Roadbed structure of road-bridge transition area and construction method

Abstract

The road and bridge transition area roadbed structure comprises a bridge abutment pile foundation, first and second waterproof geotechnical cloth, a light soil layer, an improved soil layer, a retaining wall, an abutment rear pile foundation, a first bearing platform and a second bearing platform, a steel corrugated plate arch is arranged above the area between a bracket and the second bearing platform, and the two ends of the steel corrugated plate arch are fixed to the bracket and the second bearing platform respectively. The construction method comprises the following steps: a) pile foundation construction; b) pouring a first bearing platform and a bracket; c) pouring a second bearing platform; d) constructing a thin wall and an abutment cap; e) pouring the retaining wall; (f) mounting a corrugated arch; g) lower waterproof construction; h) constructing a light soil layer; i) performing waterproof construction; and j) improving soil layer construction. According to the roadbed structure of the road-bridge transition area, the weight of the road-bridge transition area is reduced, the lateral thrust on the thin-wall walls is reduced, the situation that double-row piles of a bridge abutment are reduced to single-row piles due to forward inclination and instability caused by overlarge stress of the bridge abutment is avoided, and the construction cost of a project is reduced. And the sedimentation is reduced.

Description

Technical Field

[0001] The present invention relates to a subgrade structure and a construction method, and more specifically, to a subgrade structure and a construction method for a road-bridge transition zone. Background Art

[0002] In bridge engineering, for the high platform back subgrade where the abutment height exceeds 3m, under the action of the earth pressure behind the abutment and the vehicle load, not only will the subgrade generate large settlements, but also large lateral pressures will be generated on the bridge pile foundation and the front wall. In severe cases, it will cause the abutment to tilt forward and lead to the instability of the bridge structure. In order to ensure the stability of the abutment and the subgrade behind the abutment, traditional designs usually need to adopt double-row pile foundations or gravity-type abutment structures to enhance the overall stability.

[0003] However, the double-row pile foundation or the gravity-type abutment structure has the following technical problems: (1) High cost: The construction cost of the double-row pile foundation or the large-volume concrete gravity-type abutment is high, the material consumption is large, and the economy is poor. (2) Large settlement at the back of the abutment: Due to the high backfill of the abutment and its large self-weight, the backfill behind the abutment is prone to uneven settlement under long-term loads, resulting in the phenomenon of bump at the bridgehead, affecting the driving comfort and safety. (3) Concentration of earth pressure: The earth pressure behind the high abutment is large, which is easy to cause the abutment to tilt forward or crack, affecting the durability of the structure. (4) Complex construction: Traditional backfill behind the abutment needs to be compacted layer by layer, and it is inconvenient for large-scale machinery construction. There are problems such as insufficient compaction prone to occur in high fill sections.

[0004] To solve the above problems, methods such as using lightweight fill reinforced retaining walls have been adopted in the prior art, but there are still problems such as large lateral deformation of the fill and insufficient overall stiffness. Therefore, there is an urgent need for a new type of high platform back subgrade structure that can effectively reduce the earth pressure, reduce the settlement, optimize the stress state of the abutment, and improve the economy and construction efficiency. Summary of the Invention

[0005] The present invention overcomes the above-mentioned technical problems and provides a subgrade structure and a construction method for a road-bridge transition zone.

[0006] The roadbed structure of the road-bridge transition area of the present invention includes a bridge abutment pile foundation, a first waterproof geotextile, a lightweight soil layer, a second waterproof geotextile, an improved soil layer, and a retaining wall. The bridge abutment pile foundation is located in the foundation. A first bearing platform is fixed at the upper end of the bridge abutment pile foundation. A corbel is fixed on the side of the first bearing platform facing the foundation. A thin-walled wall is cast above the first bearing platform; retaining walls are cast on both sides between the thin-walled wall and the roadbed; it is characterized in that: a post-back pile foundation is arranged outside the bridge abutment pile foundation. The post-back pile foundation is inserted into the foundation. A second bearing platform is fixed at the upper end of the post-back pile foundation. The length directions of the second bearing platform and the first bearing platform are consistent with the width direction of the road. The upper edge of the second bearing platform is flush with the upper edge of the corbel; a steel corrugated plate arch is arranged above the area between the corbel and the second bearing platform. The two ends of the steel corrugated plate arch in the width direction of the road are in sealed contact with the inner walls of the two retaining walls. The two ends of the steel corrugated plate arch in the driving direction of the road are respectively fixed on the corbel and the second bearing platform. An arch cavity area is formed between the steel corrugated plate arch and the foundation below; The first waterproof geotextile is laid on the upper surfaces of the corbel, the first bearing platform, the second bearing platform on both sides of the steel corrugated plate arch, and the contact surfaces between the roadbed and the lightweight soil layer. The lightweight soil layer is laid above the first waterproof geotextile and the steel corrugated plate arch; a metal mesh is laid on the upper part of the lightweight soil layer. The second waterproof geotextile is laid above the lightweight soil layer. The improved soil layer is laid above the second waterproof geotextile.

[0007] In the roadbed structure of the road-bridge transition area of the present invention, channel steels are fixed on the upper surfaces of the corbel and the second bearing platform. "U-shaped" anchor bars anchored in the corbel or the second bearing platform are evenly welded on the lower surfaces of the channel steels. The lower end of the steel corrugated plate arch is placed in the groove of the channel steel and is fixedly connected with the channel steel through high-strength bolts.

[0008] In the roadbed structure of the road-bridge transition area of the present invention, the bridge abutment pile foundation is a bored cast-in-place pile, and the post-back pile foundation is a prestressed pipe pile. The diameter of the bridge abutment pile foundation is 1.0 m to 1.5 m, the diameter of the post-back pile foundation is 300 mm to 400 mm, and the distance between the bridge abutment pile foundation and the post-back pile foundation is 3.0 m to 7.0 m.

[0009] In the roadbed structure of the road-bridge transition area of the present invention, the steel corrugated plate arch is a semi-circular arc arch. The span of the steel corrugated plate arch is 3.0 m to 7.0 m. The wave pitch and wave height are 150 mm and 50 mm respectively. The wall thickness is 4.0 mm to 8.0 mm. The material is Q335 steel; a rubber water stop is embedded at the joint of two adjacent steel corrugated plate arches and filled with asphalt mastic; hot asphalt for sealing is coated on the inner walls of the two retaining walls at the two ends of the steel corrugated plate arch in the width direction of the road, and a felt is pasted on the outer surface of the hot asphalt.

[0010] The roadbed structure of the road-bridge transition area of the present invention. The lightweight soil used in the lightweight soil layer is made by mixing fly ash, cement and EPS particles in a volume ratio of 1:(0.2 - 0.3):(0.05 - 0.1). The wet density of the lightweight soil is ≤12kN / m³ and the 28-day compressive strength is ≥0.5MPa. Among the EPS particles constituting the lightweight soil, the particles with a particle size within 1.0mm - 3.0mm account for ≥80%. When filling the lightweight soil layer, the layered filling method is adopted, and the loose paving thickness of each layer during layered filling is ≤100cm.

[0011] The roadbed structure of the road-bridge transition area of the present invention. The metal mesh uses a galvanized steel wire mesh with a wire diameter of 3.0mm - 5.0mm. The tensile strength of the steel wire constituting the galvanized steel wire mesh is ≥500MPa. The mesh size of the galvanized steel wire mesh is 50mm×50mm. The overlapping length of two adjacent metal meshes is ≥10cm, and the overlapping position is tied and fixed with galvanized steel wires. The compaction degree of the improved soil layer is ≥93%.

[0012] The roadbed structure of the road-bridge transition area of the present invention. The width of the corbel along the road driving direction is 40cm - 50cm, and the width of the second bearing platform along the road driving direction is 60cm - 80cm. The concrete grade of the corbel and the second bearing platform is C35 - C40. The distance range from the top of the steel corrugated plate arch to the upper surface of the improved soil layer is 0.8m - 1.2m.

[0013] The roadbed structure of the road-bridge transition area of the present invention. The contact surface between the lightweight soil layer and the roadbed is a multi-level stepped contact surface. The width of each step is not less than 3m, and the height of each step is not less than 2m.

[0014] The roadbed structure of the road-bridge transition area of the present invention. The material of the channel steel is Q355B steel, the section height of the channel steel is 200mm - 250mm, and the anchoring bars use HRB335 steel bars with a diameter of 16mm - 18mm.

[0015] The construction method of the roadbed structure of the road-bridge transition area of the present invention is characterized in that it is realized through the following steps: a). Pile foundation construction: Use a rotary drilling rig to form a hole and pour the abutment pile foundation, and use the synchronous static pressure method to sink the prestressed pipe pile as the pile foundation behind the abutment, and control the elevation error of the abutment pile foundation and the pile foundation behind the abutment within ±20mm. b). Pour the first bearing platform and the corbel: First, bind the structural steel bars of the first bearing platform and the corbel, then evenly weld the anchoring bars at the bottom of the channel steel, and tie the channel steel welded with the anchoring bars to the upper part of the corbel to be poured, and finally pour the concrete to form the first bearing platform and the corbel. c). Pour the second bearing platform; first, bind the structural steel bars of the second bearing platform, then bind the anchor bars welded to the channel steel to the upper part of the structural steel bars of the second bearing platform, and finally pour concrete to form the second bearing platform; d). Construct the thin-walled wall and the coping; first, bind the structural steel bars of the thin-walled wall and the coping on the first bearing platform, and then pour concrete to form the thin-walled wall and the coping; e). Pour the retaining wall; first, lay a crushed stone cushion on the foundation on both sides of the abutment pile foundation and the pile foundation behind the platform, and then pour the retaining wall foundation and the retaining wall above the crushed stone cushion; f). Install the corrugated arch; install the steel corrugated plate arch according to steps f-1) to f-4): f-1). Hoist the steel corrugated plate arch so that the two ends of the steel corrugated plate arch are respectively placed in the grooves of the corbels and the channel steel on the second bearing platform; f-2). Use high-strength bolts with a torque ≥ 300 N·m to fixedly connect with the corbels and the channel steel on the second bearing platform respectively; f-3). Install a rubber water stop at the joint of two adjacent steel corrugated plate arches in the road width direction and then pour asphalt mastic; f-4). Coat hot asphalt on the two ends of the steel corrugated plate arch and the parts where it contacts the inner wall of the retaining wall, and paste tarpaulin on the outer surface of the hot asphalt; g). Conduct the lower waterproof construction; lay the first waterproof geotextile on the upper surfaces of the corbels, the first bearing platform, the second bearing platform on both sides of the steel corrugated plate arch, and the contact surface between the roadbed and the lightweight soil layer. The overlapping width of the waterproof geotextile ≥ 30 cm, and the overlapping position of the waterproof geotextile is sealed with a hot melt welding gun; h). Conduct the lightweight soil layer construction; conduct the construction of the lightweight soil layer according to steps h-1) to h-4): h-1). Pour the lightweight soil layer in a layered filling method, and the thickness of the lightweight soil poured each time is not more than 1 m; h-2). Lay a metal mesh on the upper part of the lightweight soil layer, and then pour a certain thickness of lightweight soil after the metal mesh is laid; h-3). Cure for 28 days after the construction of the lightweight soil layer is completed; h-4). Conduct anti-corrosion treatment on the lower surface of the steel corrugated plate arch using an anti-rust process; i). Conduct the upper waterproof construction; lay the second waterproof geotextile above the lightweight soil layer to form the upper waterproof of the lightweight soil layer; j). Conduct the improved soil layer construction; lay the improved soil above the second waterproof geotextile to form the improved soil layer.

[0016] The beneficial effects of the present invention are as follows: The roadbed structure of the road-bridge transition zone of the present invention is provided with abutment pile foundations, post-abutment pile foundations, corrugated steel plate arches, lightweight soil layers, improved soil layers, first and second waterproof geotextiles, and retaining walls. The post-abutment pile foundations are arranged outside the abutment device. A corbel is provided on the first bearing platform at the upper end of the abutment pile foundation. The upper end of the post-abutment pile foundation is the second bearing platform. The corrugated steel plate arch is arranged above the area between the corbel and the second bearing platform, and its two ends are respectively fixed on the corbel and the second bearing platform. The lightweight soil layer is filled above and on both sides of the corrugated steel plate. The second and first waterproof geotextiles are respectively arranged on the upper side and the lower side of the lightweight soil layer. This structural form of the roadbed structure of the road-bridge transition zone has the following beneficial effects: (1) Significantly reduces the lateral pressure on the thin-walled wall. The corrugated steel arch forms an arch-shaped stress structure. Since the two ends of the corrugated steel plate arch are respectively fixed on the corbel and the second bearing platform, the constant load of the roadbed structure and the moving load during vehicle driving received by the corrugated steel plate arch will be transmitted to the abutment pile foundation and the post-abutment pile foundation through the corbel and the second bearing platform, partially converting the lateral pressure of the lightweight soil layer and the improved soil layer behind the abutment on the thin-walled wall and the abutment cap into the vertical axial force acting on the pile foundation, reducing the lateral thrust on the thin-walled wall, changing the abutment from a double-row pile to a single-row pile, and reducing the project cost.

[0017] (2) Effectively reduces the settlement of the road-bridge transition zone. Since there is an arch cavity area under the corrugated steel plate arch and no filling is required, and the lightweight soil is filled above the corrugated steel plate arch, this combination of lightweight soil and the arch cavity area effectively reduces the weight of the road-bridge transition zone, thus reducing its settlement and avoiding the occurrence of the phenomenon of bump at the bridgehead.

[0018] (3) Optimizes the stress of the abutment. Since the corrugated steel plate arch is a semi-circular arch structure, the downward pressure received by the corrugated steel plate arch near the bridge side will generate a tensile force on the side of the corbel facing the foundation after acting on the corbel, and the moment generated is opposite to the moment direction of the forward pressure of the lightweight soil layer received by the thin-walled wall, which can be said to balance the stress of the abutment pile foundation and the thin-walled wall, avoiding the forward instability of the abutment pile foundation and the thin-walled wall due to excessive moment.

[0019] (4) Saves materials and reduces the project cost. The corrugated steel plate arch is prefabricated in the factory and assembled on site, with fast construction speed and no need for complex formwork support. The lightweight soil does not require heavy compaction equipment, and the layered paving efficiency is high, shortening the construction period. Compared with the double-row pile foundation, this structure only uses a single-row abutment pile foundation, saving the amount of concrete used and reducing the project cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the roadbed structure of the road-bridge transition zone of the present invention; Figure 2 is Figure 1 a cross-sectional view taken along line A-A in Figure 3 This is a schematic diagram of the connection between the corbel or the second bearing platform and the end of the steel corrugated plate arch in the present invention.

[0021] In the figure: 1 abutment pile foundation, 2 post-abutment pile foundation, 3 first bearing platform, 4 second bearing platform, 5 foundation, 6 corbel, 7 steel corrugated plate arch, 8 first waterproof geotextile, 9 lightweight soil layer, 10 metal mesh, 11 second waterproof geotextile, 12 improved soil layer, 13 cavity area under the arch, 14 roadbed, 15 thin-walled wall, 16 coping, 17 retaining wall, 18 retaining wall foundation, 19 gravel cushion, 20 channel steel, 21 anchor bar, 22 high-strength bolt, 23 welding part. Specific embodiments

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] As Figure 1 shown, a structural schematic diagram of the roadbed structure in the road-bridge transition area of the present invention is given. Figure 2 A sectional view of the A-A section in Figure 1 is given. The roadbed structure in the road-bridge transition area shown is composed of an abutment pile foundation 1, a post-abutment pile foundation 2, a first bearing platform 3, a second bearing platform 4, a corbel 6, a steel corrugated plate arch 7, a first waterproof geotextile 8, a lightweight soil layer 9, a metal mesh 10, a second waterproof geotextile 11, and an improved soil layer 12. The abutment pile foundation 1 extends into the foundation 5. The first bearing platform 3 is fixed at the upper end of the abutment pile foundation 1. A thin-walled wall 15 and a coping 16 are also cast above the first bearing platform 3. The corbel 6 is arranged on the side of the first bearing platform 3 facing the roadbed, and the corbel 6 is fixedly connected by a method of casting simultaneously with the first bearing platform 3. The length direction of the first bearing platform 3 is consistent with the road width direction (i.e., the bridge width direction), and a row of abutment pile foundations 1 is cast below the first bearing platform 3 to support it.

[0024] The post-abutment pile foundation 2 is vertically arranged in the foundation 5 outside the abutment pile foundation 1. The post-abutment pile foundation 2 and the abutment pile foundation 1 are arranged at intervals. The second bearing platform 4 is fixed at the upper end of the post-abutment pile foundation 2. The length direction of the second bearing platform 4 is also consistent with the road width direction, so that the second bearing platform 4 and the first bearing platform 3 are parallel to each other. Retaining walls 17 are arranged on both sides of the abutment pile foundation 2 and the post-abutment pile foundation 2. The bottom of the retaining wall 17 is a retaining wall foundation 18, and below the retaining wall foundation 18 is a gravel cushion 19. The gravel cushion 19 is laid in the foundation 5, and the retaining wall foundation 18 and the retaining wall 17 are cast on the gravel cushion 19.

[0025] The steel corrugated plate arch 7 is arranged above the area between the bracket 6 and the second bearing platform 4. The steel corrugated plate arch 7 is a semi-circular arc-shaped arch, and both ends of the steel corrugated plate arch 7 in the road driving direction are fixed on the bracket 6 and the second bearing platform 4 respectively. In order to fix and stably support the steel corrugated plate arch 7, the upper edges of the second bearing platform 4 and the bracket 6 are at the same height. The two sides of the steel corrugated plate arch 7 in the road width direction are in contact with the inner walls of the two retaining walls 17. In order to seal the ends where the steel corrugated arch 7 is in contact with the retaining wall 17, hot asphalt for sealing is coated on the ends of the steel corrugated plate arch 7 and the inner walls of the retaining wall 17, and a felt is pasted on the outer surface of the hot asphalt.

[0026] Lightweight soil layers 9 are filled above and on both sides of the steel corrugated plate arch 7. In order to achieve a stable transition at the contact part between the lightweight soil layer 9 and the roadbed 14, the contact surface between the shown lightweight soil layer 9 and the foundation 14 is a multi-step contact surface. First waterproof geotextiles 8 are laid on the upper surfaces of the brackets 6 on both sides of the steel corrugated plate arch 7, the upper surface of the first bearing platform 3, the upper surface of the second bearing platform 4, and the stepped contact surface between the roadbed 14 and the lightweight soil layer 9. After laying the first waterproof geotextiles 8, it can prevent water from entering the lightweight soil layer 9 from the bottom.

[0027] A metal mesh 10 is laid on the upper part of the shown lightweight soil layer 9. After laying the metal mesh 10, a certain thickness of lightweight soil is laid above the metal mesh 10. The metal mesh 10 can increase the strength of the lightweight soil layer 9. A second waterproof geotextile 11 is laid above the lightweight soil layer 9, and the improved soil layer 12 is laid above the second waterproof geotextile 11. The first waterproof geotextile 8 and the second waterproof geotextile 11 wrap the lightweight soil layer 9, which can prevent external water from entering the lightweight soil layer 9 and causing changes in its structure, thereby affecting the mechanical properties of the lightweight soil layer 9.

[0028] It can be seen that due to the arrangement of the post - abutment pile foundation 2 outside the abutment pile foundation 1, and the steel corrugated plate arch 7 fixed on the upper end of the post - abutment pile foundation 2 and the bracket 6 on the upper end of the abutment pile foundation 1, the steel corrugated plate arch 7 forms an arch - shaped stress structure. After the constant loads of the lightweight soil layer 9, the improved soil layer 12 and the road surface layer and the variable loads generated by the driving vehicles act on the steel corrugated plate arch 7, they will be transmitted to the bracket 6 and the second bearing platform 4 fixedly connected to the bottom end of the steel corrugated plate arch 7, and then converted into vertical axial forces applied to the abutment pile foundation 1 and the post - abutment pile foundation 2, significantly reducing the lateral pressure of the lightweight soil layer 9 and the improved soil layer 12 on the first bearing platform 3, the thin - walled wall 15 and the abutment cap 16. In this way, a row of abutment pile foundations 1 can achieve stable support for the road - bridge transition zone roadbed, without the need to use double - row pile foundations. While ensuring the stability of the road - bridge transition zone roadbed, the project cost is reduced.

[0029] The steel corrugated plate arch 7 is divided into front and rear parts from its top for stress analysis. For the front half of the steel corrugated plate arch 7 close to the thin-walled wall 15, after the upper load acting on it is transmitted to the corbel 6 through the steel corrugated plate arch 7, a tensile force towards the subgrade 14 side will be generated on the corbel 6. That is, the thin-walled wall 15, the first bearing platform 3, and the abutment pile foundation 1 will receive the tensile force from the steel corrugated plate arch 7 towards the subgrade 14 side. This tensile force will offset the lateral pressure towards the bridge direction generated by the lightweight soil layer 9, the improved soil layer 12, and the vehicle load, which can be said to balance the pressure in the driving direction of the abutment back and is beneficial to maintaining the stability of the abutment pile foundation 1.

[0030] At the same time, since the lower part of the steel corrugated plate arch 7 is the arch cavity area 13, and the lightweight soil layer 9 uses lightweight soil, the self-weight of the roadbed structure in the road-bridge transition area is effectively reduced, which is beneficial to reducing the post-construction settlement and avoiding the occurrence of vehicle jumping at the bridgehead.

[0031] In order to achieve the firm connection between the corbel 6, the second bearing platform 4, and the steel corrugated plate arch 7, channels 20 are fixed on the corbel 6 and the second bearing platform 4, and then the channels 20 are fixedly connected to the steel corrugated plate arch 7. As Figure 3 shown, the connection diagram of the corbel or the second bearing platform and the end of the steel corrugated plate arch in the present invention is given. The bottom of the shown channel 20 is evenly welded with anchor bars 21 along its length direction. The welded part 23 is formed at the welded part of the anchor bars 21 and the channel 20, and the anchor bars 21 are anchored in the corbel 6 and the second bearing platform 4. The bottom of the steel corrugated plate arch 7 is fixedly connected to the side wall of the channel 20 through high-strength bolts 22. In this way, the lower end of the steel corrugated plate arch 7 can be firmly fixed on the corbel 6 and the second bearing platform 4.

[0032] Among them, the abutment pile foundation 1 can adopt bored cast-in-place piles, the pile foundation 2 behind the abutment can adopt prestressed pipe piles. The diameter range of the abutment pile foundation 1 is 1.0m - 1.5m, the diameter range of the pile foundation 1 behind the abutment is 300mm - 400mm, and the distance between the abutment pile foundation 1 and the pile foundation 2 behind the abutment is 3.0m - 7.0m.

[0033] The span of the steel corrugated plate arch 7 is 3.0m - 7.0m, the wave pitch and wave height are 150mm and 50mm respectively, the wall thickness is 4.0mm - 8.0mm, and the material is Q335 steel. In the road width direction, if more than two sections of the steel corrugated plate arch 7 are used for lapping, a rubber water stop is embedded at the joint of two adjacent steel corrugated plate arches 7 and filled with asphalt mastic to ensure the sealing performance at the lapping position.

[0034] The lightweight soil used in the lightweight soil layer 9 is made by mixing fly ash, cement, and EPS particles in a volume ratio of 1:(0.2 - 0.3):(0.05 - 0.1). The wet density of the lightweight soil is ≤12kN / m³ and the 28-day compressive strength is ≥0.5MPa; among the EPS particles constituting the lightweight soil, the particles with a particle size within 1.0mm to 3.0mm account for ≥80%; when filling the lightweight soil layer, the layered filling method is adopted, and when filling in layers, the loose paving thickness of each layer is ≤100cm.

[0035] The metal mesh 10 can use a galvanized steel wire mesh with a wire diameter of 3.0mm to 5.0mm. The tensile strength of the steel wire constituting the galvanized steel wire mesh is ≥500MPa. The mesh size of the galvanized steel wire mesh is 50mm × 50mm. The lapping length of two adjacent metal meshes 10 is ≥10cm, and the lapping position is tied and fixed with galvanized steel wires; the compaction degree of the improved soil layer 12 is ≥93%.

[0036] The width of the corbel 6 along the road driving direction is 40cm to 50cm, the width of the second bearing platform 4 along the road driving direction is 60cm to 80cm, and the concrete grade used for the corbel 6 and the second bearing platform 4 is C35 - C40. The distance from the top of the steel corrugated plate arch 7 to the upper surface of the improved soil layer 12 ranges from 0.8m to 1.2m.

[0037] The contact surface between the lightweight soil layer 9 and the roadbed 14 is a multi-step contact surface. The width of each step is not less than 3m, and the height of each step is not less than 2m. The material of the channel steel 20 is Q355B steel, the cross-sectional height of the channel steel 20 is 200mm to 250mm, and the anchoring bars 21 use HRB335 steel bars with a diameter of 16mm to 18mm.

[0038] The construction method of the road and bridge transition zone roadbed structure of the present invention is specifically realized through the following steps: a). Pile foundation construction; use a rotary drilling rig to form a hole and pour the abutment pile foundation 1, use the synchronous static pressure method to sink the prestressed pipe pile as the back abutment pile foundation 2, and control the elevation error of the abutment pile foundation 1 and the back abutment pile foundation 2 within ±20mm; b). Pour the first bearing platform and the corbel; first tie the structural steel bars of the first bearing platform 3 and the corbel 6, then evenly weld the anchoring bars 21 at the bottom of the channel steel 20, and tie the channel steel 20 welded with the anchoring bars 21 to the upper part of the corbel 6 to be poured, and finally pour the concrete to form the first bearing platform 3 and the corbel 6; c). Pour the second bearing platform; first tie the structural steel bars of the second bearing platform 4, then tie the anchoring bars 21 welded to the channel steel 20 to the upper part of the second bearing platform structural steel bars, and finally pour the concrete to form the second bearing platform 4; d). Construction of thin-walled wall and abutment cap; First, bind the structural steel bars of the thin-walled wall and abutment cap on the first bearing platform 3, and then pour concrete to form the thin-walled wall 15 and the abutment cap 16; e). Pour the retaining wall; First, lay a gravel cushion layer 19 on the foundation 5 on both sides of the bridge abutment pile foundation 1 and the pile foundation 2 behind the platform, and then pour the retaining wall foundation 18 and the retaining wall 17 above the gravel cushion layer; f). Install the corrugated arch; Install the steel corrugated plate arch 7 according to steps f-1) to f-4): f-1). Hoist the steel corrugated plate arch 7 so that both ends of the steel corrugated plate arch 7 are respectively placed in the grooves of the channel steel 20 on the corbel 6 and the second bearing platform 4; f-2). Use high-strength bolts 22 with a torque ≥ 300 N·m to fixedly connect with the corbel 6 and the channel steel 20 on the second bearing platform 4 respectively; f-3). Install a rubber waterstop at the joint of two adjacent steel corrugated plate arches 7 in the road width direction and then pour asphalt mastic; f-4). Coat hot asphalt on both ends of the steel corrugated plate arch 7 and the parts where it contacts the inner wall of the retaining wall, and paste felt on the outer surface of the hot asphalt; g). Lower waterproof construction; Lay the first waterproof geotextile 8 on the upper surfaces of the corbels 6, the first bearing platform 3, the second bearing platform 4 on both sides of the steel corrugated plate arch 7, and the contact surface between the roadbed 14 and the lightweight soil layer 9. The overlapping width of the waterproof geotextile is ≥ 30 cm, and the overlapping position of the waterproof geotextile is sealed with a hot melt welding gun; h). Lightweight soil layer construction; Construct the lightweight soil layer 9 according to steps h-1) to h-4): h-1). Pour the lightweight soil layer 9 by means of layered filling, and the thickness of the lightweight soil poured each time is not greater than 1 m; h-2). Lay a metal mesh 10 on the upper part of the lightweight soil layer 9, and then pour a certain thickness of lightweight soil after the metal mesh 10 is laid; h-3). Cure for 28 days after the construction of the lightweight soil layer 9 is completed; h-4). Carry out anti-corrosion treatment on the lower surface of the steel corrugated plate arch 7 by using an anti-rust process; i). Upper waterproof construction; Lay the second waterproof geotextile 11 above the lightweight soil layer 9 to form the upper waterproof of the lightweight soil layer; j). Improved soil layer construction; Lay improved soil above the second waterproof geotextile 11 to form the improved soil layer 12.

[0039] It can be seen that the roadbed structure and construction method of the road-bridge transition zone of the present invention achieve the construction of a structure and construction method with low soil pressure, small settlement, excellent stress, fast construction, and low cost for the high embankment roadbed in the road-bridge transition area through the innovative arch support system and lightweight soil filling technology. It is especially applicable to the approach road projects of bridges with high abutments over 3m and in soft soil areas. Compared with the existing roadbed structures in the road-bridge transition zone, it has obvious technical advantages.

Claims

1. A road and bridge transition zone subgrade structure, comprising a bridge abutment pile foundation (1), a first waterproof geotextile (8), a lightweight soil layer (9), a second waterproof geotextile (11), an improved soil layer (12) and a retaining wall (17). The bridge abutment pile foundation is located in the foundation (5), the upper end of the bridge abutment pile foundation is fixed with a first bearing platform (3), a corbel (6) is fixed on the side surface of the first bearing platform facing the foundation, and a thin-walled wall (15) is cast above the first bearing platform; retaining walls are cast on both sides between the thin-walled wall and the subgrade (14); characterized in that: There is a post - abutment pile foundation (2) arranged outside the abutment pile foundation. The post - abutment pile foundation is inserted into the foundation. A second bearing platform (4) is fixed at the upper end of the post - abutment pile foundation. The length directions of the second bearing platform and the first bearing platform are consistent with the width direction of the road. The upper edge of the second bearing platform is flush with the upper edge of the corbel; above the area between the corbel and the second bearing platform, there is a corrugated steel plate arch (7). The two ends of the corrugated steel plate arch in the width direction of the road are in sealed contact with the inner walls of the two retaining walls. The two ends of the corrugated steel plate arch in the driving direction of the road are respectively fixed on the corbel and the second bearing platform. An arch - under cavity area (13) is formed between the corrugated steel plate arch and the underlying foundation. The first waterproof geotextile is laid on the upper surfaces of the corbel, the first bearing platform, the second bearing platform on both sides of the corrugated steel plate arch (7), and the contact surface between the roadbed and the lightweight soil layer. The lightweight soil layer is laid above the first waterproof geotextile and the corrugated steel plate arch; a metal mesh (10) is laid on the upper part of the lightweight soil layer. The second waterproof geotextile is laid above the lightweight soil layer, and the improved soil layer is laid above the second waterproof geotextile.

2. The roadbed structure of the road-bridge transition zone according to claim 1, characterized in that: Channel steels (20) are fixed on the upper surfaces of the corbel (6) and the second bearing platform (4). "U - shaped" anchor bars (21) anchored in the corbel or the second bearing platform are evenly welded on the lower surfaces of the channel steels. The lower end of the corrugated steel plate arch (7) is placed in the groove of the channel steel and is fixedly connected with the channel steel by high - strength bolts (22).

3. The roadbed structure of the road-bridge transition zone according to claim 1 or 2, characterized in that: The abutment pile foundation (1) is a bored cast - in - place pile, and the post - abutment pile foundation (2) is a prestressed pipe pile. The diameter of the abutment pile foundation is 1.0m - 1.5m, the diameter of the post - abutment pile foundation is 300mm - 400mm, and the distance between the abutment pile foundation and the post - abutment pile foundation is 3.0m - 7.0m.

4. The roadbed structure of the road-bridge transition zone according to claim 1 or 2, characterized in that: The corrugated steel plate arch (7) is a semi - circular arc arch. The span of the corrugated steel plate arch is 3.0m - 7.0m, the wave pitch and wave height are 150mm and 50mm respectively, the wall thickness is 4.0mm - 8.0mm, and the material is Q335 steel; a rubber water stop is embedded at the joint of two adjacent corrugated steel plate arches and filled with asphalt mastic; on the inner walls of the two ends of the corrugated steel plate arch in the width direction of the road and the retaining wall (17), hot asphalt for sealing is coated, and a felt is pasted on the outer surface of the hot asphalt.

5. The roadbed structure of the road-bridge transition zone according to claim 1 or 2, characterized in that: The lightweight soil used in the lightweight soil layer (9) is mixed by fly ash, cement and EPS particles according to a volume ratio of 1:(0.2 - 0.3):(0.05 - 0.1). The wet density of the lightweight soil ≤12kN / m³ and the 28 - day compressive strength ≥0.5MPa; the proportion of EPS particles with a particle size within 1.0mm - 3.0mm in the EPS particles constituting the lightweight soil ≥80%; the lightweight soil layer is filled in a layered filling method, and the loose paving thickness of each layer during layered filling ≤100cm.

6. The roadbed structure of the road-bridge transition zone according to claim 1 or 2, characterized in that: The metal mesh (10) uses a galvanized steel wire mesh with a wire diameter of 3.0mm - 5.0mm. The tensile strength of the steel wires constituting the galvanized steel wire mesh ≥500MPa. The mesh size of the galvanized steel wire mesh is 50mm×50mm. The lapping length of two adjacent metal meshes ≥10cm, and the lapping position is tied and fixed with galvanized steel wires; the compaction degree of the improved soil layer (12) ≥93%.

7. The roadbed structure of the road-bridge transition zone according to claim 1 or 2, characterized in that: The width of the corbel (6) along the road driving direction is 40 cm to 50 cm, and the width of the second bearing platform (4) along the road driving direction is 60 cm to 80 cm. The concrete grade used for the corbel and the second bearing platform is C35 to C40; the distance from the top of the steel corrugated plate arch (7) to the upper surface of the improved soil layer (12) ranges from 0.8 m to 1.2 m.

8. The roadbed structure of the road-bridge transition zone according to claim 1 or 2, characterized in that: The contact surface between the lightweight soil layer (9) and the roadbed (14) is a multi-level stepped contact surface. The width of each step is not less than 3 m, and the height of each step is not less than 2 m.

9. The roadbed structure of the road-bridge transition area according to claim 2, wherein: The material of the channel steel (20) is Q355B steel. The section height of the channel steel is 200 mm to 250 mm, and the anchoring bars (21) are made of HRB335 steel bars with a diameter of 16 mm to 18 mm.

10. A construction method for the roadbed structure of the road-bridge transition zone according to claim 1, characterized in that, It is achieved through the following steps: a). Pile foundation construction; Use a rotary drilling rig to form holes and pour the abutment pile foundation (1), and use the synchronous static pressure method to sink the prestressed pipe piles as the back abutment pile foundation (2), and control the elevation error of the abutment pile foundation (1) and the back abutment pile foundation (2) within ±20 mm. b). Pour the first bearing platform and the corbel; First, tie the structural steel bars of the first bearing platform (3) and the corbel (6), then evenly weld the anchoring bars (21) at the bottom of the channel steel (20), and tie the channel steel (20) welded with the anchoring bars (21) to the upper part of the corbel (6) to be poured. Finally, pour the concrete to form the first bearing platform (3) and the corbel (6). c). Pour the second bearing platform; First, tie the structural steel bars of the second bearing platform (4), then tie the anchoring bars (21) welded to the channel steel (20) to the upper part of the structural steel bars of the second bearing platform. Finally, pour the concrete to form the second bearing platform (4). d). Thin-wall wall and coping construction; First, tie the structural steel bars of the thin-wall wall and the coping on the first bearing platform (3), and then pour the concrete to form the thin-wall wall (15) and the coping (16). e). Pour the retaining wall; First, lay a gravel cushion layer (19) on the foundation (5) on both sides of the abutment pile foundation (1) and the back abutment pile foundation (2), and then pour the retaining wall foundation (18) and the retaining wall (17) above the gravel cushion layer. f). Install the corrugated arch; Install the steel corrugated plate arch (7) according to steps f-1) to f-4): f-1). Lift and install the steel corrugated plate arch (7) so that both ends of the steel corrugated plate arch (7) are respectively placed in the grooves of the channel steel (20) on the corbel (6) and the second bearing platform (4). f-2). Use high-strength bolts (22) with a torque ≥ 300 N·m to fixedly connect with the channel steel (20) on the corbel (6) and the second bearing platform (4) respectively. f-3). Install a rubber water stop at the joint of two adjacent steel corrugated plate arches (7) in the road width direction and then pour asphalt mastic. f-4). Coat hot asphalt on both ends of the steel corrugated plate arch (7) and the parts where it contacts the inner wall of the retaining wall, and paste tarpaulin on the outer surface of the hot asphalt. g). Lower waterproof construction; lay the first waterproof geotextile (8) on the upper surfaces of the corbels (6), the first bearing platform (3), the second bearing platform (4) on both sides of the corrugated steel plate arch (7), and the contact surface between the subgrade (14) and the lightweight soil layer (9). The overlapping width of the waterproof geotextile is ≥ 30 cm, and the overlapping position of the waterproof geotextile is sealed with a hot melt welding gun; h). Lightweight soil layer construction; construct the lightweight soil layer (9) according to steps h-1) to h-4): h-1). Pour the lightweight soil layer (9) in a layered filling method, and the thickness of the lightweight soil poured each time is not more than 1 m; h-2). Lay a metal mesh (10) on the upper part of the lightweight soil layer (9), and then pour a certain thickness of lightweight soil after the metal mesh (10) is laid; h-3). Cure for 28 days after the construction of the lightweight soil layer (9) is completed; h-4). Carry out anti-corrosion treatment on the lower surface of the corrugated steel plate arch (7) using an anti-rust process; i). Upper waterproof construction; lay the second waterproof geotextile (11) above the lightweight soil layer (9) to form the upper waterproof layer of the lightweight soil layer; j). Improved soil layer construction; lay improved soil above the second waterproof geotextile (11) to form an improved soil layer (12).

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