Permafrost region shallow buried catenary pile foundation normal frost heaving force prevention and control structure and construction method

Abstract

The application discloses a frozen soil area shallow-buried catenary pile foundation normal frost heaving force prevention structure and a construction method. A plurality of combination grooves are uniformly formed in the circumferential direction of the side wall of a fixing cylinder. An upper heat insulation layer is arranged on the outer wall of the fixing cylinder. An elastic buffer mechanism is arranged at the position where the fixing cylinder and a bottom cylinder are connected. 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. A plurality of inclined braces are arranged in the buffer gap. The inclined braces include upper inclined braces and lower inclined braces. The two ends of the upper inclined braces are fixedly connected with the pile foundation and the fixing cylinder respectively. One end of the lower inclined brace is fixed to the pile foundation, and the other end is abutted against the inner wall of the fixing cylinder. A hydraulic buffer mechanism is arranged at the lower part of the pile foundation. The inclined braces disperse the horizontal frost heaving force from the side. The elastic buffer mechanism and the hydraulic buffer mechanism work cooperatively. Through the double effects of elastic deformation and hydraulic damping, the normal frost heaving force is effectively offset.

Description

Technical Field

[0001] This invention relates to the field of construction technology for freeze-thaw deformation control, and in particular to a structure and construction method for controlling normal frost heave force of shallow buried contact wire pile foundation in frozen soil areas. Background Technology

[0002] The stable operation of electrified railways in permafrost regions is highly dependent on the long-term reliability of the 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 affect the pile foundation structure. This is especially true in permafrost degradation areas affected by climate warming, where the stability of the catenary pile foundations faces severe challenges. In traditional railway engineering in permafrost regions, subgrade filling significantly alters the original surface thermal balance, leading to a distortion in the depth distribution of the upper limit of permafrost, i.e., the top of the permafrost layer. Specifically, the upper limit of permafrost in the subgrade area exhibits a non-uniform rise, with the upper limit in the middle of the road being higher than that in the shoulder area. Since catenary pile foundations are typically located at the shoulder, the thickness and freezing development pattern of the active seasonal freeze-thaw layer at their location differ fundamentally from the natural surface. The subgrade freezing process is multidirectional, with freezing fronts developing simultaneously and superimposed from three directions: the road surface, the slope surface, and the upper limit of permafrost below the subgrade. This results in exceptionally complex freezing rates, moisture migration paths, and frost heave force distribution patterns around the piles. Especially in high-fill roadbed sections, due to structural space and load requirements, catenary pile foundations often adopt a shallow-buried design, with the main body of the piles even entirely located within the active layer of the roadbed, where the roadbed soil is typically weakly frost-susceptible. In this situation, the normal frost heave force at the pile base (the frost heave force acting on the pile base surface and perpendicular to the bottom surface) directly acts on the pile tip, causing uneven heaving, lateral displacement, and even structural damage to the pile. However, current prevention and control technologies for frost heave damage in catenary pile foundations mainly focus on reducing the impact of tangential frost heave force (the frost heave force acting parallel to the pile-soil contact surface), such as using low-friction coatings and improving backfill materials around the piles, while lacking effective technical means to control the normal frost heave force.

[0003] Therefore, it is urgent to propose a structure and construction method for controlling the normal frost heave force of shallow-buried contact wire pile foundations in frozen soil areas, so as to achieve efficient reduction of the normal frost heave force of the pile foundation and improve the stability of the pile body under shallow-buried conditions, thereby improving the stability and service life of the pile foundation. Summary of the Invention

[0004] The purpose of this invention is to address the technical deficiencies in the existing technology by providing a structure for controlling the normal frost heave force of shallow-buried contact wire pile foundations in frozen soil areas. Through the synergistic effect of hydraulic buffer mechanism and elastic buffer mechanism, it effectively alleviates the adverse effects of frost heave force in all directions during the frost pull-up process of the pile foundation, while reducing the interference of pile foundation heat conduction on the temperature field of frozen soil.

[0005] Another objective of this invention is to provide a construction method for the normal frost heave force control structure of the shallow buried contact wire pile foundation in the frozen soil area.

[0006] The technical solution adopted to achieve the purpose of this invention is:

[0007] A structure for controlling normal frost heave force of shallow-buried contact wire pile foundation in permafrost areas includes a fixed cylinder, a bottom cylinder, and pile foundations, wherein:

[0008] The side wall of the fixed cylinder is evenly provided with several connecting grooves along the circumference, the outer wall of the fixed cylinder is provided with an upper heat insulation layer, and an elastic buffer mechanism is provided at the connection position between the fixed cylinder and the bottom cylinder.

[0009] The fixed cylinder is equipped with a pile foundation. A buffer gap is reserved between the outer wall of the pile foundation and the inner wall of the fixed cylinder. Multiple diagonal braces are installed in the buffer gap. The diagonal braces include an upper diagonal brace and a lower diagonal brace. The two ends of the upper diagonal brace are fixedly connected to the pile foundation and the fixed cylinder, respectively. One end of the lower diagonal brace is fixed to the pile foundation, and the other end abuts against the inner wall of the fixed cylinder.

[0010] A hydraulic buffer mechanism is provided at the lower part of the pile foundation. The hydraulic buffer mechanism includes a hydraulic chamber fixed at the lower part of the pile foundation, a piston with a sealing ring, and a hydraulic rod. The hydraulic chamber is filled with antifreeze. The piston divides the hydraulic chamber into a pressure-bearing chamber and a pressure-applying chamber. Several damping channels are opened on the side wall of the hydraulic chamber. The upper end of the hydraulic rod passes through an opening at the bottom of the hydraulic chamber and is fixedly connected to the bottom of the piston. The lower end of the hydraulic rod extends through the opening of the bottom cylinder to the outside of the structure, and the hydraulic rod is welded to the opening.

[0011] In the above technical solution, the height centerline of the hydraulic chamber is taken as the transverse centerline, and the openings at both ends of a plurality of damping channels are symmetrically arranged along the transverse centerline, and the height difference between any one end opening of the plurality of damping channels and the transverse centerline increases progressively.

[0012] In the above technical solution, the top of the pile foundation is at the same height as the top of the fixed cylinder.

[0013] In the above technical solution, several upper and lower diagonal braces are arranged in a “Z” shape.

[0014] In the above technical solution, the elastic buffer mechanism includes a telescopic cylinder coaxially arranged with the fixed cylinder. The telescopic cylinder includes an inner cylinder and an outer cylinder that are slidably fitted. The outer cylinder wraps around the outside of the inner cylinder. The top end 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 end of the bottom cylinder. The gap between the outer wall of the telescopic cylinder and the inner wall of the upper heat insulation layer and the bottom cylinder forms a buffer cavity. Several springs are provided in the buffer cavity. The two ends of the springs are welded to the bottom end of the fixed cylinder and the top end of the bottom cylinder, respectively.

[0015] In the above technical solution, a heat insulation component is provided on the outer side of the bottom cylinder.

[0016] In the above technical solution, the heat insulation component includes a lower heat insulation layer disposed on the outer wall of the bottom cylinder, and an antifreeze layer is formed between the lower heat insulation layer and the bottom cylinder. The lower heat insulation layer is a flexible heat insulation layer filled with aerogel. The bottom cylinder includes an upper bottom cylinder and a lower bottom cylinder that are fixedly connected. The material of the lower bottom cylinder is a shape memory alloy.

[0017] In the above technical solution, the bottom cylinder has a conical structure.

[0018] In the above technical solution, a connecting member is provided between the upper bottom cylinder and the hydraulic cavity. A fluid passage is opened in the connecting member. One end of the fluid passage is connected to the top of the pressure-bearing cavity, and the other end is connected to the antifreeze layer.

[0019] Another aspect of the present invention includes a working method for a structure for controlling normal frost heave force based on shallow buried contact wire pile foundations in the frozen soil region, comprising the following steps:

[0020] During the pile extraction process, the elastic buffer mechanism compresses, absorbs, and buffers the frost heave force. The hydraulic rod moves vertically before the pile foundation. When it moves upward, it drives the piston to move towards the pressure chamber in the hydraulic chamber, causing the volume of the pressure chamber to shrink. When the antifreeze in the pressure chamber is subjected to hydraulic pressure, it flows towards the pressure chamber. When the antifreeze passes through the damping channel, the flow rate slows down due to the friction of the damping channel, resulting in a local pressure drop. This achieves active adjustment and energy dissipation of the normal frost heave force. In addition, as the piston rises, the number of damping channels available for antifreeze flow gradually decreases, the flow area between the pressure chamber and the pressure chamber gradually decreases, and the resistance of the damping channel to the flow of antifreeze also increases, thereby increasing the buffering and offsetting force.

[0021] During the settling stage, the elastic buffer mechanism returns from the compressed state to the normal state, and the antifreeze flows back from the pressure chamber to the pressure chamber. Due to the flow resistance of the damping channel, the decrease in the spring rebound force on the bottom cylinder is effectively slowed down.

[0022] Another aspect of the present invention includes a construction method for the shallow-buried contact wire pile foundation normal frost heave force control structure in frozen soil areas, comprising the following steps:

[0023] S1, Construction preparation: Clean and level the construction site, arrange drilling machinery and material storage areas in a reasonable manner, set up standardized safety protection measures, and deploy a ground temperature monitoring system;

[0024] S2, Pile foundation positioning: A total station is used to conduct high-precision pile position layout, control positioning error, and set permanent cross-shaped protective piles as construction benchmarks;

[0025] S3, Drilling and Hole Bottom Forming: Staged drilling, the drilling diameter is 10cm larger than the outer diameter of the bottom cylinder, and the bottom of the hole is precisely trimmed after drilling to the design elevation to ensure that the shape of the hole bottom is completely matched with the geometry of the hydraulic rod and the bottom of the bottom cylinder;

[0026] S4, Installation of control structure: The modular pre-assembly of the control structure for normal frost heave force of shallow buried contact network pile foundation in frozen soil area is completed on the ground, and the hoisting equipment is used in conjunction with a laser centering instrument for precise hoisting and positioning;

[0027] S5, Backfilling 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. Control the compaction coefficient to be no less than 0.93 through penetration test.

[0028] S6, Overall Acceptance: After construction is completed, the entire structure is inspected to check whether the stability, thermal insulation performance and frost resistance of the pile foundation meet the design requirements.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. This scheme employs a hydraulic buffer mechanism. Through the coordinated action of the hydraulic rod and piston, the hydraulic rod can preferentially respond to and transmit the frost heave force generated by the frozen soil on the pile foundation. When the frozen soil expands due to low temperature, the frost heave force first acts on the hydraulic rod, which acts as the force transmission medium. Its upward movement drives the piston to slide within the hydraulic chamber, thereby compressing the antifreeze in the pressure chamber. Since the antifreeze is incompressible and restricted by the damping channel, the pressure in the pressure chamber gradually increases. This pressure acts in the opposite direction on the hydraulic rod and piston system, providing a downward anti-frost heave force for the pile foundation. This effectively disperses and mitigates the impact of frost heave force on the pile foundation, preventing the pile from being uplifted due to frost heave and improving its stability in seasonally frozen soil areas.

[0031] 2. The diagonal bracing not only enhances the structural stability between the fixed cylinder and the pile foundation, but also effectively disperses the horizontal frost heave force from the sides (the lateral pressure exerted on the pile body in the horizontal direction when the soil around the pile frosts) through reasonable distribution and angle design. Simultaneously, since the shallow layer freezes first, the horizontal frost heave force compresses the upper part of the fixed cylinder, causing it to contract inwards and form a wedge-shaped variable cross-section structure, which better suppresses upward displacement of the structure. Furthermore, the upper insulation layer effectively reduces heat exchange between the pile foundation and the surrounding frozen soil, minimizing the thermal disturbance of the permafrost caused by the pile foundation's thermal conductivity, and ensuring the load-bearing stability of the pile foundation under extreme climatic conditions. This design comprehensively considers the stress conditions of the pile foundation in both horizontal and vertical directions, as well as the impact of temperature changes on its load-bearing capacity, thereby achieving comprehensive protection for the pile foundation.

[0032] 3. During the winter frost heave stage, the elastic buffer component and the hydraulic buffer mechanism work together to effectively counteract the normal frost heave force and suppress the upward movement of the pile foundation through the dual effects of elastic deformation and hydraulic damping. During the summer thaw settlement stage, as the frozen soil thaws, the bottom cylinder gradually descends under the rebound force of the elastic buffer component. Simultaneously, the antifreeze in the hydraulic chamber recovers with the shape of the bottom cylinder and flows back from the pressure chamber to the pressure bearing chamber under the guidance of the piston. The flow is restricted by the damping channel, thus slowing down the descent speed of the bottom cylinder, preventing excessive rebound force from causing excessive pile foundation settlement, improving the pile foundation's adaptability to seasonal changes, and ensuring the stability and safety of the hydraulic mechanism during long-term use. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the shallow buried contact wire pile foundation normal frost heave force control structure in frozen soil areas according to the present invention.

[0034] Figure 2 This is an isometric sectional view of the normal frost heave force control structure for shallow buried contact wire pile foundations in frozen soil areas according to the present invention.

[0035] Figure 3 This is an axonometric sectional view of the bottom cylinder in the normal frost heave force control structure for shallow buried contact wire pile foundations in frozen soil areas according to the present invention.

[0036] Figure 4 This is an isometric sectional view of the lower structure of the shallow buried contact wire pile foundation normal frost heave force control structure in frozen soil areas according to the present invention.

[0037] Figure 5 This is a schematic diagram of the arrangement of diagonal bracing in the normal frost heave force control structure of shallow buried contact wire pile foundation in frozen soil area according to the present invention.

[0038] Figure 6 This is a schematic diagram of the arrangement of connectors in the normal frost heave force control structure of shallow buried contact network pile foundation in frozen soil area according to 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.

[0039] Figure 7 This is a schematic diagram showing the initial state (a) and the filled state (b) of the antifreeze layer in the normal frost heave force control structure of the shallow buried contact wire pile foundation in the frozen soil area of ​​the present invention.

[0040] Figure 8 This is a schematic diagram of the construction method of the present invention.

[0041] 1. Fixed cylinder; 2. Connecting 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-hole; 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 insulation layer; 19. Lower insulation layer; 1901. Geotextile; 1902. Aerogel; 20. Connector; 21. Liquid passage. Detailed Implementation

[0042] 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 merely illustrative of the invention and are not intended to limit the invention.

[0043] Example 1

[0044] like Figure 1 , Figure 2 , Figure 5 As shown, a structure for controlling normal frost heave force of shallow buried contact wire pile foundation in frozen soil areas includes three main parts: a fixed cylinder 1, a bottom cylinder 3, and a pile foundation 6.

[0045] The sidewall of the fixed cylinder 1 is evenly provided with several connecting grooves 2 along its circumference. The design of the connecting grooves 2 can improve the deformation coordination ability of the fixed cylinder 1 under frost heave, making it better adapt to the influence of frost heave force. An upper heat insulation layer 18 is sleeved on the outside of the fixed cylinder 1, and the bottom cylinder 3 is slidably connected to the bottom of the fixed cylinder 1. The upper heat insulation layer 18 can isolate the fixed cylinder 1 from direct contact with the soil and reduce tangential frost heave force. The connecting grooves 2 can reduce horizontal frost heave force, and the bottom cylinder 3 can reduce the supporting effect of normal frost heave force on the bottom of the pile foundation 6.

[0046] The combined effect of tangential and normal frost heave forces may cause frost pull-up of pile foundation 6. To control the impact of vertical frost pull-up on pile foundation 6, an elastic buffer mechanism is installed at the connection between the fixed cylinder 1 and the bottom cylinder 3. The elastic buffer mechanism dynamically adjusts the tangential anti-frost heave force according to the magnitude of the tangential frost heave force, which can effectively absorb and buffer 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 frost heave force on pile foundation 6.

[0047] The fixed cylinder 1 houses a pile foundation 6. A buffer gap is provided between the outer wall of the pile foundation 6 and the inner wall of the fixed cylinder 1. Multiple diagonal braces 4 are installed within this buffer gap. Each diagonal brace 4 includes an upper diagonal brace 401 and a lower diagonal brace 402. The two ends of the upper diagonal brace 401 are fixedly connected to the pile foundation 6 and the fixed cylinder 1, respectively. One end of the lower diagonal brace 402 is fixed to the pile foundation 6, and the other end abuts against the inner wall of the fixed cylinder 1. Preferably, to control the impact of horizontal frost heave 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 cylinder 1, and several diagonal braces 4 are provided between the outer wall of the pile foundation 6 and the fixed cylinder 1, specifically as follows: Figure 5 As shown, several upper diagonal braces 401 and lower diagonal braces 402 are arranged in a "Z" shape, which can effectively disperse and consume the influence of horizontal frost heave force and increase the horizontal bearing capacity of the fixed cylinder 1 and the pile foundation 6.

[0048] The Z-shaped arrangement of the upper and lower diagonal braces 401 and 402 more efficiently disperses and resists horizontal frost heave forces from the sides. Compared to traditional straight diagonal braces, this layout provides a longer lever arm and more support points with the same amount of material, thus significantly improving the stability and load-bearing capacity of the overall control structure. In permafrost regions, this design is particularly crucial for preventing the pile foundation 6 from tilting or being damaged by horizontal frost heave forces, ensuring the long-term stability and structural safety of the pile foundation 6 in complex freeze-thaw environments.

[0049] like Figure 2 and Figure 3 As shown, a hydraulic buffer mechanism is provided at the lower part of the pile foundation 6. The hydraulic buffer mechanism includes a hydraulic chamber 7 fixed to the lower part 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. The piston 8 divides the hydraulic chamber 7 into a pressure-bearing chamber 11 at the upper part and a pressure-applying chamber 12 at the lower part. A damping channel 13 is provided on the side wall of the hydraulic chamber 7 to connect 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 cylinder 3 to the outside of the bottom cylinder 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 antifreeze leakage.

[0050] When the bottom of pile 6 is subjected to normal frost heave force, the hydraulic rod 10 will move vertically before pile 6. As it moves upward, it drives the piston 8 to move towards the pressure chamber 11 within the hydraulic chamber 7, causing the pressure chamber 11 to shrink in volume. To utilize the hydraulic pressure generated by the shrinkage of the pressure chamber 11, several damping channels 13 are designed to be formed on the sidewall of the hydraulic chamber 7, specifically as follows... Figure 3As shown. Preferably, with the height centerline of the hydraulic chamber 7 as the transverse centerline, the openings at both ends of a 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 progressively.

[0051] As the height difference between any end of the damping channel 13 and the center line increases, during the movement of the piston 8, some openings will be gradually blocked by the piston 8 and the sealing ring 9, causing a change in the pressure difference required for the antifreeze to flow through the damping channel 13. This design achieves dynamic adjustment against frost heave force, automatically adjusting according to the amount of frost pull-out of the pile foundation 6 or the magnitude of the frost heave force, ensuring flexible response of the control structure under different working conditions. This mechanism avoids excessive restriction on the movement of the pile foundation 6, preventing excessive constraint on the pile foundation 6 and resulting in structural stress concentration, while also preventing the pile foundation 6 from becoming unstable due to excessive stress, effectively balancing the stability and adaptability of the pile foundation 6, thereby improving its long-term reliability in seasonal freeze-thaw environments.

[0052] Specifically, when the antifreeze in the pressure chamber 11 is subjected to hydraulic pressure and flows to the pressure chamber 12, the damping channel 13 functions similarly to a damping orifice in a conventional hydraulic system. As the antifreeze passes through the damping channel 13, its flow rate slows due to friction, resulting in a local pressure drop, thus achieving active regulation and energy dissipation of the normal frost heave force. Furthermore, as the piston 8 rises, the number of damping channels 13 available for antifreeze flow gradually decreases, the flow area between the pressure chamber 11 and the pressure chamber 12 gradually decreases, and the resistance of the damping channel 13 to the antifreeze flow increases accordingly, thereby increasing the buffering force. The dynamic adjustment of the hydraulic buffering force helps improve the service life of the hydraulic buffer mechanism and enhances the pile foundation 6's effectiveness in controlling the normal frost heave force. In addition, when the normal frost heave force is transmitted to the pile foundation 6 through the hydraulic rod 10, the diagonal brace 4 can also convert part of the vertical frost heave force into a horizontal supporting force radiating outwards from the pile foundation 6, reducing the risk of deformation of the pile foundation 6 and the fixed cylinder 1 under the action of horizontal frost heave force.

[0053] By combining the elastic buffer mechanism and the hydraulic buffer mechanism, during the pull-out process of pile 6, both can jointly counteract the normal frost heave force, thereby mitigating the tendency of pile 6 to freeze and pull out. During the thawing and settlement phase of the frozen soil in summer, the hydraulic buffer mechanism and the elastic buffer mechanism work together. When the elastic buffer mechanism returns from the compressed state to the normal state, as the bottom cylinder 3 descends, the antifreeze in the hydraulic chamber 7 flows back from the pressure chamber 12 to the pressure chamber 11 along with the fall of the piston 8. This process is also affected by the flow resistance of the damping channel 13, effectively mitigating the impact of the rebound force of the elastic buffer mechanism on the bottom cylinder 3, and avoiding the risk of excessive settlement of pile 6 due to excessive rebound force.

[0054] Example 2

[0055] This embodiment is a further optimization based on Embodiment 1.

[0056] like Figure 4 As shown, the elastic buffer mechanism includes a telescopic cylinder 14 coaxially arranged with the fixed cylinder 1. The telescopic cylinder 14 includes an inner cylinder 1401 and an outer cylinder 1402 that are slidably fitted together. Preferably, the outer cylinder 1402 wraps around the outside of the inner cylinder 1401. The inner wall of the outer cylinder 1402 is slidably fitted with the inner cylinder 1401 through a clamp structure. The top end of the outer cylinder 1402 is welded to the bottom end of the fixed cylinder 1, and the bottom end of the inner cylinder 1401 is welded to the top end of the bottom cylinder 3. The gap between the outer wall of the telescopic cylinder 14 and the upper insulation layer 18 and the inner wall of the bottom cylinder 3 forms a buffer cavity 15, and a plurality of springs 16 are provided in the buffer cavity 15. The two ends of the springs 16 are welded to the bottom end of the fixed cylinder 1 and the top end of the bottom cylinder 3, respectively. When the pile foundation 6 is subjected to frost heave caused by frost heave force, the sliding fit between the bottom cylinder 3 and the fixed cylinder 1 causes the bottom cylinder 3 to move upward with the pile foundation 6 first. At this time, several springs 16 located in the buffer cavity 15 will change from the normal state to the compressed state. The compressed springs 16 will apply a supporting force to the bottom cylinder 3 that is opposite to the tangential frost heave force, thereby inhibiting or slowing down the upward trend of the pile foundation 6 and ensuring the stability of the pile foundation 6 under the action of frost heave force.

[0057] 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 for a certain degree of relative displacement between the two during frost heave and thaw settlement, thereby enhancing the stability of the overall anti-freeze structure and improving its adaptability to frozen soil deformation. This allows the pile foundation 6 to maintain its original bearing capacity and positional stability even in complex freeze-thaw cycles. Furthermore, the spring 16 installed within the buffer cavity 15, as the core component of the elastic buffer assembly, effectively absorbs and releases frost heave forces. During the winter frost heave phase, the spring 16 absorbs and disperses the frost heave forces generated by the frozen soil, preventing them from directly acting on the pile foundation 6, thus reducing the risk of upward displacement of the pile foundation 6. During the summer thaw settlement phase, as the frozen soil thaws, the spring 16 gradually releases its stored energy, allowing the bottom cylinder 3 to descend smoothly, preventing the pile foundation 6 from being pulled out due to insufficient settlement, thereby ensuring the long-term stability of the pile foundation 6 under seasonal freeze-thaw conditions.

[0058] Preferably, a heat insulation component is also provided on the outside of the bottom cylinder 3. 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 temperature of the frozen soil.

[0059] As a preferred option, such as Figure 4 As shown, to address the impact of temperature changes on the bearing capacity of the pile foundation 6, the thermal insulation component includes a lower thermal insulation layer 19 disposed on the outer wall of the bottom cylinder 3. The lower thermal insulation layer 19 forms the antifreeze layer 17 between itself and the bottom cylinder 3. The lower thermal insulation layer 19 is a flexible thermal insulation layer internally filled with aerogel. This flexible thermal insulation layer has good deformation compatibility, better adapting to frost heave deformation at the bottom. Preferably, as shown... Figure 6As shown, the lower insulation layer 19 is a composite shell structure of geotextile 1901 wrapping aerogel 1902, which has excellent thermal insulation performance. It can reduce heat exchange between frozen soil and pile foundation 6, and suppress the direct impact of temperature changes on the bearing capacity of pile foundation 6. This design effectively maintains the stability of pile foundation 6 under different temperature conditions, ensuring the long-term reliability of the structure. Aerogel 1902 is a highly efficient thermal insulation material with extremely low thermal conductivity, and its thermal insulation performance is far superior to traditional thermal insulation materials. Filling the flexible geotextile 1901 with aerogel 1902 can significantly reduce heat transfer, thereby significantly improving the thermal insulation effect of the entire insulation component.

[0060] The flexible lower insulation layer 19 is designed to not only adapt to the slight deformation of the bottom cylinder 3 under temperature changes or external forces, but also ensure that the lower insulation layer 19 always fits tightly against the bottom cylinder 3, avoiding heat leakage due to gaps, and improving the stability and long-term reliability of the insulation system.

[0061] Furthermore, since the pile foundation 6 penetrates from the surface layer to the frozen soil layer, it acts as a heat conductor during this process. When the surface temperature is higher than the frozen soil temperature, the pile foundation 6 will transfer surface heat to the frozen soil layer, thereby affecting the physical properties of the frozen soil around the pile foundation 6 and causing thermal disturbance to the frozen soil. To address this, the bottom cylinder 3 includes a fixedly connected upper bottom cylinder 301 and a lower bottom cylinder 302. The upper bottom cylinder 301 is located inside the roadbed, which is coarse-grained, weakly frost-susceptible soil. The lower bottom cylinder 302 is mainly subjected to the strong normal frost heave force of the base. The lower bottom cylinder 302 is made of shape memory alloy material, which shrinks when the temperature is below or equal to 0°C and expands when the temperature is above or equal to 5°C, maintaining a fixed shape within the range of 0 to 5°C. This design allows the bottom cylinder 3 to adaptively adjust its shape according to changes in ambient temperature, thereby adapting to the frost heave deformation at the bottom of the pile foundation 6.

[0062] like Figure 7 As shown, when the frozen soil temperature drops below 0℃, the sidewalls of the lower cylinder 302 shrink, causing the outer antifreeze layer 17 to thicken, thereby improving the deformation coordination ability of the antifreeze layer 17 and enhancing its sensitivity to temperature drops. Conversely, when the temperature rises above 5℃, the sidewalls of the lower cylinder 302 expand, effectively filling the pores after soil thawing and settling, thus preventing excessive deformation of the pile foundation 6 during thawing. This temperature-adaptive regulation mechanism not only ensures the stability of the pile foundation 6 but also provides better protection under different seasonal conditions, ensuring the long-term stability and reliability of the structure.

[0063] The space between the fixed cylinder 1 and the pile foundation 6 is a hollow structure, allowing air circulation. In winter, the air temperature in the upper part of the fixed cylinder 1 decreases while its density increases, causing it to flow downwards. This forces the relatively warmer air in the lower part to rise, and the rising air, pre-cooled and denser, continues to flow downwards. This creates temperature-driven forced convection, with the cold air continuously descending to cool the bottom cylinder 3 most quickly. This structure makes the temperature of the bottom cylinder 3 highly sensitive to atmospheric temperature. This also ensures that the deformation of the bottom cylinder 3 is no later than the upward movement of the hydraulic rod 10, guaranteeing that the hydraulic rod 10 effectively withstands the normal frost heave force.

[0064] Preferably, the bottom cylinder 3 adopts a conical structure. The conical structure effectively reduces the contact area between the bottom cylinder 3 and the frozen soil, thereby reducing the effect of heat conduction. This design can effectively reduce the thermal disturbance of the frozen soil's physical properties by the pile foundation 6, further protect the stability of the frozen soil, and avoid potential damage to the frozen soil caused by the heat conduction of the pile foundation 6.

[0065] Example 3

[0066] To further optimize the structure, such as Figure 6 As shown, a connecting member 20 is provided between the bottom cylinder 3 and the hydraulic chamber 7. The two ends of the connecting member 20 are connected to the inner wall of the upper bottom cylinder 301 and the outer wall of the hydraulic chamber 7, respectively, and a fluid passage 21 is formed inside the connecting member 20. One end of the fluid passage 21 communicates with the top of the pressure chamber 11, and the other end is connected to the antifreeze layer 17. During the freezing and lifting process of the pile foundation 6, the addition of the antifreeze layer 17 causes some antifreeze 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 antifreeze, the antifreeze layer 17 further improves the heat insulation performance of the side wall of the bottom cylinder 3, effectively slowing down the heat exchange between the pile foundation 6 and the frozen soil, ensuring that the shrinkage deformation of the bottom cylinder 3 during freezing and lifting is controlled.

[0067] The design of the fluid passage 21 provides an additional circulation path for the antifreeze, allowing it to flow not only between the pressure chamber 11 and the pressure application chamber 12 during the operation of the hydraulic buffer mechanism, but also into the antifreeze layer 17, forming a more balanced thermostatic regulation system. The antifreeze layer 17, acting as an isolation barrier between the bottom cylinder 3 and the external environment, possesses excellent thermal insulation properties, effectively reducing heat exchange between the bottom cylinder 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, which dynamically circulates with the hydraulic buffer mechanism, optimizes the antifreeze circulation efficiency, improves the response speed and adjustment capability of the hydraulic buffer mechanism, and ensures the bearing stability and long-term reliability of the pile foundation 6 under extreme climatic conditions.

[0068] Example 4

[0069] As attached Figure 8As shown, a construction method for a shallow-buried contact wire pile foundation normal frost heave force control structure in permafrost areas is carried out based on the shallow-buried contact wire pile foundation normal frost heave force control structure described in Examples 1-3, including the following steps:

[0070] S1, Construction Preparation: Clean and level the construction site, arrange drilling machinery and material storage areas in a reasonable manner, set up standardized safety protection measures, ensure that the working surface meets the requirements for frozen soil construction, and at the same time set up a ground temperature monitoring system to monitor the changes in the thermal stability of frozen soil in real time.

[0071] S2, Pile Foundation 6 Positioning: A total station is used for high-precision pile location layout, and positioning errors are strictly controlled. Permanent cross-shaped protective piles are set as construction benchmarks. A three-level verification system involving surveyors, technical supervisors, and supervising engineers is implemented to ensure that the pile location coordinates are completely consistent with the design drawings.

[0072] S3, Drilling and Hole Bottom Forming: A high-performance rotary drilling rig is used for staged drilling. The borehole diameter is 10cm larger than the outer diameter of the bottom cylinder. After drilling to the design elevation, a special profile drill bit is used to precisely trim the bottom of the hole to ensure that the shape of the bottom of the hole is completely matched with the geometric dimensions of the hydraulic rod and the bottom of the bottom cylinder.

[0073] S4, Installation of the control structure: The modular pre-assembly of the control structure for normal frost heave force of shallow buried contact network pile foundation in frozen soil area is completed on the ground. The hoisting equipment is used in conjunction with the laser alignment instrument for precise hoisting and positioning. A dual-person synchronous verification system is implemented to ensure that the key parameters such as the orientation and verticality of the structure meet the design requirements.

[0074] S5, Backfilling and Compaction: Use fine sand with a particle size of 0.25-0.5mm for backfilling in layers. Each 30cm layer is a compaction layer. Use pneumatic compaction equipment to compact each layer. Control the compaction coefficient to be no less than 0.93 through penetration test to ensure that the backfill body is tightly bonded to the hole wall.

[0075] S6, Overall Acceptance: After construction is completed, the entire structure will be inspected to check whether the stability, thermal insulation performance and frost resistance of pile foundation 6 meet the design requirements.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A frozen soil area shallow buried catenary pile foundation normal frost heaving force prevention structure, characterized in that, The utility model relates to a pile foundation structure, including fixed cylinder, bottom cylinder and pile foundation, wherein: The side wall of the fixed cylinder is uniformly provided with a plurality of combination grooves along the circumference, and the outer wall of the fixed cylinder is provided with an upper heat insulation layer; the fixed cylinder and the bottom cylinder are connected through an elastic buffering mechanism; The pile foundation is arranged in the fixed cylinder, a buffering gap is reserved between the outer wall of the pile foundation and the inner wall of the fixed cylinder, and a plurality of inclined braces are arranged in the buffering gap; the inclined braces include upper inclined braces and lower inclined braces, wherein the two ends of the upper inclined braces are fixedly connected with the pile foundation and the fixed cylinder respectively, one end of the lower inclined braces is fixed on the pile foundation, and the other end abuts against the inner wall of the fixed cylinder; A hydraulic buffering mechanism is arranged at the lower part of the pile foundation, the hydraulic buffering mechanism includes a hydraulic cavity fixed to the lower part of the pile foundation, a piston with a sealing ring, and a hydraulic rod, the hydraulic cavity is filled with anti-freezing liquid, the piston divides the hydraulic cavity into a pressure-bearing cavity and a pressure-exerting cavity, a plurality of damping channels are formed in the side wall of the hydraulic cavity, the upper end of the hydraulic rod is fixedly connected with the bottom of the piston after penetrating through an opening formed in the bottom of the hydraulic cavity, the lower end of the hydraulic rod extends to the outside of the structure through a through hole of the bottom cylinder, and the hydraulic rod is welded with the through hole; The elastic buffering mechanism includes a telescopic cylinder coaxially arranged with the fixed cylinder, the telescopic cylinder includes an inner cylinder and an outer cylinder in sliding fit, the outer cylinder is wrapped outside the inner cylinder, the top end of the outer cylinder is welded with the bottom end of the fixed cylinder, the bottom end of the inner cylinder is welded with the top end of the bottom cylinder, a buffering cavity is formed between the outer wall of the telescopic cylinder and the upper heat insulation layer and the inner wall of the bottom cylinder, a plurality of springs are arranged in the buffering cavity, and the two ends of the springs are welded with the bottom end of the fixed cylinder and the top of the bottom cylinder respectively; An insulating assembly is arranged outside the bottom cylinder; The insulating assembly includes a lower heat insulation layer arranged on the outer side wall of the bottom cylinder, a freezing prevention layer is formed between the lower heat insulation layer and the bottom cylinder, the lower heat insulation layer is a flexible heat insulation layer filled with aerogel, the bottom cylinder includes an upper bottom cylinder and a lower bottom cylinder fixedly connected, and the material of the lower bottom cylinder is shape memory alloy; A connecting piece is arranged between the upper bottom cylinder and the hydraulic cavity, a liquid passing channel is formed in the connecting piece, one end of the liquid passing channel is communicated with the top of the pressure-bearing cavity, and the other end is connected with the freezing prevention layer.

2. The permafrost shallow-buried overhead contact system pile foundation normal frost-heave force prevention structure of claim 1, wherein, The height difference between the opening at one end of the plurality of damping channels and the transverse center line increases gradually.

3. The permafrost shallow-buried overhead contact system pile foundation normal frost-heave force prevention structure according to claim 1, characterized in that, The top end of the pile foundation is at the same height as the top end of the fixed cylinder.

4. The permafrost shallow buried overhead contact system pile foundation normal frost heaving force prevention structure according to claim 1, characterized in that, The plurality of upper inclined braces and lower inclined braces are arranged in a "Z" shape in sequence.

5. The permafrost shallow buried overhead contact system pile foundation normal frost heaving force prevention structure according to claim 1, characterized in that, The bottom cylinder is in a conical structure.

6. The construction method of the normal freezing force prevention structure of the shallow buried overhead contact system pile foundation in the permafrost region according to claim 1, characterized in that, The utility model relates to a pile foundation structure, including the following steps: S1, construction preparation: clean up and level the construction site, reasonably arrange the drilling machinery and material stacking area, set up standard safety protection measures, and lay out the ground temperature monitoring system; S2, pile foundation positioning: high-precision pile position lofting is carried out by using a total station, positioning error is controlled, and a permanent cross guard pile is set as a construction reference point; S3, drilling and hole bottom forming: grading drilling, the drilling diameter is 10cm larger than the outer diameter of the bottom cylinder, the hole bottom is accurately trimmed after drilling to the design elevation, and the hole bottom shape is ensured to be completely matched with the geometric size of the hydraulic rod and the bottom of the bottom cylinder; S4, installation of prevention and control structure: the modular pre-assembly of the normal frost heaving force prevention and control structure of the shallow-buried catenary pile foundation method in the frozen soil area is completed on the ground, and precise lifting into position is carried out by using lifting equipment in cooperation with a laser centering instrument; S5, backfilling and compaction: fine sand with a particle size of 0.25-0.5 mm is selected for layered backfilling, pneumatic tamping equipment is used for layer-by-layer compaction, and the compaction coefficient is controlled to be not less than 0.93 through penetration detection; S6, overall acceptance: after the construction is completed, the overall acceptance of the entire structure is carried out, and whether the stability, heat insulation performance and frost resistance of the pile foundation meet the design requirements are checked.

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