A pile end combined extrusion grouting construction method for precast hollow piles

Abstract

The present application relates to a kind of pile end combined extrusion grouting construction method for precast hollow pile, comprising the following construction steps: S1, the assembled pile end extrusion grouting device is installed on the bottom end plate of the precast pile with inner hole of last section;S2, pile body and each pipeline are connected respectively, and according to the requirement of on-site construction, different pile sinking mode is used to form pile;S3, after the pile body maintenance 1-3 days, the soil body of base pile end is extruded and compacted by controlling pile end extrusion grouting device, and the extruded and compacted area of pile bottom is formed;S4, high-pressure grouting device carries out high-pressure grouting to splitting space and the inside of pile end extrusion grouting device, and grout returns along the sidewall of precast pile, and forms grouting reinforcement area;The present application aims at improving base pile end bearing force and reducing construction cost.

Description

Technical Field

[0001] This invention belongs to the field of pile foundation engineering construction technology, and in particular relates to a method for combined compaction grouting construction at the pile end of precast hollow piles. Background Technology

[0002] Precast piles, as a relatively mature type of pile in terms of production and construction technology, have the advantages of high construction efficiency and low cost, and are therefore widely used in engineering construction. However, precast pile technology also has some objective shortcomings that limit its widespread application. First, because precast piles are processed in a factory, their quality is guaranteed. However, due to limitations imposed by site geological conditions, insufficient foundation bearing capacity, and inadequate utilization of the pile strength, this results in significant material waste. Second, precast piles are driven using hammer driving or static pressure driving, which involves severe soil squeezing during the driving process, requiring strict adherence to the construction sequence. This also limits their application near important buildings. While static pressure driving is currently widely used, this technology has weak penetration capabilities and struggles to penetrate deep sand, gravel, pebbles, and crushed stone layers. To address the above technical problems, this invention provides a pile-end combined compaction grouting method for precast hollow piles and a pile-end combined compaction grouting system that is compatible with this construction method. By changing different types of precast piles and adding pile-end compaction grouting devices, the application range of precast piles is expanded, and their working mechanism is redefined. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a construction method for combined compaction grouting at the pile end of precast hollow piles. This construction method uses a hydraulic compaction grouting device added to the bottom of the precast pile to compact and enhance the bearing capacity of the soil at the pile bottom. High-pressure grouting is then performed in the formed pore space to further reinforce the pile bottom, thereby improving the bearing capacity of the pile.

[0004] The objective of this invention is achieved through the following technical solution: the pile end combined compaction grouting construction method for precast hollow piles includes the following steps:

[0005] S1. Assemble the hydraulic extrusion unit, upper bearing plate, lower pressure plate, transverse hydraulic pipeline and one-way grouting valve to form a pile end compaction grouting device, and install it on the bottom end plate of the last section of the precast pile with an inner hole. The lower pressure plate is fixedly connected to the outer steel cylinder, and the outer steel cylinder is connected to the upper bearing plate by a hoisting anti-detachment device. At least one hydraulic extrusion unit is installed between the upper bearing plate and the lower pressure plate. The hydraulic extrusion unit is connected to the internal hydraulic oil pipe of the hydraulic device through the transverse hydraulic pipeline.

[0006] S2. According to the requirements of on-site construction, if the pile driving process is static pressure or hammer driving, a pile tip needs to be installed at the bottom of the pile end grouting device. Before the precast pile is driven into the soil, the outer steel cylinder and the upper bearing plate need to be separated by hoisting anti-detachment device. The precast pile is driven through the pile tip and the static pressure or hammer driving method is used to complete the pile driving construction. The precast pile, internal hydraulic oil pipe and internal grouting pipe are independently connected and fixed in sections according to the pile driving sequence. The internal hydraulic oil pipe and the internal grouting pipe pass through the inner hole of the precast pile and are fixed until the pile top elevation is reached. After the pile driving is completed, the oil pipe and grouting pipe are protected.

[0007] If the pile driving process involves drilling, pre-grouting, mixing, and jet grouting before core pile installation, the diameter of the formed hole must be larger than the diameter of the precast pile. The precast pile driving must be carried out within 6 hours after drilling, pre-grouting, mixing, and jet grouting. Before the precast pile is driven into the ground, the outer steel cylinder must be separated from the upper bearing plate using a hoisting anti-detachment device. The precast pile, internal hydraulic oil pipe, and internal grouting pipe must be independently connected and fixed in sections according to the pile driving sequence. The internal hydraulic oil pipe and the internal grouting pipe must pass through the inner hole of the precast pile and be fixed until the top elevation of the pile is reached. After the pile driving is completed, the oil pipe and grouting pipe must be protected.

[0008] S3. After the pile body has been cured for 1 to 3 days, the high-pressure grouting pump in the high-pressure grouting device is connected to the internal grouting pipe through the external grouting pipe. The hydraulic station in the hydraulic device is connected to the internal hydraulic oil pipe through the external hydraulic oil pipe. The hydraulic station controls the hydraulic extrusion units of the pile end compaction grouting device to press down, thereby pushing the lower plate downward and forcefully compacting the soil at the end of the pile to form a compaction area at the bottom of the pile.

[0009] S4. After the lower pressure plate is pushed vertically downward, the bottom of the pile body will be split horizontally. Then, the high-pressure grouting pump is started. The cement grout reaches the grouting pipeline under pressure and causes the grouting holes in the one-way grouting valve to open under pressure. Then, high-pressure grouting is carried out in the split space of the bottom pile section and the inside of the pile end grouting device through the one-way grouting valve within the grouting range. The grout returns with the side wall of the pile body and forms a grouting reinforcement area.

[0010] S5. After several days of pile curing, the compacted area at the bottom of the pile and the grouting reinforcement area are stabilized and solidified, forming a complete end-reinforced pile.

[0011] The beneficial effects of this invention are as follows: Compared with the prior art, 1. The pile end compaction grouting device compacts and compacts the soil at the pile end through controllable vertical downward extrusion. The device can precisely control the extrusion pressure and stroke through a hydraulic system, thereby controlling the lifting and splitting space as needed and precisely controlling the grouting volume accordingly. The combined application and effective implementation of the pile end compaction grouting device and the high-pressure grouting device can significantly improve the bearing capacity of the pile body and allow for confident changes to the pile foundation design, such as shortening the design length of the foundation pile or reducing the total number of foundation piles, thereby shortening the construction period and significantly reducing project costs; 2. This construction method is applicable to both traditional static pressure and hammering construction processes, and can also be used for precast piles that require mixing or pre-drilling, making it widely applicable; 3. This construction method allows for the reasonable setting of the number of hydraulic extrusion units, the jacking pressure, and the jacking stroke, and can be designed for different strata, thereby achieving the goal of saving materials and controlling costs.

[0012] Preferably, there is one hydraulic extrusion unit, which is located at the center between the upper bearing plate and the lower pressure plate. The upper part of the hydraulic extrusion unit is fixed to the upper bearing plate with several first diagonal bracing ribs for support, and the lower part of the hydraulic extrusion unit is fixed to the lower pressure plate with several second diagonal bracing ribs for support. The hydraulic extrusion unit is connected to the hydraulic device via a transverse hydraulic pipeline. By providing the first diagonal bracing ribs, the insufficient rigidity of the upper bearing plate during the downward pressing of the lower pressure plate by the hydraulic extrusion unit prevents local bulging deformation. Simultaneously, by providing the second diagonal bracing ribs, the rigidity of the lower pressure plate is ensured, preventing local denting deformation.

[0013] Preferably, there are at least two hydraulic extrusion units, which are located between the upper bearing plate and the lower pressure plate and are distributed in a circular manner at equal intervals. Adjacent hydraulic extrusion units are connected in series through the transverse hydraulic pipeline and are connected to the hydraulic device; this makes the pressure of the pile end compaction grouting device greater and more uniform.

[0014] Preferably, the upper surface of the upper bearing plate is provided with at least two positioning pins, which are used to position and fix the pile end compaction grouting device to the bottom end plate of the precast pile; a sealing rubber ring is installed on the lower surface of the upper bearing plate, and the rubber ring abuts against the upper end face of the outer steel cylinder; when the upper bearing plate and the bottom end plate of the precast pile are installed, effective positioning can be achieved to prevent position deviation. At the same time, by setting the rubber ring, external soil can be prevented from entering the outer steel cylinder during the pile driving process, ensuring the cleanliness of the inside of the pile end compaction grouting device.

[0015] Preferably, the hoisting anti-detachment device includes an anti-detachment plate and an anti-detachment bolt. The anti-detachment plate is fixed to the lower surface of the upper support plate and located outside the outer steel cylinder. The anti-detachment plate is provided with a first bolt hole, and the side wall of the outer steel cylinder corresponding to the first bolt hole is provided with a second bolt hole. The first bolt hole and the second bolt hole are fixed by the anti-detachment bolt. In step S2, the anti-detachment bolt is used to disengage from the first bolt hole and the second bolt hole, thereby separating the outer steel cylinder from the upper support plate. With the above structure, when the pile end compaction grouting device connected to the precast pile is hoisted, the power end of the hydraulic extrusion unit can be prevented from falling off. At the same time, the anti-detachment bolt can be easily pulled out before the pile body is inserted into the soil.

[0016] Preferably, the upper bearing plate is also provided with a plurality of third bolt holes for fixing the hydraulic extrusion unit. The third bolt holes are located in the inner hole area of ​​the precast pile, and the upper part of the hydraulic extrusion unit is fixedly connected to the upper bearing plate and the lower part of the hydraulic extrusion unit is fixedly connected to the lower pressure plate by the cooperation of the bolts with the third bolt holes; thus facilitating the installation of the hydraulic extrusion unit with the upper bearing plate and the lower pressure plate.

[0017] Preferably, the internal grouting pipe is provided in several sections and installed and fixed in sections. One end of the internal grouting pipe is connected to the external grouting pipe, and the external grouting pipe is connected to the high-pressure grouting pump. The other end of the internal grouting pipe is connected to one end of the pre-reserved threaded hole of the grouting pipe in the upper bearing plate through a reverse threaded joint. The one-way grouting valve is connected to the other end of the pre-reserved threaded hole of the grouting pipe in the upper bearing plate through a joint, and the pre-reserved threaded hole of the grouting pipe is located in the inner hole area of ​​the precast pile. The one-way grouting valve is located in the upper bearing plate. Below the plate, the side wall of the one-way grouting valve has several grouting holes, and a rubber sleeve is fitted on the outer wall of the valve body of the grouting hole. With the above structure, after grouting is completed, the internal grouting pipe can be rotated in the opposite direction and removed through the reverse thread of the reverse threaded joint, so as to achieve the recycling and reuse of the grouting pipe. At the same time, with the rubber sleeve fitted on the grouting hole of the one-way grouting valve, under the pressure of high-pressure grouting, the multiple grouting holes can only be grouted in one direction from the grouting hole to the outside in advance, to prevent the external medium from blocking the grouting hole before grouting and to prevent the backflow of grout after grouting.

[0018] Preferably, the internal hydraulic oil pipe is provided with several sections and installed and fixed in sections. One end of the internal hydraulic oil pipe is connected to the external hydraulic oil pipe, and the external hydraulic oil pipe is connected to the hydraulic station. The other end of the internal hydraulic oil pipe is connected to one end of the hydraulic oil pipe pre-reserved threaded hole provided in the upper bearing plate through a reverse threaded joint. The other end of the hydraulic oil pipe pre-reserved threaded hole is connected to the transverse hydraulic pipeline through a joint, and the hydraulic oil pipe pre-reserved threaded hole is located in the inner hole area of ​​the precast pile. With the above structure, after grouting is completed, the internal hydraulic oil pipe can be rotated in the opposite direction and removed through the reverse thread of the reverse threaded joint, so as to achieve the recycling and reuse of the hydraulic oil pipe and make disassembly and assembly more convenient.

[0019] Preferably, the pile tip is a steel pile tip or a concrete pile tip, the pile tip is fixed to the lower pressure plate, and the concrete pile tip is provided with a supporting bar, which is fixedly connected to the lower pressure plate; when the precast pile is driven by static pressure or hammering, setting a pile tip can effectively improve the penetration efficiency of the precast pile. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the pile end combined compaction grouting system of the present invention.

[0021] Figure 2 This is a schematic diagram of the high-pressure grouting device of the present invention.

[0022] Figure 3 This is a schematic diagram of the hydraulic device structure of the present invention.

[0023] Figure 4 This is a schematic diagram of the pile end compaction grouting device of the present invention.

[0024] Figure 5 This is a schematic diagram of the upper support plate structure of the present invention. Figure 1 .

[0025] Figure 6 This is a schematic diagram of the upper support plate structure of the present invention. Figure 2 .

[0026] Figure 7 This is a schematic diagram of the structure between the lower pressure plate and the outer steel cylinder of the present invention.

[0027] Figure 8 This is a schematic diagram of the pile end compaction grouting device in Embodiment 1 of the present invention.

[0028] Figure 9 This is a schematic diagram of the pile end compaction grouting device in Embodiment 2 of the present invention.

[0029] Figure 10 This is a schematic diagram of the pile end compaction grouting device in Embodiment 3 of the present invention.

[0030] Figure 11 This is a schematic diagram of the pile end compaction grouting device with steel pile tip of the present invention.

[0031] Figure 12 This is a top view schematic diagram of the hydraulic extrusion unit of the present invention in different arrangement forms of circular precast piles.

[0032] Figure 13 This is a top view schematic diagram of the hydraulic extrusion unit of the present invention in different arrangement forms of square precast piles.

[0033] Figure 14 This is a schematic diagram of the working state of the pile end compaction grouting device of the present invention.

[0034] Figure 15 This is a diagram illustrating the pile formation effect of the pile end compaction grouting device of the present invention.

[0035] The labels in the attached drawings are as follows: 100, pile tip compaction grouting device; 200, precast pile; 300, high-pressure grouting device; 400, hydraulic device; 600, splitting space; 700, grouting reinforcement area; 800, pile bottom compaction area; 101, upper bearing plate; 102, lower pressure plate; 103, outer steel cylinder; 104, hydraulic extrusion unit; 105, hoisting anti-detachment device; 106, transverse hydraulic pipeline; 107, first diagonal brace reinforcing rib; 108, positioning pin; 109, rubber ring; 110, steel pile tip; 111, concrete pile tip; 112, support reinforcement. ; 113, Second diagonal brace reinforcing rib; 201, Inner hole; 301, High-pressure grouting pump; 302, External grouting pipe; 303, Internal grouting pipe; 304, One-way grouting valve; 305, Grouting hole; 306, Rubber sleeve; 401, Hydraulic station; 402, External hydraulic oil pipe; 403, Internal hydraulic oil pipe; 101-1, Third bolt hole; 101-2, Reserved threaded hole for grouting pipe; 101-3, Reserved threaded hole for hydraulic oil pipe; 105-1, Anti-detachment plate; 105-2, Anti-detachment bolt; 105-3, First bolt hole; 105-4, Second bolt hole. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings: The present invention includes the following construction steps: as shown in the attached drawings. Figures 1 to 15 As shown,

[0037] S1. Assemble the hydraulic extrusion unit 104, upper bearing plate 101, lower pressure plate 102, transverse hydraulic pipeline 106 and one-way grouting valve 304 to form a pile end compaction grouting device 100. Install it on the bottom end plate of the last section of the precast pile 200 with an inner hole 201. The lower pressure plate 102 is fixedly connected to the outer steel cylinder 103. The outer steel cylinder 103 is connected to the upper bearing plate 101 by the hoisting anti-detachment device 105. At least one hydraulic extrusion unit 104 is installed between the upper bearing plate 101 and the lower pressure plate 102. The hydraulic extrusion unit 104 is connected to the internal hydraulic oil pipe 403 of the hydraulic device 400 through the transverse hydraulic pipeline 106.

[0038] S2. According to the requirements of on-site construction, if the pile driving process is static pressure or hammer driving, a pile tip needs to be installed at the bottom of the pile end grouting device 100. Before the precast pile 200 is driven into the soil, the outer steel cylinder 103 and the upper bearing plate 101 need to be separated by the hoisting anti-detachment device 105. The precast pile 200 is driven through the pile tip and the static pressure or hammer driving method is used to complete the pile driving construction. The precast pile 200, the internal hydraulic oil pipe 403, and the internal grouting pipe 303 are connected and fixed independently in sections according to the pile driving sequence. The internal hydraulic oil pipe 403 and the internal grouting pipe 303 pass through the inner hole 201 of the precast pile 200 and are fixed until the pile top elevation is reached. After the pile driving is completed, the oil pipe and the grouting pipe are protected.

[0039] If the pile driving process involves drilling, pre-grouting, mixing, and jet grouting followed by core pile installation, the diameter of the formed hole must be larger than the diameter of the precast pile 200. The driving of the precast pile 200 must be carried out within 6 hours after the drilling, pre-grouting, mixing, and jet grouting operations. Before the precast pile 200 is driven into the ground, the outer steel cylinder 103 must be separated from the upper bearing plate 101 using a hoisting anti-detachment device 105. The precast pile 200, internal hydraulic oil pipe 403, and internal grouting pipe 303 must be independently connected and fixed in sections according to the pile driving sequence. The internal hydraulic oil pipe 403 and internal grouting pipe 303 must pass through the inner hole 201 of the precast pile 200 and be fixed until the pile top elevation is reached. After pile driving is completed, the oil pipes and grouting pipes must be properly protected.

[0040] S3. After the pile body has been cured for 1 to 3 days, the high-pressure grouting pump 301 in the high-pressure grouting device 300 is connected to the internal grouting pipe 303 through the external grouting pipe 302. The hydraulic station 401 in the hydraulic device 400 is connected to the internal hydraulic pipe 403 through the external hydraulic oil pipe 402. The hydraulic drive of the hydraulic station 401 controls each hydraulic extrusion unit 104 of the pile end compaction grouting device 100 to press down, thereby pushing the lower pressure plate 102 downward and forcefully compacting the soil at the end of the pile to form the pile bottom compaction area 800.

[0041] S4. After the lower pressure plate 102 is pushed vertically downward, the bottom of the pile body will generate a transverse splitting space 600. Then, the high-pressure grouting pump 301 is started. The cement grout reaches the grouting pipeline under pressure and causes the grouting holes 305 in the one-way grouting valve 304 to open under pressure. Then, high-pressure grouting is carried out in the splitting space 600 of the bottom pile section and the pile end compaction grouting device 100 within the grouting range through the one-way grouting valve 304. The grout returns with the outer wall of the pile body and forms a grouting reinforcement area 700.

[0042] S5. After several days of pile curing, the compacted area 800 and the grouting reinforcement area 700 at the bottom of the pile are grouted and solidified to form a complete end-reinforced pile.

[0043] The precast pile 200 connected to the pile end compaction grouting device 100 can be a square pile, pipe pile, expanded diameter bamboo joint pile, or other precast pile with an inner hole. Currently, the precast piles widely used include the above pile types, which greatly limits their applicability. At the same time, the inner hole of the precast pile provides space for the internal grouting pipe 303 and the internal hydraulic oil pipe 403, and fixing the two pipes in the inner hole can more effectively play a protective role.

[0044] The hydraulic extrusion unit 104 uses a hydraulic cylinder. Each hydraulic extrusion unit 104 is connected in series through a transverse hydraulic pipeline 106 to provide hydraulic power. After the hydraulic station 401 is turned on, the hydraulic extrusion unit 104 generates internal pressure. The hydraulic piston rod extends downward to drive the lower pressure plate 102 to compact the lower soil, thereby improving the bearing capacity of the soil at that location. At the same time, when the hydraulic extrusion unit 104 is opened, it will create a crack space 600 at the bottom of the pile body, providing directional space for subsequent grout injection, preventing the grout from spreading everywhere and affecting the grouting effect.

[0045] The hydraulic extrusion unit 104 is a single unit located at the center between the upper support plate 101 and the lower pressure plate 102. The upper part of the hydraulic extrusion unit 104 is fixed to the upper support plate 101 by welding with several first diagonal bracing ribs 107 for support. The lower part of the hydraulic extrusion unit 104 is fixed to the lower pressure plate 102 by welding with several second diagonal bracing ribs 113 for support. The hydraulic extrusion unit 104 is connected to the hydraulic device 400 through a transverse hydraulic pipeline 106.

[0046] There are at least two hydraulic extrusion units 104, such as two, three or four. The hydraulic extrusion units 104 are located between the upper bearing plate 101 and the lower pressure plate 102 and are distributed in a ring-shaped manner with equal spacing. Adjacent hydraulic extrusion units 104 are connected in series through transverse hydraulic pipelines 106 and are connected to the hydraulic device 400.

[0047] As attached Figure 5 , 6As shown, the upper surface of the upper bearing plate 101 is provided with at least two positioning pins 108, generally four positioning pins 108, which are evenly distributed around the center of the upper bearing plate 101. The positioning pins 108 are used to position and fix the pile end compaction grouting device 100 to the bottom end plate of the precast pile 200. A sealing rubber ring 109 is installed on the lower surface of the upper bearing plate 101. The rubber ring 109 abuts against the upper end face of the outer steel cylinder 103 and forms a closed structure to prevent the entry of external soil during the pile driving process and ensure that the inside of the pile end compaction grouting device 100 is clean.

[0048] As attached Figure 4 As shown, the lifting anti-detachment device 105 includes an anti-detachment plate 105-1 and an anti-detachment bolt 105-2. The anti-detachment plate 105-1 is fixed to the lower surface of the upper support plate 101 and located on the outside of the outer steel cylinder 103. The anti-detachment plate 105-1 is provided with a first bolt hole 105-3, and the side wall of the outer steel cylinder 103 corresponding to the first bolt hole 105-3 is provided with a second bolt hole 105-4. The first bolt hole 105-3 and the second bolt hole 105-4 are connected by the anti-detachment bolt. The bolt 105-2 is used to fix the hydraulic piston rod in the hydraulic extrusion unit 104 to prevent it from falling off during hoisting. In step S2, before the pile is driven into the soil, the anti-detachment bolt 105-2 is used to disconnect the first bolt hole 105-3 and the second bolt hole 105-4, so that the outer steel cylinder 103 is separated from the upper bearing plate 101. When driven into the soil, the upper part of the outer steel cylinder 103 is in contact with the rubber ring 109 but not connected, thus sealing and isolating the inside and outside of the pile end compaction grouting device 100.

[0049] The upper support plate 101 is also provided with several third bolt holes 101-1 for fixing the hydraulic extrusion unit 104. Depending on the size of the hydraulic extrusion unit 104, one to three third bolt holes 101-1 can be provided on one hydraulic extrusion unit 104. The third bolt holes 101-1 are located in the inner hole area of ​​the precast pile 200, and the upper part of the hydraulic extrusion unit 104 is fixed to the upper support plate 101 by the cooperation of the bolts and the third bolt holes 101-1. The lower part of the hydraulic extrusion unit 104 is fixed to the lower pressure plate 102 by welding. The upper part of the hydraulic extrusion unit 104 is the hydraulic cylinder body, and the lower part is the hydraulic piston rod. If the hydraulic extrusion unit 104 is a hydraulic cylinder, the upper part is the cylinder body, and the lower part is the lifting end of the hydraulic cylinder.

[0050] The internal grouting pipe 303 is divided into several sections and installed and fixed in sections. Generally, the length of the internal grouting pipe 303 is slightly larger than the length of the precast pile, and the internal grouting pipe 303 is a rigid pipe, which facilitates the section installation. One end of the internal grouting pipe 303 is connected to the external grouting pipe 302, and the external grouting pipe 302 is connected to the high-pressure grouting pump 301. The other end of the internal grouting pipe 303 is connected to one end of the grouting pipe pre-reserved threaded hole 101-2 provided on the upper bearing plate 101 through a reverse threaded joint. A one-way grouting valve 30... 4. The grouting pipe is connected to the other end of the threaded hole 101-2 of the grouting pipe provided in the upper bearing plate 101 through the connector, and the threaded hole 101-2 of the grouting pipe is located in the inner hole 201 area of ​​the precast pile 200. The one-way grouting valve 304 is located below the upper bearing plate 101. Several grouting holes 305 are opened on the side wall of the one-way grouting valve 304. These several grouting holes 305 are evenly distributed in a ring along the side wall of the valve body. A rubber sleeve 306 is sleeved on the outer wall of the valve body located at the grouting holes 305 to form a one-way grouting device.

[0051] The internal hydraulic oil pipe 403 is provided in several sections and is installed and fixed in sections. Generally, the length of the internal hydraulic oil pipe 403 is slightly larger than the length of the precast pile, and the internal hydraulic oil pipe 403 is a rigid pipe, which facilitates the installation in sections. One end of the internal hydraulic oil pipe 403 is connected to the external hydraulic oil pipe 402, and the external hydraulic oil pipe 402 is connected to the hydraulic station 401. The other end of the internal hydraulic oil pipe 403 is connected to one end of the hydraulic oil pipe reserved threaded hole 101-3 provided on the upper bearing plate 101 through a reverse threaded joint. The other end of the hydraulic oil pipe reserved threaded hole 101-3 is connected to the transverse hydraulic pipeline 106 through a joint, and the hydraulic oil pipe reserved threaded hole 101-3 is located in the area of ​​the inner hole 201 of the precast pile 200.

[0052] The pile tip is a steel pile tip 110 or a concrete pile tip 111, which is fixed on the lower pressure plate 102. The concrete pile tip 111 is provided with a supporting bar 112, which is fixed to the lower pressure plate 102. If there are soil layers such as sand, gravel, or crushed stone that are difficult to penetrate by static pressure pile driving, or if there are important facilities or buildings around the site and the environmental protection requirements are very strict, the pile driving method of mixing and implanting, jet grouting and mixing, or pre-drilling and implanting precast piles 200 can be adopted. In this case, the pile tip does not need to be set.

[0053] The cross-sectional shape of the precast pile 200 can be, but is not limited to, hollow triangle, hollow square, hollow cross, hollow polygon, etc.; the cross-sectional shape of the inner hole 201 can be, but is not limited to, triangle, square, cross, hollow polygon, etc., thus expanding the application range.

[0054] Example 1:

[0055] The following is combined with Figure 1 , Figures 4-8 , Figure 12 c. Figure 14 , Figure 15 To further illustrate the present invention, the engineering background of this embodiment is the static pressure precast pipe pile of an industrial plant in a coastal area. The pile is 25m long and 500mm in diameter. The soil layer within the pile length is silty clay, the bearing layer is dense silt, and the standard value of the pile end resistance is 1600kPa.

[0056] like Figure 4 , Figure 12 As shown in Figure c, in this embodiment, the pile end compaction grouting device 100 adopts three hydraulic extrusion units 104, which are arranged in an equilateral triangle. The outer diameter of the hydraulic extrusion unit 104 is 120mm. The upper part of each hydraulic extrusion unit 104 is connected to the upper bearing plate 101 by two bolts, and the lower part is fixedly connected to the lower pressure plate 102. The three hydraulic extrusion units 104 are connected in series by a transverse hydraulic pipeline 106. The internal hydraulic oil pipe 403 is connected to the transverse hydraulic pipeline 106 through the hydraulic oil pipe reserved thread hole 101-3 on the upper bearing plate 101, and is connected to the external hydraulic station 401 to form a hydraulic device 400. The internal grouting pipe 303 is connected to the one-way grouting valve 304 through the grouting pipe reserved thread hole 101-2 on the upper bearing plate 101, and is connected to the high-pressure grouting pump 301 to form a high-pressure grouting device 300.

[0057] In this embodiment, the downward pressing capacity of the hydraulic extrusion unit 104 depends on the standard value of the ultimate end resistance of the soil at the pile tip and the design parameters and quantity of the hydraulic extrusion unit 104. According to the pile foundation design, the diameter of the precast pipe pile in this embodiment is 500mm, and the ultimate bearing capacity at the pile tip is 310kN. In this embodiment, the downward pressing pressure provided by a single hydraulic extrusion unit 104 is about 150kN. The combination of three hydraulic extrusion units 104 can effectively compact the soil at the pile tip. At the same time, in order to control the splitting space 600 generated by the extrusion action and reasonably control the grouting volume, the stroke of the hydraulic extrusion unit 104 is 15cm. In this embodiment, the threaded hole 101-2 of the grouting pipe and the threaded hole 101-3 of the hydraulic oil pipe are set in the middle part of the upper bearing plate 101, and the oil pipe and the grouting pipe are fixed in the inner hole 201 of the precast pile 200 before the pile is spliced.

[0058] This embodiment uses static pressure construction technology for pile driving, such as Figure 8 As shown, a concrete pile tip 111 is provided at the lower part of the lower pressure plate 102 of the pile end compaction grouting device 100. The concrete pile tip 111 is connected to the lower pressure plate 102 through the internal support bar 112.

[0059] The construction process in this embodiment is basically similar to that described in the basic embodiment, except that it only includes static pressure pile driving of precast piles and does not include pre-drilling processes such as mixing piles. Therefore, the implementation steps of this embodiment will not be described again.

[0060] Example 2:

[0061] The following is combined with Figure 1 , Figures 4 to 7 , Figure 9 , Figure 12 This invention will be further described below. The engineering background of this embodiment is a high-rise residential project. The pile length contains a relatively thick, medium-dense silty sand layer, making static pressure penetration difficult. The bearing layer is dense silt, and the standard value of the pile end resistance is 1200 kPa. The design scheme adopts short-core stiffened composite piles, including mixing piles with a diameter of 600 mm and a length of 30 m, and precast pipe piles with a diameter of 400 mm and a length of 25 m.

[0062] like Figures 4 to 6 , Figure 12 As shown in Figure a, in this embodiment, the pile end compaction grouting device 100 adopts a single hydraulic extrusion unit 104 arranged in the center. The outer diameter of the hydraulic extrusion unit 104 is 140mm. The upper part of the hydraulic extrusion unit 104 is connected to the upper bearing plate 101 by three bolts, and the lower part is fixedly connected to the lower pressure plate 102. The hydraulic extrusion unit 104 is connected to the internal hydraulic oil pipe 403 through the transverse hydraulic pipeline 106. The internal hydraulic oil pipe 403 is connected to the transverse hydraulic pipeline 106 through the hydraulic oil pipe reserved thread hole 101-3 on the upper bearing plate 101, and is connected to the external hydraulic station 401 to form a hydraulic device 400. The internal grouting pipe 303 is connected to the one-way grouting valve 304 through the grouting pipe reserved thread hole 101-2 on the upper bearing plate 101, and is connected to the high-pressure grouting pump 301 to form a high-pressure grouting device 300.

[0063] In this embodiment, the downward pressing capacity of the hydraulic extrusion unit 104 depends on the compressive strength of the soil at the pile tip and the design parameters and quantity of the hydraulic extrusion unit 104. According to the pile foundation design, the diameter of the precast pile in this embodiment is 400mm. After the mixing pile is cured for 1-3 days, extrusion grouting is performed. At this time, the soil is not completely cured. In this embodiment, the downward pressing pressure provided by a single hydraulic extrusion unit 104 is about 160kN. According to the design calculation, the soil can be compressed and compacted. At the same time, in order to control the splitting space 600 generated by the extrusion action and reasonably control the grouting volume, the stroke of the hydraulic extrusion unit 104 is 25cm. In this embodiment, the threaded hole 101-2 of the grouting pipe and the threaded hole 101-3 of the hydraulic oil pipe are set on both sides of the upper bearing plate 101, and the oil pipe and the grouting pipe are fixed in the inner hole 201 of the precast pile 200 before the pile is spliced.

[0064] The construction process in this embodiment is basically similar to that described in the basic embodiment, including the construction of mixing piles and the static pressure driving of precast piles. Therefore, the implementation steps of this embodiment will not be described again.

[0065] Example 3:

[0066] The following is combined with Figure 1 , Figure 4 , Figure 5 , Figure 10 , Figure 12 b、 Figure 14 , Figure 15 To further illustrate this invention, the engineering background of this embodiment is a corporate office building. The pile length contains a relatively thick layer of medium-dense sand, making static pressure penetration difficult. The bearing layer is a medium-dense silty clay layer, and the standard value of the pile end resistance is 1000 kPa. The design scheme uses root-planted piles, including jet grouting piles with a diameter of 600 mm and a length of 27 m, and precast bamboo-joint piles with a diameter of 500 mm and a length of 27 m. Figure 4 , Figure 10 , Figure 12 As shown in b, in this embodiment, the pile end compaction grouting device 100 adopts two hydraulic extrusion units 104 arranged symmetrically at the center. The outer diameter of the hydraulic extrusion unit 104 is 120mm. The upper part of the hydraulic extrusion unit 104 is connected to the upper bearing plate 101 by two bolts, and the lower part is fixedly connected to the lower pressure plate 102. The two hydraulic extrusion units 104 are connected in series by a transverse hydraulic pipeline 106. The internal hydraulic oil pipe 403 is connected to the transverse hydraulic pipeline 106 through the hydraulic oil pipe reserved thread hole 101-3 on the upper bearing plate 101, and is connected to the external hydraulic station 401 to form a hydraulic device 400. The internal grouting pipe 303 is connected to the one-way grouting valve 304 through the grouting pipe reserved thread hole 101-2 on the upper bearing plate 101, and is connected to the high-pressure grouting pump 301 to form a high-pressure grouting device 300.

[0067] In this embodiment, the downward pressing capacity of the hydraulic extrusion unit 104 depends on the standard value of the ultimate end resistance of the soil at the pile tip and the design parameters and quantity of the hydraulic extrusion unit 104. According to the pile foundation design, the precast pile in this embodiment has a diameter of 500mm and an ultimate bearing capacity of 200kN at the pile tip. After the mixing pile is cured for 1 to 3 days, extrusion grouting is performed. In this embodiment, the downward pressing pressure provided by a single hydraulic extrusion unit 104 is about 160kN. According to the design calculation, the soil at the pile tip can be compressed and compacted. At the same time, in order to control the crack space generated by the extrusion action and reasonably control the grouting volume, the stroke of the hydraulic extrusion unit 104 is 25cm. In this embodiment, the threaded hole 101-2 of the grouting pipe and the threaded hole 101-3 of the hydraulic oil pipe are set in the middle part of the upper bearing plate 101, and the oil pipe and the grouting pipe are fixed in the inner hole 201 of the precast pile 200 before the pile is spliced.

[0068] The construction process in this embodiment is basically similar to that described in the basic embodiment, including the construction of jet grouting piles and the static pressure driving of precast piles. Therefore, the implementation steps of this embodiment will not be described again.

[0069] This invention is not limited to the above-described embodiments. Any changes made to its shape or material composition, or any structural design using the methods provided by this invention, are considered variations of this invention and should be considered within the scope of protection of this invention.

Claims

1. A method for combined compaction grouting construction at the pile end of precast hollow piles, characterized in that: The construction method for combined compaction grouting at the pile end includes the following steps: S1. Assemble the hydraulic extrusion unit (104), upper bearing plate (101), lower pressure plate (102), outer steel cylinder (103), transverse hydraulic pipeline (106) and one-way grouting valve (304) to form a pile end compaction grouting device (100), and install it on the bottom end plate of the last section of the precast pile (200) with an inner hole (201). The lower pressure plate (102) is fixedly connected to the outer steel cylinder (103), and the outer steel cylinder (103) is connected to the upper bearing plate (101) by a hoisting anti-detachment device (105). At least one hydraulic extrusion unit (104) is installed between the upper bearing plate (101) and the lower pressure plate (102). The hydraulic extrusion unit (104) is connected to the internal hydraulic oil pipe (403) of the hydraulic device (400) through the transverse hydraulic pipeline (106). S2. According to the requirements of on-site construction, if the precast hollow pile driving process is vibration, static pressure or hammer driving, the pile tip needs to be installed at the bottom of the pile end grouting device (100). Before the precast pile (200) is put into the soil, the outer steel cylinder (103) and the upper bearing plate (101) need to be separated by the hoisting anti-detachment device (105). The precast pile (200) is driven through the pile tip and the precast pile (200) is driven by vibration, static pressure or hammer driving. The precast pile (200), internal hydraulic oil pipe (403) and internal grouting pipe (303) are connected and fixed independently according to the pile driving sequence. The internal hydraulic oil pipe (403) and the internal grouting pipe (303) pass through the inner hole (201) of the precast pile (200) and are fixed until the pile top elevation is reached. After the pile driving is completed, the oil pipe and grouting pipe are protected. If the pile driving process is to first drill and pre-grout, then mix the piles or jet grouting piles and then insert the core piles, the diameter of the formed hole must be larger than the diameter of the precast pile (200). The pile driving of the precast pile (200) must be carried out within 6 hours after the drilling, pre-grouting, mixing, or jet grouting pile construction. Before the precast pile (200) is driven into the soil, the outer steel cylinder (103) and the upper bearing plate (101) must be separated by the hoisting anti-detachment device (105). The precast pile (200), the internal hydraulic oil pipe (403), and the internal grouting pipe (303) are connected and fixed independently in sections according to the pile driving sequence. The internal hydraulic oil pipe (403) and the internal grouting pipe (303) pass through the inner hole (201) of the precast pile (200) and are fixed until the top elevation of the pile is reached. After the pile driving is completed, the oil pipe and the grouting pipe are protected. S3. After the pile body has been cured for 1 to 3 days, the high-pressure grouting pump (301) in the high-pressure grouting device (300) is connected to the internal grouting pipe (303) through the external grouting pipe (302). The hydraulic station (401) in the hydraulic device (400) is connected to the internal hydraulic pipe (403) through the external hydraulic oil pipe (402). The hydraulic drive of the hydraulic station (401) controls each hydraulic extrusion unit (104) of the pile end compaction grouting device (100) to press down, thereby pushing the lower plate (102) downward and forcefully compacting the soil at the end of the pile to form the pile bottom compaction area (800). S4. After the lower pressure plate (102) is pushed vertically downward, the bottom of the pile body will generate a transverse splitting space (600). Then, the high-pressure grouting pump (301) is started. The cement grout reaches the grouting pipeline under pressure and causes the grouting holes (305) in the one-way grouting valve (304) to open under pressure. Then, the one-way grouting valve (304) performs high-pressure grouting in the splitting space (600) of the bottom pile section and the pile end compaction grouting device (100) within the grouting range. The grout returns with the outer wall of the pile body and forms a grouting reinforcement area (700). S5. After several days of pile curing, the compacted area (800) at the bottom of the pile and the grouting reinforcement area (700) are grouted and stabilized to form a complete pile end reinforced pile body; The lifting anti-detachment device (105) includes an anti-detachment plate (105-1) and an anti-detachment bolt (105-2). The anti-detachment plate (105-1) is fixed on the lower surface of the upper support plate (101) and located on the outside of the outer steel cylinder (103). The anti-detachment plate (105-1) is provided with a first bolt hole (105-3). The side wall of the outer steel cylinder (103) corresponding to the first bolt hole (105-3) is provided with a second bolt hole (105-4). The first bolt hole (105-3) and the second bolt hole (105-4) are fixed by the anti-detachment bolt (105-2). In step S2, the anti-detachment bolt (105-2) is used to disengage from the first bolt hole (105-3) and the second bolt hole (105-4), thereby separating the outer steel cylinder (103) from the upper support plate (101).

2. The method for combined compaction grouting at the pile end of precast hollow piles according to claim 1, characterized in that: The hydraulic extrusion unit (104) is one unit. The hydraulic extrusion unit (104) is located at the center between the upper support plate (101) and the lower pressure plate (102). The upper part of the hydraulic extrusion unit (104) is fixed with a number of first diagonal bracing ribs (107) between it and the upper support plate (101) for support. The lower part of the hydraulic extrusion unit (104) is fixed with a number of second diagonal bracing ribs (113) between it and the lower pressure plate (102) for support. The hydraulic extrusion unit (104) is connected to the hydraulic device (400) through a transverse hydraulic pipeline (106).

3. The method for combined compaction grouting at the pile end of precast hollow piles according to claim 1, characterized in that: There are at least two hydraulic extrusion units (104). The hydraulic extrusion units (104) are located between the upper support plate (101) and the lower pressure plate (102) and are distributed in a ring-shaped manner with equal spacing. Adjacent hydraulic extrusion units (104) are connected in series through the transverse hydraulic pipeline (106) and communicate with the hydraulic device (400).

4. The method for combined compaction grouting at the pile end of precast hollow piles according to any one of claims 1 to 3, characterized in that: The upper surface of the upper bearing plate (101) is provided with at least two positioning pins (108), which are used to position and connect the pile end compaction grouting device (100) to the bottom end plate of the precast pile (200); a sealing rubber ring (109) is installed on the lower surface of the upper bearing plate (101), which abuts against the upper end face of the outer steel cylinder (103).

5. The method for combined compaction grouting at the pile end of precast hollow piles according to claim 1, characterized in that: The upper support plate (101) is also provided with a number of third bolt holes (101-1) for fixing the hydraulic extrusion unit (104). The third bolt holes (101-1) are located in the inner hole area of ​​the precast pile (200), and the upper part of the hydraulic extrusion unit (104) is fixedly connected to the upper support plate (101) by the cooperation of the bolts with the third bolt holes (101-1), and the lower part of the hydraulic extrusion unit (104) is fixedly connected to the lower pressure plate (102).

6. The method for combined compaction grouting at the pile end of precast hollow piles according to claim 1, characterized in that: The internal grouting pipe (303) is provided with several sections and is installed and fixed in sections. One end of the internal grouting pipe (303) is connected to the external grouting pipe (302), and the external grouting pipe (302) is connected to the high-pressure grouting pump (301). The other end of the internal grouting pipe (303) is connected to one end of the grouting pipe reserved thread hole (101-2) provided on the upper bearing plate (101) through a reverse threaded joint. The one-way grouting valve (304) is connected through a joint. The grouting pipe is connected to the other end of the threaded hole (101-2) provided on the upper bearing plate (101), and the threaded hole (101-2) of the grouting pipe is located in the inner hole area of ​​the precast pile (200). The one-way grouting valve (304) is located below the upper bearing plate (101). The side wall of the one-way grouting valve (304) is provided with several grouting holes (305). A rubber sleeve (306) is sleeved on the outer wall of the valve body of the grouting hole (305).

7. The method for combined compaction grouting at the pile end of precast hollow piles according to claim 1, characterized in that: The internal hydraulic oil pipe (403) is provided with several sections and is installed and fixed in sections. One end of the internal hydraulic oil pipe (403) is connected to the external hydraulic oil pipe (402), and the external hydraulic oil pipe (402) is connected to the hydraulic station (401). The other end of the internal hydraulic oil pipe (403) is connected to one end of the hydraulic oil pipe reserved thread hole (101-3) provided on the upper bearing plate (101) through a reverse threaded joint. The other end of the hydraulic oil pipe reserved thread hole (101-3) is connected to the transverse hydraulic pipeline (106) through a joint, and the hydraulic oil pipe reserved thread hole (101-3) is located in the inner hole (201) area of ​​the precast pile (200).

8. The method for combined compaction grouting at the pile end of precast hollow piles according to claim 1, characterized in that: The pile tip is a steel pile tip (110) or a concrete pile tip (111). The pile tip is fixed on the lower pressure plate (102). The concrete pile tip (111) is provided with a supporting bar (112). The supporting bar (112) is fixedly connected to the lower pressure plate (102).

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