Post-grouting expanded-base composite tubular pile and construction method

Abstract

According to the post-grouting expanded-base composite tubular pile and the construction method, an expanded-base technology and a post-grouting technology are combined, pile end post-grouting can efficiently fill pores of an expanded-base part, the strength and compactness of a pile end soil body are remarkably enhanced, the bearing performance of a pile foundation is improved, meanwhile, the settlement amount of the pile foundation is effectively reduced, and the construction efficiency is improved. The stability and the safety of the building in the long-term use process are ensured; a technical solution; comprising a grouting pipe, a prefabricated tubular pile and a composite pile outer wrapping body. The grouting pipes are symmetrically arranged in the prefabricated tubular pile in the axial direction, the outer sides of the grouting pipes are wrapped with water stop adhesive tape, and the length of the grouting pipes is larger than that of the prefabricated tubular pile. A composite pile wrapping body is arranged on the outer side of the prefabricated tubular pile, the prefabricated tubular pile is in a cylindrical shape, the upper portion of the composite pile wrapping body is also in a cylindrical shape, and the lower portion of the composite pile wrapping body is in a circular truncated cone shape.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering pile foundations, and in particular relates to a post-grouting bottom-expanded composite tubular pile and a construction method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Traditional construction methods often fail to achieve the ideal reinforcement effect when dealing with soft soil foundations, resulting in frequent foundation settlement and deformation problems. In order to overcome the shortcomings of traditional composite pile construction methods, post-grouting technology has been widely used in the field of foundation treatment. Post-grouting technology pre-buries grouting pipes during the construction of the pile body. After the pile body is solidified, a specific slurry is injected into the soil layer at the pile end through the grouting pipe, which penetrates, fills, and diffuses into the pores and weak points of the soil at the pile end, fills the pores and cracks generated by the bottom expansion, and improves the density of the soil. At the same time, the cement hydration products are bonded with the soil particles to form a high-strength cement-soil composite structure, which enhances the strength and bearing capacity of the soil at the pile end and effectively resists vertical loads. However, although the simple post-grouting technology has improved the foundation reinforcement effect to a certain extent, its reinforcement effect still needs to be further improved when facing complex geological conditions.

[0004] In order to further improve the foundation reinforcement effect, bottom expansion technology has been introduced into composite pile construction. As the drill bit rotates and presses down, the cut soil is brought out of the hole through the mud circulation system, gradually forming an enlarged head. The existing technology uses static pressure to form holes and uses a special device for post-grouting. However, the bottom expansion is achieved through the size of the device itself, and the bottom expansion effect is not good compared to drilling. In addition, the static pressure construction method is difficult to apply to piles with longer lengths. Summary of the invention

[0005] In view of the above problems, the present invention provides a post-grouting and bottom-expanded composite tubular pile and a construction method. By combining the bottom expansion technology with the post-grouting technology, the post-grouting at the pile end can efficiently fill the pores in the expanded bottom part, significantly enhance the strength and density of the soil at the pile end, improve the bearing capacity of the pile foundation, and effectively reduce the settlement of the pile foundation, thereby ensuring the stability and safety of the building during long-term use.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In the first aspect, the present invention provides a post-grouting and bottom-expanded composite tubular pile, comprising: a grouting pipe, a prefabricated tubular pile, and a composite pile outer body; the grouting pipe is axially symmetrically arranged inside the prefabricated tubular pile, and a water-stop tape is wrapped on the outside of the grouting pipe, and the length of the grouting pipe is greater than the length of the prefabricated tubular pile; the prefabricated tubular pile is cylindrical, and a composite pile outer body is arranged on the outside of the prefabricated tubular pile, and the upper part of the composite pile outer body is cylindrical, and the lower part is truncated cone-shaped.

[0008] Furthermore, the prefabricated tubular piles are made of prestressed high-strength concrete pipe piles; the grouting pipes are made of galvanized iron pipes; and the outer body of the composite pile is made of concrete pouring.

[0009] In a second aspect, the present invention further provides a construction method for post-grouting and bottom-expanding composite tubular piles, comprising the following steps:

[0010] S1. Use measuring instruments to accurately place the pile positions, and make pile position markings and protective measures for the prefabricated tubular piles to prevent the pile positions of the prefabricated tubular piles from being damaged;

[0011] S2. Select the specifications of the casing according to the diameter of the prefabricated tubular pile; fill the gap between the casing and the surrounding soil with clay and perform compaction;

[0012] S3. Adjust the rotary drilling rig so that the center of the drill rod is aligned with the center of the pile position; use the drill bit to cut and crush the soil layer and discharge the soil out of the hole;

[0013] S4. After drilling to the designed depth, stop drilling and use the slurry replacement method to clean the hole for the first time, replacing the sediment at the bottom of the hole and the slurry with a high sand content to the outside of the hole;

[0014] S5. Determine the bottom expansion stroke according to the design and install the stroke limiter; when the bottom expansion drill bit is lowered into the bottom of the hole, rotate the bottom expansion drill bit to drill for a set time;

[0015] S6. During the second hole cleaning, the sediment at the bottom of the pile needs to be sucked out of the hole;

[0016] S7. Use prefabricated tubular piles to carry out pile planting operations, accurately place the prefabricated tubular piles in the pile holes, ensure that the prefabricated tubular piles remain centered in the holes, and then measure the elevation of the top of the prefabricated tubular piles;

[0017] S8. Use the conduit method to pour concrete, and immediately pull out the casing after pouring;

[0018] S9. After the composite pile outer package is formed for a set time, post-grouting is performed at the bottom of the pile;

[0019] S10. Adopt the construction procedure of interval pile construction to construct adjacent piles.

[0020] Furthermore, the casing is made of steel plate, and the inner diameter of the casing is slightly larger than the designed diameter of the drill hole; the inner diameter of the casing when drilling with an impact drill and an impact grab drill is larger than the inner diameter of the casing when drilling with a rotary drill.

[0021] Furthermore, the casing has a set burial depth; the elevation of the top of the casing meets the requirements for setting the water level in the hole; and steel bar hanging rings are symmetrically welded on the upper part of the casing.

[0022] Furthermore, in the drilling construction in S3, the drilling bucket is rotated, soil is cut, the drill is lifted, and soil is thrown away, and the operation is repeated many times to form a hole until the bottom of the hole reaches the elevation.

[0023] Furthermore, before using the bottom expansion drill bit in S5, it is necessary to check whether the opening and contraction of the drill cutter are flexible; when performing bottom expansion drilling, ensure that the drilling speed is uniform and reasonable.

[0024] Furthermore, in S7, the grouting pipe needs to be protected during the pile planting process; after the prefabricated tubular piles are planted, the sealing of the grouting pipe is checked, and the portion of the grouting pipe above the ground is sealed and protected.

[0025] Furthermore, the entire pouring process of pouring concrete in S8 should be continuous, and the height of the concrete surface should be measured each time the conduit is removed to ensure that the conduit is buried to the set depth, and the conduit should be lifted and lowered vertically.

[0026] Furthermore, in S9, before the formal grouting, the construction control parameters of the prepared slurry need to be checked; the prepared slurry for post-grouting is pressurized by a grouting pump and input into the grouting pipe arranged in the prefabricated tubular pile, and the slurry is injected into the soil at the bottom of the pile by high pressure; during the grouting process of the pile bottom, the slurry concentration should change from thin slurry to thick slurry.

[0027] Compared with the prior art, the present invention has the following advantages and positive effects:

[0028] Based on the traditional bored composite pile, the present invention combines the pile bottom expansion technology with the post-grouting technology to improve the bearing capacity of the pile foundation. By constructing an enlarged head at the bottom of the pile body, the contact area between the pile end and the bearing layer is effectively increased, thereby creating favorable geometric conditions for bearing a larger vertical load. The subsequent post-grouting process is to inject grout into the soil at the pile end through a grouting pipe pre-buried in the pile body after the construction of the composite tubular pile is completed and reaches a specific strength. Post-grouting of the pile end can efficiently fill the pores of the expanded bottom part, significantly enhance the strength and density of the soil at the pile end, improve the bearing capacity of the pile foundation, and effectively reduce the settlement of the pile foundation, ensuring the stability and safety of the building during long-term use.

[0029] The present invention combines the bottom expansion technology and the post-grouting technology in the construction of the composite pile, so that the bearing area of ​​the pile end is significantly increased, which can effectively increase the proportion of the pile end resistance in the total bearing capacity, thereby greatly improving the bearing capacity of the single pile, and can effectively reduce the pile diameter and pile length, and reduce the project cost; the grouting pipe is buried in the core of the prefabricated tubular pile, so that the prefabricated tubular pile core and the grouting pipe are integrated, and the grouting pipe is fixed more firmly and is not easy to deform and move during the construction process; the drilling and bottom expansion technology and the post-grouting technology are combined through reasonable construction process and quality control measures, which can effectively ensure the integrity of the pile body and the grouting effect, and improve the overall stability of the pile foundation; compared with some traditional deep foundation construction methods, a large amount of earth excavation and transportation are reduced, and the impact on the surrounding environment is relatively small. In terms of vibration, the vibration generated by the drilling and bottom expansion operations is extremely small, and will not cause a significant impact on surrounding buildings and underground pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute improper limitations on the present invention.

[0031] Figure 1 is a cross-sectional view of an underground composite tubular pile of the present invention;

[0032] Figure 2 For the present invention Figure 1 Cross-sectional view at AA in the middle.

[0033] In the figure: 1. Soil around the pile; 2. Water-stop tape; 3. Prefabricated tubular pile; 4. Composite pile outer casing; 5. Grouting pipe; 6. Slurry; 7. Casing; 8. Bottom expansion drill bit. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0036] This embodiment discloses a post-grouting bottom-expanding composite tubular pile, such as Figure 1-Figure 2As shown, it includes: a grouting pipe 5, a prefabricated tubular pile 3, and a composite pile outer body 4; the grouting pipe 5 is axially symmetrically arranged inside the prefabricated tubular pile 3, and a water-stop tape 2 is wrapped on the outside of the grouting pipe 5, and the length of the grouting pipe 5 is greater than the length of the prefabricated tubular pile 3; a composite pile outer body 4 is arranged on the outside of the prefabricated tubular pile 3, the prefabricated tubular pile 3 is cylindrical, and the upper part of the composite pile outer body 4 is also cylindrical, and the lower part is truncated cone-shaped.

[0037] The prefabricated tubular pile 3 is made of prestressed high-strength concrete pipe pile; the grouting pipe 5 is made of galvanized iron pipe; and the composite pile outer body 4 is made of concrete pouring.

[0038] The model of the rotary drilling rig for the pile hole of the composite tubular pile can be selected according to project requirements. The operating height usually ranges from 25m to 45m, and the weight of the whole machine ranges from about 80 tons to 200 tons. The replaceable drilling tool system it is equipped with can adapt to barrel drill bits or spiral drill bits of different diameters, ensuring that the equipment can be accurately and flexibly adjusted to the target pile position in a complex construction environment, greatly improving construction efficiency and flexibility.

[0039] A construction method for post-grouting bottom-expanded composite tubular piles comprises the following steps:

[0040] S1. According to the measurement control points provided by the construction unit, the positions of the prefabricated tubular piles 3 are accurately laid out using measuring instruments such as a total station, and the positions of the prefabricated tubular piles 3 are marked and protected to prevent the positions of the prefabricated tubular piles 3 from being damaged.

[0041] S2. During the construction process, the specifications of the casing 7 are selected according to the diameter of the prefabricated tubular pile 3. The casing 7 is made of steel plate, and the inner diameter of the casing 7 is slightly larger than the design diameter of the bored pile; the diameter should be increased by 20cm to 30cm when drilling with a rotary drill; the diameter should be increased by 30cm to 40cm when drilling with an impact drill and a punching drill; the gap between the casing 7 and the surrounding soil is filled with clay and compacted. In order to facilitate lowering and pulling, steel bar lifting rings are welded symmetrically on the upper part of the casing 7; when burying the casing 7, digging or hammering, vibration, pressurization and other methods can be used; the burial setting depth is generally 2m to 4m, and in special cases such as sand layers, it should be deepened to weathered rock; the elevation of the top of the casing 7 should meet the requirements of the water level setting height in the hole, and ensure that the length of the protected pile head is greater than 0.5m.

[0042] S3. Move the rotary drilling rig to the pile position, adjust the chassis and mast of the rotary drilling rig to align the center of the drill rod with the center of the bored pile position, and use a spirit level to check the flatness of the rotary drilling rig to ensure that the rotary drilling rig does not tilt or shift during the drilling process; during drilling, the power head is used to drive the drill rod and drill bit to rotate, and the drill bit is used to cut and crush the soil layer. The cut soil is squeezed into the drill bucket, and when it is full, the drill bucket is lifted out of the hole. The chassis of the rotary drilling rig is reversed, and the drill bucket valve is opened to discharge the soil to the ground or directly unload it on a car for transportation; the drilling construction is repeated many times by rotating the drill bucket, cutting soil, lifting the drill, and throwing soil until the bottom elevation of the hole.

[0043] S4. After drilling to the designed depth, stop drilling and use the slurry replacement method to carry out the first hole cleaning to replace the sediment at the bottom of the hole and the mud with a high sand content so that the thickness of the sediment at the bottom of the hole meets the design requirements. After cleaning the hole, the mud density, sand content and viscosity in the hole should meet the requirements of the specifications.

[0044] S5. According to the design, determine the stroke of bottom expansion and install the stroke limiter; before using the bottom expansion drill bit 8, check whether the opening and contraction of the drill cutter are flexible; when the bottom expansion drill bit 8 is lowered into the bottom of the hole, the determined main shaft sliding stroke is converted into the drilling stroke of the active drill rod, and marked with chalk for easy control; when performing bottom expansion drilling, lightly press and slowly rotate the bottom expansion drill bit 8 to ensure a uniform and reasonable drilling speed; when the drilling rig reaches the marked stroke, gradually loosen the drilling rig wire rope; when the drilling resistance of the drill tool is reduced and it rotates freely, it indicates that the bottom expansion stroke has reached the bottom expansion limiter; then, re-tighten the drill tool wire rope, rotate and drill for a few minutes, gradually cut the soil to form an enlarged head, and complete the construction of the bottom expansion area; when lifting the bottom expansion drill bit 8, slowly pull it up to retract the bottom expansion drill bit 8; if the lifting and pulling of the bottom expansion drill bit 8 is blocked, slowly rotate it to slowly retract the bottom expansion drill bit 8.

[0045] S6. After hole expansion, the volume of the bottom of the composite tubular pile increases, forming a lower expanded bottom area; when cleaning the hole, a large amount of sediment is likely to be deposited in the expanded bottom area; whether the hole is cleaned thoroughly directly affects the effect of pile formation; when cleaning the hole, the sediment at the bottom of the pile needs to be sucked out of the hole to achieve the purpose of hole cleaning.

[0046] S7. Use prefabricated tubular piles 3 to carry out pile planting operations. Fix the prefabricated tubular piles 3 with buckles, then use the crane hook to lift them vertically and accurately place them in the pile hole, ensuring that the prefabricated tubular piles 3 remain centered in the hole. The grouting pipes 5 need to be protected during placement, and then the pile top elevation is measured. After the prefabricated tubular piles 3 are placed, the sealing of the grouting pipes 5 should be checked. If problems such as poor sealing occur, the faults should be eliminated in a timely manner. The part of the grouting pipes 5 that is higher than the ground should be well sealed and protected to prevent debris from entering and causing blockage.

[0047] S8. When pouring with the conduit method, the conduit should be tested for sealing in advance to ensure that there is no water leakage during the pouring process; use a crane or a pile grouting frame to pour concrete, and the initial pouring volume should ensure that the buried pipe depth is greater than 1m. The entire pouring process should be continuous, and the height of the concrete surface should be measured each time the conduit is removed to ensure that the conduit is buried to the set depth, generally 2m to 6m. The conduit should be lifted and lowered vertically; the pile top should be over-filled by 0.5m to ensure the quality of the pile top; after the pouring is completed, the casing 7 should be pulled out immediately.

[0048] S9. After the composite pile outer package 4 is formed for a set time, the pile bottom post-grouting is carried out; the prepared slurry 6 is pressurized and input into the grouting pipe 5 set in the prefabricated tubular pile 3 through a grouting pump, and the high-pressure slurry 6 enters the soil at the bottom of the composite tubular pile. Before the formal grouting, the construction control parameters such as the fluidity, stability, uniformity, solidification time and slurry concentration adjustment timing of the prepared slurry 6 need to be tested. During the pile bottom grouting process, the concentration of the slurry 6 should change from thin slurry to thick slurry. The strong permeability of thin slurry can expand the reinforcement range, and the thick slurry is beneficial to improve the strength of the reinforcement area. The grouting pressure, slurry concentration, injection rate and grouting volume will all change, and their range of change needs to be reasonably determined and controlled to improve the pile bottom grouting effect and ensure the quality of grouting construction.

[0049] S10. After completing the above steps, when the post-grouting area at the end of the composite tubular pile is stable and reaches the designed strength, the construction of adjacent piles can be carried out by adopting the construction process of interleaved piles, that is, the construction process of a single post-grouting and bottom-expanding composite tubular pile is completed.

[0050] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A post-grouting bottom-expanded composite tubular pile, characterized in that: include: Grouting pipe, prefabricated tubular pile, composite pile outer body; the grouting pipe is axially symmetrically arranged inside the prefabricated tubular pile, the outer side of the grouting pipe is wrapped with a water stop tape, and the length of the grouting pipe is greater than the length of the prefabricated tubular pile; the prefabricated tubular pile is cylindrical, and a composite pile outer body is arranged on the outer side of the prefabricated tubular pile, the upper part of the composite pile outer body is cylindrical, and the lower part is truncated cone-shaped.

2. The post-grouting bottom-expanded composite tubular pile according to claim 1, characterized in that: The prefabricated tubular piles are made of prestressed high-strength concrete pipe piles; the grouting pipes are made of galvanized iron pipes; and the outer body of the composite pile is made of concrete pouring.

3. A construction method for post-grouting bottom-expanded composite tubular piles according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Use measuring instruments to accurately place the pile positions, and make pile position markings and protective measures for the prefabricated tubular piles to prevent the pile positions of the prefabricated tubular piles from being damaged; S2. Select the specifications of the casing according to the diameter of the prefabricated tubular pile; fill the gap between the casing and the surrounding soil with clay and perform compaction; S3. Adjust the rotary drilling rig so that the center of the drill rod is aligned with the center of the pile position; use the drill bit to cut and crush the soil layer and discharge the soil out of the hole; S4. After drilling to the designed depth, stop drilling and use the slurry replacement method to clean the hole for the first time, replacing the sediment at the bottom of the hole and the slurry with a high sand content to the outside of the hole; S5. Determine the bottom expansion stroke according to the design and install the stroke limiter; when the bottom expansion drill bit is lowered into the bottom of the hole, rotate the bottom expansion drill bit to drill for a set time; S6. During the second hole cleaning, the sediment at the bottom of the pile needs to be sucked out of the hole; S7. Use prefabricated tubular piles to carry out pile planting operations, accurately place the prefabricated tubular piles in the pile holes, ensure that the prefabricated tubular piles remain centered in the holes, and then measure the elevation of the top of the prefabricated tubular piles; S8. Use the conduit method to pour concrete, and immediately pull out the casing after pouring; S9. After the composite pile outer package is formed for a set time, post-grouting is performed at the bottom of the pile; S10. Adopt the construction procedure of interval pile construction to construct adjacent piles.

4. A construction method for post-grouting bottom-expanded composite tubular piles as claimed in claim 3, characterized in that: The casing is made of steel plate, and the inner diameter of the casing is slightly larger than the designed diameter of the drill hole; the inner diameter of the casing when drilling with an impact drill and an impact grab drill is larger than the inner diameter of the casing when drilling with a rotary drill.

5. A construction method for post-grouting bottom-expanded composite tubular piles as claimed in claim 4, characterized in that: The buried depth of the casing is set; the elevation of the top of the casing meets the requirements of the water level setting height in the hole; and steel bar hanging rings are symmetrically welded on the upper part of the casing.

6. A construction method for post-grouting bottom-expanded composite tubular piles as claimed in claim 3, characterized in that: The drilling construction in S4 is carried out by rotating the drill bucket, cutting soil, lifting the drill, and throwing away soil, and the operation is repeated many times until the bottom of the hole reaches the elevation.

7. A construction method for post-grouting bottom-expanded composite tubular piles as claimed in claim 3, characterized in that: Before using the bottom expansion drill in S6, check whether the expansion cutter of the drill is flexible in opening and contracting; when performing bottom expansion drilling, ensure that the drilling speed is uniform and reasonable.

8. A construction method for post-grouting bottom-expanded composite tubular piles as claimed in claim 7, characterized in that: In S7, the grouting pipe needs to be protected during the pile planting process; after the prefabricated tubular piles are planted, the sealing of the grouting pipe is checked, and the portion of the grouting pipe above the ground is sealed and protected.

9. A construction method for post-grouting bottom-expanded composite tubular piles as claimed in claim 3, characterized in that: The entire pouring process of pouring concrete in S8 should be continuous. The height of the concrete surface should be measured each time the conduit is removed to ensure that the conduit is buried to the set depth. The conduit should be lifted and lowered vertically.

10. The construction method of a post-grouting bottom-expanded composite tubular pile according to claim 3, characterized in that: In S9, before formal grouting, the construction control parameters of the prepared slurry need to be checked; the prepared slurry for post-grouting is pressurized and input into the grouting pipe arranged in the prefabricated tubular pile through a grouting pump, and the slurry is injected into the soil at the bottom of the pile by high pressure; During the pile bottom grouting process, the slurry concentration should change from thin slurry to thick slurry.

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