Cast-in-place concrete pile construction method based on soft soil layer

Abstract

The invention discloses a cast-in-place concrete pile construction method based on a soft soil layer, which comprises the following steps: dynamically adjusting and determining a pile position layout through a three-dimensional geologic model; according to the determined pile position, a high-pressure jet grouting drill bit is used for vertical drilling, when the high-pressure jet grouting drill bit drills into a soft soil layer, a degradable fiber net barrel is synchronously lowered along with the high-pressure jet grouting drill bit, and nano modified mud is synchronously injected in the lowering process to form double protection walls; after the high-pressure jet grouting drill bit drills into the karst layer, circumferential high-pressure jet grouting of concrete grout is conducted through the high-pressure jet grouting drill bit, so that the concrete grout is jetted into the karst layer to fill holes and cracks, and an annular reinforcing ring layer is formed; and after drilling of the pile hole is completed, the upward lifting and pressing jet grouting drill bit leaves the pile hole, and then concrete grout is poured into the pile hole to form the cast-in-place concrete pile. The method has the advantage of being capable of adapting to the complex geological condition that a soft soil layer and a karst stratum are combined.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building construction, and particularly relates to a concrete bored pile construction method based on soft soil layers. BACKGROUND

[0002] The construction of concrete bored piles in soft soil areas faces many difficulties, and the soft soil layer has characteristics such as high compressibility, low strength, and high water content, which can easily lead to problems such as pile hole shrinkage and hole collapse, seriously affecting the construction progress and engineering quality.

[0003] Moreover, when facing the complex geological conditions of karst strata under soft soil layers, the traditional concrete bored pile construction method and wall protection technology have obvious limitations and cannot meet the requirements of efficient, high-quality construction, environmental protection and other aspects. SUMMARY

[0004] The purpose of the present application is to provide a concrete bored pile construction method based on soft soil layers, which simultaneously lowers a degradable fiber mesh cylinder and injects nano-modified mud to form a double wall during drilling in soft soil layers, and performs circumferential high-pressure jet grouting in advance to spray concrete slurry into karst strata to fill holes and cracks and form a ring-shaped reinforced circle layer, providing stable support for subsequent concrete bored pile construction.

[0005] The purpose of the present application is achieved by the following technical solution: A concrete bored pile construction method based on soft soil layers, wherein the lower part of the soft soil layer is a karst layer, characterized in that the construction method comprises the following steps: S1: Establish a three-dimensional geological model based on a BIM building information model and a GIS geographic information system; dynamically adjust and determine the pile layout through the three-dimensional geological model; S2: According to the determined pile position, use a high-pressure jet grouting drill bit on a drilling device to perform vertical drilling, and when the high-pressure jet grouting drill bit drills into the soft soil layer, a degradable fiber mesh cylinder is lowered synchronously with the high-pressure jet grouting drill bit, and nano-modified mud is injected synchronously during the lowering of the degradable fiber mesh cylinder to form a double wall; S3: After the high-pressure jet grouting drill bit drills into the karst layer, perform circumferential high-pressure jet grouting of concrete slurry through the high-pressure jet grouting drill bit to spray concrete slurry into the karst layer to fill holes and cracks and form a ring-shaped reinforced circle layer; S4: After the pile hole is drilled, the high-pressure jet grouting drill bit is lifted out of the pile hole, and then concrete slurry is poured into the pile hole to form a concrete bored pile.

[0006] The degradable fiber mesh cylinder is in a cylindrical shape, and the degradable fiber mesh cylinder is a PLA-PCL blended fiber woven mesh cylinder, wherein PLA is polylactic acid, PCL is polycaprolactone, and the mass ratio of polylactic acid to polycaprolactone in the base material of the PLA-PCL blended fiber woven mesh cylinder is 2:1.

[0007] The drilling rig device comprises a running chassis, a support, a drill rod driving mechanism, at least two slurry storage tanks, a slurry conveying pipeline, a fixed pulley block and the high-pressure rotary jet drill bit, wherein the running chassis is supported on the ground of a construction site through at least four hydraulic support legs, the support is vertically arranged on the running chassis, an equipment mounting platform is fixedly arranged on the upper portion of the support, the drill rod driving mechanism is mounted on the equipment mounting platform, the high-pressure rotary jet drill bit comprises a toothed drill bit, a horizontally telescopic cutter and a grouting drill rod, the slurry storage tank is mounted on the running chassis, one end of the slurry conveying pipeline is connected to the slurry storage tank, and the other end of the slurry conveying pipeline is connected to the top end of the grouting drill rod through the fixed pulley block fixed on the top end of the support.

[0008] An active rotary sealing connection structure is adopted between the end of the slurry conveying pipeline and the top end of the grouting drill rod; and a booster pump is connected to the slurry storage tank to pump the slurry into the cavity of the grouting drill rod through the slurry conveying pipeline for external jetting.

[0009] The end of the grouting drill rod is sequentially provided with the toothed drill bit, the horizontally telescopic cutter and a grouting nozzle from bottom to top, the horizontally telescopic cutter is arranged in at least four groups along the ring direction of the grouting drill rod, and the grouting nozzle is arranged in at least four groups along the ring direction of the grouting drill rod and is connected to the inside of the cavity of the grouting drill rod.

[0010] The bottom of the degradable fiber mesh cylinder is provided with a plurality of insertion holes along the ring direction, the front end of the horizontally telescopic cutter is fixedly provided with an insertion piece, the insertion piece is inserted into or withdrawn from the insertion hole by controlling the extension or contraction of the horizontally telescopic cutter, the degradable fiber mesh cylinder is lowered synchronously with the high-pressure rotary jet drill bit when the insertion piece is inserted into the insertion hole, and the connection between the insertion piece and the degradable fiber mesh cylinder is released by controlling the insertion piece to withdraw from the insertion hole when the degradable fiber mesh cylinder is lowered to a predetermined depth.

[0011] The mass components of the nano-modified mud are: 100 parts of water, 60-80 parts of bentonite, 1-3 parts of polymer dry powder and 5-15 parts of nano-silicon dioxide dry powder, wherein the polymer dry powder is polyacrylamide.

[0012] The advantages of the present application are: (1) It can adapt to the complex geological conditions of the combination of soft soil layer and karst stratum, temporarily support the upper soft soil layer hole by adopting degradable fiber mesh tube, and double wall protection by injecting nano modified mud; in addition, the high pressure jet grouting method is adopted to pre-construct the annular reinforced circle layer in the lower karst stratum area, and provide a stable foundation for the subsequent concrete bored pile construction; (2) The degradable fiber mesh tube is made of degradable PLA-PCL blended fiber, which can realize self-degradation in a short period of time under the condition of ensuring sufficient compressive mechanical properties, and avoid the high-cost recovery problem; (3) The nano modified mud greatly enhances the impermeability of the wall protection, effectively reduces the risk of hole collapse; bentonite can improve the viscosity and suspension of the mud; polymer can enhance the stability and flexibility of the mud; nano silicon dioxide can fill the small pores in the mud, further improve the impermeability; (4) The horizontal telescopic cutter on the grouting drill rod drives the degradable fiber mesh tube to be lowered synchronously, and the connection with the degradable fiber mesh tube is released before reaching the lower karst stratum area, realizing the automation of the synchronous lowering of the degradable fiber mesh tube. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 2 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 1 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 3 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 4 Figure 3 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 5 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 4 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 6 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; Figure 7 It is a schematic view of the high pressure jet grouting bit of the drilling rig device in the application when drilling into the soft soil layer; ​​Detailed Implementation

[0014] The features and other related features of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so as to facilitate understanding by those skilled in the art: Example: Figures 1-7 As shown, this embodiment specifically relates to a method for constructing cast-in-place concrete piles based on soft soil layers. The construction method includes the following steps: (S1) Based on BIM building information model and GIS geographic information system, establish a detailed three-dimensional geological model; through the analysis of the three-dimensional geological model, avoid unfavorable geological areas, dynamically adjust and determine the pile location layout, and ensure the feasibility and safety of pile foundation construction.

[0015] (S2) In this embodiment, the soft soil layer 14 is below the karst layer 15. According to the determined pile position, the drilling rig is moved above the pile position and the high-pressure jet grouting drill bit on the drilling rig is used to drill vertically. When the high-pressure jet grouting drill bit drills into the soft soil layer, the biodegradable fiber mesh 10 is lowered synchronously with the high-pressure jet grouting drill bit. During the lowering of the biodegradable fiber mesh 10, nano-modified mud is injected synchronously to form a double protective wall.

[0016] The drilling rig includes a traveling chassis 1, a support 6, a drill rod drive mechanism 8, at least two grout storage tanks 3, a grout delivery pipeline 4, a fixed pulley block 5, and a high-pressure jet grouting drill bit. The traveling chassis 1 is supported on the construction site ground by at least four hydraulic outriggers 2. The support 6 is vertically mounted on the traveling chassis 1, and an equipment installation platform 7 is fixedly mounted on the upper part of the support 6. The drill rod drive mechanism 8 is mounted on the equipment installation platform 7. The high-pressure jet grouting drill bit includes a toothed drill bit 12, a horizontal telescopic cutter 11, and a grouting drill rod 9. Two grout storage tanks 3 are mounted on the traveling chassis 1, one for storing nano-modified mud and the other for storing concrete slurry. One end of the grout delivery pipeline 4 is connected to one of the grout storage tanks 3, and the other end of the grout delivery pipeline 4 is wound around the fixed pulley block 5 and then extends outward to connect to the top of the grouting drill rod 9.

[0017] Furthermore, the end of the grouting pipe 4 and the top of the grouting drill rod 9 adopt a movable rotary sealing connection structure. The so-called movable rotary sealing connection structure specifically refers to a structure that can limit each other in the vertical direction and maintain mutual rotational movement. That is, the grouting drill rod 9 can maintain a sealed connection with the grouting pipe 4 when rotating, so as to ensure that synchronous grouting or subsequent high-pressure jet grouting can be achieved.

[0018] The end of the grouting drill rod 9 is sequentially provided with the toothed drill bit 12, the horizontal telescopic cutter 11 and the grouting nozzle 13 from bottom to top, the horizontal telescopic cutter 11 is provided with at least four groups along the ring direction of the grouting drill rod 9, the horizontal telescopic cutter 11 can perform telescopic action in the radial direction, and the grouting nozzle 13 is provided with at least four groups along the ring direction of the grouting drill rod 9 and is connected with the inside of the cavity of the grouting drill rod 9.

[0019] The bottom of the degradable fiber mesh cylinder 10 is provided with a plurality of insertion holes 17 along the ring direction, the front end of the horizontal telescopic cutter 11 is fixedly provided with an insertion piece 16, the insertion piece 16 is inserted into or withdrawn from the insertion hole 17 of the degradable fiber mesh cylinder 10 by controlling the extension or contraction of the horizontal telescopic cutter 11; in this step, before the toothed drill bit 12 starts to drill, the horizontal telescopic cutter 11 is controlled to contract to sleeve the degradable fiber mesh cylinder 10 to the outside of the grouting drill rod 9, when the toothed drill bit 12 drills into the soft soil layer 14, the horizontal telescopic cutter 11 is controlled to extend so that the insertion piece 16 thereon is inserted into the insertion hole 17 of the degradable fiber mesh cylinder 10 to form a connection, so that the degradable fiber mesh cylinder 10 is synchronously lowered during the downward drilling of the toothed drill bit 12 and the horizontal telescopic cutter 11.

[0020] The booster pump (not shown in the figure, built-in in the structure of the slurry storage tank 3) is arranged on the slurry storage tank 3, and the slurry stored in the inside can be pumped out through the slurry conveying pipeline 4 by the booster pump. In this step, it can be determined that the end of the slurry conveying pipeline 4 is connected with the slurry storage tank 3 storing the nano-modified mud, the nano-modified mud is pumped into the grouting drill rod 9 through the slurry conveying pipeline 4 by the booster pump and is injected into the pile hole through the grouting nozzle 13, and forms a double protective wall together with the degradable fiber mesh cylinder 10.

[0021] In this embodiment, the degradable fiber mesh cylinder 10 is in a cylindrical shape, and the degradable fiber mesh cylinder 10 is a PLA-PCL blended fiber woven mesh cylinder, wherein PLA is polylactic acid, PCL is polycaprolactone, and the mass ratio of polylactic acid to polycaprolactone in the base material of the PLA-PCL blended fiber woven mesh cylinder is 2:1. Through the above material selection, the degradable fiber mesh cylinder 10 has sufficient tensile strength and radial support force, that is, it can withstand the tensile stress and formation pressure during the lowering process to prevent fracture, and has sufficient ring stress to support the hole wall. In addition, the degradable fiber mesh cylinder 10 can accelerate degradation after the concrete slurry of the pile hole forms sufficient strength, gradually transfer the load completely to the consolidated body, and finally most of the degradation is completed within half a year to two years.

[0022] The specific quality components of the nano-modified mud are: water 100 parts, bentonite 60-80 parts, polymer dry powder 1-3 parts, and nano-silica dry powder 5-15 parts, wherein the polymer dry powder is polyacrylamide. The nano-modified mud greatly enhances the impermeability of the wall protection, effectively reducing the risk of hole collapse. The bentonite can improve the viscosity and suspensibility of the mud, the polymer enhances the stability and flexibility of the mud, and the nano-silica can fill the small pores in the mud, further improving the impermeability.

[0023] The nano-modified mud in this embodiment has the following characteristics compared with the traditional bentonite mud: (API filtration loss): The traditional bentonite mud is usually 15-25 mL; the nano-modified mud in this case is less than 10 mL.

[0024] (mud skin quality): The mud skin of the traditional bentonite mud is thick and loose; the nano-modified mud in this case is extremely thin, tough and dense.

[0025] (wall protection effect): The wall protection effect of the traditional bentonite mud is general, and it is easy to collapse in loose strata; the wall protection effect of the nano-modified mud in this case is excellent, effectively sealing micro-pores and preventing hole collapse.

[0026] (S3) After the gnawing drill bit 12 completes the drilling of the soft soil layer 14, the next step is to drill into the karst layer 15, the rotation drilling of the gnawing drill bit 12 is paused, the end of the slurry conveying pipeline 4 is connected to the slurry storage tank 3 storing the concrete slurry, in addition, the plug-in part 16 on the horizontal telescopic cutter 11 is controlled to withdraw from the plug-in hole 17 of the degradable fiber mesh tube 10 to disconnect the connection between the plug-in part 16 and the degradable fiber mesh tube 10, so that the degradable fiber mesh tube 10 remains unchanged in position at this depth range, and after disconnection, the horizontal telescopic cutter 11 is controlled to extend to the maximum length.

[0027] Then control the gnawing drill bit 12 and the horizontal telescopic cutter 11 on it to rotate and drill downward, the slurry storage tank 3 pumps the concrete slurry into the slurry injection drill pipe 9 through the slurry conveying pipeline 4 and performs circumferential high-pressure rotary jetting through the slurry injection nozzle 13, so as to spray the concrete slurry into the karst layer 15 to fill the holes and cracks, form a ring-shaped reinforced layer, and effectively prevent cave leakage, providing a stable foundation for subsequent concrete bored pile construction.

[0028] It should be noted that when drilling in the karst layer 15, the horizontal telescopic cutter 11 can be controlled to extend outward appropriately to increase the rotary digging diameter, realizing pile end expansion operation, increasing the contact area of the pile end with the foundation soil, increasing the friction and end bearing force of the pile end with the foundation soil, and improving the overall bearing capacity of the pile foundation.

[0029] (S4) After the pile hole is drilled, the high-pressure rotary jetting drill bit is removed from the pile hole, and then the reinforcement cage is lowered into the pile hole and the concrete slurry is poured to form a concrete bored pile.

[0030] The beneficial effects of the present embodiment are: (1) It can adapt to the complex geological conditions of the combination of soft soil layer and karst stratum. The upper soft soil layer is temporarily supported by the degradable fiber mesh tube, and the double wall is formed by injecting nano-modified mud. In addition, the high-pressure rotary jetting method is used to pre-construct the annular reinforcing ring in the lower karst layer area, providing a stable foundation for the subsequent concrete bored pile construction. (2) The degradable fiber mesh tube is made of degradable PLA-PCL blended fiber. Under the condition of ensuring sufficient compressive mechanical properties, it can realize self-degradation within a short period of time, and eliminate the high-cost recycling problem; (3) The nano-modified mud greatly enhances the impermeability of the wall, effectively reducing the risk of hole collapse. Bentonite can improve the viscosity and suspension of the mud. The polymer can enhance the stability and flexibility of the mud. Nano-silicon dioxide can fill the small pores in the mud, further improving the impermeability; (4) The horizontal telescopic cutter on the grouting drill rod drives the degradable fiber mesh tube to be lowered synchronously, and the connection with the degradable fiber mesh tube is released before reaching the lower karst layer area, realizing the automation of the synchronous lowering of the degradable fiber mesh tube.

Claims

1. A method for constructing cast-in-place concrete piles based on a soft soil layer, wherein the soft soil layer is below a karst layer, characterized in that... The construction method includes the following steps: S1: Based on BIM (Building Information Modeling) and GIS (Geographic Information System), establish a three-dimensional geological model; dynamically adjust and determine the pile location layout using the three-dimensional geological model; S2: Based on the determined pile location, vertical drilling is performed using the high-pressure jet grouting drill bit on the drilling rig. When the high-pressure jet grouting drill bit drills into the soft soil layer, the biodegradable fiber mesh is lowered synchronously with the high-pressure jet grouting drill bit. During the lowering of the biodegradable fiber mesh, nano-modified mud is injected synchronously to form a double protective wall. S3: After the high-pressure jet grouting drill bit enters the karst layer, the high-pressure jet grouting drill bit is used to perform circumferential high-pressure jet grouting of concrete slurry to spray the concrete slurry into the karst layer to fill the holes and cracks and form a ring-shaped reinforcement layer. S4: After the pile hole is drilled, the high-pressure jet grouting drill bit is lifted away from the pile hole, and then concrete grout is injected into the pile hole to form a concrete cast-in-place pile.

2. The method for constructing concrete cast-in-place piles based on soft soil layers according to claim 1, characterized in that... The biodegradable fiber mesh is cylindrical and is a PLA-PCL blended fiber woven mesh, wherein PLA is polylactic acid and PCL is polycaprolactone, and the mass ratio of polylactic acid to polycaprolactone in the base material of the PLA-PCL blended fiber woven mesh is 2:

1.

3. The method for constructing concrete cast-in-place piles based on soft soil layers according to claim 2, characterized in that... The drilling rig includes a traveling chassis, a support frame, a drill rod drive mechanism, at least two grout storage tanks, a grout delivery pipeline, a fixed pulley block, and the high-pressure jet grouting drill bit. The traveling chassis is supported on the construction site ground by at least four hydraulic outriggers. The support frame is vertically mounted on the traveling chassis, and an equipment installation platform is fixedly mounted on the upper part of the support frame. The drill rod drive mechanism is mounted on the equipment installation platform. The high-pressure jet grouting drill bit includes a toothed drill bit, a horizontal telescopic cutter, and a grouting drill rod. The grout storage tanks are mounted on the traveling chassis. One end of the grout delivery pipeline is connected to the grout storage tank, and the other end of the grout delivery pipeline is connected to the top of the grouting drill rod via the fixed pulley block fixed to the top of the support frame.

4. The method for constructing concrete cast-in-place piles based on soft soil layers according to claim 3, characterized in that... The end of the grout delivery pipe is connected to the top of the grouting drill rod by a movable rotary sealing connection structure; the grout storage tank is connected to a booster pump to pump the grout through the grout delivery pipe into the cavity of the grouting drill rod for outward spraying.

5. The method for constructing concrete cast-in-place piles based on soft soil layers according to claim 4, characterized in that... The end of the grouting drill rod is provided with the toothed drill bit, the horizontal telescopic cutter and the grouting nozzle in sequence from bottom to top. At least four sets of the horizontal telescopic cutter are arranged at intervals along the circumference of the grouting drill rod. At least four grouting nozzles are opened at intervals along the circumference of the grouting drill rod and are connected to the inside of the cavity of the grouting drill rod.

6. The method for constructing concrete cast-in-place piles based on soft soil layers according to claim 4, characterized in that... The bottom of the biodegradable fiber mesh tube has multiple insertion holes spaced circumferentially. A plug is fixedly installed at the front end of the horizontal telescopic cutter. By controlling the extension or retraction of the horizontal telescopic cutter, the plug can be inserted into or withdrawn from the insertion hole of the biodegradable fiber mesh tube. When the plug is inserted into the insertion hole, the biodegradable fiber mesh tube is lowered synchronously with the high-pressure rotary jet drill bit. When the biodegradable fiber mesh tube is lowered to a predetermined depth, the plug is controlled to withdraw from the insertion hole to disconnect the plug from the biodegradable fiber mesh tube.

7. The method for constructing concrete cast-in-place piles based on soft soil layers according to claim 1, characterized in that... The mass composition of the nano-modified mud is: 100 parts water, 60-80 parts bentonite, 1-3 parts polymer dry powder, and 5-15 parts nano silica dry powder, wherein the polymer dry powder is polyacrylamide.

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