Prevention and control structure for normal frost heaving force of shallow-buried contact net pile foundation in frozen soil area and construction method

Abstract

The invention discloses a normal frost heaving force prevention and control structure for a shallow-buried contact net pile foundation in a frozen soil region and a construction method. A plurality of combination grooves are uniformly formed in the side wall of a fixed cylinder in the circumferential direction, an upper heat insulation layer is arranged on the outer wall of the fixed cylinder, and an elastic buffer mechanism is arranged at the connecting position of the fixed cylinder and a bottom cylinder; a pile foundation is arranged in the fixing cylinder, a buffer gap is reserved between the outer wall of the pile foundation and the inner wall of the fixing cylinder, and a plurality of inclined struts are arranged in the buffer gap; the inclined struts comprise the upper inclined strut and the lower inclined strut, the two ends of the upper inclined strut are fixedly connected with the pile foundation and the fixing cylinder respectively, one end of the lower inclined strut is fixed to the pile foundation, and the other end of the lower inclined strut abuts against the inner wall of the fixing cylinder. A hydraulic buffering mechanism is arranged on the lower portion of the pile foundation. The horizontal frost heaving force from the side face is effectively dispersed through the arrangement of the inclined struts, the elastic buffering assembly and the hydraulic buffering mechanism work cooperatively, and the normal frost heaving force is effectively offset through the dual effects of elastic deformation and hydraulic damping.

Description

Technical Field

[0001] The present invention relates to the technical field of freeze-thaw deformation prevention and control construction technology, and in particular to a normal frost heave force prevention and control structure for a shallow-buried contact network pile foundation in a frozen soil area and a construction method. Background Art

[0002] The stable operation of electrified railways in permafrost regions is highly dependent on the long-term reliability of catenary pile foundations. Due to the unique physical and mechanical properties of permafrost, the volume changes and mechanical responses of the subgrade soil under freeze-thaw cycles significantly impact the pile foundation structure. This is particularly true in permafrost-degraded areas affected by climate warming, where the stability of the catenary pile foundation faces severe challenges. In conventional railway projects in permafrost regions, subgrade filling significantly alters the existing surface thermal equilibrium, leading to variations in the depth distribution of the permafrost ceiling—the top of the permafrost layer. Specifically, the permafrost ceiling exhibits a non-uniform rise across the subgrade, with the ceiling higher in the mid-road than in the shoulder area. Catenary pile foundations are typically located on the shoulder, where the thickness of the seasonal freeze-thaw layer and the freezing development pattern of the active layer differ fundamentally from those found on the natural surface. The subgrade freezing process is multidirectional, with freezing fronts developing simultaneously and overlapping from the pavement surface, the slope surface, and the permafrost ceiling beneath the subgrade. This results in extremely complex freezing rates, moisture migration pathways, and frost heave force distribution patterns in the soil surrounding the piles. Especially in high-fill roadbed sections, due to limited structural space and load requirements, catenary pile foundations are often shallowly buried, with the main pile body or even the entire pile body located within the active layer of the roadbed. The roadbed is usually composed of weak frost-heaving soil. In this case, the normal frost-heaving force at the bottom of the pile base (the frost-heaving force acting on the pile base surface and perpendicular to the bottom surface) will directly act on the pile tip, causing uneven uplift, lateral displacement, and even structural damage to the pile body. However, current technologies for preventing and controlling frost-heaving damage in catenary pile foundations focus on reducing the impact of tangential frost-heaving forces (frost-heaving forces acting parallel to the pile-soil interface), such as using low-friction coatings and improved backfill materials around piles. However, there is a lack of effective technical means to prevent and control normal frost-heaving forces.

[0003] In view of this, it is urgent to propose a structure and construction method for preventing and controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas, so as to achieve efficient reduction of the normal frost heave force of pile foundations and improvement of pile stability under shallow-buried conditions, thereby improving the stability and service life of pile foundations. Summary of the Invention

[0004] The stable operation of electrified railways in permafrost regions is highly dependent on the long-term reliability of catenary pile foundations. Due to the unique physical and mechanical properties of permafrost, the volume changes and mechanical responses of the subgrade soil under freeze-thaw cycles significantly impact the pile foundation structure. This is particularly true in permafrost-degraded areas affected by climate warming, where the stability of the catenary pile foundation faces severe challenges. In conventional railway projects in permafrost regions, subgrade filling significantly alters the existing surface thermal equilibrium, leading to variations in the depth distribution of the permafrost ceiling—the top of the permafrost layer. Specifically, the permafrost ceiling exhibits a non-uniform rise across the subgrade, with the ceiling higher in the mid-road than in the shoulder area. Catenary pile foundations are typically located on the shoulder, where the thickness of the seasonal freeze-thaw layer and the freezing development pattern of the active layer differ fundamentally from those found on the natural surface. The subgrade freezing process is multidirectional, with freezing fronts developing simultaneously and overlapping from the pavement surface, the slope surface, and the permafrost ceiling beneath the subgrade. This results in extremely complex freezing rates, moisture migration pathways, and frost heave force distribution patterns in the soil surrounding the piles. Especially in high-fill roadbed sections, due to limited structural space and load requirements, catenary pile foundations are often shallowly buried, with the main pile body or even the entire pile body located within the active layer of the roadbed. The roadbed is usually composed of weak frost-heaving soil. In this case, the normal frost-heaving force at the bottom of the pile base (the frost-heaving force acting on the pile base surface and perpendicular to the bottom surface) will directly act on the pile tip, causing uneven uplift, lateral displacement, and even structural damage to the pile body. However, current technologies for preventing and controlling frost-heaving damage in catenary pile foundations focus on reducing the impact of tangential frost-heaving forces (frost-heaving forces acting parallel to the pile-soil interface), such as using low-friction coatings and improved backfill materials around piles. However, there is a lack of effective technical means to prevent and control normal frost-heaving forces.

[0005] In view of this, it is urgent to propose a structure and construction method for preventing and controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas, so as to achieve efficient reduction of the normal frost heave force of pile foundations and improvement of pile stability under shallow-buried conditions, thereby improving the stability and service life of pile foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a schematic diagram of the overall structure of the normal frost heave force control structure of the shallow buried contact network pile foundation in frozen soil areas of the present invention.

[0007] Figure 2 It is an axonometric cross-sectional view of the normal frost heave force control structure of the shallow buried contact network pile foundation in the frozen soil area of the present invention.

[0008] Figure 3 It is an axonometric cross-sectional view of the bottom tube of the normal frost heave force control structure of the shallow-buried contact network pile foundation in the frozen soil area of the present invention.

[0009] Figure 4 It is an axonometric cross-sectional view of the lower structure of the normal frost heave force prevention and control structure of the shallow buried contact network pile foundation in the frozen soil area of the present invention.

[0010] Figure 5 The figure is a schematic diagram of the arrangement of diagonal braces in the normal frost heave force control structure of the shallow-buried contact network pile foundation in frozen soil areas according to the present invention.

[0011] Figure 6 The figure is a schematic diagram of the arrangement of the connectors in the normal frost heave force control structure of the shallow-buried contact network pile foundation in the frozen soil area of the present invention, wherein (a) is the connection structure between the connector and the bottom cylinder and (b) is the structure of the lower insulation layer.

[0012] Figure 7 Schematic diagram of the initial state (a) and filling state (b) of the antifreeze layer in the normal frost heave force control structure of the shallow-buried contact network pile foundation in frozen soil areas of the present invention.

[0013] Figure 8 It is a schematic flow chart of the construction method of the present invention.

[0014] 1. Fixed cylinder; 2. Combination groove; 3. Bottom cylinder; 301. Upper bottom cylinder; 302. Lower bottom cylinder; 4. Diagonal brace; 401. Upper diagonal brace; 402. Lower diagonal brace; 5. Through port; 6. Pile foundation; 7. Hydraulic chamber; 8. Piston; 9. Sealing ring; 10. Hydraulic rod; 11. Pressure-bearing chamber; 12. Pressure-applying chamber; 13. Damping channel; 14. Telescopic cylinder; 1401. Inner cylinder; 1402. Outer cylinder; 15. Buffer chamber; 16. Spring; 17. Antifreeze layer; 18. Upper thermal insulation layer; 19. Lower thermal insulation layer; 1901. Geotextile; 1902. Aerogel; 20. Connector; 21. Liquid passage. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] Example 1 like Figure 1 、 Figure 2 、 Figure 5 As shown, a normal frost heave force control structure for shallow-buried contact network pile foundations in frozen soil areas includes three major parts: a fixed tube 1, a bottom tube 3 and a pile foundation 6.

[0017] The sidewall of the fixed tube 1 is uniformly provided with a number of coupling grooves 2 along the circumference. The design of the coupling grooves 2 improves the deformation coordination ability of the fixed tube 1 under frost heave, allowing it to better adapt to the influence of frost heave forces. An upper insulation layer 18 is provided on the outside of the fixed tube 1, and the bottom tube 3 is slidably connected to the bottom of the fixed tube 1. The provision of the upper insulation layer 18 isolates the fixed tube 1 from direct contact with the soil, reducing tangential frost heave forces. The provision of the coupling grooves 2 reduces horizontal frost heave forces, and the bottom tube 3 reduces the supporting effect of normal frost heave forces on the bottom of the pile foundation 6.

[0018] The combined effects of tangential and normal frost heave forces may cause frost heave uplift in pile foundation 6. To prevent and control the impact of vertical frost heave uplift on pile foundation 6, an elastic buffer mechanism is installed at the connection between the fixed cylinder 1 and the bottom cylinder 3. This elastic buffer mechanism dynamically adjusts the tangential anti-frost heave force according to the magnitude of the tangential frost heave force, effectively absorbing and buffering the frost heave force. The direction of the anti-frost heave force is opposite to that of the tangential frost heave force, thereby effectively controlling the impact of the frost heave force on pile foundation 6.

[0019] A pile foundation 6 is provided inside the fixed tube 1, and a buffer gap is reserved between the outer wall of the pile foundation 6 and the inner wall of the fixed tube 1. A plurality of diagonal braces 4 are provided in the buffer gap; the diagonal braces 4 include an upper diagonal brace 401 and a lower diagonal brace 402, wherein the two ends of the upper diagonal brace 401 are fixedly connected to the pile foundation 6 and the fixed tube 1 respectively, and one end of the lower diagonal brace 402 is fixed to the pile foundation 6, and the other end is against the inner wall of the fixed tube 1. Preferably, in order to prevent and control the influence of the horizontal frost heave force on the pile foundation 6, the top of the pile foundation 6 is designed to be at the same height as the top of the fixed tube 1, and a plurality of diagonal braces 4 are provided between the outer wall of the pile foundation 6 and the fixed tube 1, specifically as follows Figure 5 The plurality of upper diagonal braces 401 and lower diagonal braces 402 are sequentially arranged in a "Z"-shaped structure, which can effectively disperse and consume the influence of the horizontal frost heave force and increase the horizontal bearing capacity of the fixing tube 1 and the pile foundation 6.

[0020] The "Z"-shaped arrangement of upper and lower diagonal braces 401 and 402 more effectively disperses and resists horizontal frost heave forces from the side. Compared to traditional linear diagonal braces, this layout provides longer lever arms and more support points with the same material usage, significantly improving the stability and load-bearing capacity of the overall control structure. In permafrost areas, this design is particularly critical for preventing pile foundation 6 from tilting or being damaged by horizontal frost heave forces, ensuring the long-term stability and structural safety of pile foundation 6 in complex freeze-thaw environments.

[0021] like Figure 2 and Figure 3 As shown, a hydraulic buffer mechanism is provided at the bottom of the pile foundation 6. The hydraulic buffer mechanism includes a hydraulic chamber 7 fixed to the bottom of the pile foundation 6, a piston 8 with a sealing ring 9, and a hydraulic rod 10. The hydraulic chamber 7 is filled with antifreeze fluid. The piston 8 divides the hydraulic chamber 7 into an upper pressure-bearing chamber 11 and a lower pressure-applying chamber 12. A damping channel 13 is provided on the side wall of the hydraulic chamber 7, connecting the pressure-bearing chamber 11 and the pressure-applying chamber 12. The upper end of the hydraulic rod 10 passes through an opening at the bottom of the hydraulic chamber 7 and is fixedly connected to the bottom of the piston 8. The lower end of the hydraulic rod 10 extends through the opening 5 of the bottom barrel 3 to the outside of the bottom barrel 3. The hydraulic rod 10 is welded to the opening 5. A sealing gasket is embedded in the opening at the bottom of the hydraulic chamber 7 to prevent leakage of the antifreeze fluid.

[0022] When the bottom of the pile foundation 6 is subjected to the normal frost heave force, the hydraulic rod 10 will move vertically before the pile foundation 6. When moving upward, it drives the piston 8 to move in the hydraulic chamber 7 toward the pressure chamber 11, causing the volume of the pressure chamber 11 to shrink. In order to utilize the hydraulic pressure generated by the shrinking volume of the pressure chamber 11, a number of damping channels 13 are designed to be opened on the side wall of the hydraulic chamber 7. Figure 3 Preferably, with the height centerline of the hydraulic chamber 7 as the transverse centerline, the openings at both ends of the plurality of damping channels 13 are symmetrically arranged along the transverse centerline, and the height difference between any one end opening of the plurality of damping channels 13 and the transverse centerline increases gradually.

[0023] Since the height difference between the opening at either end of the damping channel 13 and the height centerline increases, during the movement of the piston 8, part of the opening will be gradually blocked by the piston 8 and the sealing ring 9, causing the pressure difference required for the antifreeze to flow through the damping channel 13 to change. This design realizes dynamic regulation of the anti-frost heave force, and can automatically adjust according to the amount of frozen pullout or the size of the frost heave force of the pile foundation 6, ensuring that the prevention and control structure responds flexibly under different working conditions. This mechanism can avoid excessive restriction of the movement of the pile foundation 6, prevent the pile foundation 6 from being subjected to excessive constraints resulting in structural stress concentration, and prevent the pile foundation 6 from being subjected to excessive force and becoming unstable, effectively balancing the stability and adaptability of the pile foundation 6, thereby improving its long-term reliability in seasonal freeze-thaw environments.

[0024] Specifically, when the antifreeze fluid in the pressure-bearing chamber 11 is hydraulically acted upon and flows toward the pressure-applying chamber 12, the damping channel 13 acts similarly to a damping orifice in a conventional hydraulic system. As the antifreeze fluid passes through the damping channel 13, the friction of the damping channel 13 slows its flow, resulting in a localized pressure drop. This actively regulates the normal frost heave force and dissipates energy. Furthermore, as the piston 8 ascends, the number of damping channels 13 available for antifreeze fluid flow gradually decreases, reducing the flow area between the pressure-bearing chamber 11 and the pressure-applying chamber 12. The resistance of the damping channel 13 to the flow of antifreeze fluid also increases, thereby increasing the buffering force. Dynamic regulation of the hydraulic buffering force helps extend the service life of the hydraulic buffer mechanism and improves the effectiveness of the pile foundation 6 in controlling the normal frost heave force. Furthermore, when the normal frost heave force is transmitted to the pile foundation 6 via the hydraulic rod 10, the diagonal brace 4 can convert some of the vertical frost heave force into a horizontal support force radiating outward from the pile foundation 6, reducing the risk of deformation of the pile foundation 6 and the fixed cylinder 1 under the action of the horizontal frost heave force.

[0025] Combining the elastic buffer mechanism and the hydraulic buffer mechanism, during the pulling-up process of the pile foundation 6, the two can jointly offset the normal frost heave force, thereby slowing down the tendency of the pile foundation 6 to pull out by freezing. In the thawing and settling stage of the frozen soil in summer, the hydraulic buffer mechanism and the elastic buffer mechanism work together. When the elastic buffer mechanism recovers from the compressed state to the normal state, as the bottom cylinder 3 descends, the antifreeze liquid in the hydraulic chamber 7 flows back from the pressure chamber 12 to the pressure chamber 11 as the piston 8 falls. This process is also affected by the flow resistance of the damping channel 13, which effectively slows down the influence of the rebound force of the elastic buffer mechanism on the bottom cylinder 3, and avoids the risk of excessive settlement of the pile foundation 6 due to excessive rebound force.

[0026] Example 2 This embodiment is further optimized based on embodiment 1.

[0027] like Figure 4 As shown, the elastic buffer mechanism includes a telescopic tube 14 coaxially arranged with the fixed tube 1. The telescopic tube 14 comprises an inner tube 1401 and an outer tube 1402 that slide together. Preferably, the outer tube 1402 wraps around the outer tube 1401, and its inner wall slides with the inner tube 1401 via a clamp structure. The top of the outer tube 1402 is welded to the bottom of the fixed tube 1, and the bottom of the inner tube 1401 is welded to the top of the bottom tube 3. Preferably, based on existing experience with the maximum frost heave of soil, the outer tube 1402 and the inner tube 1401 overlap by 10 cm in the initial state, and the outer tube 1402 and the inner tube 1401 slide within a range of 5 cm. The gap between the outer wall of the telescopic tube 14, the upper insulation layer 18, and the inner wall of the bottom tube 3 forms a buffer chamber 15, within which are located several springs 16. The ends of the springs 16 are welded to the bottom of the fixed tube 1 and the top of the bottom tube 3, respectively. When pile foundation 6 is subjected to frost heave caused by frost heave, the sliding fit between bottom cylinder 3 and fixed cylinder 1 causes bottom cylinder 3 to first move upward along with pile foundation 6. At this point, the springs 16 located in buffer chamber 15 transition from a normal state to a compressed state. The compressed springs 16 exert a supporting force on bottom cylinder 3 that is opposite to the tangential frost heave force, thereby suppressing or slowing the upward movement of pile foundation 6 and ensuring the stability of pile foundation 6 under the action of frost heave.

[0028] The design of the telescopic cylinder 14 not only ensures a stable connection between the fixed cylinder 1 and the bottom cylinder 3, but also allows a certain degree of relative displacement between the two during frost heave and thaw settlement, thereby enhancing the stability of the overall antifreeze structure, improving its adaptability to frozen soil deformation, and enabling the pile foundation 6 to maintain its original bearing capacity and positional stability in a complex freeze-thaw cycle environment. In addition, the spring 16 provided in the buffer chamber 15 serves as the core part of the elastic buffer assembly and can effectively absorb and release frost heave force. In the winter frost heave stage, the spring 16 can absorb and disperse the frost heave force generated by the frozen soil, preventing it from directly acting on the pile foundation 6, thereby reducing the risk of the pile foundation 6 moving up. In the summer thaw settlement stage, as the frozen soil melts, the spring 16 gradually releases its stored energy, causing the bottom cylinder 3 to descend steadily, preventing the problem of pile foundation 6 freezing and pulling out due to insufficient settlement, thereby ensuring the long-term stability of the pile foundation 6 under seasonal freeze-thaw conditions.

[0029] Preferably, a heat insulation component is further provided on the outside of the bottom tube 3, and the heat insulation component can effectively block the heat exchange between the frozen soil and the pile foundation 6, thereby reducing the impact of the structure on the frozen ground temperature.

[0030] As a preferred Figure 4 As shown, in order to cope with the influence of temperature changes on the bearing capacity of the pile foundation 6, the thermal insulation assembly includes a lower thermal insulation layer 19 provided on the outer wall of the bottom cylinder 3. The antifreeze layer 17 is formed between the lower thermal insulation layer 19 and the bottom cylinder 3. The lower thermal insulation layer 19 is a flexible thermal insulation layer filled with aerogel. The flexible thermal insulation layer has good deformation coordination and is better adapted to the frost heave deformation of the bottom. Preferably, as shown in FIG. Figure 6 As shown, the lower insulation layer 19 is a composite shell structure of geotextile 1901 wrapped with aerogel 1902, which has excellent thermal insulation performance, can reduce the heat exchange between frozen soil and pile foundation 6, and inhibit the direct impact of temperature changes on the bearing capacity of pile foundation 6. Through this design, the stability of pile foundation 6 under different temperature conditions can be effectively maintained, ensuring the long-term reliability of the structure. Aerogel 1902 is a high-efficiency thermal insulation material with extremely low thermal conductivity, and its thermal insulation performance is far superior to traditional thermal insulation materials. Filling aerogel 1902 into the flexible geotextile 1901 can greatly reduce heat transfer, thereby significantly improving the thermal insulation effect of the entire insulation assembly.

[0031] The design of the flexible lower insulation layer 19 not only enables it to adapt to the slight deformation of the bottom tube 3 caused by temperature changes or external forces, but also ensures that the lower insulation layer 19 always fits tightly to the bottom tube 3, avoiding heat leakage due to gaps, and improving the stability and long-term reliability of the insulation system.

[0032] Furthermore, since the pile foundation 6 extends from the surface layer to the permafrost layer, the pile foundation 6 acts like a heat conductor during this process. When the surface temperature is higher than the permafrost layer temperature, the pile foundation 6 transfers surface heat to the permafrost layer, thereby affecting the physical properties of the permafrost surrounding the pile foundation 6 and causing thermal disturbances of the permafrost by the pile foundation 6. To this end, the bottom barrel 3 includes a fixedly connected upper bottom barrel 301 and a lower bottom barrel 302. The upper bottom barrel 301 is located within the roadbed, which is a coarse-grained, weakly frost-heaving soil. The lower bottom barrel 302 is primarily subject to the strong normal frost-heaving force of the base. The lower bottom barrel 302 is made of a shape memory alloy material, which contracts at temperatures below or equal to 0°C, expands at temperatures greater than or equal to 5°C, and maintains a fixed shape within the range of 0-5°C. This design enables the bottom barrel 3 to adaptively adjust its shape according to changes in ambient temperature, thereby adapting to frost heaving deformation at the bottom of the pile foundation 6.

[0033] like Figure 7 As shown, when the frozen soil temperature drops below 0°C, the sidewalls of the lower base tube 302 contract, causing the outer antifreeze layer 17 to thicken. This improves the deformation coordination ability of the antifreeze layer 17 and enhances its sensitivity to temperature drops. When the temperature rises above 5°C, the sidewalls of the lower base tube 302 expand, effectively filling the voids left by the thawing soil and preventing excessive deformation of the pile foundation 6 during the thawing process. This temperature-adaptive adjustment mechanism not only ensures the stability of the pile foundation 6 but also provides better protection in different seasonal conditions, ensuring the long-term stability and reliability of the structure.

[0034] There is a hollow structure between the fixed tube 1 and the pile foundation 6, which allows air circulation. When winter comes, the temperature of the air above the fixed tube 1 decreases, the density increases, and it flows downward, forcing the relatively high-temperature air below to move upward. The upward air is pre-cooled and the density increases, and it continues to flow downward. This forms a temperature-dominated forced convection. The cold air continues to descend, which can cool the bottom tube 3 as quickly as possible. This structure makes the temperature of the bottom tube 3 very sensitive to the atmospheric temperature. This also determines that the deformation of the bottom tube 3 is no later than the upward movement of the hydraulic rod 10, ensuring that the hydraulic rod 10 can well cope with the normal frost heave force.

[0035] Preferably, the bottom barrel 3 adopts a conical structure. The conical design effectively reduces the contact area between the bottom barrel 3 and the frozen soil, thereby reducing the effect of heat conduction. This design can effectively reduce the thermal disturbance of the pile foundation 6 on the physical properties of the frozen soil, further protecting the stability of the frozen soil and avoiding potential damage to the frozen soil caused by heat conduction from the pile foundation 6.

[0036] Example 3 In order to further optimize the structure, such as Figure 6As shown, a connector 20 is provided between the bottom cylinder 3 and the hydraulic chamber 7. The two ends of the connector 20 are respectively connected to the inner wall of the upper bottom cylinder 301 and the outer wall of the hydraulic chamber 7, and a liquid passage 21 is provided in the connector 20. One end of the liquid passage 21 is connected to the top of the pressure chamber 11, and the other end is connected to the antifreeze layer 17. During the freeze-drawing and lifting process of the pile foundation 6, the addition of the antifreeze layer 17 causes a part of the antifreeze liquid to flow from the pressure chamber 11 into the antifreeze layer 17, resulting in an increase in the volume of the antifreeze layer 17. Due to the filling of the antifreeze liquid, the antifreeze layer 17 further improves the thermal insulation performance of the side wall of the bottom cylinder 3, effectively slows down the heat exchange between the pile foundation 6 and the frozen soil, and ensures that the shrinkage deformation amplitude of the bottom cylinder 3 during the freeze-drawing and lifting period is controlled.

[0037] The design of the fluid passage 21 provides an additional circulation path for the antifreeze liquid, allowing the antifreeze liquid to flow not only between the pressure-bearing chamber 11 and the pressure-applying chamber 12 when the hydraulic buffer mechanism is operating, but also to enter the antifreeze layer 17, forming a more balanced thermal regulation system. The antifreeze layer 17 acts as an isolation barrier between the bottom tube 3 and the external environment, and has excellent thermal insulation properties. It can effectively reduce the heat exchange between the bottom tube 3 and the surrounding frozen soil, thereby protecting the thermal stability of the frozen soil and reducing the thermal disturbance of the pile foundation 6 to the permafrost. This design of dynamic circulation with the hydraulic buffer mechanism optimizes the circulation efficiency of the antifreeze liquid, improves the response speed and adjustment ability of the hydraulic buffer mechanism, and ensures the bearing stability and long-term reliability of the pile foundation 6 under extreme climatic conditions. When frost heave occurs, the movement of the piston 8 will compress the liquid in the pressure chamber 11, and at the same time form a negative pressure in the pressure chamber 12, thereby sucking the liquid in the pressure chamber 11 to ensure that the liquid fills the pressure chamber 12 first; and the excess liquid will be squeezed through the liquid channel 21 into the antifreeze layer 17, so that the volume of liquid discharged from the pressure chamber 11 is equal to the volume of liquid entering the antifreeze layer 17 and the pressure chamber 12.

[0038] Example 4 As attached Figure 8 As shown, a method for constructing a normal frost heave force control structure for a shallow-buried catenary pile foundation in a frozen soil region is constructed based on the normal frost heave force control structure for a shallow-buried catenary pile foundation in a frozen soil region described in Examples 1-3, comprising the following steps: S1, Construction Preparation: Clean and level the construction site, reasonably arrange the drilling machinery and material storage area, set up standardized safety protection measures, ensure that the working surface meets the requirements of frozen soil construction, and deploy a ground temperature monitoring system to grasp the changes in the thermal stability of frozen soil in real time.

[0039] S2, Pile foundation 6 positioning: Use total station for high-precision pile position layout, strictly control positioning error, set up permanent cross piles as construction reference points, and implement a three-level review system involving surveyors, technical leaders, and supervising engineers to ensure that the pile position coordinates are completely consistent with the design drawings.

[0040] S3, drilling and bottom shaping: Use a high-performance rotary drilling rig for staged drilling. The drill hole diameter is 10cm larger than the outer diameter of the bottom barrel. After drilling to the designed elevation, use a special profiling drill bit to accurately trim the bottom of the hole to ensure that the shape of the bottom of the hole fully matches the geometric dimensions of the hydraulic rod and the bottom of the bottom barrel.

[0041] S4, installation of control structures: Complete modular pre-assembly of the normal frost heave control structure for shallow-buried contact network pile foundations in permafrost areas on the ground, use lifting equipment in conjunction with a laser centering instrument to precisely lift the structure into place, and implement a two-person synchronous verification system to ensure that key parameters such as the structure's installation orientation and verticality meet design requirements.

[0042] S5, backfill and compaction: Use fine sand with a particle size of 0.25-0.5mm for layered backfilling, with each 30cm being a compaction layer. Use pneumatic compaction equipment to compact each layer, and control the compaction coefficient to be no less than 0.93 through penetration detection to ensure that the backfill body is tightly combined with the hole wall.

[0043] S6, overall acceptance: After the construction is completed, the entire structure is inspected to check whether the stability, thermal insulation performance and frost resistance of the pile foundation 6 meet the design requirements.

[0044] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas, characterized in that: It includes a fixed tube, a bottom tube and a pile foundation, of which: The side wall of the fixed cylinder is uniformly provided with a plurality of coupling grooves along the circumference, the outer wall of the fixed cylinder is provided with an upper heat insulation layer, and the position where the fixed cylinder and the bottom cylinder are connected is provided with an elastic buffer mechanism; A pile foundation is arranged inside the fixed cylinder, and a buffer gap is reserved between the outer wall of the pile foundation and the inner wall of the fixed cylinder. A plurality of diagonal braces are arranged in the buffer gap; the diagonal braces include an upper diagonal brace and a lower diagonal brace, wherein the two ends of the upper diagonal brace are fixedly connected to the pile foundation and the fixed cylinder respectively, and one end of the lower diagonal brace is fixed to the pile foundation, and the other end is against the inner wall of the fixed cylinder; A hydraulic buffer mechanism is provided at the lower part of the pile foundation, and the hydraulic buffer mechanism includes a hydraulic chamber fixed to the lower part of the pile foundation, a piston with a sealing ring, and a hydraulic rod. The hydraulic chamber is filled with antifreeze liquid, and the piston divides the hydraulic chamber into a pressure-bearing chamber and a pressure-applying chamber. A plurality of damping channels are provided on the side wall of the hydraulic chamber. The upper end of the hydraulic rod passes through an opening provided at the bottom of the hydraulic chamber and is fixedly connected to the bottom of the piston. The lower end of the hydraulic rod passes through the through port of the bottom cylinder and extends to the outside of the structure, and the hydraulic rod is welded to the through port.

2. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: With the height center line of the hydraulic chamber as the transverse center line, the openings at both ends of the plurality of damping channels are symmetrically arranged along the transverse center line, and the height difference between any one end opening of the plurality of damping channels and the transverse center line increases gradually.

3. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: The top of the pile foundation is at the same height as the top of the fixing tube.

4. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: Several upper diagonal braces and lower diagonal braces are arranged in a "Z"-shaped structure.

5. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: The elastic buffer mechanism includes a telescopic cylinder arranged coaxially with the fixed cylinder, and the telescopic cylinder includes an inner cylinder and an outer cylinder that are slidably matched. The outer cylinder is wrapped around the outside of the inner cylinder, the top of the outer cylinder is welded to the bottom end of the fixed cylinder, and the bottom end of the inner cylinder is welded to the top of the bottom cylinder. The gap between the outer wall of the telescopic cylinder and the upper insulation layer and the inner wall of the bottom cylinder forms a buffer cavity. Several springs are provided in the buffer cavity, and the two ends of the springs are respectively welded to the bottom end of the fixed cylinder and the top of the bottom cylinder.

6. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: A heat insulation component is provided on the outer side of the bottom cylinder.

7. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: The thermal insulation assembly includes a lower thermal insulation layer arranged on the outer side wall of the bottom tube, an antifreeze layer is formed between the lower thermal insulation layer and the bottom tube, the lower thermal insulation layer is a flexible thermal insulation layer filled with aerogel, the bottom tube includes an upper bottom tube and a lower bottom tube fixedly connected, and the material of the lower bottom tube is shape memory alloy.

8. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 1, characterized in that: The bottom cylinder is a conical structure.

9. The structure for controlling the normal frost heave force of shallow-buried contact network pile foundations in permafrost areas according to claim 7, characterized in that: A connecting piece is provided between the upper bottom cylinder and the hydraulic chamber. A liquid passage is provided in the connecting piece. One end of the liquid passage is communicated with the top of the pressure-bearing chamber, and the other end is connected to the antifreeze layer.

10. The construction method of the normal frost heave force control structure of the shallow buried catenary pile foundation in permafrost areas according to claim 1, characterized in that: The following steps are involved: S1, Construction Preparation: Clean and level the construction site, reasonably arrange drilling machinery and material storage areas, set up standardized safety protection measures, and deploy a ground temperature monitoring system; S2, Pile foundation positioning: Use a total station to perform high-precision pile position setting, control positioning errors, and set up permanent cross piles as construction benchmarks; S3, drilling and bottom shaping: Drilling is carried out in stages, with the diameter of the hole being 10 cm larger than the outer diameter of the bottom barrel. After drilling to the designed elevation, the bottom of the hole is precisely trimmed to ensure that the shape of the bottom of the hole fully matches the geometric dimensions of the hydraulic rod and the bottom of the bottom barrel; S4, installation of control structures: modular pre-assembly of the normal frost heave control structures for shallow-buried catenary pile foundations in permafrost areas is completed on the ground, and they are precisely hoisted into place using hoisting equipment and a laser alignment instrument. S5, backfill and compaction: Use fine sand with a particle size of 0.25-0.5mm for layered backfilling, and use pneumatic compaction equipment to compact each layer. The compaction coefficient is controlled to be no less than 0.93 through penetration test; S6, overall acceptance: After the construction is completed, the entire structure is inspected to check whether the stability of the pile foundation, thermal insulation performance and frost resistance meet the design requirements.

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