Cast-in-place pile foundation construction method based on collapsible loess environment

Abstract

The invention discloses a cast-in-place pile foundation construction method based on the collapsible loess environment. The cast-in-place pile foundation construction method specifically comprises the following steps that a pile casing hole is dug in the pile position of a cast-in-place pile foundation, and a pile casing is buried in the pile casing hole; drilling multiple times along the pile position mark position through a decompression drill bit of the drilling machine to form a pile hole; tamping the bottom of the pile hole and cleaning scum; at least three concrete cushion blocks which are annularly arranged at equal intervals are arranged on the outer wall of the same section of each section of reinforcement cage, and then the reinforcement cages are lowered into the pile hole till lowering of all the reinforcement cages is completed; the uppermost reinforcement cage is fixed to the hole opening position of the pile hole; the guide pipe is put down and installed in the pile hole, and a pouring gap is reserved between the bottom of the guide pipe and the bottom of the pile hole; and concrete pouring is completed through the guide pipe. The construction method relates to the technical field of cast-in-place pile foundation construction, through the steps, the construction safety can be improved, and the situation that in the construction process, due to lowering of the reinforcement cage, the hole wall of a pile hole collapses is prevented.

Description

Technical Field

[0001] This invention belongs to the field of building construction and relates to the construction technology of cast-in-place pile foundations, specifically a construction method for cast-in-place pile foundations in collapsible loess environments. Background Technology

[0002] Collapsible loess is an unsaturated, undercompressed soil characterized by a significant decrease in soil strength when wetted with water, resulting in large settlement and rapid settlement under the combined effects of additional pressure and the soil's own weight.

[0003] Currently, certain technical challenges exist in the construction of cast-in-place piles in collapsible loess environments. For example, in actual operation, issues such as deviations in pile hole verticality, irregular hole diameter, and unstable hole walls can make it difficult to place the reinforcing cage. Specifically, when the pile hole is tilted, the reinforcing cage may not be able to be lowered smoothly, and forcibly lowering it may cause deformation of the cage or damage to the hole wall. Moreover, in collapsible loess environments, the hole wall is more prone to collapse once it is subjected to impact or friction from the reinforcing cage.

[0004] Therefore, a construction method for cast-in-place pile foundations in collapsible loess environments is needed to solve the above problems. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a construction method for cast-in-place pile foundations in collapsible loess environments to improve construction safety and prevent the collapse of the pile hole wall due to the lowering of the reinforcing cage during construction. During the drilling process, this invention utilizes multiple drilling operations and limits the initial drilling pressure and the drilling depth of each single drilling operation. This allows for adjustments to the subsequent drilling depth and drilling pressure based on the forming state of the pile hole after each drilling operation. Therefore, it effectively avoids significant deviations between the formed pile hole and the pre-set pile hole, ensuring the quality of the pile hole formation. This effectively reduces the difficulty of lowering the reinforcing cage and improves construction safety. Furthermore, by setting at least three equidistantly spaced, annular concrete pads on the outer wall of the reinforcing cage, a protective layer is formed around the reinforcing cage, which guides the lowering of the reinforcing cage. This effectively prevents the collapse of the pile hole inner wall caused by contact or friction between the reinforcing cage and the pile hole during construction.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for constructing cast-in-place pile foundations in collapsible loess environments, specifically comprising the following steps:

[0007] S1. Before construction, clean up the construction site, dig casing holes at the pile positions of the cast-in-place pile foundation and bury the casing inside the casing holes;

[0008] S2. The drilling rig uses a depressurized drill bit to perform multiple drilling operations along the marked pile position. The initial drilling pressure of the depressurized drill bit is 80kPa-100kPa, and the drilling depth of a single drilling operation is 40cm-50cm. When the depth of the depressurized drill bit is 5m, the drilling depth of a single drilling operation is 70cm-90cm, until the preset depth is reached to form a pile hole.

[0009] S3. Replace the pressure relief drill bit of the drilling rig with a bottom cleaning drill bit and extend it to the bottom of the pile hole. Start the drilling rig to compact the bottom of the pile hole and clean the scum, so that the sediment at the bottom of the pile hole is less than 50mm.

[0010] S4. Set at least three equidistant concrete pads in a ring on the outer wall of the same section of each steel cage. Then lower the steel cage into the pile hole. When the steel cage is lowered to the preset height, weld the two steel cage sections together and continue to lower the other steel cage section until all steel cages are lowered.

[0011] S5. Fix the position of the uppermost steel cage to the opening of the pile hole;

[0012] S6. Lower the guide pipe into the pile hole, and control the lowering depth of the guide pipe according to the depth of the pile hole, so that there is a pre-reserved pouring gap between the bottom of the guide pipe and the bottom of the pile hole.

[0013] S7. Concrete is poured through the guide pipe. After pouring is completed, the guide pipe and casing are pulled out of the pile hole.

[0014] Furthermore, in step S1, clay is used to fill and compact the casing evenly in layers around it.

[0015] Furthermore, in step S2, the initial drilling pressure includes the weight of the drill rod and the pressure-reducing drill bit, as well as the hydraulic power of the drill rig.

[0016] Furthermore, in step S2, after the decompression drill bit of the drilling rig reaches the bearing layer at the pile end, the drilled hole is cleaned and the loose soil is compacted to make the thickness of the loose soil in the hole less than 50mm.

[0017] Furthermore, in step S3, the method for cleaning the floating scum at the bottom of the pile hole includes the forward circulation cleaning method and the reverse circulation cleaning method.

[0018] Furthermore, in step S4, the concrete pad is configured as a disc-shaped structure, and the center of the plurality of concrete pads is located on the annular trajectory formed by the outer wall of the reinforcing cage.

[0019] Furthermore, the concrete pad is used to form a protective layer on the outer wall of the reinforcing cage.

[0020] Furthermore, the concrete pad block is rotatably connected to the reinforcing cage.

[0021] Furthermore, in step S6, the pouring gap is 0.5m-0.6m.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] During the drilling process, multiple drilling operations and limitations on the initial drilling pressure and the drilling depth of each drilling operation allow for adjustments to the subsequent drilling depth and pressure based on the forming state of the pile hole after each drilling operation. This effectively avoids significant deviations between the formed pile hole and the pre-set pile hole, ensuring the forming quality of the pile hole. Consequently, it effectively reduces the difficulty of subsequent steel cage placement and improves construction safety.

[0024] Furthermore, by setting at least three equidistant, ring-shaped concrete pads on the outer wall of the reinforcing cage, a protective layer is formed around the reinforcing cage, which can guide the lowering of the reinforcing cage. This can effectively prevent the collapse of the inner wall of the pile hole caused by contact or friction between the reinforcing cage and the pile hole during construction. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating a construction method for cast-in-place pile foundations in a collapsible loess environment, according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the connection structure between the reinforcing cage and the concrete pad in a method for constructing a cast-in-place pile foundation in a collapsible loess environment, according to an embodiment of the present invention.

[0028] Reference numerals: 1. Reinforcing cage; 2. Concrete pad block. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figure 1 and Figure 2 The first aspect of this invention provides a method for constructing cast-in-place pile foundations in a collapsible loess environment, specifically including the following steps:

[0031] S1. Before construction, clean up the construction site, dig casing holes at the pile positions of the cast-in-place pile foundation and bury the casing inside the casing holes;

[0032] S2. The drilling rig uses a depressurized drill bit to perform multiple drilling operations along the marked pile position. The initial drilling pressure of the depressurized drill bit is 80kPa-100kPa, and the drilling depth of a single drilling operation is 40cm-50cm. When the depth of the depressurized drill bit is 5m, the drilling depth of a single drilling operation is 70cm-90cm, until the preset depth is reached to form a pile hole.

[0033] S3. Replace the pressure relief drill bit of the drilling rig with a bottom cleaning drill bit and extend it to the bottom of the pile hole. Start the drilling rig to compact the bottom of the pile hole and clean the scum, so that the sediment at the bottom of the pile hole is less than 50mm.

[0034] S4. At least three concrete pads 2 arranged in a ring at equal intervals are set on the outer wall of the same section of each section of the steel cage 1. Then the steel cage 1 is lowered into the pile hole. When the steel cage 1 is lowered to the preset height, the welding between the two sections of the steel cage 1 is carried out, and the other section of the steel cage 1 is lowered continuously until all the steel cages 1 are lowered.

[0035] S5. Fix the uppermost steel cage 1 to the position of the pile hole opening;

[0036] S6. Lower the guide pipe into the pile hole, and control the lowering depth of the guide pipe according to the depth of the pile hole, so that there is a pre-reserved pouring gap between the bottom of the guide pipe and the bottom of the pile hole.

[0037] S7. Concrete is poured through the guide pipe. After pouring is completed, the guide pipe and casing are pulled out of the pile hole.

[0038] Through the above steps, this application enables rapid construction of cast-in-place piles. During the drilling stage, multiple drilling operations and limitations on the initial drilling pressure and the drilling depth of each operation allow for adjustments to the subsequent drilling depth and pressure based on the forming state of the pile hole after each drilling operation. This effectively avoids significant deviations between the formed pile hole and the pre-set pile hole, ensuring the quality of the pile hole formation. Consequently, it effectively reduces the difficulty of lowering the reinforcing cage 1 and improves construction safety.

[0039] Furthermore, by setting at least three equidistant, ring-shaped concrete pads 2 on the outer wall of the reinforcing cage 1, a protective layer is formed around the reinforcing cage 1, which can guide the lowering of the reinforcing cage 1. This can effectively prevent the collapse of the inner wall of the pile hole caused by contact or friction between the reinforcing cage 1 and the pile hole during construction.

[0040] In this embodiment, to improve the stability of the casing installation, step S1 is further defined. Specifically, in step S1, clay is used to fill and compact the casing in even layers around it.

[0041] In addition, the initial drilling pressure proposed in step S2 is further explained to ensure that the inner wall of the pile hole will not collapse due to excessive initial drilling pressure during operation of the pressure-reducing drill bit.

[0042] Specifically, in step S2, the initial drilling pressure includes the weight of the drill rod and the pressure-reducing drill bit, as well as the hydraulic power of the drill rig.

[0043] In addition, in step S2, after the decompression drill bit of the drilling rig reaches the bearing layer at the pile end, the drilled hole is cleaned and the loose soil is compacted to make the thickness of the loose soil in the hole less than 50mm, so as to improve the effect of subsequent pile hole formation.

[0044] In other embodiments, step S3 is further defined to improve the cleaning effect of scum and prepare for the subsequent installation of the reinforcing cage 1.

[0045] Specifically, in step S3, the method for cleaning the floating slag at the bottom of the pile hole includes the forward circulation cleaning method and the reverse circulation cleaning method.

[0046] In a further embodiment, the concrete pad 2 is further defined to enhance the protection and guiding effect on the reinforcing cage 1.

[0047] Specifically, in step S4, the concrete pad 2 is configured as a disc-shaped structure, and the center of the plurality of concrete pads 2 is located on the annular trajectory formed by the outer wall of the reinforcing cage 1. That is, the concrete pad 2 has an exposed end that is exposed to the outside of the reinforcing cage 1, so that the concrete pad 2 can be used to form a protective layer on the outer wall of the reinforcing cage 1 to prevent the reinforcing cage 1 from directly contacting the inner wall of the pile hole, which would cause the pile hole to collapse.

[0048] It should be noted that the concrete pad 2 is rotatably connected to the reinforcing cage 1, meaning that the concrete pad 2 can rotate around the outer wall trajectory of the reinforcing cage 1 when subjected to external force. Therefore, it can effectively reduce the resistance when the concrete pad 2 contacts the pile hole, and under the rotation and rolling action of the concrete pad 2, it can play a guiding role for the reinforcing cage 1, thereby further reducing the difficulty of lowering the reinforcing cage 1.

[0049] In other embodiments, the dimensions of the pouring gap are further described to better facilitate the flow of concrete. Specifically, in step S6, the pouring gap is 0.5m-0.6m.

[0050] The above embodiments are only used to illustrate the technical method of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A method for constructing a cast-in-place pile foundation in a collapsible loess environment, characterized in that: The specific steps include: S1. Preparation before construction: clean up the construction site, dig casing holes on the pile positions of the cast-in-place pile foundation and bury the casing in the casing holes; S2, the decompression drill bit of the drilling rig is used to perform multiple drilling operations along the pile position mark position; wherein, the initial drilling pressure of the decompression drill bit is 80kPa-100kPa, and the drilling depth of a single drilling operation is 40cm-50cm; when the drilling depth of the decompression drill bit is 5m, the drilling depth of a single drilling operation of the decompression drill bit is 70cm-90cm, until the preset depth is reached to form a pile hole; S3, replace the decompression drill bit of the drilling rig with a bottom cleaning drill bit, and extend it to the bottom of the pile hole, start the drilling rig, compact the bottom of the pile hole and clean the scum, so that the sediment at the bottom of the pile hole is less than 50mm; S4, at least three concrete pads (2) are arranged in a ring shape and equidistantly on the outer wall of the same cross section of each steel cage (1), and then the steel cage (1) is lowered into the pile hole. When the steel cage (1) is lowered to a preset height, welding is performed between two steel cages (1), and another steel cage (1) is continuously lowered until all steel cages (1) are lowered; S5, fixing the topmost reinforcement cage (1) and the opening of the pile hole; S6, lowering the conduit into the pile hole, and controlling the lowering depth of the conduit according to the depth of the pile hole, so that a casting gap is reserved between the bottom of the conduit and the bottom of the pile hole; S7. The concrete is poured through the guide tube. After the pouring is completed, the guide tube and the casing are pulled out from the pile hole.

2. A method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1, characterized in that: In step S1, clay is evenly filled in layers around the casing and compacted.

3. The method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1, characterized in that: In step S2, the initial drilling pressure includes the weight of the drill pipe of the drilling rig, the pressure relief drill bit and the hydraulic power of the drilling rig.

4. The method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1, characterized in that: In step S2, after the decompression drill bit of the drilling rig is rotated to the bearing layer of the pile end, the drilled hole is cleaned and the loose soil is compacted to make the loose soil thickness in the hole less than 50 mm.

5. The method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1, characterized in that: In step S3, the method for cleaning the scum at the bottom of the pile hole includes a positive circulation scum cleaning method and a reverse circulation scum cleaning method.

6. The method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1, characterized in that: In step S4, the concrete pad (2) is configured as a disc-shaped structure, and the centers of the multiple concrete pads (2) are located on the annular track formed by the outer wall of the steel cage (1).

7. A method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1 or 6, characterized in that: The concrete pad (2) is used to form a protective layer on the outer wall of the steel cage (1).

8. A method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1 or 6, characterized in that: The concrete pad (2) is rotatably connected to the steel cage (1).

9. The method for constructing a cast-in-place pile foundation in a collapsible loess environment according to claim 1, characterized in that: In step S6, the casting gap is 0.5m-0.6m.

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