Pile-raft surface integrated roadbed and pavement structure in high-temperature permafrost region and construction method thereof

Abstract

The invention discloses a piled raft surface integrated roadbed and pavement structure in a high-temperature permafrost region. The piled raft surface integrated roadbed and pavement structure comprises a high-temperature permafrost layer, a seasonal activity layer, an embankment reinforcing region, a cast-in-situ bored pile, a mattress layer, a heat insulation layer, a reinforced concrete raft plate, an asphalt surface layer and a pile top inverted umbrella-shaped rigid hook. The embankment reinforcing area, the mattress layer, the heat insulation layer, the reinforced concrete raft plate and the asphalt surface layer are sequentially laid above the seasonal activity layer from bottom to top; the cast-in-situ bored piles are arranged at intervals, vertically penetrate through the heat insulation layer, the mattress layer, the embankment reinforcing area and the seasonal activity layer and are driven into the high-temperature permafrost layer; and the inverted umbrella-shaped rigid hook at the pile top and the pile top of the cast-in-situ bored pile are cast in the reinforced concrete raft plate together to form pile-plate rigid connection integration. According to the invention, the problem of deformation of roads in high-altitude high-temperature permafrost regions caused by degeneration of frozen soil, high-frequency repeated freezing and thawing of active layers and differential settlement of embankment filling can be solved, and the defects of horizontal rigidity, flexural rigidity and shear rigidity of a traditional raft roadbed are overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of roadbed maintenance in permafrost areas, and particularly relates to a pile-raft surface integrated roadbed and pavement structure in high-temperature permafrost areas and a construction method thereof. Background Art

[0002] The subsidence of highway subgrades in the high-altitude, high-temperature, high-ice-content permafrost areas of the Qinghai-Tibet Plateau is a long-term problem that cannot be effectively solved. The main reason for the subsidence of the subgrade is the continuous degradation and subsidence of the underlying high-temperature, high-ice-content thick permafrost layer. The existing active subgrade cooling engineering measures such as hot rod subgrade, ventilation pipe subgrade, block stone subgrade and insulation board subgrade cannot effectively control and adapt to the potential large deformation of the foundation. According to the results of the field investigation, the measures such as hot rod subgrade, ventilation pipe subgrade, block stone subgrade and insulation board subgrade have a better effect on low-temperature (<-2℃) permafrost, but have a poor effect on high-temperature (-2℃~0℃) permafrost that is easily degraded.

[0003] The invention patent CN108265735A proposes a raft-pile composite foundation suitable for highway roadbeds in high-latitude high-temperature frozen soil areas. Its core requirement is that the pile foundation needs to penetrate the permafrost layer to reach the bedrock bearing layer to adapt to the characteristics of thin permafrost layer in high-latitude foundations. However, in the high-altitude permafrost areas of the Qinghai-Tibet Plateau, a large amount of high-temperature frozen soil layers with a thickness of more than tens of meters are developed, and the cost of penetrating them is unacceptable.

[0004] Invention patent CN111364495A, its structural design has a certain effect on earthquake deformation and frost heave of small-area building foundations in cold zones. However, the strip roads in the high-temperature permafrost zone in the northwest are long, and this invention structure is difficult to bear heavy loads all year round; secondly, the design cost is high and the raw materials are difficult to transport. The pile-raft is not an integrated structure, but shares the load through the lower cushion layer of the raft slab, which makes it extremely difficult to adapt to the harsh conditions of high-altitude road construction and operation.

[0005] Invention patent CN115075281B, its structural design is intended to block the thermal disturbance of the frozen soil around the piles caused by the hydration heat release of CFG piles during the pile foundation construction process, and the blocking design is extremely complicated. Summary of the invention

[0006] The purpose of the present invention is to provide an integrated roadbed and pavement structure with pile-raft surface in high-temperature permafrost areas and a construction method thereof, which are used to solve the deformation problems of roads in high-altitude high-temperature permafrost areas caused by frozen soil degradation, high-frequency repeated freezing and thawing of active layers, and differential settlement of embankment fill, overcome the shortcomings of the discontinuous pile cap structure of the traditional raft pile foundation, the complex construction process, and the high construction cost under high-altitude conditions, and overcome the deficiencies of the traditional raft roadbed in horizontal stiffness, bending stiffness and shear stiffness.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses an integrated roadbed and pavement structure with pile-raft surface in a high-temperature permafrost area, comprising a high-temperature permafrost layer, a seasonally active layer, an embankment reinforcement area, bored cast-in-place piles, a cushion layer, an insulating layer, a reinforced concrete raft slab, an asphalt surface layer and an inverted umbrella-shaped rigid hook on the pile top.

[0008] In the roadbed and pavement structure of the present invention, the high-temperature permafrost layer is a soil layer with a temperature between -1.5 and 0°C and frozen for two years or more, also known as near-phase change zone permafrost; the seasonally active layer is a soil layer that melts in summer and freezes in winter; the embankment reinforcement area is artificially compacted fill on the surface, laid above the seasonally active layer; the cushion layer is laid below the insulation layer and above the embankment reinforcement area; the reinforced concrete raft slab is formed by an integral steel frame and C40 concrete slurry cast in place, and is located above the insulation layer; the asphalt surface layer is asphalt concrete, paved on the reinforced concrete raft slab; the bored piles are arranged at intervals and vertically penetrate the insulation layer, the cushion layer, the embankment reinforcement area, and the seasonally active layer into the high-temperature permafrost layer; the inverted umbrella-shaped rigid hook on the pile top is connected to the pile top of the bored pile, and is cast together with the pile top in the integral steel frame inside the reinforced concrete raft slab to form a pile-slab rigid connection integration.

[0009] As a further illustration of the present invention, the bored cast-in-place pile is a bored cast-in-place concrete pile using a rotary drilling process, with a pile length of less than 15m, a diameter of greater than 0.8m, and a pile spacing of greater than 4m. The bored cast-in-place concrete pile contains a special positioning steel cage inside; the special positioning steel cage includes vertical main steel bars, stirrups and positioning steel bars; the vertical main steel bars are arranged in a circular array; the stirrups are tied to the vertical main steel bars in a circular manner from top to bottom; the positioning steel bars are arranged in a group every 2 to 5 meters, and 4 steel bars in each group are evenly arranged.

[0010] As a further illustration of the present invention, the inverted umbrella-shaped rigid hook on the pile top is an extension of the vertical main steel bar of the special positioning steel cage, or is connected to the top of the vertical main steel bar by welding or threading. The material of the inverted umbrella-shaped rigid hook on the pile top is high-strength corrosion-resistant steel, and is cast together with the bored pile top in the integral steel frame structure inside the reinforced concrete raft slab to form a pile-raft integrated structure.

[0011] As a further illustration of the present invention, the reinforced concrete raft slab has a thickness of 30 to 50 cm, the slab length can be 10 meters, and 4 to 9 bored piles are laid at the bottom of each reinforced concrete raft slab; a 1 cm wide expansion joint should be set at the joint of the two reinforced concrete raft slabs, and the joint should be filled with insulation board or other soft materials.

[0012] As a further explanation of the present invention, the overall steel frame of the reinforced concrete raft slab includes hidden beams, panel reinforcements and transverse and longitudinal steel bars; the hidden beam is a steel frame, the external stirrups are spaced 10 cm apart and are tied with iron wire and steel bars; the panel reinforcements are steel bars with a diameter of 20 mm; the intersection of the horizontal and vertical steel bars is tied and connected by fine tying wire.

[0013] As a further illustration of the present invention, the embankment reinforcement area is a pile of fill soil of a certain height (the specific height is determined according to the design height of the roadbed) on the natural surface and is manually compacted. The compaction degree should be ≥95%, and the surface is guaranteed to be flat after the compaction degree reaches the requirement. The paving material of the cushion layer is sand or gravel, and the laying thickness is 20 to 40 cm; when laying the cushion layer, a layer of bidirectional geogrid and geotextile should be laid on the leveling layer of the embankment reinforcement area first, and then the cushion layer should be spread, and then the upper grid or geotextile should be laid and rolled to compact. The thermal insulation layer is made of high-performance polystyrene resin material mixed with foaming agent, anti-aging agent and other additives in proportion, or other high-performance heat-resistant materials. The asphalt surface layer is an anti-freeze and anti-ultraviolet radiation asphalt concrete material, and the paving thickness is more than 10 cm.

[0014] The present invention also provides a construction method for the above-mentioned pile-raft integrated roadbed and pavement structure in high-temperature permafrost regions, comprising the following steps: a. Site leveling; b. Laying gravel cushion (embankment reinforcement area); c. The rotary drilling rig enters the site to locate the drilling hole; d. Binding and lowering of specially positioned reinforcement cage inside the pile foundation; e. Pour concrete after forming the hole; f. Crushing the pile head according to the designed elevation and installing the inverted umbrella-shaped rigid hook on the pile top; g. Laying of bidirectional geogrids, geotextiles and cushion layers; h. Lay out high-performance thermal insulation layers; i. Tie up the raft slab steel beams and steel mesh, and support the formwork; j. Raft slab concrete pouring and curing; K. Asphalt surface pouring and curing maintenance.

[0015] Advantages of the present invention: 1. A pile-raft-surface integrated roadbed and pavement structure provided by the present invention in a high-altitude, high-temperature permafrost area: Piles are used as reinforcement bodies to form a bearing system with the soil around the piles and the raft foundation; compared with the single-pile and single-cap structure of other pile rafts, the inside of the raft above the piles of the present invention is a sealed "field" shape composed of a steel bar framework, and then steel bar meshes are tied to the upper and lower surfaces of the framework. The inverted umbrella-shaped hooks at the top of the piles are rigidly connected to the hidden beam framework in the raft to form an integrated structure. After pouring, the pile-raft integrated structure can greatly improve the overall bearing capacity of the roadbed. The soil arch effect formed by the piles can radiate the soil between the piles under the raft over a larger range, enabling the piles and the soil to reasonably share the load.

[0016] 2. The present invention saves the force transmission process of the embankment fill. The upper load is directly borne by the piles and the soil between the piles, making the designed structure have a higher force-bearing efficiency and reducing the settlement and deformation of the roadbed caused by the compression of the embankment fill. The cushion layer and the high-performance heat insulation layer can both block the intrusion of external heat of the roadbed, effectively solving the roadbed deformation problems caused by permafrost degradation, high-frequency repeated freezing and thawing of the active layer, insufficient soil arch effect of the pile foundation, and differential settlement of the embankment fill in the highway corridor belt.

[0017] 3. The heat insulation layer of the present invention selects a high-performance XPS thermal insulation board or other thermal resistance materials. It is an extruded polystyrene thermal insulation board, which is made of polystyrene resin as the raw material, plus butane foaming agent and flame retardant and other additives, and is extruded into a rigid foam plastic board by heating and stirring while adding a catalyst. Its extremely low thermal conductivity can effectively block heat transfer, provide excellent thermal insulation performance, isolate the heat conduction of the ground, keep the roadbed temperature stable, and reduce the frost heave or thaw settlement phenomenon of the roadbed caused by temperature changes; its high compressive strength and durability can ensure that the thermal insulation board maintains its performance in the harsh plateau construction environment and bears the heavy load of the road surface without deformation, sufficient to cope with the high-load environment of the plateau heavy load, and cooperate with the cushion layer to evenly disperse the load to the piles, improving the stability of the roadbed; its closed-cell structure results in low water absorption, improves the drainage performance, and is not easily damaged in the freeze-thaw cycle; there are also advantages such as being lightweight, environmentally friendly, non-toxic and harmless, and recyclable, which all meet the requirements of plateau construction in all aspects.

[0018] 4. The present invention optimizes the pile foundation diameter, pile foundation spacing, hidden beam structure and raft reinforcement ratio, shortens the pile length to within 15m and allows the pile foundation to be located in the high-temperature frozen soil layer. The pile spacing is increased to more than 4m so that 3 piles can be set in the cross-section direction of the roadbed to meet the deformation control requirements. Compared with the patent CN108265735A, the underground engineering volume and process complexity are greatly reduced, and it is suitable for the harsh climate environment and complex geological environment of the plateau. Compared with the drilling and sinking prefabricated pile process adopted by the patent CN108265735A, the present invention adopts bored cast-in-place piles. Since the freezing force of the pile-soil interface is greatly improved, the number of pile foundations is reduced while ensuring that the bearing capacity meets the requirements. At the same time, the present invention adds hidden beams in the raft to connect the pile foundations in each unit as a whole, which can better adapt to the differential settlement caused by uneven degradation of high-temperature frozen soil. Compared with the invention patent CN115075281B, the bored pile concrete mentioned in the present invention can use low-heat cement, control the hydration heat of concrete, and simply and easily realize the protection of frozen soil around the pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The cross-sectional structure schematic diagram of a pile-raft integrated roadbed and pavement structure in a high-temperature permafrost region according to an embodiment of the present invention.

[0020] Figure 2 It is a top view schematic diagram of the buried inverted umbrella-shaped hooks on the top surface of the pile foundation and the wavy geogrid in the pile-raft integrated roadbed and pavement structure in a high-temperature permafrost region according to one embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the steel mesh inside the raft slab in a pile-raft integrated roadbed and pavement structure in a high-temperature permafrost region according to an embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the inverted umbrella-shaped rigid structure of the rigid pile reinforcement cage and the pile body in the pile-raft integrated roadbed and pavement structure in a high-temperature permafrost region according to an embodiment of the present invention.

[0023] In the accompanying drawings, A-natural ground, 1-high-temperature permafrost layer, 2-seasonal active layer, 3-embankment reinforcement area, 4-bored cast-in-place piles, 41-special positioning steel cage, 411-hoops, 412-vertical main steel bars, 413-positioning steel bars, 5-cushion layer, 6-insulation layer, 7-reinforced concrete raft, 71-hidden beam, 72-panel reinforcement, 73-horizontal and vertical steel bars, 8-asphalt surface layer, 9-inverted umbrella-shaped rigid hook on the top of the pile. DETAILED DESCRIPTION

[0024] The following will further describe the implementation of the technical solution of the present invention in detail with reference to the accompanying drawings and specific embodiments, but they do not constitute a limitation of the present invention. The advantages of the present invention are made clearer and easier to understand through the description.

[0025] Embodiment: A pile-raft integrated roadbed and pavement structure in a high-temperature permafrost region, such as Figure 1 The structure shown includes: a high-temperature permafrost layer 1, a seasonally active layer 2, an embankment reinforcement area 3, bored cast-in-place piles 4, a cushion layer 5, an insulation layer 6, a reinforced concrete raft slab 7, an asphalt surface layer 8 and an inverted umbrella-shaped rigid hook 9 on the pile top.

[0026] The high-temperature permafrost layer 1 is a soil layer with a temperature between -1.5 and 0°C and frozen for two years or more, also known as near-phase change zone permafrost; the seasonally active layer 2 is a soil layer that melts in summer and freezes in winter; the embankment reinforcement area 3 is artificially compacted fill on the surface, laid above the seasonally active layer 2; the cushion layer 5 is laid below the insulation layer 6 and above the embankment reinforcement area 3; the reinforced concrete raft 7 is formed by an integral steel frame and C40 concrete slurry cast in situ, and is located above the insulation layer 6; the asphalt surface layer 8 is asphalt concrete, paved on the reinforced concrete raft 7; the bored piles 4 are arranged at intervals and vertically penetrate the insulation layer 6, the cushion layer 5, the embankment reinforcement area 3, and the seasonally active layer 2 into the high-temperature permafrost layer 1; the pile top inverted umbrella-shaped rigid hook 9 is connected to the pile top of the bored pile 4, and is cast together with the pile top in the integral steel frame inside the reinforced concrete raft 7 to form a pile-plate rigid connection integration.

[0027] This embodiment further illustrates that the bored pile 4 is a bored cast-in-place concrete pile using a rotary drilling process, with a pile length of 5 to 15 m. The pile diameter is 0.2 to 0.8 m, and the longitudinal and transverse spacing of the piles is set at 3 to 6 times the pile diameter. The vertical spacing passes through the seasonal active layer and is driven into the permafrost bearing layer. The distance between the center of the bored pile and the edge of the foundation should not be less than 1 times the pile diameter; the distance between the edge of the pile and the edge of the foundation (strip foundation) should not be less than 75 mm. The pile length should be such that the pile end passes through the active soil layer with higher compressibility and enters the permafrost soil layer with relatively lower compressibility. The interior of the bored cast-in-place concrete pile contains a specially positioned steel cage 41; Figure 4 As shown, the special positioning steel cage 41 includes vertical main steel bars 412, stirrups 411 and positioning steel bars 413; the vertical main steel bars 412 are arranged in a circular array; the stirrups 411 are circularly tied to the vertical main steel bars from top to bottom; the positioning steel bars 413 are arranged in a group every 2 to 5 meters, and 4 steel bars are evenly arranged in each group.

[0028] This embodiment further illustrates that the pile top inverted umbrella-shaped rigid hook 9 is connected to the top of the vertical main steel bar 412 by welding.

[0029] This embodiment further illustrates that Figure 2As shown, the thickness of the reinforced concrete raft 7 is 30 to 50 cm, the length of the slab connection can be 10 meters, and 4 to 9 bored piles 4 are laid at the bottom of each reinforced concrete raft 7; a 1 cm wide expansion joint should be set at the joint of the two reinforced concrete rafts, and the joint should be filled with insulation board or other soft materials.

[0030] This embodiment further illustrates that Figure 3 As shown, the integral reinforcement frame of the reinforced concrete raft 7 includes a hidden beam 71, a panel reinforcement rib 72 and horizontal and vertical reinforcement 73; the hidden beam 71 is a reinforcement frame, and the external stirrups are spaced 10 cm apart and are tied with iron wire and reinforcement; the panel reinforcement rib 72 is a reinforcement with a diameter of 20 mm; the intersection of the horizontal and vertical reinforcement 73 is tied and connected by fine tying wire.

[0031] This embodiment further illustrates that the embankment reinforcement area 3 is formed by piling up fill on the natural surface and performing artificial compaction, and the compaction degree should be ≥ 95%. After the compaction degree reaches the requirement, the surface is guaranteed to be flat.

[0032] This embodiment further illustrates that the paving materials of the cushion layer 5 are medium sand, coarse sand, and well-graded gravel, the maximum sand and gravel particle size should not be greater than 30 mm, and the paving thickness is 20 to 40 centimeters; when laying the cushion layer 5, a layer of bidirectional geogrid and geotextile should be laid on the leveling layer of the embankment reinforcement area 3 first, and then the cushion layer is spread, and then the upper grid or geotextile is laid, and then compacted.

[0033] This embodiment further illustrates that the thermal insulation layer 6 is made of a high-performance polystyrene resin material mixed with a foaming agent and an anti-aging agent in proportion and extruded, or other high-performance heat-resistant materials; the asphalt surface layer 8 is an antifreeze and anti-ultraviolet radiation asphalt concrete material with a paving thickness of more than 10 cm.

[0034] In this embodiment, the specific implementation process of bored cast-in-place concrete pile construction in high-temperature permafrost areas is as follows: ① Before construction, understand the geological survey data of permafrost at the construction site, prepare the construction organization design, and complete the preparations and emergency measures for the raw materials required during the drilling and grouting process; ② After marking the hole position, the drilling rig is put in place and debugged properly; ③ Prepare mud wall protection and slag removal, inject clean water and additives, and use original soil to make mud wall protection; ④ During the drilling process, pay attention to the operation of the machine, observe whether there are any abnormal conditions at the hole mouth and the surrounding area, ensure that the machine arm operates within a certain range, and the inclination of the borehole is controlled within the standard range, and the original soil of the borehole is transported away in time; ⑤ After the hole is formed, the hole depth, hole diameter, and inclination are tested and qualified, and the drilling is terminated; ⑥ For the steel cage After the length, diameter and welding condition are inspected and found to meet the standards, the steel cage is hoisted into the hole; ⑦ Concrete is poured with the help of a conduit. For a pile diameter of 60cm, a pouring conduit with a diameter of 200mm and a wall thickness of 3-5mm is used to keep the inner wall smooth, with a flow capacity of 10m³ / h; the conduit is sealed with a quick connector and cleaned in time after the pouring is completed; ⑧ After the concrete is solidified and formed, the hole shape is repaired. When the concrete reaches a certain strength, a low-strain dynamic test is used to detect the integrity of the pile body; The detailed operation process should also be determined based on the actual situation on the engineering site. This process is only some of the main operations of the present invention during implementation.

[0035] At the same time, the reinforced concrete pile contains a specially positioned steel cage (such as Figure 4 ); The specially designed positioning steel cage includes vertical main steel bars, stirrups and positioning steel bars; the vertical main steel bars are arranged in a circular array; the stirrups are tied to the vertical main steel bars in a circular manner from top to bottom; the positioning steel bars are arranged in a group every 2m, and each group of 4 bars is evenly arranged; the overlapped part of the steel bars themselves is welded on one side, and each section of the main bars is welded with a steel sleeve connector or butt welding. The allowable deviation of the steel cage diameter is ±10mm, and the allowable deviation of the steel cage length is ±100mm. The inverted umbrella-shaped rigid hook on the pile top is made after the cushion layer is laid, and its connection with the steel cage can be welded or assembled with a threaded interface.

[0036] The cushion layer material is medium-coarse sand or crushed stone with a thickness of 20 to 40 cm. When laying the cushion layer, a layer of geogrid should be laid on the pile top leveling layer first, and then the material should be spread. High-strength corrugated geogrid should be added at the center position below the pile raft. If the soil properties of the construction site are poor, one layer can be laid at the bottom and middle layer of the cushion layer, and then the geotextile can be laid and compacted.

[0037] The thermal insulation layer uses XPS insulation board or other high-performance heat-resistant materials. The insulation board is an extruded polystyrene insulation board, which is made of polystyrene resin as raw material, butane foaming agent and flame retardant and other additives. It is a rigid foam plastic board extruded by heating, stirring and adding catalyst. Its extremely low thermal conductivity can effectively block heat transfer, provide excellent thermal insulation performance, isolate ground heat conduction, maintain the stability of the roadbed, and reduce the frost heave or thaw settlement of the roadbed due to temperature changes; its high compressive strength and durability can ensure that the insulation board maintains its performance in the harsh plateau construction environment and withstands heavy road loads without deformation, thereby improving the stability of the roadbed. The construction technology of reinforced concrete raft slab mainly includes: 1. Repair the road surface flatness and the extra steel bar structure of the pile foundation within the allowable range; 2. Design the raft frame according to the pile foundation hole position, and then place the horizontal and vertical raft support internal steel bars based on the frame foundation; 3. After the reinforcement is tied, use the conduit to evenly pour concrete into all positions of the panel, and use a concrete vibrator to make it dense and improve the strength; use a ground trowel to process the concrete pavement to meet the flatness requirements; and conduct a quality inspection after a period of solidification.

[0038] The reinforced concrete raft slab is a C40 cast-in-place antifreeze concrete slab with a thickness of 50cm, a joint length of 10m, and a joint width of 1cm. After pouring, it is immediately covered and maintained. After the raft slab concrete reaches the designed strength, the pavement structure layer is laid; the raft slab (such as Figure 2 , Figure 3 ) includes hidden beam, panel reinforcement and horizontal and vertical steel bars; the hidden beam is a steel frame, the external stirrups are 10cm apart and are tied with iron wire and steel bars; the intersection of horizontal and vertical steel bars is connected by thin binding wire; the inverted umbrella-shaped rigid hook on the top of the pile is made of corrosion-resistant high-strength material, which can be directly welded or connected with the steel cage inside the pile by threaded interface, and cast in the rigid raft.

[0039] Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation of the present invention. For ordinary technicians in the relevant technical field, other different forms of changes or modifications can be made based on the above description; it is not necessary and impossible to list all the implementation methods here; and the obvious changes or modifications derived from them are still within the protection scope of the present invention.

Claims

1. A pile-raft integrated roadbed and pavement structure in high-temperature permafrost areas, characterized in that include: High-temperature permafrost layer (1), seasonally active layer (2), embankment reinforcement area (3), bored cast-in-place piles (4), cushion layer (5), thermal insulation layer (6), reinforced concrete raft slab (7), asphalt surface layer (8) and inverted umbrella-shaped rigid hook on the pile top (9); The high-temperature permafrost layer (1) is a layer of soil with a temperature between -1.5 and 0°C and frozen for two years or more, also known as permafrost in the near phase transition zone; The seasonally active layer (2) is a soil layer that melts in summer and freezes in winter; The embankment reinforcement area (3) is artificially compacted fill on the surface, laid above the seasonal activity layer (2); The cushion layer (5) is laid below the thermal insulation layer (6) and above the embankment reinforcement area (3); The reinforced concrete raft (7) is formed by an integral steel frame and C40 concrete slurry cast in situ, and is located above the thermal insulation layer (6); The asphalt surface layer (8) is asphalt concrete and is paved on the reinforced concrete raft slab (7); The bored piles (4) are arranged at intervals and driven vertically through the insulation layer (6), the cushion layer (5), the embankment reinforcement area (3), and the seasonal activity layer (2) into the high-temperature permafrost layer (1); The pile top inverted umbrella-shaped rigid hook (9) is connected to the pile top of the bored pile (4) and is cast together with the pile top in the integral steel frame inside the reinforced concrete raft slab (7) to form a pile-slab rigid connection integration.

2. The high temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 1, characterized in that: The bored cast-in-place piles (4) are bored cast-in-place concrete piles produced using a rotary drilling process, with a pile length of less than 15 m, a diameter of greater than 0.8 m, and a pile spacing of greater than 4 m.

3. The high temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 2, characterized in that: The bored cast-in-place concrete pile contains a special positioning steel bar cage (41) inside; the special positioning steel bar cage (41) comprises vertical main steel bars (412), stirrups (411) and positioning steel bars (413); the vertical main steel bars (412) are arranged in a circular array; the stirrups (411) are circularly tied to the vertical main steel bars from top to bottom; the positioning steel bars (413) are arranged in a group every 2 to 5 meters, and 4 steel bars in each group are evenly arranged.

4. The high temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 3, characterized in that: The pile top inverted umbrella-shaped rigid hook (9) is an extension of the vertical main steel bar (412) of the special positioning steel bar cage (41), or is connected to the top of the vertical main steel bar (412) by welding or threaded connection.

5. The high temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 1, characterized in that: The reinforced concrete raft slab (7) has a thickness of 30 to 50 cm and a slab length of 10 m. 4 to 9 bored piles (4) are laid at the bottom of each reinforced concrete raft slab (7). A 1 cm wide expansion joint should be provided at the joint of two reinforced concrete raft slabs, and the joint is filled with an insulation board or other soft material.

6. The high-temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 1 or 5, characterized in that: The integral steel reinforcement frame of the reinforced concrete raft slab (7) comprises a hidden beam (71), a panel reinforcement bar (72) and transverse and longitudinal reinforcement bars (73); the hidden beam (71) is a reinforcement frame, and the external stirrups are spaced 10 cm apart and are tied with iron wire and reinforcement bars; the panel reinforcement bar (72) is a reinforcement bar with a diameter of 20 mm; and the intersection of the transverse and vertical reinforcement bars (73) is tied and connected by thin binding wire.

7. The high-temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 1, characterized in that: The embankment reinforcement area (3) is formed by piling up fill soil on the natural surface and performing artificial compaction. The compaction degree should be ≥ 95%. After the compaction degree reaches the required level, the surface is guaranteed to be flat.

8. The high-temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 1, characterized in that: The paving material of the cushion layer (5) is sand or gravel, and the paving thickness is 20 to 40 cm. When laying the cushion layer (5), a layer of bidirectional geogrid and geotextile should be laid on the leveling layer of the embankment reinforcement area (3) first, and then the cushion layer is spread, and then the upper grid or geotextile is laid and compacted.

9. The high-temperature permafrost region pile-raft integrated roadbed and pavement structure according to claim 1, characterized in that: The heat insulating layer (6) is made of a high-performance polystyrene resin material mixed with a foaming agent and an anti-aging agent in a certain proportion and extruded, or other high-performance heat-resistant materials; the asphalt surface layer (8) is an antifreeze and anti-ultraviolet radiation asphalt concrete material, with a paving thickness of more than 10 cm.

10. A construction method for a pile-raft integrated roadbed and pavement structure in a high-temperature permafrost region as claimed in any one of claims 1 to 9, characterized in that The following steps are involved: a. Site leveling; b. Laying gravel cushion; c. The rotary drilling rig enters the site to locate the drilling hole; d. Binding and lowering of specially positioned reinforcement cage inside the pile foundation; e. Pour concrete after forming the hole; f. Crushing the pile head according to the designed elevation and installing the inverted umbrella-shaped rigid hook on the pile top; g. Laying of bidirectional geogrids, geotextiles and cushion layers; h. Lay out high-performance thermal insulation layers; i. Tie up the raft slab steel beams and steel mesh, and support the formwork; j. Raft slab concrete pouring and curing; K. Asphalt surface pouring and curing maintenance.

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