Road structure paved in deep slag backfill areas

Abstract

This utility model discloses a road structure for paving deep slag backfill areas, including a backfill trench carved into the slag backfill area. Boiled piles and a foundation are installed below the backfill trench, with the top surface of the foundation flush with the bottom surface of the backfill trench. An isolation layer is installed inside the backfill trench, its edge extending outward along the top surface of the slag backfill area. A first basalt fiber grid layer is installed above the isolation layer. End walls, attached to the sidewalls of the backfill trench, are installed inside the isolation layer. A lime-soil replacement layer is installed between the end walls, with the top surfaces of the lime-soil replacement layer and the end walls flush with the top surface of the backfill trench. A roadbed structure and a pavement structure are installed above the lime-soil replacement layer and the end walls. This utility model is low-cost and easy to construct, providing a roadbed and pavement structure with high load-bearing capacity, adaptive deformation capacity, and pollution and corrosion resistance for deep slag backfill areas. It effectively suppresses uneven settlement of the roadbed, reduces the occurrence of reflective cracks in the pavement, and thus improves driving stability and safety.

Description

Technical Field

[0001] This utility model relates to the field of road construction technology, and in particular to a road structure for paving in deep slag backfill areas. Background Technology

[0002] Mine pit backfilling refers to the artificial filling of mined-out areas with materials such as slag, waste rock, and fly ash to control rock strata movement and surface subsidence. Timely mine pit backfilling can significantly delay surface subsidence and deformation, but for deep foundation pit backfilling areas with large depths and wide areas, the subsequent subsidence problem is more prominent.

[0003] The reuse of backfilled areas typically depends on the quality, stability, and environmental safety of the backfill. Stable and reliable shallow backfill areas can be used for construction, greening, and warehousing after treatment. However, their use as highway subgrades with extremely high requirements for post-construction settlement and bearing capacity is relatively rare. This is mainly due to the following two reasons: First, the risk of long-term uneven settlement is enormous. Due to the complex composition of backfill materials, uneven particle size distribution, difficulty in ensuring compaction, and limitations of backfilling technology, the backfill will undergo consolidation and rheological effects under its own weight and the dynamic load of traffic above over a long period of time. This can lead to significant secondary settlement or uneven collapse of the foundation even after several years or even decades. This settlement is insidious and delayed, posing a fatal threat to the pavement structure and easily causing longitudinal cracks, rutting, pavement fractures, and other defects, seriously endangering driving safety.

[0004] Secondly, there is the potential hazard of pollutants to the roadbed system. Mining pits often contain pollutants such as heavy metals, acidic wastewater, and mineral processing reagents. During backfilling, these harmful substances may be buried along with the roadbed, subsequently contaminating the soil and groundwater through infiltration. When a highway passes through this area, these pollutants will erode roadbed building materials, reduce the stability of the hydration products of cement and lime-stabilized soil, and exacerbate the dissolution and softening of base materials, thereby fundamentally weakening the overall strength and durability of the roadbed.

[0005] However, with the expansion of urban space and transportation networks, some highway routes inevitably need to traverse these deep slag backfill areas. Therefore, developing a composite roadbed and pavement structure system that combines high load-bearing capacity, adaptive deformation capability, and pollution and corrosion resistance has become an urgent need to ensure the long-term safe operation of highways in slag backfill areas. Summary of the Invention

[0006] This utility model provides a road structure for paving in deep slag backfill areas, which can improve the overall bearing capacity of the backfill foundation, enhance road toughness, and prevent the roadbed material from being contaminated and corroded. Specifically, the following technical solution can be adopted: The road structure paved in a deep slag backfill area according to this utility model includes a backfill trench opened in the slag backfill area. A bored pile is set below the backfill trench, with its lower part connected to a hard soil layer or rock layer. A pile cap is cast on the top surface of the bored pile. The top surface of the pile cap is flush with the bottom surface of the backfill trench. An isolation layer is set on the inner wall of the backfill trench. The edge of the isolation layer extends outward along the top surface of the slag backfill area. A first basalt fiber grid layer is set above the isolation layer and laid along the bottom surface of the backfill trench. An end wall is set inside the isolation layer and attached to the side wall of the backfill trench. A lime-soil replacement layer is set between the end walls. The top surface of the lime-soil replacement layer and the top surface of the end wall are flush with the top surface of the backfill trench. A roadbed structure and a pavement structure are set above the lime-soil replacement layer and the end wall.

[0007] The aforementioned method involves installing bored piles within the slag backfill area, with a pile cap atop each pile. This pile cap provides rigid support to the superstructure, effectively enhancing the bearing capacity of the foundation and mitigating the adverse effects of uneven collapse or secondary settlement in the backfill area on the roadbed and pavement. An isolation layer is installed within the backfill trench, extending its edge to the outside of the trench. This effectively isolates pollutants within the slag backfill area from eroding the roadbed materials, improving the durability of the roadbed structure. The backfill trench also includes a basalt fiber grid layer and a lime-soil replacement layer. The basalt fiber grid layer possesses corrosion resistance, outstanding mechanical properties, and high tensile strength, effectively dispersing stress concentration from the superstructure load and contributing to the stability of the roadbed structure. The lime-soil replacement layer further enhances the roadbed's bearing capacity, reduces post-construction settlement, and provides seepage prevention. Preferably, end walls are installed at both ends of the lime-soil replacement layer to provide confining pressure and lateral restraint, thereby improving structural stability. Through the above-mentioned treatment measures, the roadbed and pavement structure in the deep slag backfill area has high load-bearing capacity, adaptive deformation capacity and pollution and corrosion resistance, which can effectively reduce the occurrence of uneven settlement of the roadbed, reduce the probability of pavement reflective cracks, and improve driving stability and driving safety.

[0008] Preferably, the bored piles are arranged in groups, with each group connected to a pile cap, and the pile caps are evenly spaced within the backfill trench. In this invention, the structure of multiple bored piles connected to the same pile cap improves the compressive strength and stability of the pile cap structure. The spaced distribution of the pile caps within the backfill trench saves investment and shortens the construction period while ensuring the roadbed's bearing capacity.

[0009] Preferably, the isolation layer comprises a lower cement-fly ash solidified soil seal layer and an upper modified bitumen waterproof membrane layer, with both ends of the isolation layer extending outward from the backfill trench by 1-1.2 meters. In this invention, a cement-fly ash solidified soil seal layer with a mass ratio of cement:fly ash:soil = 5:15:80 is first laid on the inner wall and a certain range outside the backfill trench, followed by a layer of SBS modified bitumen waterproof membrane. This not only reinforces the underlying backfill slag but also blocks pollutants in the slag, preventing them from contaminating the upper subgrade materials.

[0010] Preferably, the end wall is a cast-in-place reinforced concrete structure, and the wall thickness is 30-100cm. In this invention, the reinforced concrete end walls constructed at both ends of the backfill trench have high strength and good resistance to soil and water pressure, providing confining pressure and lateral restraint for the lime-soil replacement layer filled within it, thereby improving the compaction and bearing capacity of the lime-soil replacement layer. Preferably, the aforementioned lime-soil replacement layer is lime-stabilized soil composed of lime and cohesive soil. Under normal circumstances, the lime content (based on dry soil mass) is 3-8%, resulting in a CBR ≥ 3 and a compaction degree ≥ 93% for the lime-soil replacement layer.

[0011] Preferably, the roadbed structure comprises, from bottom to top, a lower embankment, a 70cm thick upper embankment, and an 80cm thick cement-stabilized soil subgrade, with a second basalt fiber grid layer between the lower and upper embankments. The lower embankment, like the lime-soil replacement layer, is constructed using lime-stabilized soil with a lime content (based on dry soil mass) of 3-8%, while the upper embankment is constructed using lime-stabilized soil with a lime content (based on dry soil mass) of 5-10%, and the upper embankment has a CBR ≥ 4 and a compaction degree ≥ 94%. Furthermore, a basalt fiber grid layer is provided between the upper and lower embankments to accommodate roadbed deformation and improve the roadbed bearing capacity.

[0012] Preferably, the pavement structure comprises, from bottom to top, an 18cm thick graded crushed stone subbase, a 36cm thick cement-stabilized crushed stone base course, and a 20cm thick asphalt concrete surface course. This structure is low in cost, has high load-bearing capacity, good durability, and is easy to construct and maintain.

[0013] Preferably, the asphalt concrete surface layer comprises, from bottom to top, a 10cm thick coarse-grained ATB-25 asphalt mixture lower layer, a 6cm thick medium-grained AC-20 modified asphalt mixture middle layer, and a 4cm thick fine-grained AC-13 rubber asphalt mixture upper layer. This structure provides good load-bearing capacity, noise reduction, and skid resistance. The reasonable modulus gradient from bottom to top avoids abrupt stress changes and minimizes uneven loads on the roadbed and pavement caused by traffic.

[0014] Preferably, a third basalt fiber grid layer is provided between the subgrade structure and the pavement structure. In this invention, a basalt fiber grid layer is also provided between the 80cm thick cement-stabilized soil subgrade and the 18cm thick graded crushed stone cushion layer to further enhance the bearing capacity of the subgrade.

[0015] This utility model provides a road structure for use in deep slag backfill areas. Addressing the risks of settlement and pollutant erosion of the roadbed in these areas, it strengthens the roadbed's bearing capacity and corrosion resistance by excavating backfill trenches, installing bored piles and pile caps at the bottom, laying a corrosion-resistant isolation layer within the trench, and replacing the soil with lime. Furthermore, the coordinated design of the roadbed and pavement structures further enhances the roadbed's bearing capacity and pavement toughness. This utility model is low-cost and easy to construct, providing a roadbed and pavement structure with high bearing capacity, adaptive deformation capability, and pollution and corrosion resistance for deep slag backfill areas. It effectively suppresses uneven roadbed settlement, reduces reflective cracking in the pavement, and thus improves driving stability and safety. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model.

[0017] Figure 2 yes Figure 1 Enlarged view of part A in the image. Detailed Implementation

[0018] The embodiments of this utility model will be described in detail below with reference to the accompanying drawings. These embodiments are implemented based on the technical solution of this utility model and provide detailed implementation methods and specific construction processes. However, the protection scope of this utility model is not limited to the following embodiments.

[0019] like Figure 1 , 2 As shown, the road structure of this utility model, paved in a deep slag backfill area, firstly, according to the design drawings, the slag backfill area 1 within the road paving area is subjected to dynamic compaction to reduce the compressibility of the foundation soil and increase its strength. Next, a backfill trench is excavated 300cm downwards along the roadbed width at the road paving area. Then, using the bored pile method, holes are drilled into the bottom of the compacted backfill trench to the hard soil or rock layer. A reinforcing cage is placed in the hole, and concrete is poured to form a bored pile 2. Reinforced concrete is then poured onto the top of the bored pile 2 to form a pile cap 3, with the top surface of the pile cap 3 flush with the bottom surface of the backfill trench. The bored piles 2 are arranged in groups; typically, four bored piles 2 form a group, and each group of bored piles 2 is connected to a pile cap 3. Furthermore, the pile caps 3 are evenly distributed within the backfill trench, which not only improves the compressive strength and stability of the pile cap structure but also saves investment and shortens the construction period while ensuring the roadbed's bearing capacity.

[0020] After the construction of the aforementioned cast-in-place piles 2 and pile caps 3 is completed, an isolation layer 4 is constructed within the backfill trench. In this embodiment, the isolation layer 4 adopts a double-layer structure, including a lower cement-fly ash solidified soil seal layer and an upper modified bitumen waterproof membrane layer. The cement-fly ash solidified soil seal layer is prepared by mixing cement, fly ash, and soil in a mass ratio of 5:15:80 and then laying it. A layer of SBS modified bitumen waterproof membrane is then laid on top of this. This structure not only reinforces the underlying backfill slag but also blocks pollutants in the slag, preventing them from contaminating the upper subgrade materials. Furthermore, both ends of the isolation layer 4 extend outward from the backfill trench by 1-1.2 meters to ensure that pollutants such as heavy metal ions are isolated from the subgrade at the edge of the backfill trench, further enhancing the isolation effect between pollutants and the subgrade.

[0021] After the isolation layer 4 is completed, the first basalt fiber grid layer 5 is laid on top of it along the bottom of the backfill trench. The basalt fiber grid has high strength and strong stability. It is located above the pile cap 3 or overlapped between adjacent pile caps 3. It can transfer the upper load to the pile cap 3 and the bored pile 2, avoiding direct action on the slag backfill area 1, and effectively reducing the probability of uneven settlement in the slag backfill area 1.

[0022] An end wall 6, attached to the sidewall of the backfill trench, is provided inside the isolation layer 4. The end wall 6 is typically made of cast-in-place reinforced concrete and has a thickness of 50cm. Between the end walls 6, lime-stabilized soil with a lime content (based on dry soil mass) of 3-8% is filled as a lime-soil replacement layer 7, with a CBR ≥ 3 and a compaction degree ≥ 93%. The top surfaces of the lime-soil replacement layer 7 and the end walls 6 are flush with the top surface of the backfill trench. The lime-soil replacement layer 7 uses high-strength materials, which improves the bearing capacity and durability of the roadbed. The end walls 6 are located at both ends to provide confining pressure and lateral restraint to the lime-soil replacement layer 7, further improving its compaction and bearing capacity.

[0023] A roadbed structure and a pavement structure are set above the lime-soil replacement layer 7 and the end wall 6. The cross-section of the roadbed structure and the pavement structure is a trapezoidal structure with a smaller top and a larger bottom, and the bottom width of the roadbed structure is the same as the width of the backfill trench.

[0024] Specifically, the roadbed structure includes, from bottom to top, a 2-10m thick lower embankment 81, a 70cm thick upper embankment 82, and an 80cm thick cement-stabilized soil subgrade 83. A second basalt fiber grid layer 84 is installed between the lower embankment 81 and the upper embankment 82. The lower embankment 81, like the lime-soil replacement layer 7, is constructed using lime-stabilized soil with a lime content (based on dry soil mass) of 3-8%. The upper embankment 82 is constructed using lime-stabilized soil with a lime content (based on dry soil mass) of 5-10%. A basalt fiber grid layer 84 is installed between the two to accommodate roadbed deformation and improve the roadbed's bearing capacity.

[0025] The pavement structure consists of, from bottom to top, an 18cm thick graded crushed stone subbase 91, a 36cm thick cement-stabilized crushed stone base course 92, and a 20cm thick asphalt concrete surface course 93. This structure is low in cost, has high load-bearing capacity, good durability, and is easy to construct and maintain.

[0026] Preferably, the aforementioned asphalt concrete surface layer 93 comprises, from bottom to top, a 10cm thick coarse-grained ATB-25 type asphalt mixture lower layer, a 6cm thick medium-grained AC-20 type modified asphalt mixture middle layer, and a 4cm thick fine-grained AC-13 type rubber asphalt mixture upper layer. This structure provides good load-bearing capacity, noise reduction, and skid resistance. The reasonable modulus gradient from bottom to top avoids sudden stress changes and minimizes uneven loads on the roadbed and pavement caused by traffic.

[0027] Furthermore, a third basalt fiber grid layer 94 is also provided between the subgrade structure and the pavement structure. That is, the basalt fiber grid is placed between the 80cm thick cement-stabilized soil subgrade 83 and the 18cm thick graded crushed stone cushion layer 9 to enhance the bearing capacity of the subgrade.

[0028] After the road structure is completed, a median strip is set in the center, and curb stones, hard shoulders and earth shoulders are set on both the left and right sides of the lanes.

[0029] Through the above implementation methods, the paving of roads in deep backfill areas can be realized. This type of pavement structure can effectively improve the bearing capacity of the foundation, make the roadbed fill material form a uniformly stressed whole, reduce uneven settlement, and at the same time, the high-toughness pavement structure can effectively reduce the occurrence of reflective cracks and improve driving stability and safety.

[0030] It should be noted that in the description of this utility model, terms such as "front", "rear", "left", "right", "vertical", "horizontal", "inner", and "outer" indicating orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

Claims

1. A road structure paved in a deep slag backfill area, characterized in that: The backfill includes a backfill trench within a slag backfill area. A bored pile, whose lower part is in contact with a hard soil or rock layer, is installed below the backfill trench. A foundation is cast on the top surface of the bored pile, and the top surface of the foundation is flush with the bottom surface of the backfill trench. An isolation layer is installed on the inner wall of the backfill trench, with its edge extending outwards along the top surface of the slag backfill area. A first basalt fiber grid layer is installed above the isolation layer, laid along the bottom surface of the backfill trench. An end wall, attached to the side wall of the backfill trench, is installed inside the isolation layer. A lime-soil replacement layer is installed between the end walls, with the top surface of the lime-soil replacement layer and the top surface of the end walls flush with the top surface of the backfill trench. A roadbed structure and a pavement structure are installed above the lime-soil replacement layer and the end walls.

2. The road structure paved in a deep slag backfill area according to claim 1, characterized in that: The bored piles are arranged in groups, with each group of bored piles connected to a pile cap, and the pile caps are evenly distributed in the backfill trench.

3. The road structure paved in a deep slag backfill area according to claim 1, characterized in that: The isolation layer includes a cement-fly ash solidified soil seal layer below and a modified bitumen waterproof membrane layer above, with both ends of the isolation layer extending outward from the backfill trench by 1 to 1.2 meters.

4. The road structure paved in a deep slag backfill area according to claim 1, characterized in that: The end wall is made of cast-in-place reinforced concrete and the wall thickness is 30~100cm.

5. The road structure paved in a deep slag backfill area according to claim 1, characterized in that: The roadbed structure includes a lower embankment, a 70cm thick upper embankment, and an 80cm thick cement-stabilized soil subgrade arranged sequentially from bottom to top, and a second basalt fiber grid layer is provided between the lower embankment and the upper embankment.

6. The road structure paved in a deep slag backfill area according to claim 1, characterized in that: The road structure includes, from bottom to top, an 18cm thick graded crushed stone subbase, a 36cm thick cement-stabilized crushed stone base course, and a 20cm thick asphalt concrete surface course.

7. The road structure paved in a deep slag backfill area according to claim 6, characterized in that: The asphalt concrete surface layer comprises, from bottom to top, a 10cm thick coarse-grained ATB-25 type asphalt mixture lower layer, a 6cm thick medium-grained AC-20 type modified asphalt mixture middle layer, and a 4cm thick fine-grained AC-13 type rubber asphalt mixture upper layer.

8. The road structure paved in a deep slag backfill area according to claim 1, characterized in that: A third basalt fiber grid layer is provided between the roadbed structure and the pavement structure.

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