Group pile cast-in-place pile foundation cleaning method and construction method

Abstract

The invention relates to the technical field of bridge foundation construction, and particularly discloses a pile foundation cleaning method and a construction method.According to the cleaning method, before concrete is poured into a pile group cast-in-place pile, a slurry pumping and discharging device is adopted for conducting slurry replacement and hole cleaning on a pile hole, and the slurry pumping and discharging device comprises a rotary hydraulic pump and a slurry pumping and sucking steel pipe; the rotary hydraulic pump is connected with the hydraulic pump station through a hydraulic pump pipe, a stirring head is arranged on the rotary hydraulic pump, an air supply pipe used for supplying air into the mud suction steel pipe is arranged on the mud suction steel pipe, sediment is rotationally cut through the stirring head, an air compressor is used for supplying air to form a mud pumping and discharging path, and then sediment is cleaned after being settled. Not only are the construction quality and the construction efficiency improved, but also the construction safety is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge foundation construction, and particularly relates to a method for cleaning a group of cast-in-place pile foundations and a construction method thereof. Background Art

[0002] During the bridge construction process, in order to improve the bearing capacity of the foundation, cast-in-place piles are often used as a foundation treatment method. The cast-in-place piles are formed by drilling or digging holes, and then a steel cage is arranged in the hole and concrete is poured to form a pile foundation. By transmitting the load to the deep soil layer or rock layer through the cast-in-place piles, the settlement of the building can be effectively reduced and the stability of the bridge structure can be improved. In addition, the bridge construction also involves different construction parts such as the river section and the shore section, and it is necessary to arrange bridge pile foundations and road support pile foundations, etc., so as to pour and form a group of cast-in-place pile foundations, making the overall structure of the bridge have sufficient stability and bearing capacity.

[0003] Since the pier part of the bridge is an underwater pile foundation, multiple cast-in-place piles are arranged under the bearing platform of each pier. And the part where the bridge connects to the shore usually also involves abutments and road support retaining walls, and multiple cast-in-place piles are also arranged under each abutment and the road support retaining wall. In order to ensure the structural stability of the piers, abutments and road support retaining walls, it is necessary to control the construction quality of the pouring of the group of cast-in-place pile foundations. As the foundation part of the cast-in-place piles, the construction process of the cast-in-place pile foundation is particularly important. During the construction process of the cast-in-place pile foundation, the following multiple problems are usually faced: Firstly, after the cast-in-place pile has completed drilling and most of the large-diameter sediment has been cleared, the small-diameter sediment at the bottom of the hole is relatively thick and not easy to clean. Whether using manual cleaning or using a mud pump in cooperation with a diver to dive underwater and then using a high-pressure water gun to disperse the sediment and then pumping it out, there are problems of slow cleaning speed and high operation risk. Secondly, the steel cage of the cast-in-place pile is relatively slender, and it is easy to deform when directly hoisted, which affects the pouring quality of the cast-in-place pile. The prior art has adopted the method of connecting and lengthening in the air by a crane, but there are problems of poor fixing due to the shaking of the steel cage and high-altitude operation, low construction efficiency and insecurity. Thirdly, before the concrete of the cast-in-place pile foundation is poured, the installed steel cage has problems of insecure fixation and easy floating, resulting in the problem that the position of the pile foundation is offset and affects the construction quality. The prior art adopts the method of setting a support at the pile hole opening for fixation, which not only has a complex structure but also has a poor fixation effect.

[0004] Therefore, how to clean the pile hole before pouring the cast-in-place pile, how to control the lowering and fixation of the steel cage during the pile foundation construction process, and thus ensure the construction quality of the pile foundation have become the key issues considered by technicians during the pile foundation construction process. Summary of the Invention

[0005] One of the purposes of the present invention is at least to provide a cleaning method for a group of cast-in-place pile foundations. Before pouring concrete into the cast-in-place pile foundation, due to the thick small-diameter sediment at the bottom of the hole, which is difficult to clean, and using other cleaning methods will have problems such as deepening the hole depth and construction insecurity. This cleaning method uses a stirring head to cut the sediment by rotation and uses an air compressor to supply air to form a mud pumping and discharging path, and then the sediment is cleaned after precipitation, which not only improves the construction quality and construction efficiency, but also greatly improves the construction safety.

[0006] In order to achieve the above purpose, the technical solutions adopted by the present invention include the following aspects.

[0007] A cleaning method for a group of cast-in-place pile foundations. Before pouring concrete into the group of cast-in-place pile foundations, a mud pumping and discharging device is used to replace the slurry and clean the pile hole. The mud pumping and discharging device includes a rotary hydraulic pump and a mud suction steel pipe. The rotary hydraulic pump is connected to a hydraulic pump station through a hydraulic pump pipe. A stirring head is provided on the rotary hydraulic pump. An air supply pipe for supplying air into the mud suction steel pipe is provided on the mud suction steel pipe. The process of replacing the slurry and cleaning the hole mainly includes the following steps: Step 1: Assemble the mud pumping and discharging device, including first installing the stirring head on the rotary hydraulic pump, then assembling the rotary hydraulic pump and the mud suction steel pipe so that the height of the stirring head corresponds to the bottom of the mud suction steel pipe, then connecting a mud guiding and discharging steel pipe to the upper port of the mud suction steel pipe, connecting the rotary hydraulic pump to the hydraulic pump station through the hydraulic pump pipe, and at the same time connecting the air supply pipe to the air compressor through an air compressor connecting pipe; the hydraulic pump pipe and the air compressor connecting pipe are both provided with a remaining length corresponding to the depth of the pile hole, and the mud guiding and discharging steel pipe leads to the outside of the pile hole.

[0008] Step 2: Lift the assembled structure of the rotary hydraulic pump and the mud suction steel pipe into the pile hole of the group of cast-in-place pile foundations, and the mud guiding and discharging steel pipe leads to the outside of the casing; Step 3: Start the mud pumping and discharging device. The rotary hydraulic pump drives the stirring head to rotate, stir and cut the mud. The air supply pipe supplies air into the mud suction steel pipe, and the mud is driven by the wind to be discharged through the mud guiding and discharging steel pipe; Step 4: After completing the cleaning before pouring the pile foundation concrete in a certain pile hole of the group of cast-in-place pile foundations, lift the assembled structure of the rotary hydraulic pump and the mud suction steel pipe, move it to the next pile hole, and repeat Step 2 and Step 3 until the cleaning before pouring the pile foundation of all pile holes is completed.

[0009] Preferably, the stirring head includes a second connecting plate, as well as stirring teeth and a frustum-shaped support connected to the second connecting plate; one side of the second connecting plate is detachably connected to a first connecting plate provided on a rotary hydraulic pump, and a center position on the other side plate surface of the second connecting plate is connected with the frustum-shaped support. A plurality of the stirring teeth are circumferentially arranged in a circle along the outer side of the frustum-shaped support. The stirring teeth are bent towards the frustum-shaped support, and the other end of the frustum-shaped support extends out of the outer side of the end of the stirring teeth. When the rotary hydraulic pump and the mud suction steel pipe are assembled, the slurry inlet of the mud suction steel pipe is flush with the position of the stirring head, so that when the structure after assembling the rotary hydraulic pump and the mud suction steel pipe is hoisted into the pile hole of the group pile cast-in-place pile in the second step, the slurry cut by the stirring head is discharged out of the casing through the mud suction steel pipe.

[0010] Preferably, the air supply pipe is a U-shaped structure penetrating the wall of the mud suction steel pipe, including an air inlet pipe section outside the mud suction steel pipe and an air outlet pipe section outside the mud suction steel pipe. The U-shaped bottom position penetrates the wall of the mud suction steel pipe. The air inlet pipe section is communicated with an air compressor connecting pipe, and the opening of the air outlet pipe section faces the direction of the mud discharged outwards by the mud suction steel pipe.

[0011] Correspondingly, the present invention also provides a construction method for a group pile cast-in-place pile foundation. During the construction process of pouring the group pile cast-in-place pile foundation, it includes the following construction steps: Step A: Preparation for pile foundation construction; Step B: Fabricating and burying the steel casing; Step C: The drilling rig is in place and the hole is formed by impact drilling, including respectively constructing the group pile cast-in-place pile structures of the abutment pile foundation and the group pile cast-in-place pile structures of the underwater pier pile foundation. When the drilling rig forms the hole by impact drilling, slag is fished during the drilling construction, and slag is selectively fished according to different soil layer conditions. The slag is fished using a slag bucket. Step D: Clearing the hole and detecting the formed hole. The slurry pumping and discharging device as described above is used for replacing the slurry to clear the hole. The slurry pumping and discharging device is placed into the pile hole through a crane or a cross-shaped frame erected on a steel platform. The bottom sediment of the hole is cut by the stirring head, and the cut fine sediment is discharged through the mud suction steel pipe. Step E: Lowering the steel reinforcement cage and installing the pouring conduit. After the steel reinforcement cage is lowered and installed in place, an anti-floating structure for preventing the steel reinforcement cage from floating is provided on the steel reinforcement cage. The anti-floating structure includes steel pipes arranged equally around the steel reinforcement cage. Reinforcing bar hooks are welded at the top of the casing. The top of the steel pipe is fixed by connecting through the reinforcing bar hooks, and the bottom of the steel pipe is connected to the main reinforcement bars of the steel reinforcement cage. Step F: Secondary hole clearing is carried out by using the group pile cast-in-place pile foundation cleaning method as described above. Step G: Pouring the pile foundation concrete and detecting the pile foundation.

[0012] Preferably, when performing impact drilling to form a hole in step C, the slag bucket used includes a barrel wall. The upper part of the barrel wall is an open and lidless structure. A bottom plate is provided at the bottom of the barrel wall. A slag inlet hole is opened in the middle of the bottom plate. A movable cover plate is hingedly installed on the bottom plate. The movable cover plate is used to cover the slag inlet hole. The opening angle of the movable cover plate is between 50° and 75°. Both sides of the top of the barrel wall of the slag bucket are provided with wire ropes, and the wire ropes are used to lower and lift the slag bucket.

[0013] Preferably, when lowering the steel cage in step E, the steel cage skeleton is prefabricated in sections first. Using a crane to lower and install the steel cage in sections includes the following construction contents: Step E1: Lift and place the first section of the steel cage. When lifting and placing, manually push and pull to keep the center of the steel cage at the center of the casing. Step E2: When the first section of the steel cage is lowered to the last stiffener on the steel cage, insert the support bar and support the first section of the steel cage on the steel casing at the hole opening. Step E3: Lift the second section of the steel cage. After the second section of the steel cage is erected and lowered to be close to the first section of the steel cage by 2 - 3 cm, use the hanging hoist to manually adjust the docking position of the second section of the steel cage. The docking position is obtained according to the marks made with red paint during the fabrication of the two sections of the steel cage. Step E4: Continue to lower the second section of the steel cage to make the joints of the two sections of the steel cage close together. According to the marks, align them on the same vertical axis at the original connection position, and then use a sleeve pliers to tighten the steel sleeve to connect the upper and lower sections of the steel cage together. Step E5: After the joints are connected, tie the peripheral reinforcement stirrups of this section to make the connection between the first section of the steel cage and the second section of the steel cage better connected, ensuring the quality of the cast-in-place pile formed after the later concrete pouring. The main support is provided through the stiffeners on the skeleton. After completion, use a crane to lift the entire steel cage, pull out the support bar, and lower the steel cage. Step E6: Repeat steps E2 - E5 to lower all sections of the steel cage to the design elevation after connection and position it at the center of the pile hole.

[0014] In summary, due to the adoption of the above technical solutions, the present invention has at least the following beneficial effects: 1. Using the mud pumping and discharging device of this solution to perform secondary hole cleaning on the pile hole before pouring concrete for the pile foundation solves the problem that it is not easy to clean the sediment in the casing of the cast-in-place pile, improves the construction quality and construction efficiency. At the same time, using this method to clean the pile hole avoids cleaning the hole by diving, greatly improving the construction safety. 2. Using a slag bucket that can automatically open and close to clean the mud and slag mixture generated during the drilling process can clean the mud and slag generated during the drilling process in a timely and efficient manner, improving the construction progress of impact drilling to form a hole and ensuring safe construction. 3. Use mud pumping device to change slurry and clean the hole, and clean the sediment at the bottom of the hole after bored pile drilling. The mixing head of the mud pumping device can cut the sediment at the bottom of the hole, and discharge the fine sediment through the mud suction steel pipe. This method will not deepen the drilling depth, ensuring that the depth of the pile hole meets the requirements of drilling, and the hole cleaning speed is faster, so that the mud particle size, mud density, sand content, viscosity and sediment thickness at the bottom of the hole meet the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic structural diagram of a mud pumping device used in the method for cleaning the pile foundation of a pile group cast-in-place pile of the present invention.

[0016] Figure 2 This is a schematic diagram of the installation structure of the air supply pipe and the mud suction steel pipe in the mud extraction device.

[0017] Figure 3 This is a schematic diagram of the structure of the stirring teeth in the mud pumping device.

[0018] Figure 4 The present invention is a process flow chart of the pile group cast-in-place pile foundation construction method.

[0019] Figure 5 Schematic diagram of the elevation structure of the pier pile foundation punching platform and casing arrangement.

[0020] Figure 6 This is a schematic diagram of the planar structure of the pier pile foundation punching platform and casing arrangement.

[0021] Figure 7 Schematic diagram of the structure of buried cast-in-place pile casing.

[0022] Figure 8 Schematic diagram of the construction sequence of the abutment pile foundation pile group.

[0023] Figure 9 This is a schematic diagram of the arrangement of the punching drill and the punching sequence in the construction of underwater pier pile foundation groups.

[0024] Figure 10 This is a schematic diagram of the structure of the slag scoop during the construction of the pile group cast-in-place pile foundation.

[0025] Figure 11 This is a schematic diagram of the structure of lowering the slag bailing barrel during the slag bailing construction process.

[0026] Figure 12 This is a structural schematic diagram of the movable cover of the slag bailing barrel being opened during the slag bailing construction process.

[0027] Figure 13 This is a structural schematic diagram of the slag bailing tube being filled with mud-slag mixture during the slag bailing construction process.

[0028] Figure 14 The structural schematic diagram of the movable cover plate of the slag ladle closing automatically during the slag ladling construction process.

[0029] Figure 15 The structural schematic diagram of lifting the slag ladle during the slag ladling construction process.

[0030] Figure 16 The structural schematic diagram of lowering the steel reinforcement cage during the construction process of the group pile cast-in-place pile foundation.

[0031] Figure 17 The structural schematic diagram of the anti-floating structure of the steel reinforcement cage during the construction process of the group pile cast-in-place pile foundation.

[0032] Identifications in the figure: 1 - Rotary hydraulic pump, 2 - Mud suction steel pipe, 3 - Hydraulic pump station, 4 - Mixing head, 41 - Second connecting plate, 42 - Mixing teeth, 43 - Frustum-shaped support, 44 - Tooth head, 45 - Round hole, 5 - Mounting bracket one, 6 - Connecting component two, 7 - Air supply pipe, 71 - Air inlet pipe section, 72 - Air outlet pipe section, 8 - Mud drainage steel pipe, 9 - Air compressor connecting pipe, 10 - Air compressor, 11 - Hydraulic pump pipe, 12 - Air compressor air supply path, 13 - First connecting plate, 14 - Mounting bracket two, 15 - First mounting plate, 16 - Mud pumping and drainage path, 17 - Rock surface, 18 - Platform steel pipe pile, 19 - Connecting beam, 20 - Main beam, 201 - Main cross beam, 202 - Main longitudinal beam, 21 - Steel deck, 22 - Casing, 23 - Well-shaped frame, 24 - Top surface of the construction platform, 25 - Clay backfill layer, 26 - Bottom clay layer, 27 - Groundwater level line, 28 - Cap, 29 - First punching rig, 30 - Third punching rig, 31 - Third punching rig, 32 - Slag ladle, 321 - Barrel wall, 322 - Bottom plate, 323 - Slag inlet hole, 324 - Movable cover plate, 33 - Slag and mud mixture, 34 - First section of steel reinforcement cage, 35 - Support bar, 36 - Second section of steel reinforcement cage, 37 - Hoist, 38 - Steel bar sleeve, 39 - Anti-floating structure, 391 - Steel pipe, 392 - Steel bar hook, 40 - Main steel bars of the steel reinforcement cage, 50 - Stirrup, 60 - Crane, 70 - Steel wire rope. Detailed implementation manners

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, so that the purpose, technical solution and advantages of the present invention will be more clearly understood. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Embodiment 1

[0034] The method for cleaning the pile group cast-in-place pile foundation of the exemplary embodiment of the present invention is mainly used in the process of bridge construction. It is mainly aimed at the pile cap foundation of bridge piers and abutments being of the pile group cast-in-place pile structure. Before pouring concrete into the pile group cast-in-place pile foundation, a mud pumping and draining device is used to replace the slurry and clean the pile holes. Therefore, this embodiment also provides a structure of the mud pumping and draining device, as Figures 1-3 shown.

[0035] Among them, Figure 1 shows the elevation structure of the mud pumping and draining device of the embodiment of the present invention. The mud pumping and draining device includes a rotary hydraulic pump 1 and a mud suction steel pipe 2. The rotary hydraulic pump 1 is powered by a hydraulic pump station 3. A stirring head 4 is detachably connected to the rotary hydraulic pump 1. The rotary hydraulic pump 1 drives the stirring head 4 to rotate together and cut the mud finely. An installation bracket one 5 is arranged on the rotary hydraulic pump 1. A connecting component two 6 and an air supply pipe 7 are fixedly connected to the mud suction steel pipe 2. A mud guide and discharge pipe 8 is detachably connected to the mud suction steel pipe 2. The connecting component two 6 and the installation bracket one 5 are detachably connected by a connecting bolt. The air supply pipe 7 is connected to an air compressor 10 through an air compressor connecting pipe 9. The air compressor 10 sends air into the mud suction steel pipe 2 through the air supply pipe 7, and drives the mud to be discharged through the mud guide and discharge steel pipe 8 by the wind force. The air supply pipe 7 is a U-shaped structure penetrating the wall of the mud suction steel pipe 2, including an air inlet pipe section 71 outside the mud suction steel pipe 6 and an air outlet pipe section 72 outside the mud suction steel pipe 2. The U-shaped bottom position penetrates the wall of the mud suction steel pipe 2. The air inlet pipe section 71 is communicated with the air compressor connecting pipe 9. The opening of the air outlet pipe section 72 faces the direction of discharging mud outside the mud suction steel pipe 2. A further preferred implementation is to set the air outlet pipe section 72 in a way that the axial direction is parallel to the axial direction of the mud suction steel pipe 2. The air inlet pipe section 71 is fixed on the side of the mud suction steel pipe 2 through an installation bracket two 14. The installation bracket two 14 is made of steel plate.

[0036] When using this mud pumping and draining device to replace the slurry and clean the hole, it includes the following operation construction steps: Step 1: Assemble the mud pumping and draining device, including first installing the stirring head 4 on the rotary hydraulic pump 1, then assembling the rotary hydraulic pump 1 and the mud suction steel pipe 2 so that the bottom height of the stirring head 4 corresponds to that of the mud suction steel pipe 2. Then connect the mud guide and discharge steel pipe 8 to the upper port of the mud suction steel pipe 2, and connect the rotary hydraulic pump 1 to the hydraulic pump station 11 through the hydraulic pump pipe 11. At the same time, connect the air supply pipe 7 to the air compressor 10 through the air compressor connecting pipe 9. The hydraulic pump pipe 11 and the air compressor connecting pipe 9 are both provided with a surplus length corresponding to the depth of the pile hole. The mud guide and discharge steel pipe 8 leads to the outside of the pile hole.

[0037] Step 2: Lift the assembled structure of the rotary hydraulic pump 1 and the mud suction steel pipe 2 into the pile hole of the pile group cast-in-place pile. The mud guide and discharge steel pipe 8 leads to the outside of the casing; Step 3: Start the mud pumping device. Rotate the hydraulic pump 1 to drive the stirring head 4 to rotate, stir and cut the mud finely. The air supply pipe 7 supplies air into the interior of the mud suction steel pipe 2 through the air compressor air supply path 12. Driven by the wind force, the mud is discharged from the mud guide and discharge steel pipe 2 through the mud pumping and discharge path 16. Step 4: After completing the cleaning before the pile foundation concrete pouring of a certain pile hole in the group pile cast-in-place piles, lift the structure assembled by the rotary hydraulic pump 1 and the mud suction steel pipe 2, move it to the next pile hole, and repeat Step 2 and Step 3 until the cleaning before the pile foundation pouring of all pile holes is completed.

[0038] Using this method to solve the problem of hole cleaning before the pile foundation concrete pouring, it solves the problem that the sediment in the casing of the cast-in-place pile is not easy to clean, can effectively ensure the construction quality and construction efficiency. At the same time, using this method to clean the pile hole avoids the method of diving to clean the hole, greatly improving the construction safety.

[0039] One end of the rotary hydraulic pump 1 is connected to the hydraulic pump station 3 through the hydraulic pump pipe 11. The other end of the rotary hydraulic pump 1 is provided with a first connecting plate 13. Installation holes are opened on the first connecting plate 13 and are detachably connected to the stirring head 4. The first installation bracket 5 is connected and installed through the connecting part two 6 provided on the mud suction steel pipe 2. The stirring head 4 includes a second connecting plate 41, and stirring teeth 42 and a frustum-shaped support 43 connected to the second connecting plate 41. One side of the second connecting plate 41 is detachably connected to the first connecting plate 13 provided on the rotary hydraulic pump 1. The center position of the other side plate surface of the second connecting plate 41 is connected with the frustum-shaped support 43. One or more of the stirring teeth 42 are circumferentially arranged along the outer circumference of the frustum-shaped support 43. The stirring teeth 42 are bent towards the direction of the frustum-shaped support 3. The other end of the frustum-shaped support 43 extends out of the end of the stirring teeth 42. A round hole 45 is provided in the thickness direction of the stirring teeth 42. As Figure 1 and Figure 3 shown, the round hole 45 can reduce the resistance during the rotation of the stirring teeth 42. The cross-sectional shape of the tooth head 44 is triangular. One end of the tooth head 44 is provided with a U-shaped groove. The width of the U-shaped groove is adapted to the thickness of the stirring teeth 42. The tooth head 44 is clamped into the stirring teeth 42 through the U-shaped groove and is welded to the stirring teeth 42. One end of the frustum-shaped support 43 is welded to the center position of the second connecting plate 41. In the height direction of the stirring head 4 ( Figure 1 the up and down direction), the lower bottom surface of the frustum-shaped support 43 exceeds the stirring teeth 42, which can play a role in limiting and protecting the stirring teeth. The stirring teeth 42 are bent towards the direction of the frustum-shaped support 3.

[0040] The mud suction steel pipe 2 is of a cylindrical barrel structure. The mud suction steel pipe 2 is connected to the mud drainage steel pipe 8 through the first mounting plate 15. A second connecting component 6 is provided on the mud suction steel pipe 2. The connection between the second connecting component 6 and the first mounting bracket 5 realizes the installation between the rotary hydraulic pump 1 and the mud suction steel pipe. In the assembled structure of the rotary hydraulic pump 1 and the mud suction steel pipe 2, the slurry inlet of the mud suction steel pipe 2 is within the rotation height range of the stirring teeth 42 in the stirring head 4. When the assembled structure of the rotary hydraulic pump 1 and the mud suction steel pipe 2 is hoisted into the pile hole of the group pile cast-in-place pile, the slurry cut by the stirring head 4 just discharges out of the casing through the slurry inlet of the mud suction steel pipe 2 within this height range, further improving the construction efficiency.

[0041] As one of the preferred embodiments, two rotary hydraulic pumps 1 are symmetrically arranged on the mud suction steel pipe 2. The two rotary hydraulic pumps 1 have the same structural form and are both provided with a first mounting bracket 5 detachably connected to the second connecting component 6 of the mud suction steel pipe 2. The two rotary hydraulic pumps 1 are installed on the mud suction steel pipe 2 through the first mounting bracket 5 and have the same installation height. By using two rotary hydraulic pumps 1, the stirring heads 4 on the two rotary hydraulic pumps 1 can more fully cut the sediment at the bottom of the pile hole and then discharge it through the mud suction steel pipe 2. Embodiment 2

[0042] Figure 4 The process flow chart of the construction method for the group pile cast-in-place pile foundation of the exemplary embodiment of the present invention is shown. The construction method for the group pile cast-in-place pile foundation of this embodiment mainly includes the following construction steps: Step A: Preparation for pile foundation construction; Step B: Fabricating and burying the steel casing; Step C: The drilling rig is in place and the hole is formed by impact drilling; Step D: Clearing the hole and detecting the formed hole; Step E: Lowering the steel reinforcement cage and installing the pouring conduit; Step F: Secondary hole cleaning is carried out by using the group pile cast-in-place pile foundation cleaning method in Embodiment 1; Step G: Pouring the pile foundation concrete and detecting the pile foundation.

[0043] The following is a detailed description of each step: Preparation for pile foundation construction For the pile foundation construction at the water pier part, a steel platform is erected as the punching platform. As shown in Figure 5 and Figure 6 shown, the steel platform includes platform steel pipe piles 18 embedded in the rock surface 17. The height of the platform steel pipe piles 18 is 1.5 m to 2.0 m higher than the designed elevation of the pile top. As shown in Figure 5The height of L1 in the middle is the height higher than the designed elevation of the pile top. Since the conventional pile top elevation of the bridge pier is designed according to the perennial water level elevation in the construction area, in this embodiment, the construction platform is constructed to be 1.5 m to 2.0 m higher than the conventional pile top elevation, which can fully take into account the construction during the flood season, avoid the construction being affected, and is of great help in shortening the construction period and accelerating the construction progress. The platform steel pipes 18 are arranged in rows and columns. The upper part of the platform steel pipes 18 is connected with a main beam 20, including a main cross beam 201 arranged at the top of each row of platform steel pipes 18, and a main longitudinal beam 202 vertically arranged on the main cross beam 201. A steel deck 21 is laid on the upper part of the main longitudinal beam 202. The connecting lines of each row and column of the platform steel pipes 18 form a grid structure, and the middle position of the grid is a construction space for the pile foundation, which is used for burying the casing 22 in the later stage. The casing 22 is fixed by a cross-shaped frame 23 connected to the main cross beam 201. The main longitudinal beam 202 is arranged corresponding to the number of columns of the platform steel pipes 18. The main longitudinal beam 202 is vertically erected on the main cross beam 201. The main longitudinal beam 202 is centrally arranged at the projection part of the connecting line of each row of platform steel pipes 18 and the vicinity on both sides. The steel deck 21 is laid on adjacent main longitudinal beams 202. Adopting the steel platform structure of this embodiment, the punching platform for the drill construction has strong stability, avoids the local stress of the steel platform, enables all the platform steel pipes to be uniformly stressed, and ensures the safety of the steel platform structure; at the same time, the main longitudinal beam 202 is centrally arranged at the projection part of the connecting line of each row of platform steel pipes 18 and the vicinity on both sides, so that the load is directly transmitted to the platform steel pipes 18, and the stress condition is good. In order to further improve the overall stress effect of the platform steel pipes 18, a connecting beam 19 is arranged at the top of the platform steel pipes 18, and each connecting beam 19 fixedly connects two adjacent platform steel pipes 18 together, so that the overall platform steel pipes 18 are stressed as a whole.

[0044] The main longitudinal beam and the steel deck are not laid at the projection position of the group pile cast-in-place piles, and a space is reserved for the construction of the pipe piles. A cross-shaped frame 23 is arranged at the construction position of each cast-in-place pile. The cross-shaped frame 23 is made of section steel and is used to fix the casing 22 to avoid the deviation of the casing 22 and ensure the construction quality of the cast-in-place piles. In this embodiment, the size model of the platform steel pipes is φ630×10 mm, the main cross beam and the main longitudinal beam are respectively made of 45B I-beam and 25B I-beam, the thickness of the steel deck is 10 mm, and the plane size of the steel platform is 15 m * 15 m.

[0045] The pile foundation construction of the abutment on the shore side is located on the river bank. Before the pile foundation construction, the site is first leveled to form a construction platform for installing the drill. For the bored piles at the steep slope or the section with a large slope, the semi-excavation and semi-filling method is used for leveling. The construction platform is also 1.5 m to 2.0 m higher than the conventional pile top elevation, which is flush with the pile foundation construction steel platform at the bridge pier part. At the same time, the top elevation of the steel casing is increased by 0.2 m to 0.5 m. The plane size of the pile foundation construction platform of the abutment on the shore side is 15 m * 40.5 m.

[0046] Fabrication and embedding of steel casing The steel casing for the cast-in-place pile on land is fabricated with 10-mm steel plate. The inner diameter of the fabricated casing is 20 cm larger than the drill bit. The length of the casing is at least 200 cm and meets the construction requirements at the same time. One or more stiffening ribs are welded at the upper port, lower port and the outer side of the middle part of the casing. By welding the stiffening ribs, the stiffness of the steel casing can be increased and deformation can be prevented. One or two slurry overflow ports are opened at the top of the steel casing. The burial depth of the casing is about 1.5 m to ensure the smooth progress of drilling and concrete pouring; the pile foundation casing is preferably embedded manually and accurately positioned. Specifically, the maximum deviation between the center of the casing and the center of the pile position does not exceed 5 cm, and the maximum inclination does not exceed 1%, so that the drill rig can drill along the vertical direction of the pile position.

[0047] As Figure 7 shown, the slope value α of manual excavation and embedding is controlled between 1 / 2 and 1 / 3, which is determined according to the construction site. The top height of the casing 22 is more than 0.5 m higher than the top surface of the construction platform 24 to protect the top soil layer of the pile hole from collapsing due to the repeated up and down movement of the drill bit and the vibration of the fuselage. The casing 22 is a steel casing. When embedding the steel casing, it is set out by the positioning control pile, and the position of the drill hole of the drill rig is marked at the bottom of the hole. Then the steel casing is lifted and placed into the hole, and the center position of the steel casing is found. A cross line is drawn at the top or bottom of the steel casing, and then the steel casing is moved to make the center of the steel casing coincide with the center position of the drill hole of the drill rig. At the same time, a spirit level or a plumb bob is used to check to make the steel casing vertical. After adjusting the position of the steel casing, a clay backfill layer 25 is symmetrically and evenly arranged around the steel casing. The clay backfill layer 25 is filled and tamped in layers, and the layer thickness H1 is between 30 cm and 50 cm to ensure the verticality of the steel casing and prevent its displacement. The filled clay backfill layer has the optimum moisture content. A bottom clay layer 26 is arranged at the bottom of the steel casing, and the thickness of the bottom clay layer 26 is between 300 and 500 mm. When the soil layer at the bottom of the casing is non-cohesive soil, the steel casing is fixed by digging deeper or replacing the soil. After backfilling and tamping a bottom clay layer with a thickness of 300 to 500 mm at the bottom of the hole, the casing 22 is placed, and the steel casing is avoided from being deflected during ramming. The bottom of the casing 22 should reach the groundwater level line 27.

[0048] The pier part is an underwater steel casing, using a φ1800*10 steel casing, with the rock penetration depth at least 1.0 m. The steel casing is installed by the impact hole-leading pile sinking method, and the rock penetration depth meets the design requirements. The maximum deviation between the center of the steel casing and the center of the pile position does not exceed 5 cm, and the maximum inclination does not exceed 1%, and is less than 50 cm; the top of the steel casing is flush with the punching platform. When the steel casing exceeds 9 m, it is hoisted in a segmented manner, with the length of a single-section casing being 9 m, and 2 lifting holes are symmetrically arranged at the top of the casing; the maximum weight of the casing is about 15 t, and the installation is hoisted by a 90 t crawler crane. According to the layout of the trestle, the maximum hoisting distance is 12 m. After the steel casing is installed in place, a cross-shaped frame is welded and fixed to the platform to prevent it from tilting during the construction process.

[0049] Before the pile foundation construction, first hoist the steel casing in place, and use a 90-type double-clamp vibrating hammer to sink the steel casing to the bedrock. Then, use an impact drill to conduct impact hole-leading inside the casing. The diameter of the hole-leading is about 5 cm smaller than the inner wall of the casing. The hole-leading is carried out in segments, with the segment length about 1.5 - 2.0 m. After one segment of hole-leading is completed, immediately use the vibrating hammer to follow the casing to the bottom position of the hole-leading, and then continue the hole-leading until the designed bottom elevation of the steel casing is reached.

[0050] The drilling rig is in place and the hole is formed by impact drilling Before drilling, first arrange the drilling rig and the mud pit. When constructing the pile foundations of the onshore abutment and other retaining walls, the mud pit is arranged by on-site excavation; when constructing the underwater pile foundation, a metal mud trough is used as the mud pit, which is arranged on the trestle around the pile cap of the pile foundation. The mud in the mud pit (trough) is circulated with the mud in the pile hole through a mud pump. At the same time, a spare mud truck is used to pump the excess mud into the mud truck and transport it to the centralized treatment area for treatment.

[0051] When arranging the drilling rig, first install the drill rig, and install and adjust the hoisting system. Lift the drill bit and place it into the casing. The center line of the impact hammer and the hoisting pulley on the drill rig are on the same vertical line, and the position deviation does not exceed 5 cm. After adjustment, reinforce and fix the drilling rig to ensure that the drilling rig does not displace during the drilling process.

[0052] The pile foundations of the abutment and the underwater pier are both group pile cast-in-place pile structures. The pile foundation of the abutment is specifically provided with two rows of cast-in-place piles, and the construction method of constructing the first row first and then the second row is adopted. As Figure 8 shown, first construct the cast-in-place pile holes on the river side, and then construct the cast-in-place pile holes on the bank side. During the process of drilling each row of cast-in-place pile holes, the skip pile construction method is adopted. For example, during the process of constructing the first row of group pile cast-in-place pile holes, the ①, ③, ⑤, and ⑦ cast-in-place pile holes are constructed in sequence, and then the ②, ④, ⑥, and ⑧ cast-in-place pile holes are constructed in sequence. Then, construct the second row of group pile cast-in-place pile holes, and construct them according to 9 to 16. Drilling the cast-in-place pile holes in this construction sequence can ensure the construction safety of the group pile cast-in-place pile holes and avoid problems such as collapse and subsidence that affect the normal construction.

[0053] During the construction of the pier pile foundation holes, for the group piles of each pile cap, the drilling construction is carried out according to the following drilling sequence: The pier pile cap 28 is arranged with three rows of cast-in-place piles, and the number of each row is three. As Figure 9 shown, three impact drilling rigs are arranged on each pile cap for operation. The first impact drilling rig 29 is arranged in the first horizontal row, the second impact drilling rig 30 is arranged in the second horizontal row, and the third impact drilling rig 31 is arranged in the third horizontal row. The first impact drilling rig 29 is arranged in the middle position to drill the right hole of the first horizontal row, the second impact drilling rig 30 is arranged in the right position to drill the middle hole of the second horizontal row, and the third impact drilling rig 31 is arranged in the middle position to drill the left hole of the third horizontal row. The three drilling rigs construct the first group of holes synchronously. After the construction of the first group of holes is completed, the second group of holes and the third group of holes are constructed synchronously. The construction of the second group of holes includes the first impact drilling rig 29 arranged in the middle position to drill the left hole of the first horizontal row, the second impact drilling rig 30 arranged in the middle position to drill the left hole of the second horizontal row, and the third impact drilling rig 31 arranged in the middle position to drill the right hole of the third horizontal row. The construction of the third group of holes includes the first impact drilling rig 29 arranged in the left position to drill the middle hole of the first horizontal row, the second impact drilling rig 30 arranged in the middle position to drill the right hole of the second horizontal row, and the third impact drilling rig 31 arranged in the right position to drill the middle hole of the third horizontal row. By arranging multiple impact drilling rigs for operation in this way, the mutual influence and interference of the impact drilling rigs on each pier pile cap are avoided, the limited construction space is fully utilized, and the pile hole construction efficiency is greatly improved.

[0054] During the pile foundation construction process, when starting drilling, slurry is first poured into the hole, and the performance indexes of the prepared slurry meet the following conditions: The slurry specific gravity is between 1.05 and 1.25, the funnel viscosity is 16 - 28 s, the sand content rate (%) ≤ 4, the colloid rate (%) ≥ 95, and the water loss rate ≤ 30 ml / 30 min; The preferred slurry weight ratio is: bentonite: CMC: soda ash: water = 100: 0.28: 3.3: 700. During the construction process, the slurry mix ratio is adjusted according to the specific situation to achieve the purpose of adjusting the slurry performance indexes. Specifically, the slurry specific gravity is adjusted by adjusting the weight ratio of bentonite, and the viscosity is increased by adding CMC.

[0055] After the preparatory work is completed, the drilling and hole formation construction begins. During drilling, refer to the geological data and check the geological conditions of the pile foundation position, check the slurry indexes, and determine that they meet the performance index requirements. The group pile drilling is constructed by the skip pile method, and the construction is carried out according to the determined drilling sequence. When drilling in the adjacent pile position of the already cast-in-place pile, the construction is arranged to start drilling more than 2 days after the concrete of the already drilled pile has been formed to avoid disturbing the adjacent already constructed drilled piles.

[0056] According to the different positions of the pile foundation in this project, the underground geological conditions are also different, and different drilling methods are used for the pile foundation geological conditions to carry out hole formation construction. The specific hole formation methods are as follows: When starting drilling, first pour mud into the hole. The indicators such as the relative density of the mud are determined according to the soil layer conditions.

[0057] As one of the preferred implementation methods, when there is water in the impact hole, the method of directly putting clay is adopted, and the impact hammer is used to repeatedly impact and make mud with a small stroke (not more than 0.8m). For fine-grained soil layers, thick mud, small stroke, and high frequency are used to repeatedly impact and pound to ensure the firmness of the hole wall and avoid collapse and leakage. After the drilling depth exceeds the total height of the drill bit plus the stroke, normal impact can be carried out. After drilling 4 - 5m at the beginning of the hole, in order to prevent drill cuttings from squeezing into the hole wall and reduce the number of times of cleaning out the slag, clean out the slag in time after normal drilling to ensure effective impact on the bottom of the hole.

[0058] During the drilling construction process of the impact drilling rig, different drilling speeds are adopted according to different soil layers. The stroke is determined according to the soil layer conditions: a large stroke is adopted when passing through hard and dense pebble layers or soil layers such as bedrock boulders; a medium stroke is adopted when passing through loose sand, gravel-like soil or pebble interbedded soil layers. If the stroke is too large for such soil layers, the vibration of the bottom of the hole is large and it is easy to cause hole collapse; a medium stroke is adopted when passing through high liquid limit clay and sandy low liquid limit clay; a small stroke is used in areas prone to collapse or quicksand, and the viscosity and relative density of the mud are increased; when passing through boulders or rock layers, in the case of uneven surface, first put in clay, small pieces of stone, and pebbles to level the surface, and then use the drill bit to carry out impact drilling to prevent the occurrence of inclined hole and hole collapse accidents. If the rock layer strength is uneven and inclined hole is likely to occur, the above method can also be used for backfilling and redrilling. When necessary, put in cement for hole protection or increase the buried depth of the casing; when drilling in loose layers such as sand and pebble interbedded soil, put in clay and small pieces of stone (particle size not more than 15cm) in a ratio of 1:1, and use the impact hammer to repeatedly impact with a small stroke to make the mud paste and pieces of stone squeeze into the hole wall, and repeat backfilling and repeated impact 2 - 3 times according to the situation. If there is a quicksand phenomenon, increase the proportion of clay and reduce the proportion of pieces of stone to make the hole wall firm; when passing through clayey soil layers such as sandy low liquid limit clay, because the soil layer itself can make mud, selectively reduce the consistency of the input mud, and adopt a small stroke of 0.5m to prevent sticking of the drill and burying of the drill.

[0059] During the impact process, the length of the wire rope is evenly released according to the soil layer conditions. Each time 5cm - 8cm of the wire rope is released in soft soil layers, and 3 - 5cm of the wire rope is released in dense and hard soil layers. Keep within this range to prevent too little wire rope release, forming a "hollow hammer blow", which will cause the drilling rig, drill rig and wire rope to be subjected to excessive accidental loads and suffer damage, and also prevent too much wire rope release. Too much wire rope release will reduce the stroke, lower the drilling speed, and seriously entangle the wire rope and cause accidents.

[0060] During the drilling construction, slag removal is carried out. According to different soil conditions, a method of slag removal (slag removal) is selected: when the pure drilling penetration per hour in dense and hard soil layers is less than 5cm-10cm, and the pure drilling penetration per hour in soft strata is less than 15cm-30cm, slag removal is carried out; or slag removal is carried out once every 0.5m-1.0m of penetration, and 4-5 barrels are taken each time; or until the slag content in the mud is significantly reduced, there are no coarse particles, and the relative density returns to normal. After slag removal, add mud or clean water to the hole in time to maintain the water head height. When clay is added to make slurry by itself, do not put too much at one time to avoid cone sticking and cone jam.

[0061] The pile groups include cast-in-place piles for onshore abutments and retaining walls and cast-in-place piles for water caps. The cast-in-place piles for onshore abutments and retaining walls adopt the slag removal technology of mud positive circulation or reverse circulation, while the pile foundation of water caps adopts the slag dredging technology.

[0062] Slag removal Figure 10 The slag scoop barrel 32 shown in the figure includes a barrel wall 321, which is made of φ820*10 (mm) steel pipe, with a height of 1.2m, an open structure without a cover on the upper part, and a bottom plate 322 is provided at the bottom. The bottom plate 322 is 10cm thick, and a slag inlet hole 323 is provided in the middle of the bottom plate 322. A movable cover plate 324 is hingedly installed on the bottom plate 322, and the movable cover plate 324 is used to cover the slag inlet hole 323. The opening angle of the movable cover plate 324 is between 50° and 75°. Holes are opened on both sides of the top of the barrel wall of the slag scoop barrel and steel wire ropes 325 are provided for lowering and lifting the slag scoop barrel 32. The working process of the slag scoop barrel 32 is as follows: Figures 11 to 15 As shown, after the slag bailing tube 32 is lowered into the pile hole, the movable cover plate 324 at the bottom opens upward due to the mud pressure, and the mud-slag mixture 33 enters the slag bailing tube 32 from the slag inlet hole 323. After the slag bailing tube 32 falls to the bottom of the pile hole, the internal and external pressures are balanced, and the movable cover plate 324 closes automatically under the action of its own weight. The slag bailing tube 32 is lifted to the mud tank through the steel wire rope 325 to pour out the mud-slag mixture 33 for sedimentation. The slag bailing frequency is once every 2m of impact. The slag bailing frequency can be adjusted according to actual conditions during the specific construction process. The use of this slag bailing tube that can be opened and closed automatically to clean the mud-slag mixture generated during the drilling process can timely and efficiently clean the mud slag generated during the drilling process, improve the construction progress of impact drilling, and ensure safe construction.

[0063] The bored piles for onshore bridge abutments and retaining walls are drilled by impact, and the slag is removed by positive or reverse circulation of mud. The positive circulation system of mud includes mud pools, sedimentation tanks, circulation tanks, mud conveying pipelines and mud pumps. According to the progress of drilling, the excess mud and sediment are removed in time to prevent mud from overflowing and polluting the environment. The mud is then transported to the designated location for treatment or solidification treatment by special tank trucks.

[0064] The mud pit and sedimentation tank are set at idle positions that do not affect construction and transportation. The mud pump is close to the hole position, with a distance between 0.5 and 2 m. The total length of the suction and compressed air (soft) rubber hoses should not be too long (usually not exceeding 5 m). The plane layout of the mud circulation system is as shown in the figure. The mud pump is arranged on the top of the mud pit and is transported to the pile foundation through the mud conveying pipeline for the punching rig to drill. The mud and sediment are discharged from the pile foundation through the circulation trough and are precipitated in the sedimentation tank. The sedimentation tank is the same as the mud pit, and the mud performance index is adjusted by adding different mud ingredients for the mud pump to circulate and transport to the pile foundation drilling construction.

[0065] During the drilling construction, when taking out the slag samples about every 2 m of drilling, the soil layer slag samples are inspected and preserved, and the changes of the soil layer are recorded for adjusting the construction process parameters.

[0066] Hole cleaning and hole formation inspection The purpose of hole cleaning treatment is to make the thickness of the sediment at the bottom of the hole, the amount of drill slag in the mud, and the thickness of the hole wall meet the specifications and design requirements, creating good conditions for underwater concrete pouring. When the drilling reaches the design elevation, hole cleaning operation is carried out. The hole cleaning methods include the following: Positive circulation hole cleaning is adopted, and at the same time, clean water is injected into the hole to reduce the mud specific gravity. At the same time, the mud is continuously circulated and the hole is cleaned through measures such as sedimentation and slag removal to meet the requirements of subsequent construction; The mud pumping and discharging device is used to replace the slurry for hole cleaning. The mud pumping and discharging device is in the structural form of Embodiment 1. The mud pumping and discharging device is placed into the pile hole through a crane or a cross-shaped frame erected on the steel platform. The bottom sediment of the hole is cut by the stirring head, and the cut fine sediment is discharged through the mud suction steel pipe, so that the pile hole meets the requirements of subsequent construction; By choosing any one of the above two hole cleaning methods, the pile hole reaches the following standards: the mud discharged from the hole has no 2 - 3 mm particles when felt by hand, the mud specific gravity is not greater than 1.1, the sand content is less than 2%, and the viscosity is 17 - 20 s. At the same time, ensure that the thickness of the sediment at the bottom of the hole before underwater concrete pouring: for column piles, it is not more than 5 cm. Avoid using the method of deepening the drilling depth to replace hole cleaning during hole cleaning.

[0067] After hole cleaning, the sediment thickness is detected. The sediment thickness at the bottom of the hole shall not be greater than 5 cm. After the hole cleaning of the bored cast-in-place pile is completed, the hole forming quality is detected, including hole diameter detection, hole depth and sediment thickness at the bottom of the hole detection, and hole forming verticality detection. The hole diameter detection is carried out by lowering a cage-type hole detector into the hole. Its outer diameter is equal to the diameter of the steel reinforcement cage plus 100 mm, and at the same time, it shall not be greater than the designed hole diameter of the borehole. Its length is equal to 4 to 6 times the hole diameter. During the detection, the hole detector is hoisted, and the center of the hole is kept consistent with the hoisting wire rope, and then slowly lowered into the hole. If it can pass through smoothly up and down, it indicates that the hole diameter meets the requirements; the hole depth detection is carried out by using a standard hammer. The measuring hammer is a conical hammer with a bottom diameter of 13 cm to 15 cm, a height of 20 to 22 cm, and a mass of 4 kg to 6 kg. The measuring rope is calibrated with a calibrated steel tape. The sediment thickness at the bottom of the hole is detected by the measuring hammer method; the hole forming verticality detection is carried out by the conventional plumb line method.

[0068] Lower the steel reinforcement cage and install the pouring conduit First, fabricate and place the steel reinforcement cage. Three ultrasonic testing tubes are arranged for each cast-in-place pile, and the SCG57×3.0-QY type testing tube is used. The testing tube adopts a sheathed threaded connection joint. The testing tubes are arranged at equal intervals inside the steel reinforcement cage and are tied and fixed with the steel bars. Arranging three ultrasonic testing tubes can effectively detect the quality of the formed pile. When the steel reinforcement cage is fabricated and installed in sections, the testing tubes are also connected in sections according to the length of the steel reinforcement cage. The testing tubes and the reinforcing hoops are tied into a whole form with wire ties to prevent the testing tubes from slipping when the steel reinforcement cage is butted and lowered. The top and bottom of the testing tubes are sealed with steel pipe plugs. The plugs and the connecting pipes are all standard parts. Before the upper plug and the connecting pipe, the steel pipe threads are wound with raw tape to ensure the butt joint and bottom sealing of the testing tubes. When the testing tubes are butted, the steel pipe threads are first wound with raw tape, and then the steel pipe threads are screwed into the connecting pipe with a pipe wrench. The butted steel pipes are tightened, tightened in place, and should have a certain length to ensure the butt joint strength and sealing. After the butt joint is completed, the pipe body is tied and fixed with the steel bars. The top of the tube is about 50 cm higher than the top of the pile. After filling with water, the upper part is sealed to prevent the concrete from pouring into it during the pile pouring.

[0069] The steel reinforcement cage is fabricated in sections in the fabrication yard. The standard section length of each section is 12 m, and the last section is an adjustment section. Each section of the steel reinforcement cage is fabricated on the pedestal. After fabrication, it is transported to the pile hole. The cage is lowered and installed in sections by a crane. During hoisting, manual pushing and pulling are used to keep the center of the steel reinforcement cage at the center of the steel casing; the steel reinforcement cage is lengthened at the pile hole of the cast-in-place pile, such as Figure 16As shown in the figure, a crane 60 and a steel wire rope 70 are used to lift the steel reinforcement cage. When the first section of the steel reinforcement cage 34 is lowered to the position of the last stiffener at the upper part of the steel reinforcement cage, a support bar 35 is inserted. Preferably, the support bar 35 is made of I-beam. In this embodiment, for bored piles with a pile diameter of 1.5 m to 1.8 m, 2 pieces of 25B I-beams are used to support the steel reinforcement cage on the hole mouth casing 22. Then, the second section of the steel reinforcement cage 36 is lifted. After the second section of the steel reinforcement cage 36 is erected and lowered close to the first section of the steel reinforcement cage 34 (the distance H2 between the first section of the steel reinforcement cage 34 and the second section of the steel reinforcement cage 36 is about 2 - 3 cm), the hanging hoist 37 is used to manually adjust the docking position of the second section of the steel reinforcement cage 36 (the two sections of the steel reinforcement cage are marked with red paint during manufacturing and processing). Then, continue to lower it to make the joints of the two sections of the steel reinforcement cage lean together, and align them on the same vertical axis and at the original connection position according to the original marks. Then, use a sleeve pliers to tighten the steel sleeve 38 to connect the upper and lower sections of the steel reinforcement cage together. After the joint is connected, the peripheral reinforcing stirrups 50 of this section are tied to make the connection between the first section of the steel reinforcement cage 34 and the second section of the steel reinforcement cage 36 better connected, ensuring the quality of the bored pile formed after the later concrete pouring. The main support is carried out through the stiffeners on the cage. After completion, the whole steel reinforcement cage is lifted by a crane, the support bar 34 is pulled out, and the steel reinforcement cage is lowered. Repeat this process to lower the steel reinforcement cage to the design elevation and position it at the center of the hole, completing the lowering and installation of the steel reinforcement cage. This method of installing the steel reinforcement cage can place the connected multi-section steel reinforcement cages into the pile hole, avoiding the problem of shaking when connecting with other sections of the steel reinforcement cage. Moreover, after the connected steel reinforcement cage is placed in the pile hole, it no longer occupies the ground space and can continue to stand and construct on the construction platform, avoiding high-altitude operations. This method not only has high construction efficiency but also greatly improves construction safety.

[0070] After the steel reinforcement cage is placed in position, an anti-floating structure 39 is set for the steel reinforcement cage to prevent the steel reinforcement cage from floating up, such as Figure 17 shown in the figure. The anti-floating structure 39 includes 4 steel pipes 391 arranged at equal intervals around the steel reinforcement cage. Reinforcing steel hooks 392 are welded to the top of the casing 22. The tops of the 4 steel pipes 391 are connected and fixed through the reinforcing steel hooks 392. The bottoms of the steel pipes 391 are connected to the main steel bars 40 of the steel reinforcement cage, so as to support the steel reinforcement cage in the reverse direction through the steel pipes 391, effectively preventing the steel reinforcement cage from floating up, and further ensuring the accurate positioning of the steel reinforcement cage and guaranteeing the quality of the pile foundation construction.

[0071] Install the pouring conduit Before use, the conduits shall be subjected to watertight test and tensile test of joints. The tensile strength of the joints shall not be lower than that of the base metal. Before use, the conduits shall be trial-assembled and pressure-tested, numbered and marked with scales in the order from bottom to top. After the conduits are assembled, the axis deviation shall not exceed 0.5% of the drilling depth and shall not be greater than 10 cm. When connecting, the nuts of the connecting bolts shall be on the upper side. The pressure test pressure for the watertight test shall be 1.5 times the hydrostatic pressure at the bottom of the hole. Slowly pressurize until the test pressure is reached. After reaching the test pressure, keep it stable for no less than 15 minutes. It is qualified if there is no leakage at the joints and seams.

[0072] After the steel reinforcement cage is installed in place, the casting conduit shall be installed immediately. In this embodiment, a quick-clamping vertical lifting conduit with an outer diameter of 300 mm and an inner diameter of 273 mm is used, with a sectional length of 2.5 - 3 m and the bottommost section with a length of 4 - 6 m. At the same time, a certain number of short conduits with lengths of 0.5 m, 1 m, 1.5 m, and 2.0 m are configured as spare pipes. The conduits are pre-numbered and assembled section by section in the order of the numbers during installation. The interfaces are tightly attached with rubber gaskets and the bolts are tightened. The inner diameters of each section of the conduit are the same, and the deviation is not more than ±2 mm. When installing the casting conduit, keep the conduit in the center position and straight in the up and down direction of the axis, and gradually sink it to prevent it from getting stuck on the steel reinforcement cage and colliding with the hole wall. When pouring the first batch of concrete, the distance from the bottom of the conduit to the bottom of the hole is controlled at 40 cm ± 5 mm.

[0073] The steps of pouring underwater concrete by the conduit method include: ① installing the conduit; ② placing the water-stop plug; ③ pouring the first batch of concrete; ④ cutting the iron wire and the water-stop plug falling to the bottom of the pipe; ⑤ continuing to pour concrete and lifting the conduit; ⑥ after pouring is completed, pulling out the casing.

[0074] Secondary hole cleaning After the steel reinforcement cage and the casting conduit are installed, secondary hole cleaning is carried out. The secondary hole cleaning is carried out by using the group-pile cast-in-place pile foundation cleaning method in Embodiment 1, that is, slurry replacement hole cleaning is carried out through the slurry pumping and discharging device in Embodiment 1. After hole cleaning, the sand content is less than 2%, the slurry specific gravity reaches 1.03 - 1.1, and the sediment thickness is controlled within 50 mm. According to the on-site implementation experience, when using the group-pile cast-in-place pile foundation cleaning method in Embodiment 1 for hole cleaning, it can meet the design requirements in 3 - 5 minutes. If the slurry specific gravity meets the requirements but the sand content is too large, continue to use slurry circulation for hole cleaning. If the sediment thickness is greater than 5 cm (column pile) and the slurry circulation hole cleaning cannot meet the design requirements, continue to clean for 2 - 3 minutes.

[0075] Pouring concrete and testing the pile foundation The pile foundation concrete is poured underwater and poured according to the design strength of each part of the bridge. Among them, the design strength of the pier pile foundation concrete is C35, and the design strength of the abutment pile foundation concrete is C30. Considering various factors of underwater concrete pouring comprehensively, the following parameter requirements shall be met for the concrete mix ratio: Slump: 18 - 22 cm, initial setting time of concrete: ≥ 8 h, maximum diameter of coarse aggregate: 30 mm, temperature of concrete entering the formwork < 30 °C, air content ≥ 2.0.

[0076] During the concrete pouring, it is necessary to ensure the smoothness of the road from the mixing plant to the construction site, and ensure that the pile foundation concrete is continuously poured at one time, and the intermediate pouring interval time shall not exceed the initial setting time of the concrete.

[0077] When pouring underwater concrete, it should be ensured that the pouring of underwater concrete is completed before the initial setting of the first batch of concrete. In actual construction, a retarder can be added to the concrete. Before pouring underwater concrete, the sediment thickness of the mud at the bottom of the hole should be detected again. Before pouring, water jetting or air pressure should be applied for 3 - 5 min to stir up the sediment at the bottom of the hole and then pour the concrete. When initially pouring underwater concrete, a valve switch is used for control. The valve is installed at the upper mouth of the pouring conduit. The concrete is transported by a pump machine. When the funnel and the storage hopper are filled with the pump, the valve is quickly opened to pour the first batch of concrete into the bottom of the hole. The required amount of the first batch of concrete is calculated to ensure that the depth of the conduit buried in the concrete after pouring is not less than 1 m and the gap at the bottom of the conduit can be filled.

[0078] The pouring process and quality control of the pile foundation concrete are carried out in the manner shown in the figure.

[0079] The above is only a detailed description of the specific implementation mode of the present invention, rather than a limitation of the present invention. Various substitutions, modifications and improvements made by those skilled in the relevant technical fields without departing from the principle and scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for cleaning a pile group cast-in-place pile foundation, characterized in that: Before pouring concrete for a pile group, a slurry pumping device is used to replace slurry and clean the pile hole. The slurry pumping device comprises a rotary hydraulic pump (1) and a slurry suction steel pipe (2). The rotary hydraulic pump (1) is connected to a hydraulic pump station (3) via a hydraulic pump pipe (11). The rotary hydraulic pump (1) is provided with a stirring head (4). The slurry suction steel pipe (2) is provided with an air supply pipe (7) for supplying air into the slurry suction steel pipe (2). The slurry replacement and hole cleaning process mainly comprises the following steps: Step 1: assembling the mud pumping device, including first installing the stirring head (4) on the rotary hydraulic pump (1), then assembling the rotary hydraulic pump (1) and the mud suction steel pipe (2) so that the stirring head (4) corresponds to the bottom height of the mud suction steel pipe (2), then connecting the mud drainage steel pipe (8) to the upper end of the mud suction steel pipe (2), and connecting the rotary hydraulic pump (1) to the hydraulic pump station (3) through the hydraulic pump pipe (11), and connecting the air supply pipe (7) to the air compressor (10) through the air compressor connecting pipe (9); the hydraulic pump pipe (11) and the air compressor connecting pipe (9) are both provided with a surplus length corresponding to the depth of the pile hole, and the mud drainage steel pipe (8) leads to the outside of the pile hole; Step 2: hoisting the assembled structure of the rotary hydraulic pump (1) and the mud suction steel pipe (2) into the pile hole of the pile group, and the mud drainage steel pipe (8) leads to the outside of the casing; Step 3: Start the mud pumping device, rotate the hydraulic pump (1) to drive the stirring head to rotate, stir and cut the mud, and the air supply pipe (7) supplies air to the inside of the mud suction steel pipe (2), and the wind drives the mud to be discharged through the mud guide steel pipe (8); Step 4: After the cleaning of a pile hole in a pile group before pouring the pile foundation concrete is completed, the structure assembled with the rotary hydraulic pump (1) and the mud suction steel pipe (6) is lifted and moved to the next pile hole, and steps 2 and 3 are repeated until all pile holes are cleaned before pouring the pile foundation.

2. The method for cleaning pile foundation of pile group according to claim 1, characterized in that: The stirring head (4) comprises a second connecting plate (41), and stirring teeth (42) and a truncated cone-shaped support (43) connected to the second connecting plate (41); one side of the second connecting plate (41) is detachably connected to the first connecting plate (3) provided on the rotary hydraulic pump (1); the truncated cone-shaped support (43) is connected to the center of the plate surface of the other side of the second connecting plate (41); a plurality of stirring teeth (42) are arranged circumferentially along the outer side of the truncated cone-shaped support (43); the stirring teeth (42) are bent toward the direction of the truncated cone-shaped support (3); and the other end of the truncated cone-shaped support (43) extends outside the end of the stirring teeth (42).

3. The method for cleaning pile foundation of pile group according to claim 2, characterized in that: When the rotary hydraulic pump (1) and the mud suction steel pipe (2) are assembled, the slurry inlet of the mud suction steel pipe (2) is flush with the position of the stirring head (4), so that when the assembled structure of the rotary hydraulic pump (1) and the mud suction steel pipe (2) is hoisted into the pile hole of the pile group, the mud cut by the stirring head (4) is discharged outside the casing through the mud suction steel pipe (2).

4. The method for cleaning pile foundation of pile group according to claim 1, characterized in that: The air supply pipe (7) is a U-shaped structure that penetrates into the wall of the mud suction steel pipe (2), and comprises an air inlet pipe section (71) located outside the mud suction steel pipe (2) and an air outlet pipe section (72) located outside the mud suction steel pipe (2). The bottom of the U-shape penetrates the wall of the mud suction steel pipe (2), the air inlet pipe section (71) is connected to the air compressor connecting pipe (9), and the opening of the air outlet pipe section (72) faces the mud suction steel pipe (2) to discharge mud outward.

5. A method for constructing a pile group cast-in-place pile foundation, characterized in that: The construction process of pouring pile foundation for pile groups includes the following construction steps: Step A: Preparation for pile foundation construction; Step B: making and burying steel casing; Step C: The drilling machine is positioned and the holes are impact-drilled; Step D: cleaning the hole and inspecting the formed hole; Step E: Lower the steel cage and install the casting conduit; Step F: secondary hole cleaning, using the pile group cast-in-place pile foundation cleaning method as described in claims 1-5 to perform secondary hole cleaning; Step G: Pour the pile foundation concrete and inspect the pile foundation.

6. The method for constructing a pile group cast-in-place pile foundation according to claim 5, characterized in that: When the impact drilling is performed in step C, the method includes respectively constructing the pile group cast-in-place pile structure of the abutment pile foundation and the pile group cast-in-place pile structure of the underwater pier pile foundation. The abutment pile foundation is provided with two rows of cast-in-place piles, and a construction method of first constructing the first row and then constructing the second row is adopted. The first row is the cast-in-place pile holes on the river side, and the second row is the cast-in-place pile holes on the construction bank side. In the process of drilling each row of cast-in-place pile holes, a skipping pile construction method is adopted. In the process of constructing the first row of eight pile group cast-in-place pile holes, the first, third, fifth, and seventh cast-in-place pile holes are constructed in sequence, and then the second, fourth, sixth, and eighth cast-in-place pile holes are constructed in sequence; when constructing the second row of eight pile group cast-in-place pile holes, the construction is carried out according to 9 to 16; When constructing a pile group cast-in-place pile structure of an underwater bridge pier pile foundation, three rows of cast-in-place piles are arranged on the bridge pier cap (28), with three piles in each row. Three punching drills are arranged on each cap for operation. The first punching drill (29) is arranged in the first horizontal row, the second punching drill (30) is arranged in the second horizontal row, and the third punching drill (31) is arranged in the third horizontal row. The first punching drill (29) is arranged in the middle position to drill the right hole of the first horizontal row, the second punching drill (30) is arranged in the right position to drill the middle hole of the second horizontal row, and the third punching drill (31) is arranged in the middle position to drill the left hole of the third row. The three drills simultaneously construct the first group After the construction of the first group of holes is completed, the second group of holes and the third group of holes are simultaneously constructed. The construction of the second group of holes includes the first punching drill (29) being arranged at the middle position to drill the first horizontal row of left holes, the second punching drill (30) being arranged at the middle position to drill the second horizontal row of left holes, and the third punching drill (31) being arranged at the middle position to drill the third horizontal row of right holes. The construction of the third group of holes includes the first punching drill (29) being arranged at the left position to drill the first horizontal row of middle holes, the second punching drill (30) being arranged at the middle position to drill the second horizontal row of right holes, and the third punching drill (31) being arranged at the right position to drill the third horizontal row of middle holes.

7. The method for constructing a pile group cast-in-place pile foundation according to claim 5, characterized in that: When the percussion drilling is performed in step C, slag is removed during the drilling construction, and the slag is removed selectively according to different soil layer conditions. The slag removal adopts a slag removal barrel (32), the slag removal barrel (32) comprises a barrel wall (321), the upper part of the barrel wall (321) is an open structure without a cover, a bottom plate (322) is provided at the bottom of the barrel wall (321), a slag inlet hole (323) is opened in the middle of the bottom plate (322), a movable cover plate (324) is hingedly mounted on the bottom plate (322), the movable cover plate (324) is used to cover the slag inlet hole (323), the opening angle of the movable cover plate 324 is between 50° and 75°, and holes are opened on both sides of the top of the barrel wall (321) of the slag removal barrel (32) and a steel wire rope (325) is provided, the steel wire rope (325) is used to lower and lift the slag removal barrel (32).

8. The method for constructing a pile group cast-in-place pile foundation according to claim 5, characterized in that: When cleaning the hole in step D, a mud pumping device as described in any one of claims 1 to 4 is used to replace the slurry and clean the hole. The mud pumping device is placed into the pile hole by a crane or a cross-shaped frame erected on a steel platform, and the sediment at the bottom of the hole is cut by a mixing head (4), and the finely cut sediment is discharged through a mud suction steel pipe (2).

9. The method for constructing a pile group cast-in-place pile foundation according to claim 5, characterized in that: When lowering the steel cage in step E, the steel cage frame is prefabricated in sections, and the cage is lowered and installed in sections by a crane, including the following construction contents: Step E1: hoisting the first section of the steel cage (34), during which the center of the steel cage is kept at the center of the casing (22) by manual pushing and pulling; Step E2: When the first section of the steel cage (34) is lowered to the last reinforcing bar on the steel cage, the support bar (35) is inserted to support the first section of the steel cage (34) on the steel casing at the hole mouth; Step E3: lifting the second steel cage (36). After the second steel cage (36) is erected, when it is lowered to 2-3 cm closer to the first steel cage (34), the second steel cage (36) is manually adjusted to a docking position using a hanging hoist (37). The docking position is obtained according to the markings made with red paint on the two steel cages during production and processing; Step E4: Continue to lower the second steel cage (36) so that the joints of the two steel cages are close together, and align them on the same vertical axis according to the markings according to the original connection position, and then use a sleeve pliers to tighten the steel sleeve (38) to connect the upper and lower steel cages together; Step E5: After the joint is connected, the outer reinforcing stirrups (50) of this section are tied to ensure that the first section of the steel cage (34) and the second section of the steel cage (36) are well connected at the connection part to ensure the quality of the cast-in-place pile formed after the later concrete pouring. The reinforcing bars on the skeleton are used for main support. After completion, the entire steel cage is lifted by a crane, the support bar (34) is pulled out, and the steel cage is lowered; Step E6: Loop steps E2-E5 to connect all segment reinforcement cages, lower them to the designed elevation, and position them at the center of the pile hole.

10. The method for constructing a pile group cast-in-place pile foundation according to claim 9, characterized in that: In the step E, after the steel cage is lowered and installed in place, an anti-floating structure (39) is provided on the steel cage for preventing the steel cage from floating up. The anti-floating structure (39) comprises a steel pipe (391) provided along the periphery of the steel cage, a steel hook (392) welded to the top of the casing (22), the top of the steel pipe (391) is connected and fixed by the steel hook (392), and the bottom of the steel pipe (391) is connected to the main reinforcement (40) of the steel cage.

Images