Rapid pile forming technical method for water-rich thick sand layer hole pile method

Abstract

The invention provides a water-rich thick sand layer hole pile method rapid pile forming technical method. The method comprises the following steps that (1) construction preparation is conducted, hole pile point position lofting is conducted, and a drilling machine is in place; step (2), drilling, hole depth measurement and hole cleaning; (3) a reinforcement cage is manufactured and installed; (4) mounting a guide pipe and cleaning a hole; step (5), pouring concrete; (6) mounting a reinforcement cage in the column; and (7) pouring concrete into the steel pipe column. The rapid pile forming technology is adopted, the construction period is advanced, the cost is saved, good social benefits and economic benefits are created, particularly, great contributions are made in the aspects of safety production, energy conservation, consumption reduction and environmental protection, and wide application and popularization value is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, in particular to a rapid pile forming technical method using a hole pile method in a water-rich thick sand layer. Background Art

[0002] With the vigorous development of national rail transit construction, higher requirements are put forward for tunnel construction in cities. As a common construction method for subway underground excavation stations, the PBA method is increasingly favored by subway builders. At present, the mechanical pile-driving technology in the underground excavation construction tunnel can effectively solve the difficulties of early precipitation and construction obstruction. The pile foundation construction in the underground excavation station tunnel pile method usually adopts mud wall bored cast-in-place pile technology. The mechanical pile-driving method in the tunnel can effectively shorten the entire project period and reduce the project cost. The mechanical hole construction has good adaptability in different strata.

[0003] In order to ensure the quality of pile foundation construction in the dark excavation pilot tunnel, it is necessary to monitor the quality of pile foundation. Among them, mechanical hole forming is a key step in construction, which determines the progress and quality of the project. Since this construction task is mainly carried out in hidden places and the holes are deep, it is difficult to observe and control it continuously and effectively in most constructions, which brings certain unpredictability to the construction and even becomes a hidden danger affecting the quality of the project. Problems in any link of the construction will lead to major economic losses and adverse social impacts. Therefore, the pile foundation construction must be completed with quality and quantity. In order to further improve the efficiency of mechanical hole forming construction and reduce resource waste, it is necessary to monitor and analyze the construction process parameters of the construction conditions of complex strata. By adjusting the parameters of the drilling rig during the construction process, the construction quality can be optimized, the construction period can be shortened, and the project cost can be reduced. At the same time, the on-site construction process can be guided by monitoring parameters, and the factors affecting the quality of mechanical hole forming can be predicted and the hole forming quality can be judged by using artificial neural networks. It can not only ensure the safety and quality of pile construction, but also improve the economic and environmental benefits of the project. On this basis, adjusting the resource output according to the working conditions can speed up the construction of subway projects, reduce construction costs, and achieve green energy conservation and environmental protection requirements. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a technical method for rapid pile formation by the hole pile method in a water-rich thick sand layer to solve the problems raised in the above-mentioned background technology.

[0005] The technical problem solved by the present invention is achieved by adopting the following technical solution: a rapid pile forming technical method using a hole pile method in a water-rich thick sand layer, comprising the following steps:

[0006] Step (1). Construction preparation, stakeout of pile holes and positioning of drilling rigs;

[0007] Step (2). Drilling, hole depth measurement and hole cleaning; after measuring and setting out the manually dug hole positions, they should be well protected, and protection should be strengthened during the construction process. According to the measured points, use a pneumatic pick with the pile center point as the center of the circle and the outer edge of the hole wall as the radius to break the initial support structure concrete of the bottom plate of the guide hole;

[0008] Step (3). Fabrication and installation of the steel cage; During the hoisting process, in order to ensure the quality of the steel cage, it must be noted that the steel cage must not be deformed during transportation. The steel cage is hoisted in the guide hole, and straight threads are used between the sections. In order to ensure the quality requirements of the steel cage, reinforcement measures are taken during transportation to ensure that the steel cage is not deformed. After the steel cage is vertical, check the verticality. After the steel cage enters the hole, it is straightened and slowly lowered. It is strictly forbidden for the steel cage to swing and collide with the hole wall, and while lowering, the inner support is removed and the inner diagonal support is strictly prohibited from falling into the hole;

[0009] Step (4). Installation of conduit and hole cleaning; hoisting of steel pipe columns in sections, processing of earrings, and hoisting of steel pipe columns. The top section of the steel pipe column is to be completed after plastering and final setting before dismantling and mechanical relocation. According to the construction situation, after the piles in the entire hole are completed, the last section of the steel pipe column at the top is installed;

[0010] Step (5). Concrete pouring: After the steel pipe column is installed, the guide tube is lowered and the sediment is cleaned for the second time. After it meets the requirement of no more than 50mm, the pile concrete is poured. The concrete is transported by pumping and the slump is 180-230mm. A 300mm diameter guide tube is used for underwater pouring. The length of a single section of the guide tube should not be too long. The connection of the pipe section should be tight and firm. It should be tried before use, and the air tightness and water tightness tests should be carried out. The bottom end of the guide tube should be kept 300-500mm from the bottom of the hole.

[0011] Step (6). Installation of the steel cage in the column; the steel cage in the steel pipe column is located at the top. The construction of this section of the steel pipe column and the steel cage must be carried out after the piles in the entire hole are completed. The transportation and installation methods of the steel cage in the steel pipe column are basically the same as those of the steel cage in the cast-in-place pile. Only after the steel cage is installed and the relative elevation of the steel cage and the steel pipe column is determined, the steel cage is connected and fixed to the steel pipe column by electric welding and then fixed together at the hole. After the steel pipe column and the steel cage in the column are installed, the hoisting frame is removed to provide a construction site for the next step.

[0012] Step (7). Concrete pouring of steel pipe columns; the concrete pouring is divided into two steps. The first step is to pour concrete to the joint between the top section of the steel pipe and the second section of the steel pipe. The second step is to construct the top section of the steel pipe column and the steel cage inside the column separately. The top section of the steel pipe column is reinstalled, and the steel cage inside the top section of the column is installed, and concrete is poured to the top of the column.

[0013] Furthermore, in order to ensure the stability of the sand layer during the manual excavation of the pile wall in the hole and avoid hole collapse, the sand layer near the pile in the hole is grouting reinforced. The grouting adopts double liquid slurry with a diffusion radius of 40cm. The grouting pressure and slurry ratio are determined according to field tests to ensure that the unconfined compressive strength of the soil after grouting reinforcement is not less than 0.8MPa and the permeability coefficient is not greater than 1*10 -6 cm / s, and the circumferential spacing of the side pile grouting holes is 0.6m.

[0014] Furthermore, in step (2), an artificial breach is adopted, and an artificially dug hole wall is set at the opening section of the mechanical pile in the hole, with a depth of 2.3m and 2 sections. The wall is in an inverted trapezoidal shape, and the top thickness of each section of the wall is 15cm and the bottom thickness is 10cm. The outer diameter of the opening section of the middle pile column is 2.6m and the inner diameter is 2.2m. The artificially dug hole wall of the middle pile adopts continuous drilling in sequence.

[0015] Furthermore, the steel cage manufacturing step in step (3) is:

[0016] a. Make reinforcing reinforcement rings (stirrups) according to the designed dimensions and mark the positions of the main reinforcements on them;

[0017] b. Place the main reinforcement on a flat workbench and mark the position of the stiffener;

[0018] c. Align the mark of any main reinforcement on the stiffener with the mark of the stiffener in the middle of the main reinforcement, straighten the stiffener and make it perpendicular to the main reinforcement, then perform spot welding. Do this in sequence and weld all the stiffeners on one main reinforcement;

[0019] d. Have one person at each end of the frame rotate the frame and weld the remaining main bars one by one according to the above method;

[0020] e. Place the frame on the bracket, insert the spiral reinforcement, arrange the spiral reinforcement according to the designed position, and then spot weld it firmly;

[0021] Furthermore, in the hoisting of the steel cage in step (3), when the first section of the steel cage is lowered to the position of the last section of the reinforcement bar, the steel cage hoisting frame is inserted, the steel cage hoisting frame is supported in the steel cage and hoisted into the pile hole, and then the second section of the steel cage is hoisted, and then the sleeve of the upper part of the first section of the steel cage is screwed to the full thread position, so that the sleeve of the upper part of the first section of the steel cage just protrudes out of the sleeve; then the thread head of each section of the second section of the steel cage is aligned with the thread head of the first section so that they are connected on the same vertical axis using the sleeve, and the steel cage hoisting frame is pulled out to lower the steel cage. This cycle is repeated, so that the steel cage is lowered to the designed elevation and positioned at the center of the hole, and the installation of the steel cage is completed. After the last section of the steel cage is installed in place, the steel cage is welded and fixed to the hole guard wall with steel bars; the operation process of the steel cage of the middle pile foundation is the same as above, because there is no steel cage outside the steel pipe column; the steel cage is connected with hangers so that the top of the hangers is welded and fixed to the hole guard wall to control the elevation of the pile foundation steel cage.

[0022] Furthermore, the steel pipe column installation step in step (4) is:

[0023] Step 1: Transport the steel pipe to the hole mouth, use the pile-holding integrated equipment onboard crane to hoist the steel pipe column, slowly lift the steel pipe vertically upward and leave the transport vehicle; then tow the transport vehicle away and leave the location of the steel pipe;

[0024] Step 2: Slowly tighten and lift the hole pile to the arrow position of the integrated equipment, and slowly loosen the chain hoist of the crane frame. This process must be done slowly, and the two lifting mechanisms work together to ensure that the steel pipe is always stable and 10cm off the ground;

[0025] Step 3: Move to the vertical position of the steel pipe, check to ensure that the steel pipe is stable, remove the chain hoist hook of the crane frame, gradually lower the height of the pile column integrated equipment, and slowly feed the steel pipe; wait until the upper flange of the steel pipe is close to the wellhead elevation, leaving enough distance; install the bayonet steel plate of the wellhead, fix the steel pipe on the bayonet steel plate, check to ensure that it is reliable and stable, and remove the hook;

[0026] After the steel cage is installed in the steel pipe column, the whole steel pipe column is lowered and fixed to the specified elevation through the pipe feeding method of the pile-column integrated equipment; then the guide tube is lowered into the steel pipe column and the pile foundation concrete is poured to the top elevation of the bored pile, and then fine sand is backfilled between the steel pipe column and the hole wall. The height of the fine sand backfill is enough to press down the concrete around the steel pipe column and turn it up. A 0.5m thick C15 plain concrete ring belt should be poured every 4m of sand filling to constrain the steel pipe column with the surrounding strata; finally, the concrete in the steel pipe column is poured to 1m below the node of the top section of the steel pipe column. After the concrete pouring is completed and the final setting is completed, the pile-column integrated equipment can be removed.

[0027] Furthermore, the first concrete pouring: pouring to the node between the top section of the steel pipe and the second section of the steel pipe,

[0028] ① Use C30 concrete to pour concrete to the bottom of the steel pipe column, and increase the frequency of hole depth measurement during the process.

[0029] ②Replace high-grade (C50) micro-expansive concrete and continue pouring to the top of the pile foundation (i.e. the bottom of the base plate).

[0030] ③ After removing the guide tube to 500mm above the bottom of the steel pipe column, start backfilling fine sand around the steel pipe column. The height of the fine sand backfill should be enough to press down the concrete around the steel pipe column. A 0.5m thick C15 plain concrete ring should be poured every 4m of sand filling to make the surrounding strata constrain the steel pipe column.

[0031] ④ After backfilling with fine sand and waiting for the initial setting of the concrete, use high-grade (C50) micro-expansive concrete to continue pouring concrete in the steel pipe column to the node between the top section of the steel pipe column and the second section (counting from top to bottom). When temporarily dismantling or later installing the top section of the steel pipe column, chisel out the floating slurry to 500mm below the node between the two, and move the pile-column integrated equipment after final setting.

[0032] Compared with the prior art, the beneficial effects of the present invention are: the present invention adopts rapid piling technology, which shortens the construction period, saves costs, creates good social and economic benefits, and especially makes great contributions to safe production, energy conservation and consumption reduction, and environmental protection, and has wide promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the construction process of the present invention. DETAILED DESCRIPTION

[0034] In order to make the technical means for realizing the present invention, the creative features, the objectives and effects to be achieved easy to understand, the present invention is further explained below in conjunction with specific diagrams. In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection, or an integral connection can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two elements.

[0035] like Figure 1 As shown, the rapid pile construction technology of the water-rich thick sand layer hole pile method includes the following steps:

[0036] Step (1). Construction preparation, stakeout of pile holes and positioning of drilling rigs;

[0037] Step (2). Drilling, hole depth measurement and hole cleaning; after measuring and setting out the manually dug hole positions, they should be well protected, and protection should be strengthened during the construction process. According to the measured points, use a pneumatic pick with the pile center point as the center of the circle and the outer edge of the hole wall as the radius to break the initial support structure concrete of the bottom plate of the guide hole;

[0038] Step (3). Installation of steel cage

[0039] Step (4). Catheter installation and hole cleaning

[0040] Step (5). Concrete pouring

[0041] Step (6). Installation of steel cage in column

[0042] Step (7). Steel pipe column concrete pouring

[0043] In order to ensure the stability of the sand layer during the artificial excavation of the pile wall in the hole and avoid hole collapse, the sand layer near the pile in the hole is reinforced by grouting. The grouting adopts double liquid slurry with a diffusion radius of 40cm. The grouting pressure and slurry ratio are determined according to the field test to ensure that the unconfined compressive strength of the soil after grouting reinforcement is not less than 0.8MPa and the permeability coefficient is not greater than 1*10 -6 cm / s, and the circumferential spacing of the side pile grouting holes is 0.6m.

[0044] In the step (2), an artificial breach is adopted, and an artificially dug hole wall is set at the opening section of the mechanical pile in the hole, with a depth of 2.3m and 2 sections. The wall is in an inverted trapezoidal shape, and the top thickness of each section of the wall is 15cm and the bottom thickness is 10cm. The outer diameter of the opening section of the middle pile column is 2.6m and the inner diameter is 2.2m. The artificially dug hole wall of the middle pile adopts continuous drilling in sequence.

[0045] Hole construction method

[0046] (1) After the manual hole is measured and marked, it should be well protected and protected during the construction process. According to the measured point, use a pneumatic pick to break the primary support structure concrete of the bottom plate of the guide hole with the center point of the pile as the center and the outer edge of the hole wall as the radius. The breaking radius is 1.3m.

[0047] The longitudinal bars of the grid that do not affect the hole protection wall are retained as much as possible without cutting. The double-layer reinforcement steel bars are tied to the longitudinal bars of the grid through two φ8 stirrups. The reinforced ring beam of the bored pile in the middle hole is welded into a ring with 6 22 ring steel bars, which are spot welded to the longitudinal bars of the bottom plate grid. Two φ8 stirrups are set between each grid steel frame. After the ring steel bars are welded firmly, C25 concrete is poured.

[0048] (2) The retaining wall of the artificial bored pile in the middle pile is constructed by sequential excavation. The depth of the retaining wall is 2m. The excavation is carried out twice, with the first excavation of 1m and the second excavation of 1m. The excavation area is the designed pile diameter plus the retaining wall thickness. The excavation is carried out manually from top to bottom in sections. The excavation sequence of the same section is the middle first and then the periphery. After each section of the retaining wall is excavated, the concrete should be poured and compacted by hand immediately. The retaining wall concrete uses C25 concrete, and the slump is controlled at 80-100mm.

[0049] When working in the hole, there must be someone on guard above the hole mouth. The excavated soil must be transported away from the hole mouth in time, and tools and people must not be placed on the concrete enclosure. The lifting equipment in the hole uses a self-made lifting frame with a height of approximately 1.2 to 1.4m, and a hand-cranked device (a limit device is required). The lifting equipment must be firmly installed in accordance with relevant requirements and in good condition. Workers in the hole must wear safety helmets and safety belts. When the slag bucket is used to transport soil up and down, workers under the hole should avoid being injured by falling objects under the guard plate (net). The integrity of the vertical transportation equipment and the condition of the hole wall should be checked at any time during construction. When the digging team evacuates, the hole mouth must be protected with a hard cover to prevent people from falling.

[0050] (3) Mechanical pore forming

[0051] The drilling method for the center pile is the same as that for the side piles, that is, pump suction reverse circulation construction is adopted, and the construction method is the same as the mechanical hole construction method for the side piles.

[0052] Steel cage production and installation

[0053] (1) Steel Cage Production Steps

[0054] a. Make reinforcing reinforcement rings (hoops) according to the designed dimensions and mark the positions of the main reinforcements on them.

[0055] b. Place the main reinforcement on a flat workbench and mark the position of the stiffeners.

[0056] c. Align the mark of any main reinforcement on the stiffener with the mark of the stiffener in the middle of the main reinforcement, straighten the stiffener and make it perpendicular to the main reinforcement, then perform spot welding. Do the same in sequence and weld all the stiffeners on one main reinforcement.

[0057] d. Ask one person at each end of the frame to rotate the frame and weld the remaining main reinforcements one by one using the above method.

[0058] e. Place the frame on the bracket, insert the spiral reinforcement, arrange the spiral reinforcement according to the designed position, and then spot weld it firmly.

[0059] (2) Technical requirements for steel cage processing

[0060] a. The longitudinal main reinforcement joints of the side piles are connected by first-class mechanical joints. The specific segment positions are determined according to the actual construction on site except those marked in the figure. The longitudinal reinforcement is connected to the spiral stirrups and reinforcing stirrups by spot welding. The spiral stirrups are lap welded, with a single-sided welding length of 10d and a weld height of 8mm. The longitudinal main reinforcement of the steel cage is closed inward at an angle of 1:10 at a distance of 0.7m from the bottom of the pile.

[0061] b. Oil stains, paint stains, cement slurry, loose skin, rust, etc. on the surface of the steel bars should be cleaned.

[0062] c. After processing, the surface of the steel bars should not have any scratches that weaken the cross-section of the steel bars.

[0063] d. The main reinforcement of the steel cage is mechanically connected, and the main reinforcement joints are primary joints.

[0064] e. The allowable deviation of production shall comply with the requirements of "Code for Construction and Acceptance of Underground Railway Project (GB50299-1999)".

[0065] (3) Lifting of steel cage

[0066] During the hoisting process, in order to ensure the quality of the steel cage, it must be noted that the steel cage must not be deformed during transportation. When hoisting the steel cage in the guide hole, straight threads are used to connect the sections. In order to ensure the quality requirements of the steel cage, reinforcement measures are taken during transportation to ensure that the steel cage does not deform. After the steel cage is vertical, check the verticality. After the steel cage enters the hole, straighten it and slowly lower it. It is strictly forbidden for the steel cage to swing and collide with the hole wall. While lowering it, remove the internal support and it is strictly forbidden for the internal diagonal support to fall into the hole.

[0067] When the first section of the steel cage is lowered to the position of the last section of reinforcement, the steel cage hoisting frame is inserted into the steel cage, the steel cage hoisting frame is supported in the steel cage and hoisted into the pile hole, and then the second section of the steel cage is hoisted, and then the sleeve of the upper part of the first section of the steel cage is screwed to the full thread position, so that the sleeve of the upper part of the first section of the steel cage just protrudes out of the sleeve. Then align the thread head of each section of the second section of the steel cage with the thread head of the first section so that they are connected with the sleeve on the same vertical axis, and then the steel cage hoisting frame is pulled out to lower the steel cage. In this way, the steel cage is lowered to the designed elevation and positioned at the center of the hole to complete the installation of the steel cage. After the last section of the steel cage is installed in place, the steel cage is welded and fixed to the hole wall with steel bars. The operation process of the steel cage of the pile foundation part is the same as above, because there is no steel cage outside the steel pipe column. The steel cage is connected with the hanging bar so that the top of the hanging bar is welded and fixed to the hole wall to control the elevation of the pile foundation steel cage. Total length of hanger rod = designed hole depth - length of steel cage.

[0068] Transportation and installation of steel pipe columns

[0069] (1) Transportation of steel pipe columns

[0070] The steel pipe column is processed in the processing plant and transported to the construction site after acceptance. During transportation, the finished product protection work should be strengthened. The bottom of the steel pipe column should be padded according to the specified spacing and height to prevent axial deformation. The flange and liner bolt parts should be protected from stress and collision and properly protected to avoid damage to the finished product. After being transported to the site, necessary covering and padding should be carried out to prevent rust and deformation due to collision.

[0071] During the vertical transportation of the steel pipe column from the ground to the bottom of the shaft, a double-track bridge crane is used for lifting (the shaft gantry crane can also be used). Precautions for vertical lifting:

[0072] ① Use steel wire rope for two-point horizontal lifting during lifting, and take care to prevent the steel pipe column from slipping and surface scratches.

[0073] ② Construction operators must strictly follow the safety operating procedures for lifting to prevent the occurrence of falling objects from heights.

[0074] ③ A movable probe platform is set up at the slag dumping port of the vertical shaft to facilitate the transfer of steel pipe columns from the vertical shaft to the horizontal channel, avoiding collision and damage of the steel pipe columns during the transportation and conversion from the vertical shaft to the horizontal channel.

[0075] The horizontal transportation of the steel pipe column from the bottom of the shaft to the erection working surface is completed by a self-made rack car (gun car). During the transportation process, the hoisted steel pipe column is stably placed on the rack car parked on the operating platform, and is pushed to the work point by machinery and manual labor. During the pushing process, necessary reinforcement and protection measures must be taken to avoid safety hazards caused by lateral rolling or forward and backward sliding of the steel pipe column.

[0076] (2) Installation of steel pipe columns

[0077] The steel pipe column is hoisted by the orifice machine-mounted hoisting gantry, and the steel pipe column is hoisted in sections. Earrings are processed and used for hoisting operations of steel pipe columns.

[0078] The top section of the steel pipe column will be removed and mechanically moved after the mortar is completed (the mortar surface is 1m below the top node) and the final setting. According to the construction situation, after the piles in the entire hole are completed, the last section of the steel pipe column at the top will be installed.

[0079] (3) Steel pipe column installation steps

[0080] Step 1: Transport the steel pipe to the hole mouth, use the pile-holding integrated equipment onboard crane to lift the steel pipe column, slowly lift the steel pipe vertically upward and leave the transport vehicle; then tow the transport vehicle away and leave the location of the steel pipe.

[0081] Step 2: Slowly tighten and lift the hole pile to the arrow position of the integrated equipment, and slowly loosen the chain hoist of the crane frame. This process must be carried out slowly, and the two lifting mechanisms work together to ensure that the steel pipe is always stable and about 10cm off the ground.

[0082] Step 3: Proceed to the vertical position of the steel pipe, check to ensure that the steel pipe is stable, remove the chain hoist hook of the crane frame, gradually lower the height of the pile column integrated equipment, and slowly feed the steel pipe; wait until the upper flange of the steel pipe is close to the wellhead elevation, leaving enough distance; install the bayonet steel plate of the wellhead, fix the steel pipe on the bayonet steel plate, check to ensure reliability and stability, and remove the hook.

[0083] During the hoisting process, after each section is hoisted, the pile-column integration equipment is used to temporarily fix it for precision adjustment. After the flange of the steel pipe column is firmly connected, the next section is fed down. The next section is hoisted in the same way, and then the high-strength bolts of the steel pipe column connection flange are installed. The other sections are installed section by section in the same way, and finally the pile-column integration equipment is used to fix the entire steel pipe column at the hole.

[0084] During construction, the operation platform of the pile-column integrated equipment must be stable and reliable. The high bolts used to connect the steel pipe columns in this project are M20, with a performance grade of 10.9s.

[0085] Installation of steel cage in steel pipe column

[0086] The steel cage inside the steel pipe column is located at the top. The construction of this section of steel pipe column and steel cage must be carried out after the piles in the entire hole are completed.

[0087] The transportation and installation method of the steel cage in the steel pipe column is basically the same as that of the steel cage in the cast-in-place pile. Only after the steel cage is installed and the relative elevation between the steel cage and the steel pipe column is determined, the steel cage is connected and fixed to the steel pipe column by electric welding and then fixed together at the hole. After the steel pipe column and the steel cage in the column are installed, the hoisting frame is removed to provide a construction site for the next process.

[0088] The whole steel pipe column is lowered and fixed to the specified elevation by the pipe feeding method of the pile column integrated equipment. Then the guide tube is lowered into the steel pipe column and the pile foundation concrete is poured to the top elevation of the bored pile. Then the fine sand is backfilled between the steel pipe column and the hole wall. The backfill height of the fine sand is enough to press the concrete around the steel pipe column upward. A 0.5m thick C15 plain concrete ring belt should be poured every 4m to constrain the steel pipe column with the sand filling, so that the surrounding strata will form a constraint on the steel pipe column. Finally, the concrete in the steel pipe column is poured to 1m below the node of the top steel pipe column. After the concrete pouring is completed and the final setting is completed, the pile column integrated equipment can be removed.

[0089] Follow this method to complete the construction of the rest of the middle piles. The top section of the middle pile steel pipe column needs to be installed later. The steel cage in this section of the pipe is installed in place, and the fine sand between the steel pipe column and the hole wall is backfilled. Pour concrete into the steel pipe column again to the top of the steel pipe column.

[0090] Vertical leveling machine

[0091] (1) After the steel pipe column is clamped tightly with the clamp of the vertical adjustment machine, the measurement team remeasures the positioning and elevation of the steel pipe column to ensure the accuracy of the top section of the steel pipe column.

[0092] (2) Place a high-precision inclination angle on the top of the steel column

[0093] Sensors are used to monitor the verticality of steel pipe columns in real time.

[0094] Sensor parameters:

[0095] Sensor model: SDA8200k01001000; Measurement angle range: 0-120°;

[0096] Resolution: 0.001°; Overall accuracy: 0.1%;

[0097] Working temperature range: -40-100℃;

[0098] Protection grade: IP67.

[0099] (3) The actual verticality of the steel pipe column is observed through the digital display device of the vertical adjustment machine and the high-precision sensor, and the hydraulic legs of the vertical adjustment machine are adjusted using the one-button leveling function, so that the vertical adjustment machine equipment is leveled so that the verticality of the steel pipe column meets the design requirements.

[0100] Pouring concrete

[0101] (1) Catheter installation and operation

[0102] After the steel pipe column is installed and the sediment is lowered to the lower pipe for secondary cleaning and meets the requirement of no more than 50mm, the concrete pouring of the pile is carried out. The concrete is transported by pumping and the slump is 180-230mm. The underwater pouring uses a 300mm diameter pipe. The length of a single pipe section should not be too long. The pipe section connection should be tight and firm. It should be tried before use, and the air tightness and water tightness test should be carried out. The bottom end of the pipe should be kept 300-500mm from the bottom of the hole.

[0103] During the pouring process, the depth of the conduit buried in the concrete should be maintained at 2-6m, and it should be removed as it is lifted. The hanging and lifting of the conduit must not collide with the steel cage.

[0104] (2) Concrete pouring

[0105] The concrete pouring was carried out in two stages.

[0106] (1) The first time: pouring to the node between the top section of the steel pipe and the second section of the steel pipe.

[0107] ① Use C30 concrete to pour concrete to the bottom of the steel pipe column, and increase the frequency of hole depth measurement during the process.

[0108] ②Replace high-grade (C50) micro-expansive concrete and continue pouring to the top of the pile foundation (i.e. the bottom of the base plate).

[0109] ③ After removing the guide tube to 500mm above the bottom of the steel pipe column, start backfilling fine sand around the steel pipe column. The height of the fine sand backfill should be enough to press down the concrete around the steel pipe column. A 0.5m thick C15 plain concrete ring should be poured every 4m of sand filling to make the surrounding strata constrain the steel pipe column.

[0110] ④ After backfilling with fine sand and waiting for the initial setting of the concrete, use high-grade (C50) micro-expansive concrete to continue pouring concrete in the steel pipe column to the node between the top section of the steel pipe column and the second section (counting from top to bottom). When temporarily dismantling or later installing the top section of the steel pipe column, chisel out the floating slurry to 500mm below the node between the two, and move the pile-column integrated equipment after final setting.

[0111] (2) Second time: The top section of the steel pipe column and the steel cage inside the column are constructed separately. Reinstall the top section of the steel pipe column, install the steel cage inside the top section of the column, and pour concrete to the top of the column.

[0112] Treatment measures for the construction joints of two pourings of concrete: Manually chisel away the first pouring of concrete, that is, the concrete at the first steel pipe column node from top to bottom. Chisel away at least 500mm below the node and chisel to the concrete solid surface before proceeding to the next process. Ensure the pouring quality of the concrete connection surface.

[0113] (3) Remove the pile equipment

[0114] When the concrete in the column is finally set, the top section of the steel pipe column is removed, and then the equipment is removed. The top section of the steel pipe column, the steel cage in the column, and the concrete in the column are constructed together after the entire hole is completed. During this period, safety protection and finished product protection work must be done well.

[0115] Post-grouting construction of bored piles

[0116] After bored cast-in-place piles are formed, post-grouting is required. Post-grouting can reinforce the sediment (loose soil), mud skin and a certain range of soil at the bottom of the pile.

[0117] (1) Main equipment: grouting pump, 16MPa pressure gauge, cement slurry mixer, 0.5m3 slurry storage drum (covered with filter screen)

[0118] (2) Main materials: Cement uses 42.5 ordinary Portland cement, and the water-cement ratio is adjusted according to on-site tests; the grouting pipe uses a 42mm diameter steel pipe, and the grouting pipe connection uses a threaded connection.

[0119] (3) Grouting pipe production

[0120] According to the design drawings, the grouting pipe adopts a φ42, t=3.25mm welded pipe, the end of the grouting pipe is flattened by 50mm and covered with rubber strips. The grouting valve outlet holes are divided into 4 rows, with 4 outlet holes in each row, and the spacing between each grouting valve is 6m. The grouting valve is set at 150mm from the end of the pile bottom grouting pipe, and the first grouting valve is set at 5m from the pile bottom of the pile grouting pipe, with a spacing of 6m, and the last grouting valve is set at 6m below the bottom plate. The grouting hole of the grouting valve is wrapped with a rubber sleeve.

[0121] (4) Grouting pipe installation

[0122] The grouting pipe is lowered together with the steel cage and welded to the positioning steel bars of the steel cage with a welding length of 200mm. The grouting pipes are connected by threaded connection to avoid welding. The bottom of the grouting pipe extends 400mm out of the steel cage. For the grouting pipe affected by the flange of the steel casing, an elbow is added at the steel casing to avoid the flange.

[0123] (5) Grouting pipe water testing

[0124] Each section of the grouting pipe should be subjected to a water test when it is lowered with the steel cage. If it is found that the water column drops or disappears, the grouting pipe should be checked for sand holes and whether the threaded connections are sealed.

[0125] After the steel cage is placed, the hole is cleaned for the second time. After completion, the water level in the pipe must be checked again. If there is no abnormality, the upper end of the grouting pipe is sealed with a plug.

[0126] (6) Grouting parameters

[0127] Post-grouting is carried out on the pile side and pile end of the middle pile. The grouting liquid is cement slurry. The theoretical grouting volume is not less than 10.8 cubic meters, and the spacing of the side wall grouting ring surface is 6m. Before the post-grouting operation begins, a grouting test should be carried out to optimize and finally determine the grouting parameters; it is recommended that the grouting pressure is 3-10MPa, the water-cement ratio is 0.5-0.6, the cement mass of a single pile grouting is 3.9t, and the grouting flow rate should not be greater than 75L / min; the grouting operation should be completed within 2-7 days after the pile is formed, and should not be later than 30 days after the pile is formed; the distance between the grouting operation and the hole forming operation point should not be less than 10m; the pile end grouting should be carried out in turn with equal grouting in each grouting conduit of the same pile; when the grouting pressure is lower than the normal value for a long time or there is grouting on the ground or grouting in the surrounding pile holes, it should be changed to intermittent grouting, and the intermittent time should be 30-60min, or the grouting water-cement ratio should be lowered. The grouting technology should also meet the relevant requirements of "Technical Specifications for Building Pile Foundations" (JGJ94-2008).

[0128] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. Rapid pile construction technology of hole pile method in water-rich thick sand layer, characterized by: The following steps are involved: Step (1). Construction preparation, stakeout of pile holes and positioning of drilling rigs; Step (2). Drilling, hole depth measurement and hole cleaning; after measuring and setting out the manually excavated holes, the holes should be well protected and the protection should be strengthened during the construction process; according to the measured points, a pneumatic pick is used with the center point of the pile as the center of the circle and the outer edge of the hole wall as the radius to break the initial support structure concrete of the bottom plate of the guide hole; Step (3). Fabrication and installation of the steel cage; During the hoisting process, in order to ensure the quality of the steel cage, it must be noted that the steel cage must not be deformed during transportation. The steel cage is hoisted in the guide hole, and straight threads are used between the sections. In order to ensure the quality requirements of the steel cage, reinforcement measures are taken during transportation to ensure that the steel cage is not deformed. After the steel cage is vertical, check the verticality. After the steel cage enters the hole, it is straightened and slowly lowered. It is strictly forbidden for the steel cage to swing and collide with the hole wall, and while lowering, the inner support is removed and the inner diagonal support is strictly prohibited from falling into the hole; Step (4). Installation of conduit and hole cleaning; hoisting of steel pipe columns in sections, processing of earrings, and hoisting of steel pipe columns. The top section of the steel pipe column is to be completed after plastering and final setting before dismantling and mechanical relocation. According to the construction situation, after the piles in the entire hole are completed, the last section of the steel pipe column at the top is installed; Step (5) concrete pouring; after the steel pipe column is installed, the pipe is lowered and the sediment is cleaned for the second time to meet the requirement of no more than 50mm, the pile concrete is poured. The concrete is transported by pumping and the slump is 180-230mm. The underwater pouring uses a 300mm diameter pipe. The length of a single pipe section should not be too long. The pipe section connection should be tight and firm. It should be tried before use, and the air tightness and water tightness test should be carried out. The bottom end of the pipe should be kept 300-500mm from the bottom of the hole. Step (6). Installation of steel cage in the column; the steel cage in the steel pipe column is located at the top. The construction of this section of steel pipe column and steel cage needs to be carried out after the pile in the whole hole is completed; the transportation and installation method of the steel cage in the steel pipe column is basically the same as that of the steel cage in the cast-in-place pile. Only after the steel cage is installed and the relative elevation of the steel cage and the steel pipe column is determined, the steel cage is connected and fixed to the steel pipe column by electric welding and then fixed together at the hole; after the steel pipe column and the steel cage in the column are installed, the hoisting frame is removed to provide a construction site for the next step; Step (7). Concrete pouring of steel pipe columns; the concrete pouring is divided into two steps. The first step is to pour concrete to the joint between the top section of the steel pipe and the second section of the steel pipe. The second step is to construct the top section of the steel pipe column and the steel cage inside the column separately. The top section of the steel pipe column is reinstalled, and the steel cage inside the top section of the column is installed, and concrete is poured to the top of the column.

2. The rapid pile construction technology method of hole pile method in water-rich thick sand layer according to claim 1 is characterized by: In order to ensure the stability of the sand layer during the artificial excavation of the pile wall in the hole and avoid hole collapse, the sand layer near the pile in the hole is reinforced by grouting. The grouting adopts double liquid slurry with a diffusion radius of 40cm. The grouting pressure and slurry ratio are determined according to the field test to ensure that the unconfined compressive strength of the soil after grouting reinforcement is not less than 0.8MPa and the permeability coefficient is not greater than 1*10 -6 cm / s, and the circumferential spacing of the side pile grouting holes is 0.6m.

3. The rapid pile construction technology method of hole pile method in water-rich thick sand layer according to claim 1 is characterized by: In the step (2), an artificial breach is adopted, and an artificially dug hole protective wall is set at the opening section of the mechanical pile in the hole, with a depth of 2.3m and divided into 2 sections. The protective wall is an inverted trapezoid, and the top thickness of each section of the protective wall is 15cm and the bottom thickness is 10cm. The outer diameter of the opening section of the middle pile column is 2.6m and the inner diameter is 2.2m; the artificially dug hole protective wall of the middle pile adopts continuous drilling in sequence.

4. The rapid pile construction technology method of hole pile method in water-rich thick sand layer according to claim 1 is characterized by: The steel cage production steps in step (3) are: a. Make reinforcing reinforcement rings (stirrups) according to the designed dimensions and mark the positions of the main reinforcements on them; b. Place the main reinforcement on a flat workbench and mark the position of the stiffener; c. Align the mark of any main reinforcement on the stiffener with the mark of the stiffener in the middle of the main reinforcement, straighten the stiffener and make it perpendicular to the main reinforcement, then perform spot welding; do the same in sequence and weld all the stiffeners on one main reinforcement; d. Have one person at each end of the frame rotate the frame and weld the remaining main bars one by one according to the above method; e. Place the frame on the bracket, insert the spiral reinforcement, arrange the spiral reinforcement according to the designed position, and then spot weld it firmly.

5. The rapid pile construction technology method of hole pile method in water-rich thick sand layer according to claim 1 is characterized by: In the hoisting of the steel cage in the step (3), when the first section of the steel cage is lowered to the position of the last section of the reinforcement bar, the steel cage hoisting frame is inserted into the steel cage hoisting frame, the steel cage hoisting frame is supported in the steel cage and hoisted to place in the pile hole, and then the second section of the steel cage is hoisted, and then the sleeve of the upper part of the first section of the steel cage is fully screwed to the full thread position, so that the sleeve of the upper part of the first section of the steel cage is just exposed outside the sleeve; then the thread head of each section of the second section of the steel cage is aligned with the thread head of the first section so that they are connected with the sleeve on the same vertical axis, and the steel cage hoisting frame is pulled out to lower the steel cage; this cycle is repeated to lower the steel cage to the designed elevation and position it on the center of the hole, completing the installation of the steel cage; after the last section of the steel cage is installed in place, the steel cage is welded and fixed to the hole mouth wall position with steel bars; the operation process of the steel cage of the pile foundation part is the same as above, because there is no steel cage outside the steel pipe column; the steel cage is connected with the hanging rod so that the top of the hanging rod is welded and fixed to the hole mouth wall position to control the elevation of the pile foundation steel cage.

6. The rapid pile construction technology method of hole pile method in water-rich thick sand layer according to claim 1 is characterized by: The steel pipe column installation steps in step (4) are: Step 1: Transport the steel pipe to the hole mouth, use the pile-holding integrated equipment onboard crane to hoist the steel pipe column, slowly lift the steel pipe vertically upward and leave the transport vehicle; then tow the transport vehicle away and leave the location of the steel pipe; Step 2: Slowly tighten and lift the hole pile to the arrow position of the integrated equipment, and slowly loosen the chain hoist of the crane frame; this process must be carried out slowly, and the two lifting mechanisms work together to ensure that the steel pipe is always stable and 10cm off the ground; Step 3: Proceed to the vertical position of the steel pipe, check to ensure that the steel pipe is stable, remove the chain hoist hook of the crane frame, gradually lower the height of the pile column integrated equipment, and slowly feed the steel pipe; wait until the upper flange of the steel pipe is close to the wellhead elevation, leaving enough space; install the bayonet steel plate of the wellhead, fix the steel pipe on the bayonet steel plate, check to ensure reliability and stability, and remove the hook; after the steel cage in the steel pipe column is installed, the entire steel pipe column is lowered and fixed to the specified elevation through the pile column integrated equipment pipe feeding method Position; then lower the guide tube into the steel pipe column and start pouring pile foundation concrete to the top elevation of the bored pile, then backfill the space between the steel pipe column and the hole wall with fine sand. The backfill height of the fine sand should be enough to press down the concrete around the steel pipe column and turn it up. A 0.5m thick C15 plain concrete ring should be poured every 4m of sand filling to constrain the steel pipe column with the surrounding strata; finally, pour concrete in the steel pipe column to 1m below the node of the top section of the steel pipe column. After the concrete pouring is completed and the final setting is completed, the pile-column integrated equipment can be removed.

7. The rapid pile construction technology method of hole pile method in water-rich thick sand layer according to claim 1 is characterized by: The first concrete pouring: pouring to the node between the top section of the steel pipe and the second section of the steel pipe, ① pouring concrete to the bottom of the steel pipe column with C30 concrete, increasing the frequency of hole depth measurement during the process; ② replacing high-grade (C50) micro-expansive concrete, and continuing to pour to the top elevation of the pile foundation; ③ after removing the guide tube to 500mm above the bottom of the steel pipe column, start backfilling fine sand around the steel pipe column, the fine sand backfill height can be enough to press the concrete around the steel pipe column to turn up, and a 0.5m thick C15 plain concrete ring belt should be poured every 4m of sand filling to constrain the steel pipe column with the surrounding strata; ④ after the backfilling of fine sand is completed, wait for the initial setting of the concrete, and continue to pour the concrete in the steel pipe column to the node between the top section of the steel pipe column and the second section (counting from top to bottom) with high-grade (C50) micro-expansive concrete. When temporarily dismantling or installing the top section of the steel pipe column later, the floating slurry is chiseled out to 500mm below the node between the two, and the pile column integration equipment is moved after final setting.

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