Self-locking casing isolation structure for preventing pile foundation frost heaving in seasonal frozen soil regions and construction method

Abstract

The invention discloses a self-locking casing isolation structure for preventing and controlling freezing of pile foundations in seasonal frozen soil areas and a construction method thereof. The self-locking casing isolation structure comprises a displacement cylinder and a fixed cylinder. A driving groove is arranged on the outer wall of the displacement cylinder, a first transmission groove is arranged in the fixed cylinder, a first rack is arranged in the driving groove, a first gear is arranged in the first transmission groove, a rod setting box is fixed on the top of the first transmission groove, a fixed cone is slidably connected in the rod setting box, a second rack is fixed to the bottom of the fixed cone, the first gear is transmission-connected to the second rack through a gear bevel gear reversing transmission assembly, a through rod is slidably connected in the fixed cone, a second limiting block is fixed on the side wall of the through rod, the second limiting block is slidably connected in the limiting groove arranged on the rod setting box, a reinforcing rod is hinged on the through rod, a first ring is sleeved on the through rod, a second ring is sleeved on the reinforcing rod, the second ring is hinged on a support rod, and the other end of the support rod is hinged outside the first ring. The invention realizes stable and reliable pile foundation isolation protection.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation frost heave prevention and control construction, and particularly to a self-locking sleeve isolation structure and construction method for preventing pile foundation frost heave in seasonal frozen soil areas. Background Art

[0002] The frost heave phenomenon is a key issue affecting the stability of light shallow foundations in cold regions and has not been completely solved yet. From the perspective of the interaction mechanism between frozen soil and pile foundations, pile foundations are mainly affected by the combined action of horizontal frost heave force, normal frost heave force, and tangential frost heave force. During the evolution of pile foundation frost heave, the winter temperature drops, causing the soil to freeze. The soil around the pile freezes together with the pile foundation, forming a frost heave effect. Under the action of the tangential frost heave force, the pile foundation is gradually uplifted. In summer, the temperature rises, causing the soil to melt. The shallow melted soil begins to subside, but due to the existence of the frictional resistance of the deep soil, the pile foundation fails to completely subside with the soil, resulting in a certain residual vertical displacement. As this process continues to cycle, the frost heave amount accumulates year by year, and ultimately may lead to the instability of the pile foundation. Therefore, how to effectively reduce the pile foundation uplift caused by the accumulation of frost heave amount has become an important problem that urgently needs to be solved in the field of pile foundation mechanics in cold regions.

[0003] The sleeve isolation method is a technology that inhibits the frost heave effect by reducing the interaction between the pile foundation and seasonal frozen soil. Due to its advantages such as simple construction technology, low maintenance cost, and environmental friendliness, it has been widely used. Its core idea is to install a layer of sleeve outside the pile foundation to isolate the direct contact between the pile foundation and the surrounding frozen soil, which can significantly reduce the frost heave frictional resistance of the soil around the pile, thereby reducing the uplift effect of the tangential frost heave force on the pile foundation, reducing the frost heave displacement of the pile foundation, and inhibiting the accumulation of frost heave amount. Under the action of repeated freezing and thawing, the sleeve is gradually pulled out, and its isolation effect and frost heave prevention and control efficiency are significantly weakened. Currently, there is no report on the technology for optimizing the frost heave resistance durability of the sleeve outside the pile. Therefore, it is urgent to develop a new type of sleeve isolation structure with high durability to ensure the control ability of the frost heave effect while meeting the long-term engineering life requirements, and provide a more reliable technical guarantee for the stability of pile foundations in cold regions. Summary of the Invention

[0004] The purpose of the present invention is to provide a self-locking sleeve isolation structure for preventing pile foundation frost heave in seasonal frozen soil areas in view of the technical defects existing in the prior art.

[0005] Another purpose of the present invention is to provide a working method for the self-locking sleeve isolation structure for preventing pile foundation frost heave in seasonal frozen soil areas.

[0006] Another purpose of the present invention is to provide a construction method for the self-locking sleeve isolation structure for preventing pile foundation frost heave in seasonal frozen soil areas.

[0007] The technical solution adopted to achieve the purpose of the present invention is as follows:

[0008] A self-locking casing isolation structure for preventing and controlling pile foundation freeze-up in seasonal frozen soil areas, comprising a hollow fixed cylinder and a displacement cylinder slidably sleeved inside the fixed cylinder, wherein the top surface of the fixed cylinder is located below the seasonal frozen soil layer;

[0009] One or more first transmission grooves are provided on the inner wall of the fixed cylinder, and one or more driving grooves are provided on the outer wall of the displacement cylinder. The driving grooves and the first transmission grooves are arranged opposite to each other, and a first rack is installed in each of the driving grooves, and a first gear is installed in each of the first transmission grooves. When the first rack moves upward, it meshes with the first gear;

[0010] A laterally extending rod placing box is fixed on the top of the first transmission groove, an end opening of the rod placing box is communicated with an opening formed on the fixed cylinder, a fixed cone is slidably connected in the rod placing box, a second rack is fixed on the side of the fixed cone, and the first gear is transmission-connected to the second rack through a gear bevel gear reversing transmission assembly;

[0011] A second transmission groove is provided at the front end of the fixed cone, a through rod is slidably connected in the second transmission groove, an outer end of the through rod passes through an end opening of the second transmission groove, and an inner end of the through rod is connected to the second transmission groove through a first spring; a second limit block is fixed on the side wall of the through rod, and the second limit block passes through the avoidance groove provided on the fixed cone and is slidably connected to the limit groove provided on the rod placing box;

[0012] One end of the through rod extending outside the second transmission groove is hinged with multiple reinforcing rods, and the through rod is sleeved with a first ring at the position outside the second transmission groove. Each of the reinforcing rods is sleeved with a second ring that slides with it, and the second rings are hinged with support rods, and the other ends of the support rods are hinged to the outside of the first ring.

[0013] In the above technical solution, the bottom of the fixed cylinder is slidably connected to the outside of the displacement cylinder through a slider slot structure.

[0014] In the above technical solution, the second rack is slidably connected to a through groove formed in a side wall of the rod placing box.

[0015] In the above technical solution, the through rod is slidably connected to the second transmission groove through a slider and a slide groove structure.

[0016] In the above technical solution, the bevel gear rotation and transmission assembly includes a second gear, a third gear, a fourth gear, a first bevel gear, a second bevel gear, and a fifth gear. The second gear is rotatably connected to the side wall of the first transmission groove through a bearing and a rod assembly. One side of the second gear meshes with the third gear. The third gear and the first gear are respectively located on opposite sides of the second gear. The third gear meshes with the fourth gear. The fourth gear is coaxially welded with a first bevel gear that is rotatably connected to the side wall of the first transmission groove. The tooth surface of the first bevel gear meshes with a second bevel gear that is perpendicularly arranged to the first bevel gear. The top of the second bevel gear is welded with a fifth gear that is rotatably connected to the top wall of the first transmission groove. The fifth gear is meshed and connected with the second rack.

[0017] In the above technical solution, an adjusting assembly is provided at the bottom of the first rack. The adjusting assembly includes a connecting rod welded to one side of the first rack. One end of the connecting rod away from the first rack is welded with a first limit block. The first limit block is slidably connected to a slot formed in the side wall of the displacement cylinder. A plurality of second springs are connected between the first rack and the inner side wall of the driving groove.

[0018] The cross-sectional shape of the teeth of the first rack is trapezoidal. The top surface of the teeth of the first rack is a plane, and the bottom surface of the teeth of the first rack is an inclined surface.

[0019] In the above technical solution, a plurality of the reinforcing rods are hinged to the end of the through rod in an umbrella shape.

[0020] On the other hand, the present invention also includes a working method of the anti-freezing and self-locking casing isolation structure for pile foundations in seasonally frozen soil areas, including the following steps:

[0021] The pile foundation is constructed inside the displacement cylinder. When the displacement cylinder is lifted by the action of the tangential frost heaving force, the displacement cylinder moves upward, and the first rack also moves upward accordingly, meshing with the first gear and driving the first gear to rotate. The first gear drives the second rack to move outward through the bevel gear rotation and transmission assembly. Further, the second rack drives the fixed cone to move towards the open end of the rod placing box. When the second limit block contacts the side wall of the limit groove, the through rod stops moving forward. The fixed cone continues to move forward under the drive of the second rack. At this time, the first spring will be compressed and shortened. The front end of the fixed cone presses against the first collar, causing it to slide outward along the through rod, driving the reinforcing rods to slide outward and break away from the restraint of the rod placing box. The reinforcing rods distributed in an umbrella shape pass through the opening on the fixed cylinder and unfold to form an anchor.

[0022] On the other hand, the present invention also includes a construction method of the anti-freezing and self-locking casing isolation structure for pile foundations in seasonally frozen soil areas, including the following steps:

[0023] Step S1, determine the pile position and determine the dimensions of the fixed cylinder and the displacement cylinder.

[0024] Step S2: Excavate a drainage ditch around or at a suitable position in the construction area. Use a drilling rig with a drill bit having the same diameter as the fixed cylinder to perform drilling operations. Stop drilling after reaching the designed depth of the fixed cylinder.

[0025] Step S3: Lift and place the fixed cylinder into the borehole formed in Step S2, and ensure that the top surface of the fixed cylinder is not higher than the maximum seasonal frost depth.

[0026] Step S4: Use a drill bit with the same diameter as the displacement cylinder to drill. Stop drilling after reaching the designed depth of the pile foundation.

[0027] Step S5: Clear the borehole.

[0028] Step S6: Inspect and accept the quality of the formed borehole.

[0029] Step S7: Lift and place the displacement cylinder into the borehole formed in Step S4 and fix it.

[0030] Step S8: Lift and place the steel reinforcement cage into the hole, then prepare the concrete pouring pipe and lift it into the hole. Before pouring, ensure that the bottom of the pile has been cleaned, there is no accumulated water or sediment, and then use the pouring pipe to pour concrete to complete the construction of the pile foundation.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The present invention precisely senses the tangential frost heave displacement experienced by the displacement cylinder in the seasonal frozen soil area, and drives the strengthening rod to pass through and unfold from the opening on the fixed cylinder to form an anchor. This innovative prevention and control structure can significantly reduce the deformation of the pile foundation caused by freeze-thaw cycles, thereby greatly improving the stability and durability of the pile foundation. Compared with the traditional method, this technology realizes the dynamic monitoring and coordinated automatic control of the frost heave displacement of the pile foundation, reducing potential risks caused by untimely manual monitoring or inaccurate adjustment.

[0033] 2. Through the ingeniously designed adjusting component and the first rack, this structure of the present invention can flexibly respond to frost heave displacements of different magnitudes and directions, ensuring stable and effective prevention and control effects under various complex and changeable freeze-thaw cycle conditions. This design not only improves the accuracy of prevention and control but also significantly enhances the adaptability and flexibility of the structure. Compared with traditional fixed protection means, it can better adapt to the complex and changeable seasonal frozen soil environment.

[0034] 3. The settings of the through rod, the first spring, and the reinforcing rod further enhance the fixing force of the fixing cone, providing strong support for the fixing force of the fixing cone. This not only further enhances the fastening effect of the fixing cone, enabling the pile foundation to remain stable even under extremely harsh freeze-thaw conditions, but also effectively improves the safety and reliability of the overall structure. Compared with the problems of limited fixing force and easy loosening in traditional technologies, this technology realizes more stable and reliable isolation and protection of the pile foundation through automatic adjustment and strengthening of the fixing mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0036] Figure 2 It is a schematic front sectional view of the overall structure of the present invention.

[0037] Figure 3 It is Figure 2 an enlarged view of part A in

[0038] Figure 4 It is a schematic diagram of the meshing of the gear bevel gear reversing transmission component of the present invention.

[0039] Figure 5 It is a schematic diagram of the connection structure of the fifth gear, the rod placement box body, and the through groove of the present invention.

[0040] Figure 6 It is an axonometric schematic diagram of the fixing cone of the present invention.

[0041] Figure 7 It is a front sectional view of the fixing cone.

[0042] Figure 8 It is a schematic sectional view of the connection structure of the through rod, the fixing cone, and the rod placement box body.

[0043] Figure 9 It is a flow chart of the construction method.

[0044] In the figures: 1. Fixed cylinder; 2. Displacement cylinder; 3. Driving groove; 4. First transmission groove; 5. First rack; 6. Rod placement box body; 7. Fixing cone; 8. Connecting rod; 9. First limiting block; 10. Second spring; 11. Second rack; 12. Through groove; 13. First gear; 14. Second gear; 15. Third gear; 16. Fourth gear; 17. First bevel gear; 18. Second bevel gear; 19. Fifth gear; 20. Second transmission groove; 21. Through rod; 22. Limiting groove; 23. Second limiting block; 24. First spring; 25. Reinforcing rod; 26. First collar; 27. Second collar; 28. Support rod; 29. Pile foundation; 30. Avoidance groove; 31. Opening. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The present invention is further described in detail below in conjunction with specific embodiments. 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.

[0046] Example 1

[0047] like Figures 1-8 As shown, a self-locking casing isolation structure for preventing and controlling the freezing of pile foundations in seasonal frozen soil areas comprises a hollow fixed cylinder 1 and a displacement cylinder 2 slidably sleeved inside the fixed cylinder 1; the top surface of the fixed cylinder 1 is located below the seasonal frozen soil layer, the inner diameter of the fixed cylinder 1 is larger than the outer diameter of the displacement cylinder 2, and the displacement cylinder 2 can slide up and down inside the fixed cylinder 1; preferably, the bottom of the fixed cylinder 1 is slidably connected to the outside of the displacement cylinder 2 through a slider slot structure;

[0048] One or more first transmission grooves 4 are provided on the inner wall of the fixed cylinder 1, and one or more driving grooves 3 are provided on the outer wall of the displacement cylinder 2. The driving grooves 3 and the first transmission grooves 4 are arranged opposite to each other, and a first rack 5 is installed in each driving groove 3, and a first gear 13 is installed in each first transmission groove 4. When the first rack 5 moves up, it meshes with the first gear 13; under the action of the tangential frost heave force during the frost heave process, the displacement cylinder 2 is lifted up, and the displacement cylinder 2 moves upward, and the first rack 5 in the driving groove 3 of its outer wall also moves up accordingly. When the first rack 5 moves to a position in contact with the first gear 13, since the first gear 13 can mesh with the first rack 5, the first rack 5 drives the first gear 13 to start rotating.

[0049] A laterally extending rod placing box 6 is fixed to the top of the first transmission groove 4, and the end opening of the rod placing box 6 is communicated with the opening 31 formed on the fixed cylinder 1. A fixed cone 7 is slidably connected in the rod placing box 6. Preferably, the rod placing box 6 is slidably connected with the fixed cone 7 through a slider slot structure, and a second rack 11 is fixed to the side of the fixed cone 7. The first gear 13 is transmission-connected to the second rack 11 through a gear bevel gear reversing transmission assembly;

[0050] Preferably, the second rack 11 is slidably connected to a through slot 12 provided on the side wall of the rod placing box 6; the through slot 12 allows the gear bevel gear reversing transmission assembly to have space to engage with the second rack 11. When the frost heave phenomenon occurs, the first rack 5 rises, and through the transmission of the gear bevel gear reversing transmission assembly, the second rack 11 is gradually pushed to move linearly along the track of the through slot 12.

[0051] like Figures 7-8A second transmission groove 20 is provided at the front end of the fixed cone 7, and a through rod 21 is slidably connected to the second transmission groove 20. The outer end of the through rod 21 passes through the end opening of the second transmission groove 20, and the inner end of the through rod 21 is connected to the second transmission groove 20 through a first spring 24; a second limit block 23 is fixed on the side wall of the through rod 21, and the second limit block 23 passes through the avoidance groove 30 provided on the fixed cone 7 and is slidably connected to the limit groove 22 provided on the side wall of the rod placing box 6, and the second limit block 23 extends out of the limit groove 22 on the side away from the through rod 21 and is located outside the limit groove 22.

[0052] One end of the through rod 21 extending outside the second transmission groove 20 is hinged with a plurality of reinforcing rods 25. Preferably, the plurality of reinforcing rods 25 are distributed in an umbrella shape. The portion of the through rod 21 located outside the second transmission groove 20 is sleeved with a first ring 26, and the first ring 26 is slidably matched with the through rod 21. Each reinforcing rod 25 is sleeved with a second ring 27 slidably matched therewith, and the second ring 27 is hinged with a support rod 28, and the other end of the support rod 28 is hinged to the outside of the first ring 26.

[0053] The second transmission groove 20 is connected to the extended end of the fixed cone 7. A through rod 21 is slidably connected to the second transmission groove 20 through a slider and a slide groove structure. A limiting groove 22 is provided on the side wall of the rod setting box 6. The left end of the through rod 21 is fixedly connected to a first spring 24 by a bolt. The left end of the first spring 24 is fixedly connected to the side wall of the second transmission groove 20 by a screw. When the fixed cone 7 is slowly extended, the extension amount of the fixed cone 7 reaches a certain distance, and the second limiting block 23 contacts the side wall of the limiting groove 22, the through rod 21 stops moving forward, and the fixed cone 7 continues to move forward driven by the second rack 11. At this time, the first spring 24 will The compression and shortening are performed, and the relative displacement is that the fixed cone 7 extends outward, while the through rod 21 is stationary. The front end of the fixed cone 7 presses against the first ring 26 to make it slide outward along the through rod 21, driving the reinforcing rod 25 to slide outward and break away from the constraint of the rod setting box 6. A number of supporting rods 28 will unfold a number of reinforcing rods 25 that were originally shrunk and close to the through rod 21, so as to achieve the effect of slowly extending the fixed cone 7 and at the same time stretching the reinforcing rods 25. Finally, the umbrella-shaped reinforcing rods 25 pass through the opening 31 on the fixed cylinder 1 and unfold to form an anchor, which can enhance the effect of the fixed cone 7 on limiting the up and down displacement of the fixed cylinder 1 and improve the overall stability of the structure when frost heave occurs.

[0054] Preferably, when the displacement cylinder 2 rises due to the frost heave phenomenon, the gear bevel gear reversing transmission assembly provided in the first transmission groove 4 converts the tangential frost heave vertical displacement of the displacement cylinder 2 into the horizontal displacement of the second rack 11, as shown in detail. Figure 4The schematic diagram of the meshing connection shown, the bevel gear reversing transmission assembly includes a second gear 14, a third gear 15, a fourth gear 16, a first bevel gear 17, a second bevel gear 18 and a fifth gear 19. The second gear 14 is rotatably connected to the side wall of the first transmission groove 4 through a bearing and a rod assembly. The third gear 15 is meshed with one side of the second gear 14. The third gear 15 and the first gear 13 are respectively located on the opposite sides of the second gear 14. The third gear 15 is meshed with the fourth gear 16. The fourth gear 16 is coaxially welded with a first bevel gear 17 rotatably connected to the side wall of the first transmission groove 4. The tooth surface of the first bevel gear 17 is meshed with a second bevel gear 18 arranged perpendicular to the first bevel gear 17. The top of the second bevel gear 18 is welded with a fifth gear 19 rotatably connected to the top wall of the first transmission groove 4. The fifth gear 19 is meshed and connected with the second rack 11.

[0055] When the first gear 13 is meshed with the first rack 5 and slowly rises and rotates, this rotation is effectively transmitted to the meshed second gear 14. With the rotation of the second gear 14, the third gear 15 is further driven to rotate. Immediately afterwards, the rotation of the third gear 15 drives the meshed fourth gear 16 to rotate. The rotation of the fourth gear 16 is directly converted into the rotation of the first bevel gear 17. The tooth surface of the first bevel gear 17 is meshed with the tooth surface of the second bevel gear 18, and the two are arranged perpendicular to each other. Therefore, when the first bevel gear 17 rotates, it drives the second bevel gear 18 to rotate in the horizontal direction. This change in the rotation direction is achieved through the special tooth surface shape of the bevel gears, which can ensure that while transmitting torque in the vertical direction, a 90-degree change in the rotation direction is realized. Finally, the rotation of the second bevel gear 18 is transmitted to the fifth gear 19 at the top. The fifth gear 19 can freely rotate with the rotation of the second bevel gear 18, thereby driving the second rack 11 to move horizontally.

[0056] Embodiment 2

[0057] Since when hoisting and placing the displacement cylinder 2 and the fixed cylinder 1, it is necessary to combine and install the displacement cylinder 2 and the fixed cylinder 1. The fixed cylinder 1 is placed first and the displacement cylinder 2 slides and is hoisted in the fixed cylinder 1. Considering that the first rack 5 is likely to come into contact with the first gear 13 during this hoisting process, which will affect the subsequent frost heaving transmission. Therefore, it is designed that the bottom of the first rack 5 is provided with an adjustment assembly for adjusting the meshing state of the first rack 5.

[0058] Specifically, as Figure 3 shown, the adjustment assembly includes a connecting rod 8 welded to one side of the first rack 5. One end of the connecting rod 8 away from the first rack 5 is welded with a first limit block 9. The first limit block 9 is slidably connected in a slot formed in the side wall of the displacement cylinder 2. A plurality of second springs 10 are connected between the first rack 5 and the inner side wall of the driving groove 3.

[0059] The cross-sectional shape of the teeth of the first rack 5 is a trapezoid, the top surface of the teeth of the first rack 5 is a plane, and the bottom surface of the teeth of the first rack 5 is an inclined surface, so that the first rack 5 forms a one-way meshing with the first gear 13. After assembly, when the first rack 5 moves upward, the top plane of the teeth of the first rack 5 contacts the first gear 13, and the top plane of the teeth of the first rack 5 meshes with the teeth of the first gear 13, which can drive the first gear 13 to rotate. During the assembly process, the displacement cylinder 2 slides down in the fixed cylinder 1, and the first rack 5 moves downward accordingly. The bottom inclined surface of the teeth of the first rack 5 contacts the first gear 13, and no effective meshing is generated, which will apply a pressure to the bottom inclined surface.

[0060] The elastic force and number of the second springs 10 are determined through preliminary experiments to ensure that the second springs 10 do not contract when the first rack 5 is rising, and the first rack 5 is effectively meshed with the first gear 13. When the first rack 5 is assembled and lowered, the second springs 10 contract under the pressure of the first gear 13.

[0061] The setting of the adjustment component enables the contact between the first rack 5 and the first gear 13 to present an elastic and controllable process when the displacement cylinder 2 is slid down and installed in the fixed cylinder 1. Specifically, when the displacement cylinder 2 is hoisted into the fixed cylinder 1 and slides down along the slide rail, the first gear 13 applies pressure to the bottom inclined surface of the teeth of the first rack 5. Since the bottom of the first rack 5 is connected to the inside of the displacement cylinder 2 through the connecting rod 8 and the first limit block 9, and the first rack 5 is also connected to the inner wall of the driving groove 3 through a number of second springs 10, this design allows the first rack 5 to be subjected to pressure, and the second spring 10 produces a certain elastic deformation. In the initial contact stage, the second spring 10 will play a buffering role, absorbing part of the impact force, and preventing excessive impact force from being generated between the first rack 5 and the first gear 13, thereby reducing possible damage or jamming. As the displacement cylinder 2 continues to slide down, the first rack 5 will gradually return to its original position under the elastic force of the second spring 10. In this process, due to the presence of the connecting rod 8 and the first limit block 9, the first rack 5 is confined in the driving groove 3 and will not completely deviate from its track due to the elastic force of the second spring 10. When the displacement cylinder 2 slides down to the predetermined position, that is, the first rack 5 is in a completely separated state from the first gear 13, the entire installation process is completed. At this time, the second spring 10 is in an uncompressed state, ready for subsequent frost heave transmission. The setting of the adjustment component can also flexibly cope with frost heave displacements of different sizes and directions.

[0062] Example 3

[0063] like Figure 9As shown in the figure, a construction method for a self-locking casing isolation structure for preventing pile foundation frost heave in seasonally frozen soil areas is based on the self-locking casing isolation structure for preventing pile foundation frost heave described in Embodiments 1-3 and includes the following steps.

[0064] Step S1, measuring and setting out pile positions: According to the design drawings, accurately set out and position the pile positions to ensure that the position of each pile is accurate. At the same time, accurately design and determine the dimensions of the fixed cylinder 1 and the displacement cylinder 2 according to the actual drawings and produce them. This step ensures the accuracy and efficiency of subsequent construction, avoids construction delays or quality problems caused by inconsistent dimensions, improves construction accuracy, reduces errors, and lays a solid foundation for subsequent construction.

[0065] Step S2, drilling the fixed cylinder 1: After the layout is completed, dig drainage ditches around the construction area or at a suitable location. The direction of the drainage ditches should be consistent with the low-lying areas of the terrain to ensure that rainwater can flow in smoothly. Then lay gravel or grit at the bottom of the drainage ditches to increase the water seepage performance and ensure that surface water cannot flow into the hole during drilling, affecting the drilling quality. Then use a drilling rig with a drill bit of the same diameter as the fixed cylinder 1 to carry out drilling operations. After drilling to the designed depth of the fixed cylinder 1, stop drilling, ensuring that the fixed cylinder 1 can be accurately installed in the predetermined position, preventing surface water from affecting the drilling quality and ensuring the accuracy of the installation position of the fixed cylinder 1.

[0066] Step S3, hoisting and placing the fixed cylinder 1: Hoist and place the fixed cylinder 1 into the hole formed in Step S2, and ensure that the top surface of the fixed cylinder 1 is not higher than the maximum seasonal frost depth, ensuring the stability and accuracy of the fixed cylinder 1 and providing support for subsequent construction.

[0067] Step S4, drilling the displacement cylinder 2: Replace the drill bit of the drilling rig with a drill bit of the same diameter as the displacement cylinder 2 to carry out drilling operations for the displacement cylinder 2. After drilling to the designed depth of the fixed displacement cylinder 2, stop drilling. Ensure that the displacement cylinder 2 can be accurately installed in the predetermined position, providing space for the subsequent installation of the displacement cylinder 2 and ensuring the accuracy of the installation position. Continue drilling to the designed depth of the pile foundation 29 and stop drilling.

[0068] Step S5, hole cleaning: After Step S4 is completed, carry out hole cleaning operations to suck out the sediment at the bottom of the pile hole outside the hole to ensure thorough hole cleaning.

[0069] Step S6, inspection and acceptance of the formed hole: Inspect and accept the quality of the formed hole to check whether the quality of the formed hole is qualified.

[0070] Step S7, hoisting and placing the displacement cylinder 2: Hoist and place the displacement cylinder 2 into the hole and ensure its accurate position.

[0071] Step S8, pile construction: fabricate the steel reinforcement cage according to the design requirements, lift and place the steel reinforcement cage into the hole, then prepare the concrete pouring pipe, lift and place the pouring pipe into the hole. Before pouring, ensure that the bottom of the pile has been cleaned, there is no accumulated water or sediment, and then use the pouring pipe to pour concrete to complete the construction of the pile foundation 29.

[0072] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A self-locking casing isolation structure for preventing and controlling pile foundation frost pullout in seasonal frozen soil areas, characterized in that: It comprises a hollow fixed cylinder and a displacement cylinder slidably sleeved inside the fixed cylinder, wherein the top surface of the fixed cylinder is located below the seasonal frozen soil layer; One or more first transmission grooves are provided on the inner wall of the fixed cylinder, and one or more driving grooves are provided on the outer wall of the displacement cylinder. The driving grooves and the first transmission grooves are arranged opposite to each other, and a first rack is installed in each of the driving grooves, and a first gear is installed in each of the first transmission grooves. When the first rack moves upward, it meshes with the first gear; A laterally extending rod placing box is fixed on the top of the first transmission groove, an end opening of the rod placing box is communicated with an opening formed on the fixed cylinder, a fixed cone is slidably connected in the rod placing box, a second rack is fixed on the side of the fixed cone, and the first gear is transmission-connected to the second rack through a gear bevel gear reversing transmission assembly; A second transmission groove is provided at the front end of the fixed cone, a through rod is slidably connected in the second transmission groove, an outer end of the through rod passes through an end opening of the second transmission groove, and an inner end of the through rod is connected to the second transmission groove through a first spring; a second limit block is fixed on the side wall of the through rod, and the second limit block passes through the avoidance groove provided on the fixed cone and is slidably connected to the limit groove provided on the rod placing box; One end of the through rod extending outside the second transmission groove is hinged with multiple reinforcing rods, and the through rod is sleeved with a first ring at the position outside the second transmission groove. Each of the reinforcing rods is sleeved with a second ring that slides with it, and the second rings are hinged with support rods, and the other ends of the support rods are hinged to the outside of the first ring.

2. The self-locking casing isolation structure for preventing and controlling the freezing of pile foundations in seasonal frozen soil areas according to claim 1 is characterized in that: The bottom of the fixed cylinder is slidably connected to the outside of the displacement cylinder through a slider slot structure.

3. The self-locking casing isolation structure for preventing and controlling freezing of pile foundations in seasonal frozen soil areas according to claim 1 is characterized in that: The second rack is slidably connected to a through slot provided on a side wall of the rod placing box.

4. The self-locking casing isolation structure for preventing and controlling freezing of pile foundations in seasonal frozen soil areas according to claim 1 is characterized in that: The through rod is slidably connected in the second transmission groove through a slider and a slide groove structure.

5. The self-locking casing isolation structure for preventing and controlling freezing of pile foundations in seasonal frozen soil areas according to claim 1 is characterized in that: The gear bevel gear reversing transmission assembly includes a second gear, a third gear, a fourth gear, a first bevel gear, a second bevel gear and a fifth gear. The second gear is rotatably connected to the side wall of the first transmission groove through a bearing and a rod assembly. The third gear is meshed with one side of the second gear. The third gear and the first gear are respectively located on opposite sides of the second gear. The third gear is meshed with the fourth gear. The fourth gear is coaxially welded with the first bevel gear rotatably connected to the side wall of the first transmission groove. The tooth surface of the first bevel gear is meshed with the second bevel gear arranged vertically with the first bevel gear. The fifth gear is rotatably connected to the top wall of the first transmission groove welded on the top of the second bevel gear. The fifth gear is meshed with the second rack.

6. The self-locking casing isolation structure for preventing and controlling freezing of pile foundations in seasonal frozen soil areas according to claim 1, characterized in that: An adjustment assembly is provided at the bottom of the first rack, and the adjustment assembly includes a connecting rod welded to one side of the first rack, a first limit block is welded to one end of the connecting rod away from the first rack, the first limit block is slidably connected to a slot formed on the side wall of the displacement cylinder, and a plurality of second springs are connected between the first rack and the inner side wall of the driving groove; The cross-sectional shape of the teeth of the first rack is a trapezoid, the top surface of the teeth of the first rack is a plane, and the bottom surface of the teeth of the first rack is an inclined surface.

7. The self-locking casing isolation structure for preventing and controlling freezing of pile foundations in seasonal frozen soil areas according to claim 1 is characterized in that: A plurality of reinforcing rods are distributed in an umbrella shape and are hinged to the end of the through rod.

8. The construction method of the self-locking casing isolation structure for preventing and controlling the freezing of pile foundations in seasonal frozen soil areas according to claim 1 is characterized in that: The following steps are involved: Step S1, determine the pile position, and determine the size of the fixed cylinder and the displacement cylinder; Step S2, digging a drainage ditch around the construction area or at a suitable location, using a drill rig with a drill bit of the same diameter as the fixed cylinder to perform drilling operations, and stopping drilling after drilling to the designed depth of the fixed cylinder; Step S3, placing the fixed cylinder into the drill hole formed in step S2, and ensuring that the top surface of the fixed cylinder is not higher than the maximum seasonal freezing depth; Step S4, drilling with a drill bit having a diameter equal to that of the displacement cylinder, and stopping drilling after reaching the designed depth of the pile foundation; Step S5, hole cleaning; Step S6, inspecting and accepting the quality of the hole; Step S7, placing the displacement cylinder into the drilled hole formed in step S4 and fixing it; Step S8, hang the steel cage into the hole, then prepare the concrete pouring pipe, hang the pouring pipe into the hole, before pouring, ensure that the pile bottom has been cleaned, without water accumulation and sediment, and then use the pouring pipe to pour concrete to complete the pile foundation construction.

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