Integrated prevention and control system and design method for road engineering diseases in permafrost regions

Abstract

The application provides a permafrost region road engineering disease integrated prevention and control system and a design method, the system comprises a foundation unit, a roadbed unit and a drainage unit, the roadbed unit is arranged above the foundation unit, and the drainage unit is arranged in the roadbed unit; the roadbed unit comprises a roadbed slope, a roadbed layer and a pavement layer arranged on the upper surface of the roadbed layer, the pavement layer comprises a base layer and a surface layer arranged on the upper surface of the base layer, a waterproof layer is arranged between the base layer and the surface layer; the drainage unit comprises water permeable pipes arranged on both sides of the pavement layer and a geotechnical drainage layer arranged in the roadbed layer, and the geotechnical drainage layer extends out of the roadbed layer. The application effectively avoids the defects that most permafrost road section disease treatment measures in the prior art only rely on single roadbed temperature control measures, improves the permafrost region road disease prevention and control design concept, and greatly improves the permafrost region road construction and maintenance ability.

Description

Technical Field

[0001] This invention belongs to the field of road engineering construction and maintenance technology, and in particular relates to an integrated prevention and control system and design method for road engineering defects in permafrost regions. Background Technology

[0002] Permafrost generally refers to various rocks or soils that are below zero degrees Celsius and contain ice. Permafrost includes transient permafrost, seasonal permafrost, and perennial permafrost, with perennial permafrost referring to soil layers that remain frozen for more than two years.

[0003] The construction of road infrastructure in permafrost regions alters the original water and heat exchange between the natural permafrost surface and the surrounding atmosphere, further deteriorating the permafrost environment and causing rapid degradation. In particular, the strong heat absorption effect of wide black asphalt pavements leads to a continuous increase in the thickness of the active layer of the permafrost foundation, resulting in increasingly severe road surface and subgrade subsidence, slippage cracking, water and mud accumulation, and other problems. The long-term stability of permafrost subgrade engineering is crucial for ensuring safe road operation. In recent years, to reduce the adverse effects of permafrost degradation on road service safety, a series of protective measures have been adopted during the construction of projects such as the Qinghai-Tibet Highway and the Gongyu Expressway, including rubble roadbeds, heat pipes, ventilation ducts, insulation boards, and their combined structures. However, while these measures are effective in the early stages of road construction, their medium- and long-term preventative effects are less than ideal. Many permafrost road sections commonly experience subsidence, deformation, slippage cracking, and other problems after 5 to 10 years of operation. The fundamental reason is that these measures, from proposal and design to construction, are all based on the concept of "subgrade temperature control". By reducing the heat transfer effect of the subgrade, they ignore the influence of internal and external factors such as permafrost temperature, fine particle content, and rain and snow melting infiltration. This inevitably results in very limited treatment of diseases and may even accelerate permafrost degradation to some extent.

[0004] Furthermore, the distribution of soil moisture field and the migration patterns of water under the complex temperature gradient-vehicle dynamic load coupling effect are also important factors affecting the occurrence and development of road defects. Rain and snowmelt seep into the roadbed and foundation from the road surface, shoulders, and slopes, especially at the foot of slopes where the soil is often in a highly saturated or completely saturated state. According to the field survey report of the Qinghai-Tibet Highway section, waterlogged sections account for more than 87% of the total length of road defects. Therefore, the impact of poor drainage on the service safety of permafrost roads cannot be ignored. At present, there is no unified understanding of this issue at home and abroad, and the complex sources and replenishment of water make it difficult to control road defects from the perspective of water management.

[0005] Chinese invention patent application CN115897317A discloses a permafrost roadbed structure, which includes a solar power generation system, a thermal circulation temperature control system, and a permafrost roadbed. The solar power generation system is electrically connected to the thermal circulation temperature control system to provide power to it. The thermal circulation temperature control system includes a compressor, an electronic control valve, a condenser, an upper flat copper pipe, a one-way valve assembly, a throttle valve, and a lower flat copper pipe. The permafrost roadbed consists of a pavement structure layer, a roadbed body, and a replacement layer. The upper flat copper pipe is located at the bottom of the pavement structure layer, and the lower flat copper pipe is located at the bottom of the replacement layer. This patent utilizes solar energy resources for green thermal regulation of the permafrost roadbed through a solar power generation system and achieves two thermal circulation processes through a thermal circulation system. This can both cool and prevent permafrost degradation and accelerate snow and ice melting, ensuring road traffic capacity. However, this patent has high power consumption, which does not conform to the concept of green road design, and it does not propose clear drainage measures, so rainwater infiltration inevitably accelerates permafrost degradation.

[0006] Chinese invention patent application CN109811748A discloses a method for treating highway subgrade in permafrost areas, including the following steps: a. Pre-thawing the permafrost subgrade within the thawing depth line; b. Excavating all thawed soil; c. Laying a layer of coarse-grained soil and a filter layer at the bottom of the excavated layer, while laying a water-resistant layer of lime-soil and a gravel expansion-conducting layer on both sides; d. Filling and compacting the carbonized silt with active magnesium oxide layer layer by layer; e. Compacting and filling the embankment backfill and setting a layer of coarse-grained soil containing XPS insulation board below the pavement structure; f. Installing water-resistant toe protection on both sides of the embankment. This patent combines pre-thawing and replacement treatment of subgrade in permafrost areas with carbonization and solidification technology for weak soil, effectively reinforcing the permafrost subgrade, effectively avoiding engineering problems such as subgrade soil refreezing and frost heave, further reducing uneven settlement of the subgrade, and significantly reducing secondary diseases of highways in cold regions. However, this patent inevitably disturbs the surrounding permafrost during the excavation and construction process, causing safety hazards.

[0007] Chinese invention patent application CN114775354A discloses a prefabricated sheet pile composite pavement structure for traversing the permafrost region of the Qinghai-Tibet Plateau. The structure is mainly composed of bearing piles and support plates to solve the problem of reduced bearing capacity caused by the melting of permafrost. However, the structure is expensive to build and complex to construct, and cannot meet the needs of large-scale promotion and application. Summary of the Invention

[0008] The purpose of this invention is to provide an integrated prevention and control system and design method for road engineering defects in permafrost regions, so as to solve the technical problem of insufficient concepts and design methods for the prevention and control of road engineering defects in permafrost regions.

[0009] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0010] An integrated prevention and control system for road engineering defects in permafrost regions is disclosed. The system includes a foundation unit, a roadbed unit, and a drainage unit. The roadbed unit is disposed above the foundation unit, and the drainage unit is disposed within the roadbed unit.

[0011] The foundation unit includes a water temperature monitoring system and multiple sets of spaced pipe pile bodies. Each pipe pile body is equipped with a freezing pipe. One end of the freezing pipe is connected to the outlet pipe of the liquid nitrogen storage tank, and the other end of the freezing pipe is connected to the inlet pipe of the liquid nitrogen storage tank. The pipe pile body is filled with a heat-conducting medium around the freezing pipe.

[0012] The roadbed unit includes a roadbed slope, a roadbed base, and a pavement layer disposed on the upper surface of the roadbed base. The pavement layer includes a base layer and a surface layer disposed on the upper surface of the base layer, and a waterproof layer is provided between the base layer and the surface layer.

[0013] The drainage unit includes permeable pipes installed on both sides of the pavement layer and a geotextile drainage layer installed within the subgrade, the geotextile drainage layer extending from within the subgrade.

[0014] Therefore, this invention collects and guides a portion of the infiltrated water out through a pre-embedded geotechnical drainage layer. Permeable pipes vertically collect water from different cross-sections and discharge it longitudinally. A waterproof layer prevents surface water from flowing into the base layer, ensuring the effectiveness of the entire road drainage system. The drainage unit of this invention effectively inhibits the formation of stagnant water within the roadbed, reduces the moisture content of the roadbed and its underlying subgrade, mitigates freeze-thaw cycle deformation and damage, and greatly prevents water accumulation within road infrastructure. The design of the roadbed slope effectively reduces the thermal erosion impact of water on the roadbed, reduces lateral deformation differences in the roadbed, and ensures smooth road alignment. Through a combination of foundation reinforcement and temperature control, and employing a structure combining pipe piles and a liquid nitrogen freezing system, the permafrost around the pile tips can be precisely frozen, maintaining the pile tip bearing capacity.

[0015] Furthermore, the road surface layer is provided with curb stones on both sides; the road base layer also includes a sand cushion layer disposed between the base layer and the road base layer; the surface layer is a permeable asphalt pavement.

[0016] Furthermore, the drainage unit also includes a drainage ditch located at the toe of the roadbed slope, an evaporation pond located at the lower confluence of the drainage ditch, and a cutoff curtain located outside the toe of the roadbed unit slope. The geotechnical drainage layer extends along the roadbed slope into the drainage ditch, and the permeable pipe has multiple openings in the transverse direction for draining water into the drainage ditch. The bottom of the cutoff curtain extends into the permafrost layer. Thus, the drainage ditch is used to fully drain accumulated water in flat road sections, and the cutoff curtain is composed of soil modified with nano-hydrophobic materials, effectively isolating groundwater from migrating and infiltrating into the roadbed in water-rich areas.

[0017] Furthermore, a cushion layer is provided between the roadbed unit and the foundation unit. The cushion layer is mainly made of graded sand and gravel, which serves to distribute the upper load according to the pile volume and soil modulus ratio between piles, optimize the stress structure, and further reduce the uneven settlement of the roadbed structure.

[0018] Furthermore, the pipe pile body is provided with multiple sets at intervals. The pipe pile body includes an upper section pipe column, a lower section pipe column, and a heat insulation pipe column installed between the upper section pipe column and the lower section pipe column. The top of the upper section pipe column is sealed by a cover plate. The liquid outlet pipe and the air inlet pipe pass through the cover plate and are connected to the refrigeration pipe located at the bottom of the lower section pipe column.

[0019] An electromagnetic valve and a pressure gauge are installed on the outlet pipe. The pressure gauge is electrically connected to the electromagnetic valve, and the electromagnetic valve is electrically connected to the water temperature monitoring system. The water temperature monitoring system includes a temperature sensor, a humidity sensor, and a pressure sensor connected to the electromagnetic valve. The temperature sensor, humidity sensor, and pressure sensor are located on the outside of the pipe pile body. A data acquisition instrument is connected to the electromagnetic valve, and the data acquisition instrument is electrically connected to the processor.

[0020] Therefore, to comprehensively consider the requirements of heat insulation and strength, a heat-insulating pipe column is installed between the upper and lower pipe pile sections. The heat insulation performance of the heat-insulating pipe column prevents heat from the active layer around the upper pipe pile section from being transferred to the permafrost layer where the lower pipe pile section is located. The three-section pile body, consisting of the upper and lower pipe pile sections and the heat-insulating pipe column, forms a good heat insulation and force transmission structure, which helps the roadbed bear the upper load and reduces the downward transfer of heat from the upper part.

[0021] Furthermore, the foundation unit also includes a heat-conducting medium storage tank, which is connected to the inner cavity of the pipe pile body through a pipeline, preferably with a level valve on the pipeline.

[0022] Furthermore, an exhaust valve is installed on the air inlet pipe; the refrigeration pipe is a spiral pipe; a limiting plate is provided inside the lower section of the pipe column to prevent the refrigeration pipe from moving, and the liquid outlet pipe and the air inlet pipe pass through the limiting plate and communicate with the refrigeration pipe; the upper and lower sections of the pipe column are provided with clamps and reinforcing steel plates at the connection with the heat-insulating pipe column, and the upper and lower sections of the pipe column are coated with an anti-corrosion material layer at the connection with the heat-insulating pipe column; the heat-insulating pipe column includes alternating metal layers and rubber layers; both the upper and lower ends of the heat-insulating pipe column are metal layers, and the upper and lower ends of the heat-insulating pipe column are connected to the upper and lower sections of the pipe column respectively through flanges.

[0023] In addition, the vertical ultimate bearing capacity Q of the pipe pile body u The calculation is as follows:

[0024]

[0025] In the formula: u p q is the perimeter of the pile (m); si Let l be the standard value (kPa) of the ultimate lateral resistance of the i-th layer of soil around the pile; i α represents the thickness (m) of the i-th soil layer within the pile length range; p q is the end resistance utilization factor of the pile; p The standard value of the ultimate end resistance of the pile (kPa); A p The cross-sectional area of ​​the pile (m²) 2 ).

[0026] Based on the same inventive concept, this invention also provides a design method for the integrated prevention and control system for road engineering defects in permafrost regions as described above, comprising the following steps:

[0027] Step 1: Conduct drilling operations and arrange foundation units;

[0028] Step 2: Alternately lay the roadbed and geotextile drainage layer on top of the foundation unit, with the uppermost and lowermost layers being roadbeds; at the same time, set up drainage ditches at the toe of the roadbed slope. Proceed to the next step after the roadbed reaches the design height.

[0029] Step 3: Lay the pavement layer on the uppermost road base layer; and lay permeable pipes on both sides of the pavement layer.

[0030] Furthermore, the foundation unit includes a water temperature monitoring system and multiple sets of spaced pipe pile bodies. Each pipe pile body is equipped with a freezing pipe. One end of the freezing pipe is connected to the outlet pipe of the liquid nitrogen storage tank, and the other end of the freezing pipe is connected to the inlet pipe of the liquid nitrogen storage tank. The pipe pile body is filled with a heat-conducting medium around the freezing pipe.

[0031] The outlet pipe is equipped with a solenoid valve and a pressure gauge. The pressure gauge is electrically connected to the solenoid valve, and the solenoid valve is electrically connected to a water temperature monitoring system. The water temperature monitoring system includes a temperature sensor, a humidity sensor, and a pressure sensor connected to the solenoid valve. The temperature sensor, humidity sensor, and pressure sensor are located on the outside of the pipe pile body. A data acquisition instrument is connected to the solenoid valve, and the data acquisition instrument is electrically connected to a processor.

[0032] Arranging the foundation unit in step one includes the following steps:

[0033] S1. Arrange the pipe pile body and water temperature monitoring system;

[0034] S2. Add a heat-conducting medium into the pipe pile body, and set the liquid nitrogen output flow rate and target temperature on the processor based on the data collected by the temperature sensor, humidity sensor and pressure sensor.

[0035] S3. Open the solenoid valve to allow liquid nitrogen from the liquid nitrogen storage tank to enter the refrigeration tube;

[0036] S4. Continuously observe the data displayed by the water temperature monitoring system. When the temperature of the soil around the pipe pile exceeds the set value, control the solenoid valve to increase the liquid nitrogen discharge flow rate. When the soil pressure around the pipe pile reaches the warning value, control the solenoid valve to decrease the discharge flow rate. When the soil temperature around the pipe pile reaches the preset target temperature, control the solenoid valve to close the discharge.

[0037] The integrated prevention and control system and design method for road engineering defects in permafrost regions of the present invention have the following advantages:

[0038] 1. By adopting an integrated design approach and method for road disease prevention and control, we can effectively avoid the shortcomings of relying solely on single roadbed temperature control measures in the treatment of road diseases in most permafrost sections in the past. This improves the design concept for road disease prevention and control in permafrost areas and greatly enhances the construction and maintenance capabilities of roads in permafrost regions.

[0039] 2. The integrated design scheme for road disease prevention and control in permafrost regions can enhance the synergistic bearing capacity between the roadbed and the foundation, promote consistency between the roadbed structure and the composite foundation in terms of load transfer, drainage, and coordinated deformation, and effectively increase the overall stability and durability of road facilities.

[0040] 3. A prevention and control concept combining foundation reinforcement and temperature control is proposed. A structure combining precast hollow pipe piles and liquid nitrogen temperature control system is adopted, which can accurately freeze the permafrost around the pile tip and maintain the bearing capacity of the pile tip. Construction is carried out under the most unfavorable conditions, so that the pile body can adapt to the seasonal changes of the active layer of permafrost, that is, the soil around the pile tip is always frozen, which plays a role in stabilizing the bearing capacity and strengthening the foundation.

[0041] 4. This invention uses liquid nitrogen as a refrigerant, which is low-carbon, environmentally friendly, and provides rapid cooling. After construction is completed, it can immediately cool the permafrost layer, prevent the temperature inside the pile hole from rising and causing settlement and deformation, and immediately eliminate the impact of engineering thermal effects.

[0042] 5. This invention is equipped with a complete pile tip water temperature monitoring module, which can monitor the stress state and environmental information of the pile foundation in real time and control the start and stop of the freezing work. The treatment time and efficiency are highly controllable, and the equipment is flexible in operation. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the integrated prevention and control system for road engineering defects in permafrost regions according to the present invention.

[0044] Figure 2 This is a schematic diagram of the mattress padding layer structure of the present invention;

[0045] Figure 3This is a schematic diagram of the roadbed unit structure of the present invention;

[0046] Figure 4 This is a schematic diagram of the foundation unit structure of the present invention;

[0047] Figure 5 for Figure 4 Schematic diagram of the overall layout of the intermediate refrigerant pipes;

[0048] Figure 6 for Figure 4 Schematic diagram of the water temperature monitoring system;

[0049] Figure 7 for Figure 4 Schematic diagram of the structure of the central pipe pile body;

[0050] Figure 8 for Figure 4 Schematic diagram of the structure of the centrally insulated tubular column;

[0051] Figure 9 for Figure 4 A schematic diagram of the cross-section of the central pipe pile body.

[0052] Explanation of markings in the diagram: 1. Foundation unit; 11. Pipe pile body; 111. Cover plate; 112. Upper section of pipe column; 113. Insulated pipe column; 1131. Metal layer; 1132. Rubber layer; 114. Lower section of pipe column; 115. Hoop; 116. Reinforcing steel plate; 117. Corrosion-resistant material layer; 118. Flange; 12. Refrigeration pipe; 13. Liquid nitrogen storage tank; 131. Discharge pipe; 132. Inlet pipe; 133. Exhaust valve; 134. Solenoid valve; 135. Pressure gauge; 14. Heat transfer medium; 15. Heat transfer medium storage tank; 151. Piping; 152. Liquid level. 16. Valve; 17. Limiting plate; 18. Water temperature monitoring system; 19. Temperature sensor; 10. Humidity sensor; 11. Pressure sensor; 12. Data acquisition instrument; 13. Processor; 2. Subgrade unit; 20. Cushion layer; 21. Subgrade slope; 22. Subgrade layer; 23. Pavement layer; 231. Base layer; 232. Surface layer; 233. Waterproof layer; 234. Curbstone; 235. Sand cushion layer; 3. Drainage unit; 31. Geotechnical drainage layer; 32. Permeable pipe; 33. Drainage ditch; 34. Evaporation pond; 35. Cutoff curtain; 4. Ventilation pipe; 5. Photovoltaic panel. Detailed Implementation

[0053] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0054] like Figure 1 and Figure 2As shown, this invention relates to an integrated prevention and control system for road engineering defects in permafrost regions. It includes a foundation unit 1, a roadbed unit 2, and a drainage unit 3. The roadbed unit 2 is positioned above the foundation unit 1, and the drainage unit 3 is located within the roadbed unit 2. A cushion layer 20 is provided between the roadbed unit 2 and the foundation unit 1. Specifically, the cushion layer is composed of graded sand and gravel and multiple layers of geogrid. The geogrid, on the one hand, further transfers the load borne by the soil between piles to the pile top through the membrane tension effect, thereby effectively controlling the settlement and deformation of the soil between piles. On the other hand, the geogrid also coordinates deformation and enhances the overall stability of the roadbed structure.

[0055] like Figure 1 and Figure 3 As shown, the roadbed unit 2 includes a roadbed slope 21, a roadbed base 22, and a pavement layer 23 disposed on the upper surface of the roadbed base 22. The pavement layer 23 includes a base layer 231 and a surface layer 232 disposed on the upper surface of the base layer 231. A waterproof layer 233 is provided between the base layer 231 and the surface layer 232 to prevent water from the surface layer from flowing into the base layer, ensuring the effectiveness of the entire pavement drainage system. The drainage unit 3 includes permeable pipes 32 disposed on both sides of the pavement layer 23 and a geotextile drainage layer 31 disposed within the roadbed base 22, extending from within the roadbed base 22. Preferably, the geotextile drainage layer 31 can be divided into two parts: one part is inside the roadbed to absorb water from within the roadbed, and the other part is located on both sides of the roadbed slope to allow water in the geotextile drainage layer to evaporate and to guide excess water to the roadside drainage ditch. Permeable pipes 32 are designed on both sides of the pavement to vertically collect and longitudinally discharge water from different cross sections. Curbstones 234 are also provided on both sides of the pavement layer 23. The road base layer 22 also includes a sand cushion layer 235 disposed between the road base layer 231 and the road base layer 22. The surface layer 232 is a permeable asphalt pavement, and the outward cross slope angle of the pavement layer 23 is not less than 3%, which will facilitate the rapid flow of surface water to the shoulder and its discharge through drainage ditches. Preferably, the present invention uses capillary geotextile, which can quickly absorb and drain roadbed water caused by rainwater infiltration. The geotextile drainage layer has stable performance and is not affected by groundwater level or surface water. The capillary geotextile is composed of many capillary fibers with tiny grooves. The multi-fiber and multi-groove geotextile has high water absorption, moisture absorption and flow conduction characteristics, which can quickly guide water in the soil into the grooves and flow out of the roadbed in a directional manner.

[0056] The drainage unit 3 also includes a drainage ditch 33 located at the toe of the roadbed slope 21, an evaporation pond 34 located at the lower confluence of the drainage ditch 33, and a water-cutting curtain 35 located outside the toe of the roadbed unit 2. The geotechnical drainage layer 31 extends along the roadbed slope 21 into the drainage ditch 33, and the permeable pipe 32 has multiple openings in the transverse direction for draining water into the drainage ditch 33. The bottom of the water-cutting curtain 35 extends into the permafrost layer. Specifically, the permeable pipe 32 has a transverse opening every 50m to facilitate the transverse guidance of water flowing in the permeable pipe into the roadside drainage ditch. The drainage ditch has an evaporation pond built at the lower confluence according to the terrain elevation changes to fully drain the accumulated water in the flat road sections. Specifically, the bottom of the water-cutting curtain 35 needs to enter the permafrost layer, and its upper part should exceed the natural ground surface, thereby forming a vertically continuous impermeable surface to prevent free water from the natural surface from migrating and infiltrating into the roadbed. Preferably, the water-cutting curtain is made of nano-hydrophobic material modified soil, which is soil with strong water repellency and low permeability prepared by adding new hydrophobic materials to the in-situ soil and then vibrating and compacting it.

[0057] like Figures 4 to 9 As shown, to prevent accelerated thawing of permafrost caused by the construction of pile foundations and cutoff walls, artificial freezing should be used for freezing reinforcement during drilling and excavation. The foundation unit 1 includes a water temperature monitoring system 17 and multiple sets of spaced-apart pipe pile bodies 11. Each pipe pile body 11 contains a freezing pipe 12, one end of which is connected to the outlet pipe 131 of a liquid nitrogen storage tank 13. The pipe pile body 11 is a hollow cylindrical structure, reserving space for the liquid nitrogen conduit while also reducing the thermal conductivity of the pile. The other end of the freezing pipe 12 is connected to the inlet pipe 132 of the liquid nitrogen storage tank 13, and the outer periphery of the pipe pile body 11 is filled with a heat-conducting medium 14.

[0058] The pipe pile body 11 is a heat-insulated force-transfer pile. Multiple sets of pipe pile bodies 11 are spaced apart. Each pipe pile body 11 includes an upper pipe column 112, a lower pipe column 114, and a heat-insulating pipe column 113 installed between the upper and lower pipe columns 112 and 114. The top of the upper pipe column 112 is sealed by a cover plate 111. The liquid outlet pipe 131 and the air inlet pipe 132 pass through the cover plate 111 and communicate with the refrigeration pipe 12 located at the bottom of the lower pipe column 114. In one preferred embodiment, prestressed steel bars are embedded within each pipe pile body 11, enabling the pile to withstand greater tensile forces and achieving better frost pull-out resistance.

[0059] A solenoid valve 134 and a pressure gauge 135 are installed on the outlet pipe 131. The pressure gauge 135 is electrically connected to the solenoid valve 134, and the solenoid valve 134 is electrically connected to a water temperature monitoring system 17. The water temperature monitoring system 17 includes a temperature sensor 171, a humidity sensor 172, and a pressure sensor 173 connected to the solenoid valve 134. The temperature sensor 171, humidity sensor 172, and pressure sensor 173 are located on the outside of the pipe pile body 11. A data acquisition instrument 174 is connected to the solenoid valve 134, and the data acquisition instrument 174 is electrically connected to a processor 175. Specifically, the temperature sensor 171, humidity sensor 172, and pressure sensor 173 are pre-embedded in the soil around the pipe pile body 11 in groups of three, and are connected to the solenoid valve via wires to further transmit data to the data acquisition instrument. The solenoid valve controls the liquid nitrogen outlet flow rate based on the received temperature and pressure monitoring data. The processor is a computer, which is connected to the data acquisition instrument for real-time monitoring of temperature, humidity, and pressure data.

[0060] The foundation unit 1 also includes a heat transfer medium storage tank 15, which is connected to the inner cavity of the pipe pile body 11 via a pipeline 151. Preferably, a level valve 152 is provided on the pipeline 151. The level valve 152 monitors the liquid level of the heat transfer medium and opens to replenish the medium when it is insufficient. Preferably, the heat transfer medium is heat transfer oil, which enhances the transfer of cold energy between the spiral refrigeration pipe and the inner wall of the lower section of the pipe pile.

[0061] An exhaust valve 133 is installed on the air inlet pipe 132. The exhaust valve 133 is used to regulate the pressure inside the pipe to prevent the liquid nitrogen from expanding and damaging the circuit pipe due to volume expansion. The refrigeration pipe 12 is a spiral pipe. A limiting plate 16 is provided inside the lower section pipe column 114 to prevent the refrigeration pipe 12 from moving. The liquid outlet pipe 131 and the air inlet pipe 132 pass through the limiting plate 16 and communicate with the refrigeration pipe 12. The limiting plate fixes the spiral refrigeration pipe to the pile end cavity of the hollow pipe pile. The upper section pipe column 112 and the lower section pipe column 114 are provided with a clamp 115 and a reinforcing steel plate 116 at the connection with the heat insulation pipe column 113, and the upper section pipe column 112 and the lower section pipe column 114 are coated with an anti-corrosion material layer 117 at the connection with the heat insulation pipe column 113. The heat insulation pipe column 113 includes an alternately spaced metal layer 1131 and a rubber layer 1132. Both ends of the insulated pipe column 113 are metal layers 1131, and both ends are connected to the upper pipe column 112 and the lower pipe column 114 respectively via flanges 118. Preferably, the rubber insulation body is made of multiple layers of synthetic rubber and multiple layers of thin steel plates bonded together, with rubber wrapped between the steel plates and they not in direct contact. The connection points of the upper and lower pipe pile ends are equipped with steel hoop structures and welded reinforcing bars, forming a good insulated-force-transfer pile structure through flanges and insulated sections.

[0062] In this embodiment, the upper and lower sections of the pipe pile are made of precast prestressed concrete. The pile body is prefabricated and assembled in the factory, eliminating the adverse effects of on-site pouring heat. Simultaneously, the addition of prestress improves the pile's resistance to frost pull-out. Flanges and steel sleeves are installed at the ends of the upper and lower pipe piles to connect the rubber insulation body. The insulation properties of the rubber material prevent heat from the active layer surrounding the upper pipe pile from transferring to the permafrost layer where the lower pipe pile is located. The pile body retains the structural characteristics of a hollow pipe pile; the presence of the cavity effectively reduces the thermal conductivity of the pile itself, meeting the needs of work in permafrost areas. The entire three-section pile body forms a good heat insulation and force transmission structure, helping the roadbed bear the upper load and reducing the downward transfer of heat from the upper part. To ensure connection strength, a reinforcing steel plate can be added between the two sections. The rubber insulation body is made of multiple layers of synthetic rubber and thin steel plates bonded together, with flanges of the same type installed at both ends. The synthetic rubber should have sufficient strength, rigidity and durability. The rubber insulation body and the flanges of the upper and lower pipe piles are fixed by bolts, and the joint is filled with anti-corrosion asphalt material.

[0063] The composite foundation parameter design based on mechanical performance requirements requires using the most unfavorable state of permafrost as the design state, i.e., when the upper limit of permafrost reaches its lowest point with seasonal changes, at which point the bearing capacity of the entire permafrost foundation is at its worst. Accordingly, the corresponding design parameters such as pile diameter, pile length, and pile spacing are determined based on the roadbed filling height, highway grade, and deformation control requirements. Specifically, the vertical ultimate bearing capacity Q of the pipe pile body 11... u The calculation is as follows:

[0064]

[0065] In the formula: u p q is the perimeter of the pile (m); si Let l be the standard value (kPa) of the ultimate lateral resistance of the i-th layer of soil around the pile; i α represents the thickness (m) of the i-th soil layer within the pile length range; p q is the end resistance utilization factor of the pile; p The standard value of the ultimate end resistance of the pile (kPa); A p The cross-sectional area of ​​the pile (m²) 2 ).

[0066] It should be noted that, considering the temperature sensitivity of permafrost engineering, the length and spacing of the pipe piles described in this embodiment need to be adjusted according to local hydrological and meteorological data and permafrost monitoring data. Construction should be carried out when the local permafrost is in the most unfavorable state, that is, when the active layer thickness reaches its maximum value. At this time, pressing the precast insulated hollow pipe piles into the foundation can better ensure that the pile tip is stable in the permafrost bearing layer.

[0067] The thermal insulation-force transmission pile and its matching liquid nitrogen cooling technology in this embodiment can meet the construction needs of various single-road projects in permafrost. The installation method of the thermal insulation-force transmission pile in this embodiment is as follows:

[0068] First, after leveling the site, drill holes at the target pile locations according to the design requirements, and the hole diameter should be 5-10 cm smaller than the outer diameter of the pile body.

[0069] Then, after the hollow pile body and related components of the liquid nitrogen freezing module are prefabricated and assembled in the factory, the pile body is lifted by a crane to the corresponding hole position, and the pile body is driven into the soil layer at the design elevation using the hammer driving method. During the hammering process, the pile position should be checked in real time. After the pile is driven, the pile end needs to enter the permafrost bearing layer to check the pile position, pile top elevation and pile verticality. The pile top and the foundation surface must be flush.

[0070] Then, using threaded pipes and elbows of the same material and diameter, the liquid outlet pipe, air inlet pipe, and heat transfer medium replenishment pipe are led out from the top of the pile, and the pile top cover plate is fixed. After the pile is driven, insulation boards are laid on the foundation. After the laying is completed, a groove is cut at the pipeline location to lead it to the roadside refrigeration station location, leaving an interface for connection. The insulation boards are filled in layers and compacted.

[0071] Finally, a roadside refrigeration station was built, and components such as pressure gauges, solenoid valves, and liquid storage tanks were connected according to design requirements, along with a data acquisition instrument and a computer.

[0072] Preferably, an asphalt anti-seepage coating is applied inside the pile end cavity to prevent the leakage of the heat transfer medium. The liquid nitrogen outlet pipe, inlet pipe, and heat transfer medium replenishment pipe are vertically arranged longitudinally within the pile cavity and fixed in position by pre-drilled holes in the pile top cover and limiting plate. To ensure longitudinal rigidity, the liquid nitrogen outlet pipe, inlet pipe, and heat transfer medium replenishment pipe are made of stainless steel. The spiral-shaped refrigeration pipe is made of copper, whose higher thermal conductivity enhances the freezing effect at the pile end. Gas tanker trucks can replenish the liquid nitrogen storage tanks of roadside refrigeration stations when needed.

[0073] Preferably, the limiting plate and the spiral-shaped freezing pipe are fixed during the prefabrication of the lower section of the pipe pile. The limiting plate is made of nylon and serves to fix the positions of the liquid nitrogen outlet pipe, the gas inlet pipe, and the heat transfer medium replenishment pipe, and to prevent the heat transfer medium from evaporating into the upper cavity of the hollow pipe pile. The nylon material must meet the requirements of structural durability and corrosion resistance.

[0074] To mitigate the impact of thermal effects on road structures in the permafrost region of the Qinghai-Tibet Plateau and to scientifically control pavement and subgrade settlement and deformation, this embodiment provides an implementation method for a composite foundation of thermal insulation and bearing piles for roads in permafrost regions, including the following steps:

[0075] First, add heat transfer medium 14 and liquid nitrogen to the heat transfer medium storage tank 15 and the liquid nitrogen storage tank 13. Open the liquid level valve 152. When the heat transfer medium 14 reaches the set liquid level height, close the liquid level valve 152. Turn on the processor 175, solenoid valve 134, temperature sensor 171, humidity sensor 172 and pressure sensor 173. After ensuring that the initial value of the water temperature monitoring system 17 is normal, set the liquid nitrogen outlet flow rate and target temperature.

[0076] Then, the exhaust valve 133 is opened to allow the high-pressure liquefied nitrogen in the liquid nitrogen storage tank 13 to flow through the refrigeration pipe circuit, thereby compensating for the cold in the permafrost near the pipe pile body 11 and keeping it frozen.

[0077] Secondly, liquid nitrogen flows from the liquid nitrogen storage tank 13 through the solenoid valve 134 and the outlet pipe 131 to the freezing pipe 12. Under the action of temperature difference, it rapidly evaporates and vaporizes, and then conducts heat through the heat-conducting medium 14 and the outer shell of the pipe pile body 11, absorbing heat from the nearby soil. After the liquid nitrogen evaporates and expands in volume, it escapes through the air inlet pipe 132 and is discharged through the exhaust valve 133 to balance the circuit pressure.

[0078] Furthermore, during the above process, the water temperature monitoring system 17 will monitor the temperature, pressure and other conditions near the pipe pile body 11 and the liquid nitrogen freezing circuit in real time. After transmitting the relevant monitoring data to the processor 175 via the data acquisition instrument 174, the relevant parameters of the device can be adjusted when necessary.

[0079] When the temperature of the soil surrounding the pipe pile body 11 exceeds the sensor's set value, the control solenoid valve 134 increases the liquid nitrogen flow rate, and the refrigeration pipe 12 quickly cools the soil surrounding the pipe pile body 11. When the soil pressure around the pipe pile body 11 reaches the warning value, the control solenoid valve 134 reduces the liquid flow rate, and excess gas is discharged through the exhaust valve 133. When the soil temperature around the pipe pile body 11 reaches the preset target temperature, the control solenoid valve 134 closes the liquid flow, and the device stops cooling after the liquid nitrogen in the refrigeration pipe 12 is consumed. The liquid level of the heat transfer medium 14 can be viewed and adjusted through the liquid level valve 152. When the liquid level is insufficient, it can be manually replenished by a gas tanker truck.

[0080] Therefore, this application aims to address the engineering problems of frequent road subsidence, poor proactive prevention and control capabilities, and insufficient maintenance early warning mechanisms in the permafrost region of the Qinghai-Tibet Plateau, guided by the needs of the national transportation industry. Building upon traditional roadbed temperature control measures and incorporating the concept of composite foundation reinforcement, this application systematically develops a heat-insulating-bearing pile composite foundation suitable for road engineering in permafrost regions. The device uses precast hollow pipe piles, liquid nitrogen freezing modules, and supporting monitoring modules as core components. Through the cooling effect of circulating liquid nitrogen, it maintains the stability of the permafrost bearing layer around the pile tip, reducing the thermal effects during pile construction and service life, thereby regulating permafrost temperature and improving the mechanical properties of permafrost foundations. The expected results will have significant engineering value and guiding significance for improving the decision-making capabilities for road engineering disease prevention and maintenance in permafrost regions.

[0081] The design method of the integrated prevention and control system for road engineering defects in permafrost regions according to this embodiment is characterized by the following steps:

[0082] Step 1: Conduct drilling operations and arrange foundation unit 1.

[0083] Step 2: Alternately lay the roadbed 22 and the geotextile drainage layer 31 above the foundation unit 1, with the uppermost and lowermost layers both being the roadbed 22. At the same time, set up drainage ditches 33 at the toe of the roadbed slope 21. Proceed to the next step after the roadbed 22 reaches the designed height.

[0084] Step 3: Lay the pavement layer 23 on the uppermost road base layer 22. And lay permeable pipes 32 on both sides of the pavement layer 23.

[0085] Specifically, the design method of the integrated prevention and control system for road engineering defects in permafrost regions in this embodiment first determines the maximum thawing depth of permafrost in different road sections based on the road engineering survey report. The pile length is then calculated and determined based on the thawing depth, soil conditions, and other factors. Furthermore, the ultimate vertical bearing capacity of a single pile, pile diameter, and the bearing capacity of the composite foundation are determined based on geological drilling data, on-site static load tests, high-strain method, roadbed design height, and highway grade.

[0086] Secondly, drilling operations were carried out according to the pile foundation design and construction requirements. To avoid thermal disturbance to the permafrost at the pile bottom during drilling, liquid nitrogen was injected into the bottom of the pile hole after drilling to achieve rapid refreezing. During pile construction, sensors were embedded on the outside of the pile sidewall, and earth pressure gauges, hygrometers, thermometers, etc., were embedded in the boreholes, and graded sand was used for backfilling and compaction. All sensors were connected to an external data acquisition instrument via data cables, and the entire data acquisition system was powered by photovoltaic panels 5 located on the sunny slope of the roadbed.

[0087] Secondly, according to the drainage system design requirements, the foundation soil was vertically excavated beyond the permafrost limit on the outer side of the roadbed slope. Then, nano-hydrophobic materials, water, and the excavated foundation soil were mixed at a mass ratio of 1:100:500 and thoroughly stirred to prepare a water-repellent modified soil. This modified soil was then uniformly backfilled to the design height and compacted, ultimately forming a continuous vertical water-cutting curtain. The bottom of the water-cutting curtain is fixed within the permafrost layer, effectively preventing free water from the natural ground surface from migrating and infiltrating into the roadbed.

[0088] Secondly, a 20cm thick cushion layer is constructed on top of the pile foundation. This cushion layer consists of graded sand and gravel and multiple layers of geogrid. It is used to adjust the stress distribution between the pile and the surrounding soil, allowing the pile and the surrounding soil to more rationally bear the load from the superstructure. At the same time, the geogrid also plays a role in coordinating deformation and enhancing the overall stability of the roadbed.

[0089] Furthermore, based on multi-source data such as the structural type, roadbed orientation, disease characteristics, regional climate, hydrogeology, and permafrost type of road sections in permafrost areas, a comprehensive judgment is made on the roadbed structure to select the optimal roadbed temperature control scheme.

[0090] Next, coarse-grained soil is used to compact the roadbed. When the filling reaches 90cm below the pavement structure, the roadbed surface is leveled, and a geotextile drainage layer is laid. The geotextile drainage layer uses capillary geotextile, which is composed of capillary fibers and has many tiny grooves. The multi-fiber, multi-groove characteristics give the geotextile high water absorption and moisture absorption properties. The geotextile drainage layer is divided into two parts: one part is located inside the roadbed soil to absorb moisture from within the roadbed, and the other part is located on both side slopes to accelerate the evaporation of moisture from the capillary geotextile and guide it into the drainage ditch at the toe of the slope.

[0091] Next, the subgrade is compacted and filled to the design height. After the subgrade construction is accepted, the pavement layer construction begins. The permeable asphalt pavement surface layer is designed with a 3% outward cross slope, which helps to guide rainwater to both sides. Permeable pipes are installed on both sides of the pavement to collect and drain water longitudinally from each cross section. A waterproof membrane is installed between the base layer and the surface layer to prevent water from the surface layer from seeping into the base layer.

[0092] Finally, a transverse opening is installed every 50 meters in the permeable pipe to guide rainwater laterally into the roadside drainage ditch. The drainage ditch is equipped with evaporation ponds at the lower confluence points, based on changes in terrain elevation, to effectively drain accumulated water from flat road sections.

[0093] In terms of foundation reinforcement, this embodiment utilizes pile foundation methods commonly used in soft soil foundations to strengthen the active layer of permafrost, effectively ensuring that the deformation and bearing capacity of the permafrost foundation remain within a controllable range and avoiding significant uneven settlement. End-bearing piles are embedded in the surface layer of the foundation, with the pile ends fixed to the permafrost layer possessing sufficient bearing capacity. Under these conditions, the static load of the roadbed structure and the dynamic load of traffic are shared by the piles and the soil between them, effectively reducing the magnitude and distribution of stress within the weak active layer. The application of pile foundations not only reduces roadbed deformation caused by the loss of bearing capacity due to permafrost thawing in summer but also effectively prevents overall settlement and slippage deformation of the superstructure. Secondly, regarding roadbed temperature control, although existing roadbed temperature control measures have various shortcomings, scholars and experts both domestically and internationally have accumulated a wealth of valuable experience through years of engineering practice. Therefore, this embodiment, based on a thorough study of existing roadbed temperature control technologies, comprehensively considers factors such as topography, hydrology, and climate of the road section being treated, selecting the optimal solution from existing options such as rubble roadbed, heat pipes, ventilation pipes, and insulation boards. For example, in leeward slopes of mountains, air convection is slow, significantly reducing the temperature control effect of ventilation pipe roadbeds; in Gobi and arid areas, the use of rubble roadbeds commonly results in ventilation pores being blocked by wind and sand. For the aforementioned special road sections, detailed field investigations must be conducted before designing roadbed temperature control to fully demonstrate the applicability and treatment effects of various measures. Finally, regarding comprehensive drainage, addressing the challenges of complex water sources, flat terrain, and difficult drainage of road facilities in permafrost regions, this invention proposes constructing a three-dimensional comprehensive drainage system for the roadbed structure, including pavement drainage, roadbed water diversion, and foundation water collection measures, aiming to minimize the chances of water migration and accumulation within road facilities.

[0094] For "foundation reinforcement," a composite foundation design method based on mechanical performance requirements and temperature control requirements is proposed. Specifically, this involves using insulating-bearing piles with their bottoms fixed within the permafrost layer to reinforce the bearing capacity of the active layer while reducing heat transfer from top to bottom along the pile body. The end-bearing pile's end load is mainly provided by the hard permafrost layer, allowing for a shorter pile length compared to friction piles. End-bearing piles also offer another advantage: the bearing capacity of friction piles primarily comes from the side friction resistance of the pile body, thus the bearing capacity of friction piles changes significantly during freeze-thaw cycles, especially in summer when it drops sharply, while the bearing capacity of end-bearing piles remains generally stable throughout the year. A cushion layer, mainly composed of graded sand and gravel, is laid between the pile top and the subgrade to distribute the upper load according to the pile volume and soil modulus ratio, optimizing the stress structure and further reducing uneven settlement of the subgrade structure.

[0095] Furthermore, the bearing capacity of the permafrost composite foundation is calculated as follows:

[0096]

[0097] In the formula: λ is the pile bearing capacity utilization coefficient; m is the area replacement ratio; R a R is the characteristic value of the bearing capacity of a single pile (kN). a =Q u / k, k=2; A p The cross-sectional area of ​​the pile (m 2 ); β is the bearing capacity utilization coefficient of the soil between piles; f sk The characteristic value of the bearing capacity of the soil between piles (kPa).

[0098] The design of composite foundation parameters based on temperature control requirements should employ methods such as engineering tests and numerical simulations to reveal the dynamic distribution of the permafrost temperature field during construction and operation, thereby obtaining the degree and range of thermal disturbance to the pile body. Based on extensive numerical simulations and field engineering tests, the pile materials, mix proportions, and structural design parameters should be optimized to ensure that the pile body causes minimal disturbance or damage to the permafrost environment.

[0099] "Subgrade temperature control" is a crucial measure to ensure the stability and durability of road performance in permafrost regions. Through systematic research on subgrade temperature control measures in in-service highway projects on the Qinghai-Tibet Plateau in my country, this study establishes the intrinsic relationship between temperature control effectiveness and internal and external factors such as topography, hydrology, permafrost type, and climate along the road section. This provides valuable guidance for selecting the optimal subgrade temperature control scheme under different working conditions. For example, the toe of the subgrade slope is a weak point in the road structure in permafrost regions. Affected by heat transfer from both the slope surface and the ground, the maximum seasonal thawing depth at the toe is greater than that under natural ground and embankment subgrades, which is highly detrimental to the stability of the subgrade structure. Adding soil or rubble revetment can effectively reduce the thermal erosion of the subgrade by water and reduce lateral deformation differences, ensuring smoothness of the route.

[0100] "Integrated drainage" is a crucial component of integrated road defect prevention and control technology. A scientifically designed drainage system can significantly reduce the accumulation of moisture within road infrastructure, mitigating the deformation and damage caused by freeze-thaw cycles. The integrated drainage system comprises three parts: pavement, subgrade, and foundation. Surface drainage refers to the efficient and rapid collection and discharge of rainwater and snowmelt through roadside drainage ditches, achieved through the design of road longitudinal slopes, cross-sections, and drainage ditches. Subgrade drainage involves collecting and diverting some infiltrated water through pre-buried drainage pipe networks and geotextiles, effectively preventing the formation of stagnant water within the subgrade and reducing the moisture content of the subgrade and its underlying foundation. The foundation primarily considers waterproofing and water interception measures. This is achieved by installing a continuous vertical water-cutting curtain on the outer side of the subgrade slope, requiring the bottom of the curtain to be fixed within the permafrost layer, thereby effectively preventing free water from the natural surface from migrating and infiltrating into the roadbed. The design of the aforementioned drainage system must fully consider factors such as the road environment, route morphology, roadbed structure, and terrain conditions to prevent poor drainage or partial failure of some drainage ditches due to deformation or other reasons. Furthermore, the materials used for drainage ditches and pipe networks should possess sufficient strength, rigidity, frost resistance, and durability. In particular, cracks in low-grade concrete drainage ditches will inevitably lead to water seepage along the cracks, exacerbating the occurrence of defects. Strengthening the design of road drainage facilities in permafrost regions and establishing a comprehensive and effective drainage system plays a crucial role in preventing surface water accumulation at the toe of the roadbed and groundwater seepage through the foundation, thus maintaining the water and heat balance of the permafrost layer.

[0101] In summary, focusing on the problem of "serving with defects" in road infrastructure in the permafrost region of the Qinghai-Tibet Plateau, and addressing the shortcomings in the concepts and design methods for preventing and controlling road defects in permafrost areas, this patent proposes an integrated prevention and control technology for road defects in permafrost areas, combining "foundation reinforcement, subgrade temperature control, and comprehensive drainage," based on existing methods for subgrade temperature control and composite subgrade design. This technology has significant theoretical and engineering value for promoting the high-quality development of road transportation infrastructure construction and maintenance technology in the Qinghai-Tibet Plateau.

[0102] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. An integrated prevention and control system for road engineering defects in permafrost regions, characterized in that, It includes a foundation unit (1), a roadbed unit (2) and a drainage unit (3), wherein the roadbed unit (2) is disposed above the foundation unit (1) and the drainage unit (3) is disposed inside the roadbed unit (2); The foundation unit (1) includes a water temperature monitoring system (17) and multiple sets of spaced pipe pile bodies (11). The pipe pile body (11) is provided with a freezing pipe (12). One end of the freezing pipe (12) is connected to the outlet pipe (131) of the liquid nitrogen storage tank (13), and the other end of the freezing pipe (12) is connected to the air inlet pipe (132) of the liquid nitrogen storage tank (13). The pipe pile body (11) is filled with a heat-conducting medium (14) around the freezing pipe (12). The roadbed unit (2) includes a roadbed slope (21), a roadbed base (22) and a pavement layer (23) disposed on the upper surface of the roadbed base (22). The pavement layer (23) includes a base layer (231) and a surface layer (232) disposed on the upper surface of the base layer (231). A waterproof layer (233) is provided between the base layer (231) and the surface layer (232). The drainage unit (3) includes permeable pipes (32) disposed on both sides of the road surface layer (23) and a geotextile drainage layer (31) disposed in the road base layer (22), the geotextile drainage layer (31) extending out from the road base layer (22); The pipe pile body (11) is provided in multiple sets at intervals. The pipe pile body (11) includes an upper section pipe column (112), a lower section pipe column (114), and a heat insulation pipe column (113) installed between the upper section pipe column (112) and the lower section pipe column (114). The top of the upper section pipe column (112) is sealed by a cover plate (111). The liquid outlet pipe (131) and the air inlet pipe (132) pass through the cover plate (111) and are connected to the freezing pipe (12) located at the bottom of the lower section pipe column (114). A solenoid valve (134) and a pressure gauge (135) are installed on the outlet pipe (131). The pressure gauge (135) is electrically connected to the solenoid valve (134). The solenoid valve (134) is electrically connected to the water temperature monitoring system (17). The water temperature monitoring system (17) includes a temperature sensor (171), a humidity sensor (172), and a pressure sensor (173) connected to the solenoid valve (134). The temperature sensor (171), humidity sensor (172), and pressure sensor (173) are located on the outside of the pipe pile body (11). A data acquisition instrument (174) is connected to the solenoid valve (134). The data acquisition instrument (174) is electrically connected to the processor (175).

2. The integrated prevention and control system for road engineering defects in permafrost regions according to claim 1, characterized in that, The road surface layer (23) is also provided with curb stones (234) on both sides; the road base layer (22) also includes a sand cushion layer (235) between the base layer (231) and the road base layer (22); the surface layer (232) is a permeable asphalt pavement.

3. The integrated prevention and control system for road engineering defects in permafrost regions according to claim 1, characterized in that, The drainage unit (3) also includes a drainage ditch (33) set at the toe of the roadbed slope (21), an evaporation pond (34) set at the low confluence of the drainage ditch (33), and a water-cutting curtain (35) set outside the toe of the roadbed unit (2); the geotechnical drainage layer (31) extends along the roadbed slope (21) into the drainage ditch (33), and the permeable pipe (32) has multiple openings in the transverse direction for draining water into the drainage ditch (33); the bottom of the water-cutting curtain (35) extends into the permafrost layer.

4. The integrated prevention and control system for road engineering defects in permafrost regions according to claim 1, characterized in that, A mattress layer (20) is provided between the roadbed unit (2) and the foundation unit (1).

5. The integrated prevention and control system for road engineering defects in permafrost regions according to claim 1, characterized in that, The foundation unit (1) also includes a heat-conducting medium storage tank (15), which is connected to the inner cavity of the pipe pile body (11) through a pipeline (151).

6. The integrated prevention and control system for road engineering defects in permafrost regions according to claim 5, characterized in that, A level valve (152) is provided on the pipeline (151).

7. The integrated prevention and control system for road engineering defects in permafrost regions according to claim 1, characterized in that, An exhaust valve (133) is installed on the air inlet pipe (132); the refrigeration pipe (12) is a spiral pipe; a limiting plate (16) is provided inside the lower section pipe column (114) to prevent the refrigeration pipe (12) from moving; the liquid outlet pipe (131) and the air inlet pipe (132) pass through the limiting plate (16) and are connected to the refrigeration pipe (12); the upper section pipe column (112) and the lower section pipe column (114) are provided with a clamp (115) and a reinforcing steel plate (116) at the connection with the heat insulation pipe column (113). Furthermore, the upper section pipe column (112) and the lower section pipe column (114) are coated with an anti-corrosion material layer (117) at the connection with the heat insulation pipe column (113); the heat insulation pipe column (113) includes an alternately spaced metal layer (1131) and a rubber layer (1132); both the upper and lower ends of the heat insulation pipe column (113) are metal layers (1131), and the upper and lower ends of the heat insulation pipe column (113) are connected to the upper section pipe column (112) and the lower section pipe column (114) respectively through flanges (118).

8. The integrated prevention and control system for road engineering defects in permafrost regions according to any one of claims 1 to 7, characterized in that, The vertical ultimate bearing capacity of the pipe pile body (11) The calculation is as follows: In the formula: u p The perimeter of the pile (m); q si The standard value of the ultimate lateral resistance of the i-th layer of soil around the pile (kPa); l i The thickness (m) of the i-th soil layer within the pile length range; α p This is the coefficient for the utilization of end resistance at the pile tip; q p This is the standard value of the ultimate end resistance of the pile (kPa). A p The cross-sectional area of ​​the pile (m²) 2 ).

9. A design method for an integrated prevention and control system for road engineering defects in permafrost regions as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Conduct drilling operations and arrange foundation units (1); Step 2: Alternately lay the roadbed (22) and the geotechnical drainage layer (31) above the foundation unit (1), with the uppermost and lowermost layers being the roadbed (22); at the same time, set up a drainage ditch (33) at the toe of the roadbed slope (21), and proceed to the next step after the roadbed (22) reaches the design height; Step 3: Lay a pavement layer (23) on the uppermost road base layer (22); and lay permeable pipes (32) on both sides of the pavement layer (23).

10. The design method of the integrated prevention and control system for road engineering defects in permafrost regions according to claim 9, characterized in that, The foundation unit (1) includes a water temperature monitoring system (17) and multiple sets of spaced pipe pile bodies (11). The pipe pile body (11) is provided with a freezing pipe (12). One end of the freezing pipe (12) is connected to the outlet pipe (131) of the liquid nitrogen storage tank (13), and the other end of the freezing pipe (12) is connected to the air inlet pipe (132) of the liquid nitrogen storage tank (13). The pipe pile body (11) is filled with a heat-conducting medium (14) around the freezing pipe (12). A solenoid valve (134) and a pressure gauge (135) are installed on the outlet pipe (131). The pressure gauge (135) is electrically connected to the solenoid valve (134). The solenoid valve (134) is electrically connected to the water temperature monitoring system (17). The water temperature monitoring system (17) includes a temperature sensor (171), a humidity sensor (172), and a pressure sensor (173) connected to the solenoid valve (134). The temperature sensor (171), humidity sensor (172), and pressure sensor (173) are located on the outside of the pipe pile body (11). A data acquisition instrument (174) is connected to the solenoid valve (134). The data acquisition instrument (174) is electrically connected to the processor (175). Arranging the foundation unit (1) in step one includes the following steps: S1. Arrange the pipe pile body (11) and water temperature monitoring system (17). S2. Add heat-conducting medium (14) into the pipe pile body (11). Based on the data collected by temperature sensor (171), humidity sensor (172) and pressure sensor (173), set the liquid nitrogen outlet flow rate and target temperature on the processor (175). S3. Open the solenoid valve (134) to allow liquid nitrogen in the liquid nitrogen storage tank (13) to enter the cryogenic tube (12). S4. Continuously observe the data displayed by the water temperature monitoring system (17). When the temperature of the soil around the pipe pile body (11) exceeds the set value, control the solenoid valve (134) to increase the liquid nitrogen discharge flow rate. When the pressure value of the soil around the pipe pile body (11) reaches the warning value, control the solenoid valve (134) to decrease the discharge flow rate. When the temperature of the soil around the pipe pile body (11) reaches the preset target temperature, control the solenoid valve (134) to close the discharge.

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