

7. The cast-in-place pile construction method according to claim 1, characterized in that: The support structure includes four legs, an upper support ring and a lower support ring. The upper ends of the four legs are connected to the bottom of the conduit and are evenly distributed relative to the conduit. The upper support ring is sleeved on the outside of the four legs and fixedly connected to the upper ends of the four legs. The lower support ring is sleeved on the outside of the four legs and fixedly connected to the lower ends of the four legs. The diameter of the upper support ring is smaller than the diameter of the lower support ring, and the diameter of the lower support ring is 1-2 cm smaller than the inner diameter of the steel cage.

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