Highway subgrade structure filled with loess-mudstone interbedding

Abstract

The utility model discloses a kind of highway subgrade structures of loess-mudstone filler interbedded type filling, it is related to road engineering technical field, including from top to bottom including pavement structure layer and roadbed, still include loess-mudstone interbedded filling body located under roadbed;Loess-mudstone interbedded filling body is formed by at least two layers of mudstone structure layer and at least two layers of loess layer alternate horizontal laying, through the composite structure form of "mudstone structure layer-geosynthetic material layer-loess layer" alternate filling, combined with the high strength, high modulus, good water resistance of mudstone and the advantages of good compactibility, water permeability of loess.The mudstone layer constitutes solid stress skeleton, effectively improves the overall stiffness and bearing capacity of subgrade;Loess layer plays good stress diffusion and buffering effect, inhibits the development of mudstone layer shrinkage and wet expansion crack;The geosynthetic material layer in middle tightly combines material layer of different properties, greatly enhances the shear strength and anti-deformation ability of structure.

Description

Technical Field

[0001] This utility model relates to the field of road engineering technology, specifically to a highway subgrade structure constructed by interlayering loess and mudstone fillers. Background Technology

[0002] As the foundation of the road surface, the stability and durability of the highway subgrade directly affect the overall performance and lifespan of the road. Loess and mudstone are widely distributed in Northwest and North my country, and highway construction often faces the challenge of handling and utilizing large quantities of these materials. Mudstone, when used alone as subgrade fill, is relatively easy to compact into high-strength soil at its optimum moisture content. However, excessively high moisture content can lead to a rubbery texture, while excessively low moisture content results in uneven compaction, making it difficult to compact and prone to significant deformation after wetting. Under unfavorable water erosion conditions, its physical and mechanical properties will change drastically. Loess, an unsaturated structural soil, is highly water-sensitive and prone to collapsing when wetted. It is also easy to compact, exhibiting minimal deformation after wetting when filled at its optimum moisture content, thus meeting the subgrade strength requirements.

[0003] In traditional roadbed filling practices, if loess is used extensively, its collapsibility must be thoroughly treated, and waterproofing and drainage must be strictly controlled, resulting in high costs and uncertain effectiveness. If mudstone is used extensively, problems arise such as high crushing costs, difficulty in compaction, and strength degradation upon contact with water. The common practice is to discard substandard soil and rock as much as possible and borrow high-quality fill material, which not only significantly increases project costs, occupies land resources, and causes environmental pollution, but also fails to achieve effective resource utilization. Therefore, based on the above research and combined with existing technologies, from the perspective of highway waste resource utilization, and adhering to the principle of complementary advantages between loess and mudstone, a loess-mudstone interlayer filling structure for highway roadbeds is proposed to solve the aforementioned problems. Utility Model Content

[0004] The purpose of this invention is to provide a highway subgrade structure constructed with alternating layers of loess and mudstone fill, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: A highway subgrade structure constructed with alternating layers of loess and mudstone fill includes: a pavement structure layer and a roadbed from top to bottom, and a loess-mudstone alternating fill body located below the roadbed; the loess-mudstone alternating fill body is formed by at least two mudstone structure layers and at least two loess layers laid horizontally alternately, with the bottom layer being a mudstone structure layer; the mudstone structure layer is composed of crushed and compacted mudstone fill, and the loess layer is composed of loess fill with a moisture content controlled within ±2% of the optimum moisture content and compacted.

[0006] Furthermore, a geosynthetic material layer for enhancing interlayer bonding and integrity is laid between adjacent mudstone structural layers and loess layers; the geosynthetic material layer is a bidirectional geogrid or warp-knitted polyester geotextile, with an overlap width of not less than 50 cm between widths.

[0007] Furthermore, the slopes on both sides of the loess-mudstone interbedded fill body are provided with mudstone edging layers. The mudstone edging layers are formed by extending horizontally outward by at least 50 centimeters from the outer mudstone structural layer. After the roadbed is formed, the slope is brushed to ensure that the mudstone edging layers completely cover the slope surface.

[0008] Furthermore, multiple vertical drainage blind ditches are arranged longitudinally within the mudstone edging layer. These vertical drainage blind ditches penetrate the slope of the loess-mudstone interlayered fill body from top to bottom and are filled with graded gravel permeable material.

[0009] Furthermore, the road structure layer and the roadbed are positioned higher than the mudstone edging layer.

[0010] Furthermore, the compaction degree of the mudstone structural layer is not less than 95%, and the loose thickness of a single layer is 30-40 cm; the compaction degree of the loess layer is not less than 95%, and the loose thickness of a single layer is 30-40 cm; the material of the roadbed 2 is well-graded gravel or improved soil.

[0011] Compared with the prior art, the beneficial effects of this utility model are: 1. The composite structure, consisting of alternating layers of mudstone, geosynthetic material, and loess, cleverly combines the advantages of mudstone's high strength, high modulus, and good water-tightness with loess's good compaction and permeability. The mudstone layer forms a solid load-bearing skeleton, effectively improving the overall stiffness and bearing capacity of the roadbed. The loess layer plays a good role in stress diffusion and buffering, inhibiting the development of shrinkage and swelling cracks in the mudstone layer. The intermediate geosynthetic material layer tightly binds the different material layers into a cohesive whole, greatly enhancing the structure's shear strength and deformation resistance. This effectively solves the technical problems of uneven settlement and interlayer slippage that are prone to occur in traditional filling methods, thus improving the overall stability and uniformity of the roadbed. Attached Figure Description

[0012] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the loess-mudstone interbedded layer and mudstone structural layer interaction of this utility model; Figure 3 This is a schematic diagram of the connection structure between the loess-mudstone interlayer and the mudstone edging layer of this utility model; Figure 4This is a cross-sectional schematic diagram of the connection structure between the mudstone structure layer and the geosynthetic material layer of this utility model.

[0013] In the diagram: 1. Road surface structure layer; 2. Subgrade; 3. Loess-mudstone interlayer fill; 4. Mudstone structure layer; 5. Loess layer; 6. Mudstone edging layer; 7. Vertical drainage ditch; 8. Geosynthetic material layer. Detailed Implementation

[0014] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0015] In one typical embodiment of this application, please refer to Figures 1-4 A highway subgrade structure with alternating layers of loess and mudstone fill is constructed as follows: First, samples of the original loess and mudstone obtained from the borrow pit were taken for testing to determine the optimum moisture content and maximum dry density of the loess, as well as the uniaxial compressive strength and disintegration resistance of the mudstone. The materials were then pretreated. Mudstone treatment: Use a crusher to break large mudstone blocks into smaller pieces, with the maximum block diameter controlled to no more than 2 / 3 of the designed layer thickness, to ensure the compaction effect.

[0016] Loess treatment: The moisture content of loess is adjusted to within ±2% of its optimum moisture content by turning over and drying or sprinkling water.

[0017] After the original foundation surface is cleaned, leveled and compacted to meet the design requirements, the roadbed filling begins. The bottom layer must be mudstone structure layer 4. Therefore, the first layer of mudstone fill is laid first, with the loose thickness controlled at about 30-40cm. A heavy vibratory roller with a capacity of no less than 20 tons is used for compaction until the compaction degree is no less than 95%. After compaction, the elevation and flatness are checked.

[0018] After the bottom mudstone structure layer 4 passed inspection, the loess layer 5 and mudstone structure layer 4 were alternately filled. Laying geosynthetic materials: On the top surface of the compacted mudstone structure layer 4, lay bidirectional geogrids across the entire cross section. The longitudinal and transverse tensile strength of the geogrids must meet the design specifications, and the overlap width between the geogrids must be strictly guaranteed to be no less than 50 cm. Loess filler is laid on the grid, with a loose thickness of about 30-40cm. After leveling with a grader, it is compacted with a road roller until the compaction degree is not less than 95%.

[0019] Repeat the above process: lay the grid on the compacted loess layer 5, then fill and compact the next layer of mudstone structure 4, and repeat the process until the design elevation is reached, forming an integral loess-mudstone interlayered fill body 3 consisting of at least two layers of mudstone and at least two layers of loess.

[0020] Among them, by transforming the two roadbed fill materials with very different characteristics, namely traditional waste (mudstone) and borrowed (loess), into the main road construction materials, and through hierarchical design, the efficient and comprehensive utilization of earth and stone along the route is realized, which greatly reduces the amount of borrowed fill material and waste slag. The composite structure of alternating rock layers, reinforced layers, and loess layers 5 allows the high strength, high modulus, and good water-tightness of mudstone to complement the good compaction and permeability of loess. The mudstone structural layer 4 forms a solid load-bearing skeleton, effectively improving the overall stiffness and bearing capacity of the roadbed 2. The loess layer 5 in the middle plays a role in stress diffusion and buffering, inhibiting the development of drying shrinkage and wetting expansion cracks in the mudstone layer 4. The geosynthetic material layer 8 further integrates the different material layers into a synergistic whole, greatly enhancing the shear strength and deformation resistance of the structure. During the filling process, slope protection and drainage measures are implemented simultaneously. The mudstone edging layer 6 is constructed as follows: when filling each layer of mudstone structure 4 located on the outer side of the slope, it is overfilled by at least 50 centimeters. After the entire roadbed filling is completed, an excavator is used to trim the slope, removing the overfilled soil to achieve the designed slope ratio. This process ensures that the final slope surface is completely covered by a dense mudstone edging layer 6, thereby utilizing the strong erosion resistance of mudstone to protect the internal loess layer 5.

[0021] Among them, the "mudstone edging" method is adopted, which utilizes the relatively high erosion resistance and good water-proof properties of mudstone to form a solid protective shell, isolating the inner loess layer 5 from atmospheric precipitation and preventing slope erosion and water infiltration.

[0022] Construction of vertical drainage blind ditch 7: After the slope is shaped by brushing, vertical trenches are excavated at certain intervals (such as 10-15 meters) along the longitudinal direction of the road within the mudstone edging layer 6. The trenches should be dug from top to bottom through the entire slope fill body. Then, well-graded and highly permeable sand and gravel material is filled into the trenches and compacted to form vertical drainage blind ditch 7, which is used to promptly remove surface water that seeps into the slope.

[0023] Among them, the vertical drainage blind ditch 7 runs through the slope, which can intercept, collect and discharge water that has seeped into the slope in a timely manner, especially reducing the water level near the mudstone edging layer 6.

[0024] After the loess-mudstone interbedded fill 3 is constructed, the subgrade 2 will be constructed. Subgrade 2 should be filled with well-graded gravel or water-stable materials such as cement and lime-modified soil. The elevation of its top surface must be strictly controlled to ensure that its overall elevation with the pavement structure layer 1 is significantly higher than the top surface elevation of the mudstone edging layers 6 on both sides, thereby ensuring that road surface water can be quickly drained away and will not flow back into the slope. Finally, the pavement structure layer 1 will be laid and compacted in layers according to specifications.

[0025] Working principle: By layering easily collapsible loess and easily softened mudstone with optimized thickness and process, and reinforcing them with geogrid, a high-strength and well-integrated composite roadbed structure is formed. The mudstone structure layer 4 serves as the main load-bearing skeleton, and the loess layer 5 serves as the stress diffusion layer and filler. The two restrict each other and work together to effectively overcome the defects of single materials. The mudstone edging layer 6 and the vertical drainage blind ditch 7 constitute a slope protection system that combines prevention and drainage, which significantly improves the long-term stability and durability of the roadbed.

[0026] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A highway subgrade structure constructed with alternating layers of loess and mudstone fill, comprising, from top to bottom, a pavement structure layer (1) and a roadbed (2), characterized in that: It also includes a loess-mudstone interbedded fill body (3) located below the roadbed (2); the loess-mudstone interbedded fill body (3) is formed by at least two mudstone structural layers (4) and at least two loess layers (5) laid horizontally alternately, and the bottom layer is a mudstone structural layer (4); the mudstone structural layer (4) is composed of crushed and compacted mudstone fill, and the loess layer (5) is composed of loess fill with water content controlled within ±2% of the optimum water content and compacted by rolling.

2. The highway subgrade structure constructed with alternating layers of loess and mudstone fill as described in claim 1, characterized in that: Between the adjacent mudstone structure layer (4) and loess layer (5), a geosynthetic material layer (8) is laid to enhance the interlayer connection and integrity; the geosynthetic material layer (8) is a bidirectional geogrid or warp-knitted polyester geotextile, and its inter-width overlap is not less than 50 cm.

3. The highway subgrade structure constructed with alternating layers of loess and mudstone fill as described in claim 1, characterized in that: The loess-mudstone interbedded fill body (3) has mudstone edging layer (6) on both sides of the slope. The mudstone edging layer (6) is formed by extending horizontally outward at least 50 cm from the outer mudstone structural layer (4). After the roadbed is formed, the slope is brushed so that the mudstone edging layer (6) completely covers the slope surface.

4. The highway subgrade structure constructed with alternating layers of loess and mudstone fill as described in claim 3, characterized in that: Multiple vertical drainage blind ditches (7) are arranged longitudinally within the mudstone edging layer (6). The vertical drainage blind ditches (7) penetrate the slope of the loess-mudstone interlayer filling body (3) from top to bottom, and are filled with graded gravel permeable material.

5. The highway subgrade structure constructed with alternating layers of loess and mudstone fill as described in claim 4, characterized in that: The positions of the pavement structure layer (1) and the roadbed (2) are higher than the mudstone edging layer (6).

6. The highway subgrade structure constructed with alternating layers of loess and mudstone fill as described in claim 1, characterized in that: The compaction degree of the mudstone structure layer (4) is not less than 95%, and the single layer loose thickness is 30-40 cm; the compaction degree of the loess layer (5) is not less than 95%, and the single layer loose thickness is 30-40 cm; the material of the roadbed (2) is well-graded sand and gravel or improved soil.

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