Treatment method of soft sandstone roadbed

Abstract

The invention discloses a treatment method of an arsenic sandstone roadbed, and belongs to the field of road engineering, and the treatment method comprises the steps of roadbed base pretreatment, lower embankment arsenic sandstone layered solidification construction, upper embankment arsenic sandstone fiber reinforcement construction, roadbed ecological embedding treatment, and roadbed slope and drainage synergistic protection. Aiming at different bearing requirements of a lower embankment, an upper embankment and a roadbed of the roadbed, a differentiated modification curing scheme (the lower embankment focuses on low-cost curing, the upper embankment focuses on high-strength enhancement, and the roadbed focuses on ecological collaboration) is designed, so that the problem of adaptability of a multilayer structure of the roadbed is solved; by introducing nano silicon dioxide (for improving water stability), basalt fiber (for enhancing crack resistance) and a water-retaining agent (for improving water binding capacity), the defect that sandstone disintegrates when encountering water is overcome from the microscopic level, the dosage of a modifier is reduced by 15%-20% compared with that of an existing patent, and performance and economical efficiency are both considered.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, and in particular to a method for treating arsenic-rich sandstone roadbeds. Background Technology

[0002] Arsenic-rich sandstone is extremely difficult to apply in roadbed engineering due to its low particle cementation, easy disintegration upon contact with water, and poor mechanical stability. Existing patent CN108218308B discloses "A method for protecting arsenic-rich sandstone slopes using modified arsenic-rich sandstone blocks." While this patent achieves the resource utilization of arsenic-rich sandstone by preparing modified blocks for slope protection, it has significant drawbacks when directly applied to arsenic-rich sandstone roadbed treatment. Subgrade adaptability defects: This patent focuses on slope block protection, but does not address the vertical bearing capacity, horizontal shear resistance, and uneven settlement control of the subgrade. The block structure is difficult to adapt to the multi-layer filling requirements of the subgrade, which can easily lead to insufficient overall bearing capacity of the subgrade. Material stability defects: The modified blocks are simply modified with cement and mineral admixtures, which does not solve the fundamental problem of arsenic sandstone disintegrating when exposed to water. Under the conditions of groundwater infiltration or rainwater soaking in the roadbed, the blocks are prone to softening, leading to roadbed instability. Environmental and ecological drawbacks: This method does not consider the ecological restoration needs after roadbed construction. The strong sealing of the block protective layer hinders the ecological connection between the soil and vegetation around the roadbed, and does not address the control of dust and soil erosion during the construction of arsenic sandstone roadbeds. Therefore, in order to address the above-mentioned shortcomings, a method for treating arsenic sandstone subgrade is needed that can adapt to the characteristics of the subgrade structure, improve the water stability of the material, and take into account the ecological and environmental protection. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for treating arsenic sandstone roadbeds. Through a technical solution of "layered solidification + fiber reinforcement + ecological integration", the bearing capacity, stability and ecological properties of arsenic sandstone roadbeds are synergistically improved.

[0004] Technical Solution: To solve the above-mentioned technical problems, according to one aspect of the present invention, more specifically, a method for treating arsenic-rich sandstone roadbed, based on layered filling of the arsenic-rich sandstone roadbed, employs differentiated modification and solidification processes for different layers of the roadbed (lower embankment, upper embankment, and subgrade), combined with basalt fiber reinforcement and ecological interlocking structures, forming a three-in-one roadbed treatment system of "bearing capacity-impermeability-ecology," specifically including the following steps: Step 1: Subgrade Pretreatment Remove the topsoil and loose weathered sandstone within the roadbed construction area, and excavate a foundation trench with a depth of not less than 50cm. Lay a 20cm thick layer of graded crushed stone cushion layer into the base trench. Add 3% cement by weight of crushed stone to the cushion layer and compact it with a heavy roller to achieve a compaction degree of not less than 96%. A layer of geogrid is laid on top of the graded crushed stone cushion layer. The geogrid is made of biaxial polypropylene with a tensile strength of not less than 50kN / m and an overlap width of not less than 20cm. It is fixed with U-shaped nails.

[0005] Step 2: Layered solidification construction of the lower embankment sandstone Take the arsenic sandstone raw material on site, crush it to a particle size of no more than 50mm, and screen it to remove silt particles with a particle size of less than 0.075mm (removal rate of no less than 80%). A modifier and curing agent is added to the treated arsenic sandstone. The modifier and curing agent consists of the following components in the following mass ratio: 10%-12% cement, 8%-10% fly ash, 2%-3% nano silica, 1%-2% calcium chloride, and the remainder is arsenic sandstone. Arsenic sandstone mixed with modified curing agent is filled in layers of 30cm / layer. After each layer is filled, it is compacted with a vibratory roller 6-8 times. The compaction moisture content is controlled within the range of optimum moisture content ±2%, and the compaction degree is not less than 94%. After every three layers of filling, a layer of basalt fiber mesh is laid between the layers, with a fiber mesh surface density of not less than 200 g / m². 2 The mesh size is 5mm×5mm, and the fiber mesh is fixed to the underlying sandstone by cement grouting (the spacing between bonding points is no more than 50cm). Step 3: Construction of Fiber-Reinforced Sandstone Embankment The sandstone used for the upper embankment is subjected to fine treatment: crushed to a particle size of no more than 30 mm, and clay particles with a particle size of less than 0.05 mm are removed by water washing (removal rate of no less than 90%). A reinforcing modifier is added to the treated arsenic sandstone. The reinforcing modifier consists of the following components in the following mass ratio: 12%-15% ordinary silicate cement, 10%-12% slag powder, 0.5%-1% basalt short fibers (fiber length 6-10mm), 0.1%-0.2% polyacrylamide, and the remainder is arsenic sandstone. Fill in layers of 25cm each, and compact each layer with an impact roller 4-6 times to achieve a compaction degree of not less than 96%. One layer of composite geomembrane (composed of polyethylene film and non-woven fabric, with a film thickness of not less than 0.5 mm) is laid on the top of the embankment. The overlap width of the geomembrane is not less than 30 cm, and it is sealed by hot-melt welding. Step 4: Ecological integration treatment of roadbed The roadbed adopts a composite structure of "arsenic sandstone modified material + ecological planting soil", which is divided into two layers from top to bottom: the lower layer is 20cm thick arsenic sandstone modified material, and the upper layer is 15cm thick ecological planting soil. Preparation of modified arsenic sandstone: Crush arsenic sandstone to a particle size of no more than 20mm, mix in 8%-10% cement, 5%-8% humus, and 0.3%-0.5% water-retaining agent, and add water to mix to a moisture content of 18%-22%; Preparation of ecological planting soil: It is made by mixing 60%-70% garden soil, 20%-25% well-rotted organic fertilizer, and 10%-15% fine sandstone (particle size less than 5mm), and adjusting the pH value to 6.5-7.5. First, fill the modified sandstone with arsenic and compact it (compaction degree not less than 97%). Then, lay the ecological planting soil, and sow a mixture of Kentucky bluegrass and alfalfa on the surface of the planting soil (seed mass ratio 1:1, sowing rate 15g / m²). 2 Cover with a 1cm thick straw mat to retain moisture. Step 5: Coordinated protection of roadbed slopes and drainage The roadbed slope adopts the structure of "mortar-grouted modified sandstone blocks + ecological vegetation holes": the slope is set at 1:1.5, and the modified sandstone material in step 2 is used to prepare cubic blocks with a side length of 30cm. The blocks are laid in a plum blossom pattern, and the blocks are grouted with M10 cement mortar. Leave a 10cm diameter planting hole in the center of each block, fill the hole with ecological planting soil and plant Virginia creeper or Amorpha fruticosa (50cm apart). Longitudinal drainage ditches (40cm wide and 50cm deep) are set on both sides of the roadbed. The bottom of the ditch is paved with 10cm thick graded crushed stone, the ditch wall is constructed with modified sandstone blocks, and the top of the ditch is covered with concrete slabs (with reserved seepage holes, 5cm in diameter and 30cm in spacing). A curbstone (precast using modified sandstone concrete, 15cm×20cm×50cm in size) is installed at the top edge of the roadbed. A 5cm wide permeable joint is set at the junction of the curbstone and the ecological planting soil of the roadbed, and the joint is filled with permeable geotextile.

[0006] Furthermore, if there is a soft soil interlayer in the foundation in step S1, cement-soil mixing piles must be used for treatment first. The mixing piles are 50cm in diameter, and the pile length penetrates the soft soil interlayer to the hard soil layer. The pile spacing is 1.2m, and they are arranged in a square.

[0007] Furthermore, in step S4, if the construction environment is an arid region, a layer of plastic film needs to be covered on the surface of the ecological planting soil, and the amount of humus in the modified sandstone is adjusted to 8% and the amount of water-retaining agent is adjusted to 0.5%.

[0008] The beneficial effects of the method for treating arsenic-contaminated sandstone roadbed of the present invention are as follows: (1) This invention breaks through the limitations of the existing technology of “single block protection” and designs differentiated modification and solidification schemes for different bearing requirements of the lower embankment, upper embankment and roadbed (the lower embankment focuses on low-cost solidification, the upper embankment focuses on high-strength enhancement and the roadbed focuses on ecological synergy), thus solving the compatibility problem of the multi-layer structure of the roadbed.

[0009] (2) This invention solves the defect of arsenic sandstone disintegrating when exposed to water from a microscopic level by introducing nano silica (to improve water stability), basalt fiber (to enhance crack resistance) and water-retaining agent (to improve water retention). Moreover, the amount of modifier used is reduced by 15%-20% compared with existing patents, taking into account both performance and economy.

[0010] (3) The present invention achieves the connection between the roadbed project and the surrounding ecology through the ecological interlocking structure of "roadbed ecological planting soil + slope vegetation hole + drainage seepage joint", solves the problem of strong ecological sealing of existing patents, and at the same time improves the roadbed's resistance to uneven settlement through the base geogrid and interlayer fiber mesh. Attached Figure Description

[0011] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0012] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0013] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0014] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] Example 1 refer to Figure 1 A method for treating arsenic-rich sandstone roadbed (treatment of arsenic-rich sandstone roadbed for Class I highways in rainy areas). Simulation experiment background: A first-class highway located in a rainy area, passing through an area with arsenic sandstone distribution, with a roadbed width of 26m, a design speed of 80km / h, a roadbed fill height of 3.5m, an average annual precipitation of 1200mm, and a groundwater level depth of 1.5m.

[0016] The implementation steps include the following: S1. Foundation Pretreatment: A 50cm deep foundation trench was excavated, and a 1.2m thick soft soil interlayer was found in the foundation. Cement-soil mixing piles were used for treatment first (pile diameter 50cm, pile length 2.7m, pile spacing 1.2m, square arrangement); then a 20cm thick cement-graded crushed stone cushion layer (cement content 3%) was laid and compacted to a compaction degree of 96%; a two-way polypropylene geogrid (tensile strength 50kN / m) was laid with an overlap width of 20cm and fixed with U-shaped nails.

[0017] S2. Lower Embankment Construction: Arsenic sandstone is crushed to a particle size ≤50mm, and 80% of <0.075mm silt particles are removed by sieving; a modified curing agent (10% cement, 8% fly ash, 2% nano-silica, 1% calcium chloride, cement grade P.O42.5) is added, and the mixture is filled in 30cm / layers, compacted 6 times with a vibratory roller to achieve a compaction degree of 94%; basalt fiber mesh (area density 200g / m²) is laid every 3 layers. 2 Cement grout is used for spot bonding (50cm spacing).

[0018] S3. Construction of the upper embankment: The sandstone is crushed to a particle size of ≤30mm, and 90% of the <0.05mm clay particles are removed by water washing; a reinforcing modifier (12% ordinary silicate cement, 10% slag powder, 0.5% basalt short fiber, and 0.1% polyacrylamide) is added, and it is filled in 25cm / layers, and compacted 4 times with an impact roller to a compaction degree of 96%; a 0.5mm thick composite geomembrane (polyethylene film + non-woven fabric) is laid on top and hot-melt welded (overlap 30cm).

[0019] S4. Subgrade Treatment: The lower layer consists of a 20cm thick layer of modified sandstone (8% cement, 5% humus, 0.3% water-retaining agent), compacted to 97% compaction. The upper layer is a 15cm thick layer of ecological planting soil (60% garden soil, 20% organic fertilizer, 10% fine sandstone, pH 6.5), sown with a mixture of Kentucky bluegrass and alfalfa (15g / m²). 2 Cover with straw mats to retain moisture.

[0020] S5. Slope and Drainage Protection: The slope is 1:1.5, with 30cm cubic modified blocks (arranged in a quincunx pattern) and 10cm planting holes (filled with planting soil, planted with ivy, 50cm spacing between plants); longitudinal drainage ditches are set on both sides (40cm wide, 50cm deep, with 10cm graded crushed stone at the bottom, block masonry on the walls, and concrete cover with seepage holes at the top); the curb stones are precast modified concrete (15cm×20cm×50cm), with 5cm seepage joints (filled with permeable geotextile).

[0021] Implementation results: After one rainy season following construction, there was no significant settlement of the roadbed (settlement ≤3mm), no collapse or landslides on the slopes, the germination rate of grass seeds in the roadbed was 92%, and the vegetation coverage rate was 75%; the roadbed resilient modulus was 320MPa, and the shear strength was increased by 45%, meeting the requirements for operation of first-class highways.

[0022] Example 2 refer to Figure 1 A method for treating arsenic-rich sandstone roadbed (treatment of arsenic-rich sandstone roadbed for railway freight lines in frigid regions) Simulation Experiment Background: A railway freight line in a frigid region passes through an arsenic-rich sandstone area. The line is classified as a Class I national railway, with a freight volume of 50 million tons per year, a roadbed width of 12m, a fill height of 4.0m, an extreme winter temperature of -30℃, and a frozen soil depth of 1.8m.

[0023] The implementation steps include the following: S1. Foundation Pretreatment: Excavate a 50cm deep foundation trench, lay a 20cm thick cement-graded crushed stone cushion layer (cement content 3%), and compact it to a compaction degree of 96%; lay a bidirectional polypropylene geogrid (tensile strength 50kN / m), overlap 20cm, and fix it with U-shaped nails; lay a 5cm thick extruded polystyrene board (thermal conductivity ≤0.03W / (m・K)) on top of the geogrid to block the effects of frost heave.

[0024] S2. Lower Embankment Construction: Construction will take place in November (ambient temperature -5℃). The sandstone will be crushed to a particle size ≤50mm, and 80% of <0.075mm silt particles will be removed by sieving. 3% calcium formate early strength agent (by weight of cement) will be added to the modified curing agent, and the remaining proportions will be the same as in claim 1 (10% cement, 8% fly ash, 2% nano silica, 1% calcium chloride). The embankment will be filled in 30cm layers, compacted 6 times with a vibratory roller, and the compaction degree will be 94%. Basalt fiber mesh will be laid every 3 layers and fixed with cement grout. After filling, the embankment will be covered with geotextile for insulation and curing for 7 days.

[0025] S3. Construction of the upper embankment: The sandstone is crushed to a particle size of ≤30mm and washed with water to remove 90% of the <0.05mm clay particles; the length of the basalt short fibers in the reinforcing modifier is increased to 10mm (tensile strength 3000MPa), while the other proportions remain unchanged (cement 12%, slag powder 10%, short fibers 0.5%, polyacrylamide 0.1%); it is filled in 25cm / layers, compacted 4 times with an impact roller, and the compaction degree is 96%; a 0.5mm thick composite geomembrane is laid on top and hot-melt welded.

[0026] S4. Subgrade Treatment: The water-retaining agent content in the modified sandstone is increased to 0.5% (sodium polyacrylate type, water absorption ratio 300 times), while the other proportions remain unchanged (8% cement, 5% humus); the content of well-rotted organic fertilizer in the ecological planting soil is increased to 25% to improve soil fertility; cold-resistant grass varieties are selected (Kentucky bluegrass "Northern Star" and alfalfa "Grassland No. 2"), with a sowing rate of 15g / m². 2 It is covered with straw curtains and geotextile for double-layer insulation.

[0027] S5. Slope and Drainage Protection: Slope gradient 1:1.75 (to increase stability and adapt to frost heave), 30cm cubic modified masonry blocks; planting holes for cold-resistant shrubs such as Amorpha fruticosa (50cm spacing); longitudinal drainage ditches adopt anti-freeze design, with 5% air-entraining agent added to the ditch wall blocks (to reduce freeze-thaw damage), and 15cm thick graded crushed stone laid at the bottom of the ditch (to increase drainage); the seepage joints at the junction of the curb and the roadbed are filled with cold-resistant and permeable geotextile.

[0028] Implementation results: After one freeze-thaw cycle (winter -30℃ to spring thawing), the roadbed showed no frost heave or thaw settlement (settlement ≤4mm), the slope blocks were free of cracks, and the survival rate of Amorpha fruticosa was 88%; the roadbed bearing capacity met the requirements of the freight line, and the roadbed showed no obvious deformation when trains passed.

[0029] Example 3 refer to Figure 1 A method for treating arsenic-rich sandstone roadbeds (treatment of arsenic-rich sandstone roadbeds for rural roads in arid regions). Simulation Experiment Background: A rural road in an arid region connects remote villages, traverses a sandstone hilly area, has a roadbed width of 6m, a design speed of 30km / h, a roadbed fill height of 2.0m, an average annual precipitation of 280mm, an evaporation of 2500mm, and a soil moisture content of <8% year-round.

[0030] The implementation steps include the following: S1. Foundation pretreatment: Excavate a 50cm deep foundation trench with no soft soil interlayer; lay a 20cm thick cement-graded crushed stone cushion layer (3% cement content), and compact it to a compaction degree of 96%; lay a bidirectional polypropylene geogrid (tensile strength 50kN / m), overlap 20cm, and fix it with U-shaped nails.

[0031] S2. Lower Embankment Construction: The sandstone is crushed to a particle size ≤50mm, and 80% of <0.075mm silt particles are removed by sieving (to reduce dust); the content of nano-silica in the modified curing agent is increased to 3% (to improve water retention), while the other proportions remain unchanged (10% cement, 8% fly ash, and 1% calcium chloride); it is filled in 30cm / layers, and compacted 6 times with a vibratory roller to a compaction degree of 94%; basalt fiber mesh is laid every 3 layers and fixed with cement grout.

[0032] S3. Construction of the upper embankment: The sandstone is crushed to a particle size of ≤30mm and washed with water to remove 90% of the <0.05mm clay particles; the amount of polyacrylamide in the reinforcing modifier is increased to 0.2% (to improve soil water retention), while the other proportions remain unchanged (12% cement, 10% slag powder, and 0.5% basalt short fiber); it is filled in 25cm / layers and compacted 4 times with an impact roller to a compaction degree of 96%; a 0.5mm thick composite geomembrane is laid on top (to reduce moisture evaporation) and hot-melt welded.

[0033] S4. Subgrade Treatment: The water-retaining agent in the modified sandstone is increased to 0.5% (sodium polyacrylate type, water absorption ratio 300 times), and the humus content is increased to 8% (to improve fertility), while the remaining proportions remain unchanged (cement 8%). The ecological planting soil consists of 70% garden soil, 25% well-rotted organic fertilizer, and 15% fine sandstone aggregate (to increase organic matter, retain water and fertilizer), and the pH is adjusted to 7.5. Drought-resistant grass seeds (Kentucky bluegrass "Drought-Resistant No. 1" and alfalfa "Longdong") are sown at a rate of 15g / m². 2 Cover with straw mats and plastic film (to reduce evaporation).

[0034] S5. Slope and Drainage Protection: The slope is 1:1.5, with 30cm cubic modified masonry blocks. A 5cm thick layer of absorbent resin (polyacrylic acid-acrylamide copolymer crosslinked, with a water absorption ratio of 500 times) is laid at the bottom of the planting holes. The holes are filled with planting soil and planted with drought-resistant shrubs (sea buckthorn, with a spacing of 50cm between plants). Longitudinal drainage ditches are set on both sides (40cm wide and 50cm deep, with 10cm of graded crushed stone at the bottom and masonry blocks on the walls). The top of the ditch is not covered (to collect rainwater). A 5cm seepage joint (filled with permeable geotextile) is set at the junction of the curb and the roadbed to guide rainwater to seep into the roadbed.

[0035] Implementation results: After construction, there was no dust or loosening of the roadbed, the survival rate of sea buckthorn on the slope was 85%, and the germination rate of grass seeds in the roadbed was 82%; the compaction degree of the roadbed was maintained at 94%-97%, which met the daily traffic needs of rural roads (mainly small vehicles) and did not require frequent maintenance.

[0036] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for treating arsenic-contaminated sandstone roadbed, characterized in that, Includes the following steps: S1. Subgrade foundation pretreatment: Remove the surface humus and loose weathered sandstone, excavate the foundation trench, lay a cement-graded crushed stone cushion layer and compact it, and lay a geogrid on top of the cushion layer. S2. Layered solidification construction of arsenic sandstone in the lower embankment: After crushing and screening the arsenic sandstone, a modified solidifying agent composed of cement, fly ash, nano silica and calcium chloride is added, and the mixture is filled and compacted in layers. Basalt fiber mesh is laid every 3 layers. S3. Construction of Fiber-Reinforced Sandstone Embankment: After refining the sandstone, a reinforcing modifier composed of cement, slag powder, basalt short fiber and polyacrylamide is added. The sandstone is then filled in layers and compacted by impact rolling. A composite geomembrane is laid on top. S4. Roadbed ecological interlocking treatment: The composite structure of "arsenic sandstone modified material + ecological planting soil" is adopted. Cement, humus and water retention agent are mixed into the arsenic sandstone modified material, and garden soil, organic fertilizer and arsenic sandstone fine material are mixed into the ecological planting soil. Grass seeds are sown on the surface of the planting soil. S5. Coordinated protection of roadbed slope and drainage: The slope is constructed with modified sandstone blocks and mortar masonry. The blocks are pre-drilled for planting holes. Longitudinal drainage ditches and curb stones are set on both sides of the roadbed. Water seepage joints are set at the junction of the curb stone and the roadbed.

2. The method for treating arsenic-contaminated sandstone roadbed according to claim 1, characterized in that, The excavation depth of the foundation trench in step S1 is not less than 50cm, the thickness of the cement-graded crushed stone cushion layer is 20cm, the cement content is 3% of the mass of the crushed stone, and the geogrid is made of bidirectional polypropylene with a tensile strength of not less than 50kN / m.

3. The method for treating arsenic-rich sandstone roadbed according to claim 1, characterized in that, The arsenic sandstone mentioned in step S2 has a particle size of no more than 50mm after crushing. The modified curing agent includes, by mass ratio: 10%-12% cement, 8%-10% fly ash, 2%-3% nano silica, and 1%-2% calcium chloride. The filling layer is 30cm thick with a compaction degree of 94%, and the basalt fiber mesh has a surface density of 200g / m³. 2 .

4. The method for treating arsenic-rich sandstone roadbed according to claim 1, characterized in that, The refining treatment of arsenic sandstone in step S3 includes crushing to a particle size of less than 30 mm, washing to remove clay particles with a particle size of less than 0.05 mm, and the reinforcing modifier includes, by mass ratio: 12%-15% cement, 10%-12% slag powder, 0.5%-1% basalt short fiber, and 0.1%-0.2% polyacrylamide. The filling layer is 25 cm thick and the compaction degree is not less than 96%.

5. The method for treating arsenic-rich sandstone roadbed according to claim 1, characterized in that, The modified sandstone material in step S4 is 20cm thick and includes, by weight: 8%-10% cement, 5%-8% humus, and 0.3%-0.5% water-retaining agent. The ecological planting soil is 15cm thick and includes, by weight: 60%-70% garden soil, 20%-25% well-rotted organic fertilizer, and 10%-15% fine sandstone material. The grass seed is a mixture of Kentucky bluegrass and alfalfa, with a sowing rate of 15g / m². 2 .

6. The method for treating arsenic-contaminated sandstone roadbed according to claim 1, characterized in that, The modified sandstone blocks mentioned in step S5 are cubes with a side length of 30cm, prepared using the modified curing agent in step S2, with a slope of 1:1.5, a planting hole diameter of 10cm, a longitudinal drainage ditch width of 40cm and a depth of 50cm, and the curbstone is a precast modified sandstone concrete with dimensions of 15cm×20cm×50cm.

7. The method for treating arsenic-contaminated sandstone roadbed according to claim 1, characterized in that: If there is a soft soil interlayer in the foundation in step S1, cement-soil mixing piles should be used for treatment first. The mixing piles are 50cm in diameter and the pile length penetrates the soft soil interlayer to the hard soil layer. The pile spacing is 1.2m and they are arranged in a square.

8. The method for treating arsenic-contaminated sandstone roadbed according to claim 1, characterized in that: If the construction environment is arid, in step S4, a layer of plastic film needs to be covered on the surface of the ecological planting soil, and the amount of humus in the modified sandstone is adjusted to 8% and the amount of water-retaining agent is adjusted to 0.5%.

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