A foundation pit backfill structure for invading existing roads in soft soil areas

Abstract

The utility model discloses a foundation pit backfill structure for invading existing roads in soft soil areas, including an existing road and an existing roadbed, a bridge pile foundation and a bridge cap are arranged on the side of the existing road, a cap foundation pit invading the existing roadbed is arranged on the side of the bridge cap, a foam concrete layer and a reinforced concrete slab located above the foam concrete layer are arranged in the cap foundation pit, a step is arranged on the side of the existing road, a new road is arranged above the reinforced concrete slab, and a part of the new road is built on the step. This scheme further improves the connection performance of the new road and the existing road formed by the foundation pit backfill invading the existing road, and improves the safety and driving comfort of the road; the differential settlement between the cap foundation pit backfill area and the existing road is coordinated through structures such as the foam concrete layer, so as to improve the safety and driving comfort of the road.

Description

Technical Field

[0001] The utility model relates to the technical field of road construction, in particular to a foundation pit backfill structure for invading existing roads in soft soil areas. Background Art

[0002] With the rapid development of the economy and society, the demand for transportation resources is increasing. At the same time, due to the increasingly tight land resources, it is becoming more and more difficult to open up new transportation corridors. At present, some areas use existing roads to form upper and lower transportation corridors.

[0003] When constructing the upper viaduct, the piers are often dropped in the middle of the existing road. Limited by the width of the middle strip of the existing road, the excavation of the foundation pit will intrude into the existing road lane. At present, the repair of the intruded part of the existing road is often done by backfilling and compacting the original soil or backfilling with graded crushed stone combined with watertight method.

[0004] When such projects occur in soft soil areas, due to the characteristics of soft soil such as large porosity and high compressibility, when the backfill area materials generate additional loads, the soft soil layer will undergo consolidation settlement; and because the width of the foundation pit is often narrow, general engineering materials cannot be filled densely, and compression and compaction settlement will occur during the operation period. However, after several years of operation, the settlement of existing roads has been basically stable after construction. In view of the above reasons, such projects often have uneven lateral settlement between the foundation pit backfill area and the existing road. Uneven lateral settlement in the driving direction will seriously affect driving comfort, reduce vehicle speed and road capacity, and damage the social and economic benefits of transportation infrastructure construction.

[0005] For example, the Chinese patent publication number CN114718076A, published on July 8, 2022, is titled "A method for rapid excavation of foundation pits within the scope of existing municipal roads". Excavation is carried out during the night when the traffic volume of existing municipal roads is low. Before the traffic volume of existing municipal roads returns to normal, 1.5-2.0m3 ton bags filled with sand are used to quickly backfill the excavated foundation pits. Ton bags filled with sand are used to support the excavated foundation pits to prevent collapse of the excavated foundation pits, and 2.5mm-3.0mm thick steel plates (the size of the steel plates needs to be calculated based on the size of the foundation pits and the force of the driving load) are used to restore traffic.

[0006] The disadvantages of the existing patents are that the foundation pit of the pedestal that intrudes into the existing road is often backfilled and compacted with original soil or backfilled with graded crushed stone combined with a watertight method. Since the additional load in the soft soil area is prone to consolidation settlement, the backfill area of ​​the foundation pit of the pedestal that intrudes into the existing road and the existing road suffer from uneven lateral settlement, which seriously affects driving comfort and road traffic capacity. Utility Model Content

[0007] The utility model aims to solve the problem that the additional load in soft soil areas is prone to consolidation settlement, resulting in uneven lateral settlement between the foundation pit backfill area of ​​the foundation pedestal invading the existing road and the existing road, which seriously affects the driving comfort and road traffic capacity. The utility model provides a foundation pit backfill structure for invading existing roads in soft soil areas, which ensures that the foundation pit backfill area of ​​the foundation pedestal invading the existing road does not produce lateral differential settlement with the existing road and ensures the safety and comfort of road driving.

[0008] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0009] A foundation pit backfill structure for invading an existing road in a soft soil area comprises an existing road and an existing roadbed, a bridge pile foundation and a bridge pedestal are arranged on the side of the existing road, a pedestal foundation pit is arranged on the side of the bridge pedestal and the pedestal foundation pit invading the existing roadbed, a foam concrete layer and a reinforced concrete slab located above the foam concrete layer are arranged in the pedestal foundation pit, a step is arranged on the side of the existing road, a new road is arranged above the reinforced concrete slab, and a part of the new road is erected on the step. A foundation pit backfill structure for invading an existing road in a soft soil area described in this scheme comprises a bridge pile foundation and a bridge pedestal set up at the median strip of the road, and the existing road is used to form an upper and lower traffic corridor, and when the bridge pedestal is set up, the pedestal foundation pit is excavated and invading the existing road, that is, it is excavated on the basis of the existing road. In this scheme, the foundation pit of the pedestal that invades the existing road is backfilled with a foamed concrete layer. By utilizing the characteristics of the foamed concrete layer, on the one hand, the compactness of the foundation pit backfill can be ensured. On the other hand, the foamed concrete itself is a lightweight filler and does not generate additional load, thereby reducing the settlement and deformation of the newly built road within the foundation pit of the pedestal. The newly built road is the repair area of ​​the existing road that is invaded by the excavation of the foundation pit of the pedestal. The provision of the reinforced concrete slab makes the force of the foamed concrete layer uniform, thereby ensuring the service life. The lateral excavation of the existing road forms a step. The excavation of the existing road refers to the excavation of the first lane of the existing road to the thickness of the structural layer of the newly built road, and the formation of the step. The step excavation is used to avoid the formation of through cracks, further improve the connection performance of the existing road and the newly built road, and improve the safety and driving comfort of the road. This scheme ensures that the newly built road (i.e., the foundation pit backfill area of ​​the pedestal that invades the existing road) does not produce lateral differential settlement with the existing road, thereby ensuring the safety and comfort of road driving.

[0010] Preferably, a cap covering soil layer is provided above the bridge cap, and the newly built road connects the cap covering soil layer and the existing road. The newly built road is laid between the cap covering soil layer and the steps of the existing road, and the newly built road is partially built on the steps of the existing road.

[0011] Preferably, the number of the foam concrete layers is several layers, and the upper end surface of the uppermost foam concrete layer is lower than the upper end surface of the bridge cap. When the construction of the bridge pile foundation and the bridge cap is completed and passed the inspection, the cap foundation pit that invades the existing roadbed range is poured with foam concrete in layers, generally 1m per layer, and poured to 15cm below the bottom elevation of the new road subbase, to ensure the density of the backfill material and no additional load, eliminate the compression and compaction settlement of the backfill material and the further consolidation settlement of the soft soil layer; after the foam concrete layer meets the requirements, the foundation pit protection plate is removed; a 15cm reinforced concrete slab is poured to make the top surface of the foam concrete layer evenly stressed and no stress concentration occurs.

[0012] Preferably, the upper end surface of the reinforced concrete slab is higher than the upper end surface of the bridge cap, and the cap covering layer is partially built on the reinforced concrete slab. The arrangement of the reinforced concrete slab makes the foam concrete layer evenly stressed and ensures its service life.

[0013] Preferably, the horizontal surface of the step faces upward, and the number of the steps is multiple. The side of the existing road is excavated to form the step, and the excavation of the existing road refers to excavating the first lane of the existing road to the thickness of the structural layer of the newly built road, and then forming the step. The step excavation is used to avoid the formation of through cracks, further improve the connection performance of the existing road and the newly built road, and improve the safety of the road and driving comfort.

[0014] Preferably, the newly built road includes a newly built road subbase, a newly built road base and a newly built road surface layer arranged in sequence from bottom to top, and the newly built road base and the newly built road surface layer are overlapped on the steps in sequence. There are multiple steps, and the newly built road base and the newly built road surface layer are overlapped on adjacent steps respectively to avoid the formation of through cracks, thereby further improving the connection performance between the existing road and the newly built road.

[0015] Preferably, the upper end surface of the newly built road base is paved with a reinforcement net, and the reinforcement net is partially erected on the steps erected on the newly built road base. The first lane of the existing road is excavated to form a step, and the new road subbase is filled. After the maintenance is completed and the indicators are qualified, the new road base is filled. After the maintenance is completed and the indicators are qualified, the road surface reinforcement net is laid and fixed; the new road pavement is constructed to improve the deformation resistance of the new road and improve the safety of the new road.

[0016] Preferably, a part of the subbase of the newly built road is located above the existing roadbed, and another part is located above the reinforced concrete slab. The newly built road partially invades the existing road, that is, part of the newly built road is constructed based on the original existing roadbed.

[0017] Preferably, the reinforcement net includes a frame and a mesh steel wire arranged in the frame, and a plurality of reinforcement rods are arranged in the frame, and the reinforcement rods are arranged transversely. The transversely arranged reinforcement rods improve the transverse tensile strength of the reinforcement net and improve the tensile strength of the newly built road. The reinforcement net can utilize the tensile strength of metal materials to further avoid the formation of through cracks and coordinate the differential settlement between the backfill area of ​​the foundation pit and the existing road.

[0018] Preferably, a foundation pit protection plate is provided on the side of the foundation pit facing the existing roadbed, and the foundation pit protection plate is vertically arranged. A vertical foundation pit protection plate is arranged when the foundation pit is excavated, and the foundation pit protection plate is removed after the foam concrete meets the requirements. The foundation pit protection plate is used to protect the foundation pit backfill area.

[0019] Therefore, the utility model has the following beneficial effects: the foundation pit of the pedestal that intrudes into the existing road is backfilled with a foam concrete layer. By utilizing the characteristics of the foam concrete layer, on the one hand, the compactness of the foundation pit backfill can be ensured; on the other hand, the foam concrete itself is a lightweight filler and does not generate additional load, thereby reducing the settlement and deformation of the newly built road within the foundation pit of the pedestal; step excavation is adopted to avoid the formation of through cracks, thereby further improving the connection performance between the existing road and the newly built road, and improving the safety and driving comfort of the road; the differential settlement between the foundation pit backfill area of ​​the pedestal and the existing road is coordinated through structures such as the foam concrete layer, thereby improving the safety and driving comfort of the road. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the utility model.

[0021] Figure 2 It is a structural schematic diagram of the reinforced mesh in the utility model.

[0022] As shown in the figure:

[0023] Existing road 1, bridge pile foundation 2, bridge pedestal 3, pedestal cover soil layer 4, foam concrete layer 5, reinforced concrete slab 6, steps 7, new road 8, new road subbase 8.1, new road base 8.2, new road surface layer 8.3, reinforced mesh 9, frame 9.1, mesh steel wire 9.2, reinforcing rods 9.3, foundation pit protection plate 10. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the technical solution embodiments of the utility model clearer, the utility model is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0025] Embodiment 1, as Figure 1As shown, a foundation pit backfill structure for invading an existing road in a soft soil area comprises an existing road 1 and an existing roadbed. A bridge pile foundation 2 and a bridge pedestal 3 are arranged on the side of the existing road 1. A pedestal foundation pit invading the existing roadbed is arranged on the side of the bridge pedestal 3. A foam concrete layer 5 and a reinforced concrete slab 6 located above the foam concrete layer 5 are arranged in the pedestal foundation pit. A step 7 is arranged on the side of the existing road 1. A new road 8 is arranged above the reinforced concrete slab 6. Part of the new road 8 is erected on the step 7.

[0026] In the above-mentioned embodiment, a foundation pit backfill structure for a soft soil area intruding into an existing road is used. A bridge pile foundation 2 and a bridge pedestal 3 are set at the median strip of the road. The existing road 1 is used to form an upper and lower traffic corridor. When the bridge pedestal 3 is set, the pedestal foundation pit is excavated to intrude into the existing road 1, that is, it is excavated on the basis of the existing road 1. In this scheme, the pedestal foundation pit intruding into the existing road 1 is backfilled with a foam concrete layer 5. By utilizing the characteristics of the foam concrete layer 5, on the one hand, the compactness of the pedestal foundation pit backfill can be ensured. On the other hand, the foam concrete itself is a lightweight filler and does not generate additional loads, thereby reducing the settlement and deformation of the newly built road 8 within the scope of the pedestal foundation pit. The newly built road is the repair area of ​​the existing road that is intruded by the excavation of the pedestal foundation pit. The provision of the reinforced concrete slab 6 makes the force of the foam concrete layer 5 uniform, ensuring the service life. The side of the existing road 1 is excavated to form a step 7. The excavation of the existing road 1 refers to the excavation of the first lane of the existing road 1 to the thickness of the structural layer of the newly built road 8, and the step 7 is formed. The step 7 is used for excavation to avoid the formation of through cracks, further improve the connection performance of the existing road 1 and the newly built road 8, and improve the safety and driving comfort of the road. The problem that the foundation pit of the cap that invades the existing road 1 is often backfilled and compacted with original soil or backfilled with graded crushed stone combined with watertight method, and the additional load in the soft soil area is prone to consolidation settlement, resulting in uneven lateral settlement between the foundation pit backfill area of ​​the cap that invades the existing road 1 and the existing road 1, seriously affecting the driving comfort and road traffic capacity. Prevent the situation in which the foundation pit backfill area and the existing road 1 often settle laterally. Uneven settlement in the lateral direction of driving will seriously affect the driving comfort, reduce the driving speed of the vehicle and the road traffic capacity, and damage the social and economic benefits of transportation infrastructure construction.

[0027] Based on the first embodiment, further optimization is performed, such as Figure 1 , Figure 2As shown, a foundation pit backfill structure for invading an existing road in a soft soil area comprises an existing road 1 and an existing roadbed. A bridge pile foundation 2 and a bridge cap 3 are provided at the middle dividing strip of the road. A cap foundation pit invading the existing roadbed is provided on the side of the bridge cap 3. A foam concrete layer 5 and a reinforced concrete slab 6 located above the foam concrete layer 5 are provided in the cap foundation pit. A step 7 is provided on the side of the existing road 1. A new road 8 is provided above the reinforced concrete slab 6. Part of the new road 8 is built on the step 7. A cap cover soil layer 4 is provided above the bridge cap 3. The new road 8 connects the cap cover soil layer 4 and the existing road 1. The new road 8 is laid between the cap cover soil layer 4 and the step 7 of the existing road 1. Part of the new road 8 is built on the step 7 of the existing road 1. The reinforced concrete slab 6 has a thickness of 15 cm and adopts C25 cast-in-place concrete and is equipped with 10 cm×10 cm HPB300 steel bars with a diameter of 8 mm.

[0028] Specifically, the number of foam concrete layers 5 is several layers, and the upper end surface of the uppermost foam concrete layer 5 is lower than the upper end surface of the bridge cap 3. When the construction of the bridge pile foundation 2 and the bridge cap 3 is completed and passed the inspection, the cap foundation pit that invades the existing roadbed range of the existing road 1 is poured with foam concrete in layers, generally 1m per layer, and poured to 15cm below the bottom elevation 8.1 of the new road subbase, ensuring the density of the backfill material and no additional load, eliminating the compression and compaction settlement of the backfill material and the further consolidation settlement of the soft soil layer; after the foam concrete layer 5 meets the requirements, the foundation pit protection plate 10 is removed; and a 15cm reinforced concrete slab 6 is poured to make the top surface of the foam concrete layer 5 evenly stressed without stress concentration.

[0029] In this embodiment, the upper end surface of the reinforced concrete slab 6 is higher than the upper end surface of the bridge cap 3, and the cap cover 4 is partially built on the reinforced concrete slab 6. The arrangement of the reinforced concrete slab 6 makes the foam concrete layer 5 evenly stressed and ensures its service life.

[0030] Step 7 is optimized, such as Figure 1 As shown, the horizontal surface of the step 7 faces upward, and there are multiple steps 7. The existing road 1 is excavated sideways to form the step 7. The excavation of the existing road 1 refers to excavating the thickness of the structural layer of the newly built road 8 from the first lane of the existing road 1, and then forming the step 7. The step 7 is used for excavation to avoid the formation of through cracks, further improve the connection performance of the existing road 1 and the newly built road 8, and improve the safety and driving comfort of the road. The newly built road 8 includes a newly built road subbase 8.1, a newly built road base 8.2 and a newly built road surface layer 8.3 arranged from bottom to top, and the newly built road base 8.2 and the newly built road surface layer 8.3 are overlapped on the step 7 in sequence. There are multiple steps 7, and the newly built road base 8.2 and the newly built road surface layer 8.3 are overlapped on adjacent steps 7 respectively, to avoid the formation of through cracks, and further improve the connection performance of the existing road 1 and the newly built road 8.

[0031] Further optimize the new road base 8.2, such as Figure 1 As shown, the upper end surface of the newly built road base 8.2 is paved with a reinforcement net 9, and part of the reinforcement net 9 is set up on the step 7 set up on the newly built road base 8.2. The first lane of the existing road 1 is excavated to form a step 7, and the new road subbase 8.1 is filled. After the maintenance is completed and the indicators are qualified, the new road base 8.2 is filled. After the maintenance is completed and the indicators are qualified, the road surface reinforcement net 9 is laid and fixed; the pavement of the new road 8 is constructed to improve the deformation resistance of the new road 8 and improve the safety of the new road 8. A part of the new road subbase 8.1 is located above the existing roadbed, and the other part is located above the reinforced concrete slab 6. The new road 8 partially invades the existing road 1, that is, part of the new road 8 is constructed based on the original existing roadbed.

[0032] Specifically, Figure 2 As shown, the reinforcement mesh 9 includes a frame 9.1 and a mesh steel wire 9.2 arranged in the frame 9.1. A plurality of reinforcement rods 9.3 are arranged in the frame 9.1, and the reinforcement rods 9.3 are arranged transversely. The transversely arranged reinforcement rods 9.3 improve the transverse tensile strength of the reinforcement mesh 9 and improve the tensile performance of the newly built road 8. The reinforcement mesh 9 can be provided to further avoid the formation of through cracks and coordinate the differential settlement between the foundation pit backfill area and the existing road 1 by utilizing the tensile performance of the metal material. The steel wire of the road reinforcement mesh 9 is treated with hot-dip galvanizing for corrosion protection. The diameter of the mesh steel wire 9.2 is 2mm, the diameter of the edge steel wire is 2.4mm, the diameter of the transverse reinforcement rod 9.3 is 3.4mm, the ultimate tensile strength of the longitudinal mesh steel wire 9.2 is 28kN / m, and the ultimate tensile strength of the transverse mesh steel wire 9.2 is 24kN / m.

[0033] like Figure 1 As shown, a foundation pit protection plate 10 is provided on the side of the foundation pit facing the existing roadbed, and the foundation pit protection plate 10 is vertically arranged. The vertical foundation pit protection plate 10 is arranged when the foundation pit is excavated, and the foundation pit protection plate 10 is removed after the foam concrete meets the requirements. The foundation pit protection plate 10 is used to protect the foundation pit backfill area.

[0034] In the above embodiment, a foundation pit backfill structure invading the existing road is used in a soft soil area. A bridge pile foundation 2 and a bridge cap 3 are set at the median strip of the road. The existing road 1 is used to form an upper and lower traffic corridor. When the bridge cap 3 is set, the cap foundation pit is excavated to invade the existing road 1, that is, it is excavated on the basis of the existing road 1. In this scheme, the cap foundation pit invading the existing road 1 is backfilled with a foam concrete layer 5. By utilizing the characteristics of the foam concrete layer 5, on the one hand, the compactness of the cap foundation pit backfill can be ensured. On the other hand, the foam concrete itself is a lightweight filler and does not generate additional loads, thereby reducing the settlement and deformation of the newly built road 8 within the cap foundation pit range; the provision of the reinforced concrete slab 6 makes the force of the foam concrete layer 5 uniform and ensures the service life. The side of the existing road 1 is excavated to form a step 7. The excavation of the existing road 1 refers to excavating the thickness of the structural layer of the newly built road 8 from the first lane of the existing road 1, and forming the step 7. The step 7 is used for excavation to avoid the formation of through cracks, further improve the connection performance of the existing road 1 and the newly built road 8, and improve the safety and driving comfort of the road.

[0035] Implementation method of this scheme: After the construction of the bridge pile foundation 2 and the bridge pedestal 3 is completed and inspected to be qualified, the pedestal foundation pit that invades the roadbed range of the existing road 1 is poured in layers with foam concrete, generally 1m per layer, and poured to 15cm below the bottom elevation of the new road subbase 8.1, ensuring the density of the backfill material and not generating additional load, eliminating the compression and compaction settlement of the backfill material and the further consolidation settlement of the soft soil layer; after the foam concrete meets the requirements, the temporary excavation protection 10 of the foundation pit is removed; a 15cm reinforced concrete slab 6 is poured to make the top surface of the foam concrete evenly stressed and no stress concentration occurs, and after the strength of the reinforced concrete slab 6 meets the requirements; the first lane of the existing road 1 is excavated and a step 7 is formed, the subbase 8.1 of the new road is filled, and after the maintenance is completed and the indicators are qualified, the base 8.2 of the new road is filled, and after the maintenance is completed and the indicators are qualified, the road reinforcement mesh 9 is laid and fixed; the surface layer 8.3 of the new road is constructed.

[0036] In this embodiment, the designed dry density of the foamed concrete is 6.0 KN / m 3 , 28d compressive strength within the roadbed range ≥ 1.0MPa, 28d compressive strength outside the roadbed range ≥ 0.8MPa, fluidity is 180±20mm. Reinforced concrete slab 6 is 15cm thick, using C25 cast-in-place concrete and 10cm×10cm HPB300 steel bars with a diameter of 8mm. The road reinforcement mesh 9 steel wire is hot-dip galvanized for corrosion protection, mesh steel wire 9.2 diameter 2mm, edge steel wire diameter 2.4mm, transverse reinforcement rod 9.3 diameter 3.4mm, longitudinal mesh steel wire 9.2 ultimate tensile strength 28kN / m, transverse mesh steel wire 9.2 ultimate tensile strength 24kN / m.

[0037] When constructing the upper viaduct, the form of dropping piers in the existing road 1 is often adopted. Due to the width of the strip in the existing road 1, the excavation of the foundation pit of the foundation will intrude into the lane range of the existing road 1. At present, the project often adopts the original soil backfilling and compaction or the graded crushed stone combined with the watertight method backfilling. When such projects occur in soft soil areas, because soft soil has the characteristics of large porosity and high compressibility, when the backfill area material produces additional load, the soft soil layer will undergo consolidation settlement; and because the width of the foundation pit is often narrow, general engineering materials cannot be filled densely, and compression and compaction settlement will occur during the operation period. However, after several years of operation of the existing road 1, the post-construction settlement is basically stable. In view of the above reasons, such projects often have uneven lateral settlement between the foundation pit backfill area and the existing road 1. The uneven lateral settlement in the driving direction will seriously affect the driving comfort, reduce the vehicle driving speed and road traffic capacity, and damage the social and economic benefits of transportation infrastructure construction. For this reason, it is urgent to take engineering measures to ensure the coordination and smoothness between the foundation pit backfill area of ​​the pedestal and the existing road 1, and to ensure the safety and comfort of road driving. The utility model has the following beneficial effects: the foundation pit of the pedestal that invades the existing road 1 is backfilled with a foam concrete layer 5. By utilizing the characteristics of the foam concrete layer 5, on the one hand, the compactness of the foundation pit backfill can be ensured, and on the other hand, the foam concrete itself is a lightweight filler, which does not generate additional loads, and reduces the settlement deformation of the newly built road 8 within the foundation pit of the pedestal; the step 7 is used for excavation to avoid the formation of through cracks, further improve the connection performance of the existing road 1 and the newly built road 8, and improve the safety and driving comfort of the road; the differential settlement between the foundation pit backfill area of ​​the pedestal and the existing road 1 is coordinated through structures such as the foam concrete layer 5, and the safety and driving comfort of the road are improved. The invention solves the problem that the additional load in soft soil areas is prone to consolidation settlement, resulting in uneven lateral settlement between the foundation pit backfill area of ​​the cap invading the existing road 1 and the existing road 1, which seriously affects the driving comfort and road traffic capacity. A foundation pit backfill structure for invading existing roads in soft soil areas is provided, which ensures that the foundation pit backfill area of ​​the cap invading the existing road 1 does not produce lateral differential settlement with the existing road 1 and ensures the safety and comfort of road driving.

[0038] The specific embodiments described above are only preferred implementations of the present invention, and are not intended to limit the specific implementation scope of the present invention. All equivalent changes made in accordance with the shape and structure of the present invention should be included in the protection scope of the present invention.

Claims

1. A foundation pit backfill structure for invading an existing road in a soft soil area, comprising an existing road and an existing roadbed, characterized in that: A bridge pile foundation and a bridge pedestal are provided on the side of the existing road, a pedestal foundation pit invading the existing roadbed is provided on the side of the bridge pedestal, a foam concrete layer and a reinforced concrete slab located above the foam concrete layer are provided in the pedestal foundation pit, a step is provided on the side of the existing road, a new road is provided above the reinforced concrete slab, and a part of the new road is erected on the step.

2. The foundation pit backfill structure for invading existing roads in soft soil areas according to claim 1 is characterized in that: A cap covering soil layer is provided above the bridge cap, and the newly built road connects the cap covering soil layer and the existing road.

3. The foundation pit backfill structure for invading existing roads in soft soil areas according to claim 2 is characterized in that: The number of the foamed concrete layers is several, and the upper end surface of the uppermost foamed concrete layer is lower than the upper end surface of the bridge cap.

4. A foundation pit backfill structure for invading existing roads in soft soil areas according to claim 2 or 3, characterized in that: The upper end surface of the reinforced concrete slab is higher than the upper end surface of the bridge pedestal, and the pedestal covering soil layer is partially built on the reinforced concrete slab.

5. A foundation pit backfill structure for invading existing roads in soft soil areas according to claim 1, 2 or 3, characterized in that: The horizontal surface of the step faces upward, and there are multiple steps.

6. The foundation pit backfill structure for invading existing roads in soft soil areas according to claim 5 is characterized in that: The newly built road comprises a newly built road subbase layer, a newly built road base layer and a newly built road surface layer which are arranged in sequence from bottom to top, and the newly built road base layer and the newly built road surface layer are overlapped on the steps in sequence.

7. The foundation pit backfill structure for invading existing roads in soft soil areas according to claim 6 is characterized in that: The upper end surface of the newly built road base is paved with a reinforcement mesh, and the reinforcement mesh is partially erected on the steps erected on the newly built road base.

8. The foundation pit backfill structure for invading existing roads in soft soil areas according to claim 6 is characterized in that: A portion of the newly constructed road subbase is located above the existing roadbed, and another portion is located above the reinforced concrete slab.

9. The foundation pit backfill structure for invading existing roads in soft soil areas according to claim 7 is characterized in that: The reinforced mesh comprises a frame and mesh steel wires arranged in the frame. A plurality of reinforcing rods are arranged in the frame, and the reinforcing rods are arranged transversely.

10. A foundation pit backfill structure for invading existing roads in soft soil areas according to claim 1, 2 or 3, characterized in that: A foundation pit protection plate is provided on one side of the foundation pit of the cap facing the existing roadbed, and the foundation pit protection plate is vertically arranged.

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