Anti-settlement roadbed layered filling structure and construction method

Abstract

The invention discloses an anti-settlement subgrade layered filling structure and a construction method, the anti-settlement subgrade layered filling structure comprises soft rock filler layers, a silty sand layer is filled every other soft rock filler layer with a fixed thickness, and a composite geomembrane is laid on the silty sand layer; the composite geomembrane sequentially comprises a curing layer and a drainage layer from bottom to top, the curing layer comprises a plurality of reinforcing units distributed in an array mode, each reinforcing unit comprises an upper layer and a lower layer which are filled with urease and cementing liquid respectively, the urease and the cementing liquid are sealed through the geomembrane, a trigger device is arranged in the upper layer, and the drainage layer is arranged in the lower layer. When the roadbed is settled, the trigger device moves downwards along with the roadbed to solidify the settled part; the drainage layer comprises a capillary drainage structure and is used for transversely guiding water out to the side slope. All the structural layers are matched with one another, outside water is prevented from entering a soft rock filling layer, meanwhile, the drainage capacity of the soft rock roadbed is greatly improved, the disintegration and softening effects of rainwater on soft rock are reduced, the service life of the soft rock roadbed is prolonged, the long-term stability of the roadbed is improved, and applicability is high.

Description

Technical Field

[0001] The invention belongs to the technical field of roadbed disease protection, and relates to a layered filling structure for an anti-settlement roadbed and a construction method. Background Art

[0002] Soft rock is a complex rock that is prone to significant plastic deformation, including low-strength rocks such as mudstone, shale, sandy mudstone, and muddy sandstone. Its most notable feature is that it contains a large amount of expansive clay minerals, and its structural composition and mineral composition are complex. The mineral composition of soft rock includes montmorillonite, illite, quartz, kaolinite, calcite, illite-montmorillonite mixture, and iron-manganese. Its mechanical properties are mainly affected by geological structure, clay mineral content, structural characteristics, external environment and other factors.

[0003] In the southwest and northwest regions of my country, soft rock is widely distributed. In the process of traffic engineering construction in these areas, a large amount of soft rock waste is generated due to tunnel excavation and slope excavation. At the same time, the embankment design height between valleys and gullies is large, requiring a large amount of filling materials. During the construction of mountain expressways, the road transportation conditions are poor, and there is a lack of stable roadbed filling materials. At the same time, the soft rock waste generated by the project is difficult to transport, resulting in a large amount of soft rock waste accumulation, which will directly affect the original surface vegetation. Under the action of heavy rain, it is easy to cause extremely serious soil erosion, and sometimes it may form mud and rock flows, and even induce landslide disasters, resulting in waste of land resources and damage to the land ecosystem, causing irreversible impacts on the surrounding environment. In the design process of many routes, based on the principle of excavation and filling, it is recommended to directly use the soft rock soil-rock mixture generated by excavation to fill the roadbed. This design solution solves the difficulty of material transportation and can also shorten the construction period, reduce the project cost, and save land resources. Therefore, it is still feasible to use soft rock as roadbed filling material with reasonable design of structural form and strict control of construction quality.

[0004] Since soft rock has poor engineering properties such as low strength, high weathering degree and easy disintegration when exposed to water, during road operation, large pieces of soft rock in the roadbed disintegrate and soften under the action of rainfall and groundwater, and the strength decreases rapidly. Under the action of deadweight and vehicle load, a series of difficult-to-treat road diseases such as uneven roadbed settlement and road cracking are prone to occur, which greatly increases the maintenance cost of the road. Therefore, how to ensure the stability of the soft rock roadbed, make full use of soft rock fillers, and avoid engineering diseases caused by poor properties such as disintegration, softening, and weathering has become an issue that cannot be ignored.

[0005] Traditional treatment methods for soft rock roadbed include excavation and airing, heap loading, vacuum preloading, and dynamic tamping. During the construction of soft rock roadbed, the water content of the soft rock filler itself is usually high, far higher than the optimal water content required for roadbed compaction. If it is aired or mixed with dry materials before filling, it will inevitably increase the construction period and cost of the roadbed; at the same time, the water content of the filled roadbed will further increase under the influence of rain during the construction process, resulting in a significant reduction in strength, and it is far from realistic to excavate and air the filled roadbed. The heap loading construction period is long and easy to lose stability; the vacuum preloading and drainage construction period is long, and there is also the problem of rapid attenuation of the vacuum degree along the depth for the treatment of soft soil roadbed. After reinforcement, the surface strength is greatly improved, but the deep reinforcement effect is not ideal, and secondary treatment is generally required; for the dynamic tamping method, its construction noise is large, the pollution is significant, the tamping energy per unit area is small, and the tamping is only dynamic compaction. Due to the difference between the effective area and the affected area, it is difficult to achieve the compaction effect in the deep layer, and the reinforcement depth is limited. Traditional reinforcement and drainage methods will face continuous roadbed diseases during long-term service. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a layered filling structure for preventing subsidence roadbed. The structural layers cooperate with each other to prevent external moisture from entering the soft rock filling layer, while greatly improving the drainage capacity of the soft rock roadbed, reducing the disintegration and softening effect of rainwater on soft rock, extending the life of the soft rock roadbed, and improving the long-term stability of the roadbed. It has strong applicability and solves the problems of roadbed settlement and high long-term operation and maintenance costs existing in existing soft rock roadbeds.

[0007] Another object of the present invention is to provide a construction method for a layered filling structure of an anti-settlement roadbed.

[0008] The technical solution adopted by the present invention is a layered filling structure for anti-settlement roadbed, comprising a soft rock filling layer, a silt layer is filled with each soft rock filling layer with a thickness of 2-4m, and a composite geomembrane is laid on the silt layer; The composite geomembrane includes a solidification layer and a drainage layer from bottom to top, the solidification layer includes a plurality of reinforcement units distributed in an array, each reinforcement unit includes an upper and a lower layer, each of which is respectively filled with urease and a cementing liquid, the urease and the cementing liquid are respectively sealed by the geomembrane, and a trigger device is provided inside the upper layer. When the roadbed settles, the trigger device moves downward and can pierce the geomembrane between the upper and lower layers and the geomembrane at the bottom of the lower layer, and the urease and the cementing liquid are mixed and released into the silt sand layer below to solidify the settled part; The drainage layer includes a capillary drainage structure for conducting water laterally toward the slope.

[0009] Furthermore, the volume ratio of urease to binder in each reinforcement unit is 1.5-2:1, and the binder contains hydroxyethyl cellulose, CaCl2 and urea, the concentration of hydroxyethyl cellulose is 0.48-0.5 g / L, the concentration of CaCl2 is 0.8-0.85 mol / L, and the concentration of urea is 0.95-1.0 mol / L.

[0010] Furthermore, the upper layer of the reinforcement unit includes a cylindrical frame, and the cylindrical frame is sealed and wrapped by a geomembrane; the geomembrane of the lower layer is sealed and connected to the bottom of the cylindrical frame.

[0011] Furthermore, the trigger device includes an inverted T-shaped main body, the top of the main body is flush with the top of the cylindrical frame, and the end of the lower horizontal structure of the main body has a sharp portion, which is used to support the geomembrane on the top of the reinforcement unit when the roadbed has not settled. At the same time, when the roadbed settles, the trigger device moves downward to pierce the geomembrane between the upper and lower layers and the geomembrane at the bottom of the lower layer.

[0012] Furthermore, the cross-section of the lower horizontal structure of the main body is trapezoidal, and the top surface is smaller than the bottom surface, forming a sharp portion.

[0013] Furthermore, the thickness of the reinforcement unit is 2-3 cm, the reinforcement units in the middle of the roadbed are more densely distributed than those on both sides of the roadbed, and the geomembranes of adjacent reinforcement units are bonded.

[0014] Furthermore, the capillary drainage structure is a geotextile, which is covered above and below to prevent soil debris from entering the capillary drainage structure; the drainage layer extends to the roadbed slope to form an evaporation section, and slope protection vegetation is planted on the roadbed slope.

[0015] Furthermore, a crushed stone replacement layer is laid above the drainage layer in the composite geomembrane close to the pavement structure to drain gravity water.

[0016] Furthermore, a cushion layer is laid on the composite foundation at the bottom of the roadbed, a crushed stone replacement layer is laid on the cushion layer, a drainage layer is laid above the crushed stone replacement layer, the drainage layer conducts water laterally to the slope through a capillary drainage structure, and a geomembrane is laid above the drainage layer.

[0017] A construction method for a layered filling structure for an anti-settlement roadbed comprises the following steps: S1: Determine the length, width, thickness of the geomembrane, and the amount of urease and cementing liquid according to the design requirements, and prefabricate the composite geomembrane; S2: Build the composite foundation and cushion layer from bottom to top, and lay the gravel replacement layer, capillary drainage structure and waterproof geomembrane on the cushion layer. The capillary drainage structure extends to the roadbed slope to form an evaporation section. S3: Laying soft rock filler layer, compacting and leveling; S4: A layer of 8-10cm thick silt sand is filled every 2-4m thick soft rock filler layer, and a composite geomembrane is laid on top of the silt sand layer. The capillary drainage structure in the composite geomembrane extends to the roadbed slope to form an evaporation section; S5: a crushed stone replacement layer is laid above the drainage layer in the uppermost composite geomembrane to discharge gravity water; S6: Lay the pavement structure, clean the slope surface after it is formed, and plant slope protection vegetation on the evaporation section.

[0018] The beneficial effects of the present invention are: 1. The present invention improves the traditional composite geomembrane, adds a drainage layer to the original waterproof performance, and greatly improves the water stability of the roadbed. The drainage layer is a capillary drainage structure sandwiched between two layers of geotextiles. The two layers of geotextiles can prevent soil debris from entering the capillary drainage structure and affecting the drainage performance. The two layers of geotextiles can also ensure the strength of the drainage layer and ensure the long-term stability of the drainage structure. At the same time, most common geomembranes are one-membrane or two-membrane structures. The geotextile above the geomembrane is used as the lower geotextile of the drainage layer, which can save a layer of geotextile material. At the same time, the capillary drainage structure extends and is laid to the roadbed slope as an evaporation section, and combined with the roadbed slope for vegetation protection, the evaporation of the soil and the water absorption of the vegetation can produce a humidity difference and thus a suction difference, which improves the drainage efficiency of the water in the roadbed. At the same time, the water can also nourish the growth of the slope protection vegetation, so as to achieve a roadbed slope that integrates soil consolidation and dust prevention, ecological environmental protection and landscape greening. The drainage layer solves the problem that traditional roadbed gravity drainage can only discharge gravity water and has poor moisture control effect based on capillary action, thereby improving the effect of roadbed drainage.

[0019] 2. The present invention adopts urease-induced carbonate precipitation technology as support, uses hydroxyethyl cellulose as improvement, and uses urease and cementing fluid as roadbed solidification materials. When the soft rock roadbed structure settles, the composite geomembrane structure deforms, and the trigger device punctures the spacer film of the AB layer, so that the urease and cementing fluid are mixed and released into the lower silt sand. Urease hydrolyzes urea to generate CO3 2- ,CO3 2- Ca in calcium source 2+Combined with each other, CaCO3 precipitates are formed and deposited on the surface of soil particles. The water-holding, moisturizing and thickening properties of HEC colloid provide favorable conditions for the hydrolysis of urea and increase the amount of calcium carbonate generated. The "wrapping" and "connecting" effects of HEC on soil particles transform loose soil particles into more stable agglomerates. HEC provides nucleation sites for CaCO3 crystals, reducing free CaCO3 and forming more CaCO3 crystal clusters. The formation of the soil particle-HEC-CaCO3 chain network structure further improves the bonding force of soil particles, increases the density of the soil, enhances the skeleton effect, and improves the mechanical properties of silt sand. This can effectively improve the strength of the roadbed and improve the overall operational capacity of the highway, avoid the need to close the road for traditional roadbed repairs, affect the normal traffic order, avoid indirect economic losses, and reduce the cost of long-term road operation.

[0020] 3. Hydroxyethyl cellulose (HEC) is a white or light yellow environmentally friendly powdered solid that is easily soluble in water. It has good thickening, moisture protection, bonding, and film-forming advantages, and has been widely used in oil extraction, coatings, construction engineering and other fields. The introduction of HEC has changed the cementation mode of the traditional EICP-solidified soil. It not only provides nucleation sites for CaCO3 precipitation, but also its own water retention and thickening properties increase the amount of CaCO3 generated and can generate more CaCO3 in the form of stable calcite. HEC has a "wrapping" and "connecting" effect on soil particles. A chain network structure is formed between soil particles, HEC and CaCO3, which increases the density of the soil, improves the soil structure, and improves the surface strength and water stability of silt sand. The surface strength of the HEC combined with EICP-solidified silt sand sample is 6.96MPa, the disintegration rate is 2.29%, and the water immersion strength loss rate is 1.24%. Compared with traditional EICP-cured silt sand, the surface strength increased by 57.47%, and the disintegration rate and strength loss rate after immersion in water decreased by 78.64% and 83.75%, respectively. The surface strength and water stability of HEC-EICP-cured silt sand were better than those of EICP-cured silt sand alone.

[0021] 4. The composite geomembrane combines the capillary drainage layer with the urease and cementing liquid solidification layer, while taking into account slope protection and greening, organically combining drainage and waterproofing, settlement prevention, slope protection, and roadbed reinforcement functional structures. The composite geomembrane is prefabricated in the early stage, which shortens the construction period and can adjust parameters according to different engineering conditions. It is flexible. From the perspective of construction technology, the integrated composite structure adopted in the present invention is flexible and simple in construction. It only needs to place the composite geomembrane in the designated position, which is convenient for later workers to construct. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0024] Figure 2 Schematic diagram of the structure of the composite geomembrane in an embodiment of the present invention.

[0025] Figure 3 It is a schematic diagram of the soil particle-HEC-CaCO3 chain network structure in an embodiment of the present invention.

[0026] Figure 4 It is a partial diagram of a curing unit in an embodiment of the present invention.

[0027] Figure 5 yes Figure 4 Structural diagram of a single curing unit.

[0028] Among them, 1. composite foundation, 2. drainage layer, 3. soft rock filling layer, 4. composite geomembrane, 5. solidification layer, 6. drainage layer, 7. crushed stone replacement layer, 8. silt sand layer, 9. pavement structure, 10. geotextile, 11. capillary drainage structure, 12. reinforcement unit, 13. trigger device. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] Embodiment 1, A layered filling structure for anti-settlement roadbed, such as Figure 1-2 As shown, a layer of silt sand layer 8 is filled every interval of a soft rock filler layer 3 with a thickness of 2 to 4 m, and a composite geomembrane 4 is laid on the silt sand layer 8; The composite geomembrane 4 includes a solidification layer 5 and a drainage layer 6 from bottom to top, and the solidification layer 5 and the drainage layer 6 are connected by a waterproof geomembrane; like Figure 4-5As shown, the solidification layer 5 includes a plurality of reinforcement units 12 distributed in an array, each reinforcement unit 12 includes an upper and lower layer (layer A and layer B), each of which is filled with urease and a cementing liquid, which are sealed by geomembranes respectively. A trigger device 13 is provided inside the upper layer. When the roadbed settles, the trigger device 13 moves downward and can pierce the geomembrane between the upper and lower layers and the geomembrane at the bottom of the lower layer. The urease and the cementing liquid are mixed and released into the silt sand layer 8 below to solidify the settled part. Timely and accurate reinforcement is carried out when settlement occurs, and the preliminary work is transferred to the roadbed operation period, which reduces the construction difficulty and improves the reinforcement effect.

[0031] Among them, the volume ratio of urease and binder in each reinforcement unit 12 is 1.5-2:1, which improves the urea hydrolysis efficiency and compensates for the loss of urease. The rapid hydrolysis reaction helps CaCO3 to precipitate on the surface of soil particles and in pores in time, achieving the purpose of rapid reinforcement, realizing a rapid response to settlement, and avoiding further settlement of the roadbed.

[0032] In the embodiment, urease is located in layer A, and the cementing liquid is located in layer B. The cementing liquid contains hydroxyethyl cellulose (HEC), CaCl2 and urea. The concentration of hydroxyethyl cellulose (HEC) is 0.48-0.5 g / L, which can reduce the viscosity and enhance the permeability of the liquid, so that it can penetrate into the lower layer of silt sand more quickly and evenly for solidification, with a wider impact range, making the effect after consolidation more uniform.

[0033] The concentration of CaCl2 is 0.8-0.85 mol / L, and the concentration of urea is 0.95-1.0 mol / L. Increasing the concentration of calcium source can quickly generate more CaCO3 precipitation and accelerate the curing process. Due to the improvement of urea hydrolysis efficiency, the concentration can be appropriately reduced to improve permeability.

[0034] The embodiment of the present invention uses hydroxyethyl cellulose to improve the urease-induced carbonate precipitation technology, which has good permeability, does not change the soil structure, does not need to mix the soil, is more suitable for practical application, improves the curing strength and water stability, shortens the construction period, and ensures long-term operational stability.

[0035] The upper layer of the reinforcement unit 12 includes a cylindrical frame, which is sealed and wrapped by a geomembrane to form the upper layer; the bottom of the cylindrical frame is connected to a layer of geomembrane again to form the lower layer, and the geomembrane of the lower layer is sealed and connected to the bottom of the cylindrical frame; the upper and lower layers are respectively filled with urease and binder.

[0036] In some embodiments, the trigger device 13 includes an inverted T-shaped main body, the top of the main body is flush with the top of the cylindrical frame, and the end of the lower transverse structure of the main body has a sharp portion, which is used to support the geomembrane on the top of the reinforcement unit 12 when the roadbed does not settle. At the same time, when the roadbed settles, the trigger device 13 moves downward to pierce the geomembrane between the upper and lower layers and the geomembrane at the bottom of the lower layer. In the embodiment, the cross-section of the lower transverse structure of the main body is a trapezoid (trapezoidal needle), the top surface is smaller than the bottom surface, forming a sharp portion; the role is to serve as a supporting structure and will not pierce the geomembranes in the A and B layers when the roadbed does not settle; when the roadbed deforms, the geomembrane will deform with the settlement of the roadbed, and the trapezoidal needle inside it will drop accordingly. The geomembrane will be closer to the sharp sides of the trapezoidal needle due to stretching. When settlement continues to occur, the geomembrane will be pierced, solidifying the lower layer of silt sand to prevent roadbed settlement damage.

[0037] In some embodiments, the reinforcement unit 12 has a thickness of 2-3 cm and a diameter of 30 cm. The length of the horizontal trapezoidal needle of the trigger device 13 is less than the unit diameter. The horizontal length of the trapezoidal needle is 26 cm and the vertical height is 1 cm. The reinforcement units 12 in the middle of the roadbed are arranged closely adjacent to each other, and the reinforcement units 12 near the edge of the roadbed are arranged with an interval of 20 cm, that is, the middle is dense and the two sides are sparse, which can better cope with the settlement in the middle of the roadbed while reducing the cost and material usage on both sides. Adjacent geomembranes are glued with a lap width of 30 cm.

[0038] When the soft rock settles, the geomembrane of the reinforcement unit 12 is deformed, and the trigger device 13 moves downward to pierce the geomembrane between the upper and lower layers and the geomembrane at the bottom of the lower layer, so that the contents of the A and B layers are mixed and penetrated into the lower silt sand layer 8. Urease hydrolyzes urea to generate ammonium ions and carbonate ions (CO3 2- ), ammonium ions provide an alkaline environment in the solution, CO3 2- Ca in calcium source 2+ Combined with each other, CaCO3 precipitates are formed and deposited on the surface of soil particles to strengthen the soil. The water-holding, moisturizing and thickening properties of HEC colloid provide favorable conditions for the hydrolysis of urea and increase the amount of calcium carbonate generated. The "wrapping" and "linking" effects of HEC on soil particles transform loose soil particles into more stable aggregates. HEC provides nucleation sites for CaCO3 crystals, reducing free CaCO3 and forming more CaCO3 crystal clusters. Figure 3As shown, the formation of the soil particle-HEC-CaCO3 chain network structure further improves the bonding force of soil particles, increases the soil density, enhances the skeleton effect, and improves the mechanical properties of silt sand. Compared with the traditional EICP solidified silt sand, the surface strength of the embodiment of the present invention is increased by 57.47%, and the disintegration rate and the strength loss rate after immersion in water are reduced by 78.64% and 83.75%, respectively. The surface strength and water stability of HEC combined with EICP solidified silt sand are better than those of EICP solidified silt sand alone. It effectively improves the strength of the roadbed and improves the overall operation capacity of the highway, avoids the need to close the road for traditional roadbed repair, affects the normal traffic order, avoids indirect economic losses, and reduces the cost of long-term road operation. At present, the soil is mainly solidified by injecting inorganic solidifying agents such as cement and lime in the project. These inorganic solidifying agents may cause certain pollution to the ecological environment during use. The embodiment of the present invention has the advantages of good stability and green environmental protection.

[0039] The drainage layer 6 in the composite geomembrane 4 includes a capillary drainage structure 11, which is used to conduct water laterally to the slope. The drainage layer 6 extends to the roadbed slope and is fixed on the roadbed slope to form an evaporation section. The surface of the evaporation section is covered with a mixture of soil, fertilizer and humus soil, and slope protection vegetation is planted.

[0040] The capillary drainage structure 11 is a geotextile, and the top and bottom of the capillary drainage structure 11 are covered by the geotextile 10 to prevent soil debris from entering the capillary drainage structure 11, avoid affecting the drainage efficiency, and ensure the long-term stability of drainage. After the capillary drainage structure 11 "absorbs" the water by capillary force, it relies on the suction difference caused by the humidity difference on the material (any material with capillary effect can be used, such as geotextiles, etc.) to guide the water horizontally. The evaporation effect in the air and the water absorption of the slope protection vegetation accelerate this process. At the same time, the water can also nourish the growth of the slope protection vegetation, so as to achieve a roadbed slope that integrates soil consolidation and dust prevention, ecological environmental protection and landscape greening. Based on the capillary action, it solves the problem that the traditional roadbed gravity drainage can only discharge gravity water and the water control effect is poor, and improves the effect of roadbed drainage.

[0041] The geotextile of the capillary drainage structure 11 of the embodiment of the present invention is woven from hydrophobic polypropylene fibers and highly hydrophilic nylon fibers. The polypropylene fibers are mainly used for reinforcement, and the nylon fibers are mainly used for drainage. The capillary fabric is referred to as "capillary fabric". The capillary fabric is composed of hundreds of capillary fibers, each of which has multiple grooves on its surface, which are mainly used for drainage.

[0042] The geomembrane in the solidification layer 5 of the composite geomembrane 4 is a water-impermeable material to prevent water from penetrating into the soft rock filler layer 3; the geotextile 10 in the drainage layer 6 of the composite geomembrane 4 provides physical and mechanical properties such as tensile strength and tear resistance, which can meet the needs of roadbed reinforcement and ensure the long-term stability of the roadbed structure. In the embodiment, the geomembrane is made of HDPE geomembrane, and the geotextile 10 is made of polyester filament geotextile 10.

[0043] A crushed stone replacement layer 7 is laid above the drainage layer 6 in the composite geomembrane 4 near the pavement structure 9 to drain the gravity water that is easy to drain, such as rainfall, to avoid affecting the performance of the capillary drainage structure 11; the remaining water that is difficult to drain is handed over to the capillary drainage structure 11 for drainage, which not only ensures the drainage performance of the roadbed, but also reduces the differential settlement of the roadbed and improves the stability of the roadbed. The solidification layer 5 introduces hydroxyethyl cellulose (HEC) into enzyme-induced carbonate precipitation (EICP), solidifies the silt sand and combines it with the composite geomembrane 4, and improves the roadbed drainage structure through the capillary drainage structure 11 and the crushed stone replacement layer 7.

[0044] A cushion layer is laid on the composite foundation 1 at the bottom of the roadbed, a crushed stone replacement layer 7 is laid on the cushion layer, a drainage layer 6 is laid above the crushed stone replacement layer 7, the crushed stone replacement layer 7 and the drainage layer 6 constitute a drainage-proof layer 2, and the drainage layer 6 conducts moisture laterally to the slope through a capillary drainage structure 11; a geomembrane is laid above the drainage layer 6 to prevent underground moisture from seeping upward and protect the soft rock filling layer 3.

[0045] The geomembrane in the reinforcement unit 12 connects the solidification layer 5 and the drainage layer 6 together. The geomembrane with waterproof performance is located below the capillary drainage structure 11, which not only ensures the timely discharge of water, but also prevents water from further penetrating into the roadbed, while taking into account slope protection and greening, and organically combines drainage and waterproofing, settlement prevention, slope protection, and roadbed reinforcement functional structures. The composite geomembrane 4 can not only prevent water from penetrating, but also prevent and control roadbed settlement. When the soft rock roadbed settles, it will release urease cementing liquid added with hydroxyethyl cellulose (HEC) to jointly solidify the lower layer of silt sand to solve the problem of settlement and other diseases that are prone to occur in the soft rock roadbed during long-term service. In addition, the composite geomembrane 4 is prefabricated in the early stage, shortening the construction period and adjusting parameters according to different engineering conditions, which is flexible. From the perspective of construction, the integrated composite structure adopted in the embodiment of the present invention is flexible and simple in construction. It only needs to place the composite geomembrane 4 in a designated position, which is convenient for later workers to construct.

[0046] The capillary drainage layer 6, the crushed stone replacement layer 7, the evaporation section and the slope protection vegetation constitute the drainage system. The various protective layers and drainage structures work together to prevent external moisture from entering the soft rock filling layer, while greatly improving the drainage capacity of the soft rock roadbed, reducing the softening effect of rainwater on the collapse of soft rock, and self-repairing and reinforcing when the roadbed settles, extending the life of the soft rock roadbed and improving the long-term stability of the roadbed.

[0047] Embodiment 2, A construction method for anti-settlement roadbed layered filling structure, such as Figure 1 As shown, please follow the steps below: S1: According to the design requirements, survey and measure the ground, determine the location and elevation of the main body of the roadbed, clean up the garbage and weeds on the ground, and conduct geological surveys and soil tests on the ground. It is necessary to ensure that the bearing capacity and performance of the soil can meet the design requirements, and understand the influence of groundwater levels and geological conditions; According to the design requirements, the geomembrane parameters (length, width, thickness), as well as the amount of urease and cementing fluid are determined, and the specific parameters are submitted to the factory to prefabricate the composite geomembrane 4; the construction period is shortened and the construction personnel are more convenient to carry out the construction.

[0048] S2: According to the design requirements, the roadbed is excavated on the ground. During the excavation process, attention should be paid to ensuring the flatness and slope of the bottom of the roadbed, while retaining sufficient earthwork reserves for subsequent filling; The manufactured new composite geomembrane 4 is transported to the construction site and waits for laying; According to the design requirements, such as Figure 1 As shown, a composite foundation 1 and a cushion layer are built from bottom to top, and a crushed stone replacement layer 7, a capillary drainage structure 11 and a waterproof geomembrane are laid on the cushion layer in sequence. The capillary drainage structure 11 extends to the roadbed slope to form an evaporation section. The joints of the geomembrane are glued, and the overlap width is not less than 20 cm. The cushion layer is a double-layer geogrid cushion layer with a thickness of not less than 50mm and gravel or hard rock.

[0049] The capillary drainage structure 11 and the waterproof geomembrane constitute an inverted capillary drainage layer 6 .

[0050] The crushed stone replacement layer 7 above the cushion layer can prevent the underground water from penetrating into the soft rock filler, and can also improve the bearing capacity of the foundation and reduce the settlement.

[0051] S3: laying soft rock filler layer 3, compacting and leveling; After the geomembrane is laid, the soft rock filler is loaded by excavators, unloaded by dump trucks, flattened by bulldozers, and partially spread by manual labor. In order to prevent the soft rock filler from softening and disintegrating due to water, resulting in excessive post-construction settlement and affecting the function of the embankment, the soft rock is pre-treated. Before the filler is rolled, it is sprinkled with water, covered, and stewed for 24 hours to complete the pre-disintegration process. The water consumption is calculated according to the optimal moisture content, and the compaction quality is tested after compaction and leveling with a roller; The soft rock roadbed has a filling height of 3m, a road embankment body with a compaction coefficient of 0.93, and a base bed bottom layer with a compaction coefficient of 0.95.

[0052] S4: A layer of silt sand layer 8 (thickness 10 cm) is filled every 3 m of the soft rock filler layer 3, and a composite geomembrane 4 is laid on top of the silt sand layer 8. The capillary drainage structure 11 in the composite geomembrane 4 extends to the roadbed slope to form an evaporation section; the joints of the geomembranes in the composite geomembrane 4 are glued, and the overlap width is not less than 20 cm; S5: gravel is laid on the drainage layer 6 in the topmost composite geomembrane 4, and the gravel is leveled with a light roller to form a gravel replacement layer 7 (thickness 0.1m, medium-coarse sand) for draining gravity water; the graded gravel used is a graded aggregate with a reasonable particle size combination through artificial processing, and the technical standards meet the requirements of relevant specifications; S6: After the gravel layer is laid, the pavement structure 9 is laid and the slope vegetation protection is carried out in time after the slope is formed. After the slope is cleaned, the backfill soil of the mixture of soil, fertilizer and humus soil is laid on the evaporation section extending from the capillary drainage layer 6. The thickness of the backfill soil should meet the requirements of the specifications, and grass seeds are evenly spread and protective measures are taken.

[0053] The thickness of the silt sand layer 8 is 8~10cm. The effect of the curing agent is best performed in the silt sand layer 8. Exceeding the range will lead to poor curing effect. If the thickness of the silt sand layer 8 is not enough, the curing agent will penetrate into the soft rock filler, resulting in poor curing effect. If the silt sand layer 8 is too thick, the curing agent will not be able to act on the entire silt sand layer 8, resulting in insufficient roadbed strength.

[0054] In some embodiments, the specific parameters in S2 include the EICP unit size and thickness. The EICP unit size and thickness are factory preset and can be changed according to the actual project conditions. Since settlement mostly occurs in the middle of the roadbed, it is recommended that the HEC reinforcement units 12 in the middle of the roadbed be arranged adjacent to each other, and the units near the edge of the roadbed be arranged with an interval of 20 cm to better cope with the settlement in the middle of the roadbed while saving materials.

[0055] In some embodiments, in S8, the crushed stone replacement layer 7 uses rolled crushed stone from a stone quarry, the crushing value of the crushed stone should not be greater than 40%, and the maximum particle size should be controlled below 31.5 mm. The total content of needle-like particles in the crushed stone should not exceed 20%, there should be no clay blocks, plants and other harmful substances, the plasticity index should meet the requirements, the natural gravel or coarse sand should have a good gradation and the thickness should be controlled between 10 and 15 mm.

[0056] The embodiment of the present invention is suitable for soft rock roadbed. Soft rock is easy to disintegrate when it encounters water. The soft rock roadbed needs to be waterproof and drained. The embodiment of the present invention uses geomembrane for waterproofing and uses it as a medium to connect the drainage layer 6 and the solidification layer 5. The drainage layer 6 extends to the roadbed slope and adds slope protection vegetation. The suction difference generated by the evaporation of the slope vegetation is used to ensure the continuous discharge of water; at the same time, the discharged water can also nourish the growth of the slope protection vegetation, so as to achieve a roadbed slope that integrates soil consolidation, dust prevention, ecological environmental protection and landscape greening. For some roadbeds that require special treatment, such as frozen soil roadbeds, necessary measures such as ventilation ducts and heat pipes can also be added on the basis of this roadbed structure.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A layered filling structure for anti-settlement roadbed, comprising a soft rock filling layer (3), characterized in that: A layer of silt sand layer (8) is filled in every interval of the soft rock filler layer (3) with a thickness of 2 to 4 m, and a composite geomembrane (4) is laid on top of the silt sand layer (8); The composite geomembrane (4) comprises a solidification layer (5) and a drainage layer (6) from bottom to top, the solidification layer (5) comprises a plurality of reinforcement units (12) distributed in an array, each reinforcement unit (12) comprises an upper and lower layer, each of which is respectively filled with urease and a cementing liquid, the urease and the cementing liquid are respectively sealed by the geomembrane, and a trigger device (13) is provided inside the upper layer, when the roadbed settles, the trigger device (13) moves downward and punctures the geomembrane, and the urease and the cementing liquid are mixed and released into the silt sand layer (8) below, thereby solidifying the settled part; The drainage layer (6) comprises a capillary drainage structure (11) for conducting water laterally toward the slope.

2. The anti-settlement roadbed layered filling structure according to claim 1 is characterized in that: The volume ratio of urease to cementing liquid in each reinforcement unit (12) is 1.5-2:

1. The cementing liquid contains hydroxyethyl cellulose, CaCl2 and urea. The concentration of hydroxyethyl cellulose is 0.48-0.5 g / L, the concentration of CaCl2 is 0.8-0.85 mol / L, and the concentration of urea is 0.95-1.0 mol / L.

3. The anti-settlement roadbed layered filling structure according to claim 1 is characterized in that: The upper layer of the reinforcement unit (12) comprises a cylindrical frame, which is sealed and wrapped by a geomembrane; the geomembrane of the lower layer is sealed and connected to the bottom of the cylindrical frame.

4. The anti-settlement roadbed layered filling structure according to claim 3 is characterized in that: The trigger device (13) comprises an inverted T-shaped main body, the top of the main body is flush with the top of the cylindrical frame, and the end of the lower horizontal structure of the main body has a sharp portion, which is used to support the geomembrane on the top of the reinforcement unit (12) when the roadbed has not settled. At the same time, when the roadbed settles, the trigger device (13) moves downward to puncture the geomembrane between the upper and lower layers and the geomembrane at the bottom of the lower layer.

5. The anti-settlement roadbed layered filling structure according to claim 4 is characterized in that: The cross section of the lower horizontal structure of the main body is a trapezoid, and the top surface is smaller than the bottom surface, forming a sharp portion.

6. The anti-settlement roadbed layered filling structure according to claim 4 is characterized in that: The thickness of the reinforcement unit (12) is 2-3 cm, the reinforcement units (12) in the middle of the roadbed are more densely distributed than those on both sides of the roadbed, and the geomembranes of adjacent reinforcement units (12) are bonded.

7. The anti-settlement roadbed layered filling structure according to claim 1 is characterized in that: The capillary drainage structure (11) is a geotextile, and the upper and lower parts of the capillary drainage structure (11) are covered by the geotextile (10) to prevent soil debris from entering the capillary drainage structure (11); the drainage layer (6) extends to the roadbed slope to form an evaporation section, and slope protection vegetation is planted on the roadbed slope.

8. The anti-settlement roadbed layered filling structure according to claim 1 is characterized in that: A crushed stone replacement layer (7) is laid above the drainage layer (6) in the composite geomembrane (4) close to the pavement structure (9) to drain gravity water.

9. The anti-settlement roadbed layered filling structure according to claim 1, characterized in that: A cushion layer is laid on the composite foundation (1) at the bottom of the roadbed, a crushed stone replacement layer (7) is laid on the cushion layer, a drainage layer (6) is laid above the crushed stone replacement layer (7), the drainage layer (6) conducts water laterally to the slope through a capillary drainage structure (11), and a geomembrane is laid above the drainage layer (6).

10. The construction method of the anti-settlement roadbed layered filling structure according to claim 1, characterized in that: The following steps are involved: S1: Determine the length, width, thickness of the geomembrane, and the amount of urease and binder according to the design requirements, and prefabricate the composite geomembrane (4); S2: constructing a composite foundation (1) and a cushion layer in sequence from bottom to top, and laying a crushed stone replacement layer (7), a capillary drainage structure (11) and a waterproof geomembrane in sequence on the cushion layer, wherein the capillary drainage structure (11) extends to the roadbed slope to form an evaporation section; S3: laying a soft rock filler layer (3), compacting and leveling; S4: A layer of silt sand layer (8) with a thickness of 8 to 10 cm is filled in every interval of a soft rock filler layer (3) with a thickness of 2 to 4 m, a composite geomembrane (4) is laid on top of the silt sand layer (8), and a capillary drainage structure (11) in the composite geomembrane (4) extends to the roadbed slope to form an evaporation section; S5: a crushed stone replacement layer (7) is laid above the drainage layer (6) in the uppermost composite geomembrane (4) to discharge gravity water; S6: Lay the pavement structure (9), clean the slope surface after the slope is formed, and plant slope protection vegetation on the evaporation section.

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