Arid desert region reconstruction and extension highway subgrade structure and construction method

Abstract

The invention relates to the technical field of highway engineering reconstruction and extension, and particularly discloses an arid desert region reconstruction and extension highway subgrade structure and a construction method. The structure comprises an original roadbed and a reconstructed and expanded roadbed which are in lap joint through steps. The reorganized and expanded roadbed is composed of an improved roadbed filler layer, a steel-plastic geogrid laid between the improved roadbed filler layer and roadbed functional layers arranged at the bottom and the top of the improved roadbed filler layer. A roadbed retaining wall, a roadbed protection slope and a grouting waterproof curtain are arranged on the outer side of the foundation. The method comprises the steps of excavating steps of an original roadbed, constructing the waterproof curtain and the retaining wall, preparing the improved filler with the matched elasticity modulus, filling the roadbed in a layered mode, constructing the slope protection and the like. Through modulus matching, three-dimensional waterproof and drainage and thermal insulation design, the problems of differential settlement and stability of reorganization and expansion roads in the arid desert region are systematically solved.

Description

Technical Field

[0001] This invention relates to the field of highway engineering reconstruction and expansion technology, and more specifically, to a roadbed structure and construction method for reconstruction and expansion of highways in arid desert areas. Background Technology

[0002] With the continuous improvement of the national transportation network, the reconstruction and expansion of existing expressways has become an important way to enhance the capacity and service capabilities of the road network. During the reconstruction and expansion of existing roads, one side of the roadbed is the original roadbed, and the other side is a newly filled roadbed. This creates a junction between the old and new roadbeds. Differences in the properties of the fill material, the degree of compaction, and the consolidation time on both sides of the junction can easily lead to uneven settlement near the junction, which in turn causes longitudinal cracks, misalignments, and other defects in the pavement. This seriously affects the safety, comfort, and service life of the road, and this problem is particularly prominent in arid and desert areas.

[0003] First, the fill materials in arid desert areas are mainly aeolian sand, saline soil, and low-liquid-limit silt, which have poor natural properties and cannot be used directly. Aeolian sand has fine, uniform particles and almost no cohesion, resulting in a loose state. Saline soil's strong evaporation will exacerbate the migration and crystallization of salts towards the top of the roadbed, causing severe salt swelling. Low-liquid-limit silt has extremely poor water stability and is easily wetted, also facing compaction difficulties. Second, the climate of arid desert areas is characterized by extreme dryness, strong evaporation, extreme temperature differences, and frequent wind and sand activity. The annual evaporation can be tens to hundreds of times that of precipitation, which easily causes moisture loss in the roadbed fill materials (especially saline soil and low-liquid-limit silt), affecting the compaction effect and exacerbating the accumulation of salts on the surface. Finally, although the average annual precipitation in desert areas is extremely low, the precipitation is highly concentrated in both time and space. The limited annual precipitation may be concentrated in a few or even one or two severe convective weather events. At the same time, there are often high mountains around or inside desert areas, which exacerbates the accumulation of floods. Moreover, the surface of desert areas has almost no ability to "absorb", "store" or "buffer" water.

[0004] Currently, common measures for controlling differential settlement in reconstruction and expansion projects mainly include: excavating steps on the original roadbed slopes to increase the bonding surface; installing geogrids at the interface between the new and old roadbeds; and using pile foundations (such as CFG piles and pipe piles) or composite foundation treatment at the bottom of the new roadbed to improve bearing capacity. However, in the specific practice of highway reconstruction and expansion in arid desert areas, these technologies often have the following main limitations: they cannot use locally sourced materials; the mechanical and deformation parameters (such as the elastic modulus) of the newly filled roadbed materials are difficult to match with those of the original roadbed; the deformation on both sides of the roadbed is not coordinated, leading to differential settlement; step excavation only provides a physical contact surface and lacks active measures to enhance the bond and shear resistance between the new and old roadbeds; and the roadbed slopes have poor rainwater protection and erosion resistance, and do not have the functions of heat insulation, thermal insulation, and ecological protection.

[0005] Therefore, there is an urgent need for a systematic differential settlement control structure and construction method for roadbed reconstruction and expansion in arid and desert areas. This method should be able to comprehensively solve a series of problems such as uneven settlement of roadbeds in arid and desert areas, interface fusion (by setting a transition zone through overlapping grooves), thermal insulation and three-dimensional drainage system, foundation seepage prevention, slope erosion prevention and ecological protection, so as to achieve long-term, stable and coordinated operation of new and old roadbeds, and fundamentally curb the occurrence and development of traditional roadbed reconstruction and expansion diseases. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a roadbed structure and construction method for reconstructing and expanding highways that can effectively control differential settlement, have three-dimensional drainage and thermal insulation functions, and are adapted to the harsh environment of arid desert areas.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A roadbed structure for upgrading and expanding highways in arid desert areas includes an original roadbed and an upgraded roadbed connected by steps. The upgraded roadbed consists of an improved roadbed filler layer, a steel-plastic geogrid laid between the layers, and roadbed functional layers at the bottom and top. A roadbed retaining wall is provided on the outer side of the upgraded roadbed, and a roadbed slope protection is provided on its slope side. A grouting waterproof curtain is provided on the outer side of the slope protection.

[0008] Furthermore, the steps of the original roadbed are provided with multiple semi-circular overlapping grooves to increase the mechanical interlocking and shear resistance of the bonding surface, forming a transition zone between the old and new roadbeds, thereby effectively suppressing differential settlement and crack propagation at the interface.

[0009] Furthermore, the improved roadbed fill layer is made of geopolymer-modified desert undisturbed soil. The amount of geopolymer used is based on the elastic modulus after the layer is formed (…). E g ) and the original roadbed elastic modulus ( E y The design was determined based on the principle of matching the old and new roadbeds. This design ensures that the deformation of the old and new roadbeds is coordinated under load, fundamentally reducing the occurrence of uneven settlement.

[0010] Furthermore, the subgrade functional layer is formed by spraying an aerogel material. This layer is thin and lightweight, and has excellent heat insulation, heat preservation, and waterproofing properties. It can effectively block the intrusion of external extreme temperatures and moisture, and maintain the long-term stability of the soil moisture content and mechanical state inside the subgrade.

[0011] Furthermore, the roadbed retaining wall is a precast steel fiber reinforced concrete structure, divided into casting zones with different fiber densities to optimize stress distribution. A one-way drainage pipe is installed within the wall to drain any potential seepage from the roadbed while preventing external water backflow.

[0012] Furthermore, the grouting waterproof curtain is formed by high-pressure grouting of geopolymer slurry, forming a vertical seepage barrier on the outside of the roadbed to prevent underground capillary water or lateral runoff from eroding the roadbed foundation.

[0013] Furthermore, the roadbed slope protection comprises, from the inside out, a slope functional layer (aerogel coating), a slope block layer (vegetation cell), and a slope protection layer (W-OH solution curing layer), integrating heat preservation, ecological protection, and surface erosion resistance functions.

[0014] This invention also provides a method for constructing roadbeds for the reconstruction and expansion of highways in arid and desert areas, comprising the following steps: S1: Excavate steps on the original roadbed slope and chisel overlapping grooves on the step surface; S2: Construction of grouting water-proof curtain and roadbed retaining wall, with steel-plastic geogrid inserted into the bottom of the footboard of the roadbed retaining wall; S3: Prepare improved roadbed fill material to improve its elastic modulus. E g Compared with the original roadbed elastic modulus E y Consistent; S4: Lay the steel-plastic geogrid in the step and overlap area, and then fill the improved subgrade fill layer in layers on the steel-plastic geogrid and compact it to the designed compaction degree; S5: Construction roadbed slope protection, forming a three-dimensional drainage system; S6: Lay the reconstructed and expanded road surface on the top surface of the roadbed.

[0015] Furthermore, in step S3, the preparation of the improved roadbed fill material includes: The original roadbed was tested using a falling weight deflectometer or a dynamic cone penetrator to obtain the target elastic modulus. E y ; Different amounts of geopolymer were determined through experiments. α elastic modulus below E And based on the experimental data, a mathematical model of geopolymer content-elastic modulus was obtained; Based on the target elastic modulus E y The required geopolymer content is calculated using the mathematical model described above. α ; According to the dosage α Modified filler was prepared by mixing geopolymer cementitious materials with undisturbed soil.

[0016] Compared with existing technologies, the roadbed structure and construction method for upgrading and expanding highways in arid desert areas provided by this invention have the following significant advantages: 1. Effectively control differential settlement and ensure structural integrity: By excavating steps and chiseling overlapping grooves, the mechanical interlocking force and shear resistance of the interface between the new and old roadbeds are greatly increased; by using geopolymers to improve the original soil and using testing and mathematical models to match its elastic modulus with that of the original roadbed, the deformation coordination between the new and old roadbeds is ensured, and the generation of uneven settlement and longitudinal cracks is suppressed from the root.

[0017] 2. Construct a three-dimensional waterproofing and drainage system to improve roadbed stability: By setting up grouting waterproof curtains, roadbed retaining walls and their internal one-way drainage systems, as well as a series of intercepting and drainage ditches from the road surface, slopes to the toe of the slope, a three-dimensional waterproofing and drainage network with effective isolation and orderly drainage is formed, which fundamentally solves the problem of erosion and softening of the roadbed foundation by occasional heavy rainfall in arid desert areas.

[0018] 3. Achieve active thermal insulation and adapt to harsh environments: Aerogel functional layers are set at the bottom, top and slope surfaces of the roadbed, effectively blocking external extreme temperature changes and moisture migration, maintaining the long-term stability of soil moisture content and mechanical state inside the roadbed, and eliminating additional diseases caused by wet-dry cycles and freeze-thaw cycles.

[0019] 4. Combining ecological and engineering protection with high comprehensive benefits: The roadbed slope protection adopts a combination of vegetation cells and W-OH solution protective layer, which not only achieves erosion resistance and windbreak and sand fixation on the slope surface, but also provides conditions for vegetation growth, realizing the organic combination of engineering protection and ecological restoration.

[0020] 5. Green and low-carbon, convenient construction: The improved fill material can be sourced locally, making extensive use of original desert soil; the retaining wall adopts prefabricated and recycled steel fiber concrete; the construction steps are clear and the quality control points are well-defined, which reduces material transportation costs and on-site construction difficulties while ensuring project quality, and is in line with the concept of green building. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 A schematic diagram of the roadbed structure for the reconstruction and expansion of highways in arid desert areas, provided by the present invention. Figure 2 A schematic diagram of the cross-sectional structure of the roadbed for the reconstruction and expansion of highways in arid desert areas, provided by the present invention. Figure 3 A schematic diagram of the concrete sectional casting structure for the roadbed retaining wall provided by the present invention; Figure 4This is a schematic diagram of the roadbed retaining wall structure provided by the present invention; Figure 5 A schematic diagram of the unidirectional drainage structure provided by the present invention; Figure 6 This is a schematic diagram of the slope block layer structure provided by the present invention.

[0022] Among them, 1 is the original roadbed, 11 is the overlap groove, 12 is the step, 2 is the reconstructed and expanded roadbed, 21 is the improved roadbed fill layer, 22 is the steel-plastic geogrid, 23 is the roadbed functional layer, 3 is the original pavement, 31 is the pavement intercepting ditch, 4 is the reconstructed and expanded pavement, 5 is the roadbed retaining wall, 51 is the vertical wall, 511 is the low-density steel fiber concrete pouring area, 512 is the high-density steel fiber concrete pouring area, 513 is the retaining wall intercepting ditch, 52 is the toe board, 53 is the horizontal drainage ditch, 54 is the one-way drainage pipe, 541 is the water outlet pipe, 542 is the one-way valve plate, 6 is the roadbed slope protection, 61 is the slope functional layer, 62 is the slope block layer, 621 is the multi-cell block, 622 is the planting soil, 63 is the slope protection layer, 64 is the vertical drainage ditch, and 7 is the grouting water-stop curtain. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] like Figures 1 to 6 As shown, this embodiment provides a roadbed structure for the reconstruction and expansion of a highway in an arid desert area, including the original roadbed 1, the reconstruction and expansion roadbed 2, the original pavement 3, the reconstruction and expansion pavement 4, the roadbed retaining wall 5, the roadbed slope protection 6, and the high-pressure grouting water-proof curtain 7.

[0025] The original roadbed 1 and the newly constructed / expanded roadbed 2 are joined by steps 12 formed through excavation. The step height is preferably 0.25m–0.3m, and the width is preferably 0.5m–0.8m. To significantly enhance the interface bonding, multiple semi-circular overlap grooves 11 are chiseled on the side of the step 12 closest to the original roadbed 1. The groove diameter is preferably 0.15m–0.25m, and the center-to-center distance between adjacent grooves is preferably 0.3m–0.5m. In this way, the step 12 provides the basic overlap surface, while the overlap grooves 11 additionally create a three-dimensional interlocking space, allowing the subsequently filled modified filler to form a "keyway" type interlocking, greatly improving the shear resistance of the interface between the old and new roadbeds, and forming a mechanical transition zone, effectively dispersing stress concentration and preventing longitudinal cracks.

[0026] The reconstructed and expanded roadbed 2 includes an improved roadbed fill layer 21, a steel-plastic geogrid 22, and a roadbed functional layer 23. The steel-plastic geogrid 22 is laid between the layers of the improved roadbed fill layer 21, and the roadbed functional layer 23 is located at the bottom and top of the improved roadbed fill layer 21.

[0027] Specifically, and then combined Figure 2 As shown, the subgrade functional layer 23 is formed by spraying aerogel material onto the foundation or treated base, with a thickness of 3mm to 5mm. This layer firstly serves as a waterproof and moisture-proof layer, preventing groundwater from seeping upwards; secondly, its extremely low thermal conductivity effectively isolates the impact of drastic changes in ground temperature on the upper subgrade, maintaining stable internal temperature of the subgrade, which is crucial for preventing salinization and frost heave in saline soils.

[0028] The improved subgrade fill layer 21 is key to achieving coordinated deformation between the old and new subgrades. It is made from undisturbed desert soil at the project site through geopolymer modification. Its core lies in adjusting the geopolymer content α to achieve a higher elastic modulus of the modified soil at 28 days. E g The elastic modulus obtained by testing the original roadbed 1 E y Matching.

[0029] The specific formulation and implementation methods are as follows, achieving "performance customization" of the material and ensuring deformation coordination: a. Determination of target parameters: Multiple points of the existing roadbed are measured using a falling weight deflectometer (FWD) or a dynamic cone penetration tester (DCP) to obtain its representative elastic modulus. E y .

[0030] b. Establishing a mathematical model: Local undisturbed soil was taken, and test specimens with geopolymer content α of 0%, 2%, 4%, 6%, 8%, and 10% were prepared according to the standard compaction method. After standard curing for 28 days, their elastic modulus E was measured, as shown in Table 1 below.

[0031] Table 1. Unconfined compressive strength and elastic modulus of each group of specimens were tested after 28 days of curing. E Data points ( α , E By fitting the data, a model showing the relationship between doping amount and modulus can be obtained. For example, in one embodiment, the relationship is as follows: E ( α = 43.12ln( α -1.26 R =0.996). This model quantitatively reveals the law governing the effect of dosage on modulus enhancement.

[0032] c. Calculate the construction dosage: Calculate the target modulus obtained from the test. E y Substituting (e.g., 90 MPa) into the above model E(α) = 43.12 ln(α) - 1.26, the required geopolymer content can be solved. α Approximately 4%. This dosage, when mixed on-site, will increase the modulus of the new filler. E g Approaching the original roadbed modulus E y .

[0033] During the filling of the improved roadbed fill layer 21, the steel-plastic geogrid 22 is laid in layers. The geogrid provides reinforcement, improves the integrity and tensile strength of the roadbed, further constrains the lateral deformation of the fill, and enhances the integrity of the new and old roadbeds together with the steps and overlap grooves.

[0034] After the roadbed is filled to the design elevation, the same aerogel material functional layer is sprayed on the top surface of the roadbed functional layer 23, forming a closed thermal insulation wrap with the bottom functional layer, while preventing rainwater from seeping into the road surface and working in conjunction with the three-dimensional drainage system.

[0035] The original road surface 3 is located on the original roadbed 1; the reconstructed and expanded road surface 4 is located on the reconstructed and expanded roadbed 2 and overlaps with the original road surface 3.

[0036] like Figure 2 As shown, the roadbed retaining wall 5 includes a vertical wall 51, a footboard 52, a horizontal drainage ditch 53, and a one-way drainage pipe 54. The footboard 52 and the drainage ditch 53 are both connected to the vertical wall 51, and the one-way drainage pipe 54 is installed inside the vertical wall 51.

[0037] Furthermore, combined Figure 3 As shown, the roadbed retaining wall 5 is a prefabricated structure made of steel fiber reinforced concrete. It is divided into a low-density steel fiber reinforced concrete pouring area 511 and a high-density steel fiber reinforced concrete pouring area 512. The upper part of the vertical wall 51 is provided with two rows of through one-way drainage pipes 54. The spacing between the one-way drainage pipes 54 is 1.0m, and the upper and lower rows are staggered. The inner side of the one-way drainage pipe 54 is higher than the outer side, and its downward inclination angle is 30°. The top of the vertical wall 51 is also provided with a retaining wall intercepting ditch 513. The bottom layer of the reconstructed and expanded roadbed 2, the steel-plastic geogrid 22, extends into the bottom of the footboard 52.

[0038] Combined Figure 3 As shown, the steel fibers in the low-density steel fiber concrete pouring area 511 and the high-density steel fiber concrete pouring area 512 are all made of recycled steel fiber material, with a length of 8mm to 12mm.

[0039] Combined Figure 5 As shown, the one-way drainage pipe 54 consists of an outlet pipe 541 and a one-way valve plate 542. The outlet pipe 541 is a reducing pipe, with the smaller inner diameter end located on the inner side of the roadbed 2 being renovated and expanded. The one-way valve plate 542 is located at the reducing diameter of the outlet pipe 541, and the movable axis of the one-way valve plate 542 is located at the top of the outlet pipe 541. When external water flow impacts the outlet pipe 541, the one-way valve plate 542 blocks the outlet pipe 541 at the reducing diameter with the force of the water flow.

[0040] Combined Figure 1 and Figure 2 As shown, the roadbed slope protection 6 is located on the slope side of the reconstructed and expanded roadbed 2, and includes a slope functional layer 61, a slope block layer 62, a slope protection layer 63, and a vertical drainage ditch 64.

[0041] The slope functional layer 61 is an aerogel coating, which is sprayed with aerogel material that has heat insulation, heat preservation and waterproof properties, and its thickness is 2mm~3mm.

[0042] The slope block layer 62 is composed of multi-cell blocks 621 and planting soil 622. The planting soil 622 is filled in the multi-cell blocks 621. The cells stabilize the soil, and the planting soil can green the slope and achieve ecological protection.

[0043] The slope protection layer 63 is a W-OH solution curing layer, which is formed by curing with a W-OH solution with a concentration of 3% to 4%. This layer is breathable but not water-permeable, can consolidate the surface sand and soil, effectively resist rain splash erosion and wind erosion, and also has a certain degree of heat insulation.

[0044] The vertical drainage ditch 64 is connected to the road intercepting ditch 31, the retaining wall intercepting ditch 513, and the horizontal drainage ditch 53, forming a complete three-dimensional drainage network that quickly guides and drains water from the slope.

[0045] The grouting water-proof curtain 7 is set on the outside of the roadbed slope protection 6. It forms a vertical curtain with a depth of 2.5m to 3m and a width of 0.3m to 0.5m by high-pressure grouting of polymer slurry. In this way, the lateral recharge path of groundwater can be cut off, and the roadbed foundation can be protected from water damage such as subsidence and collapse. It is an important underground barrier in the three-dimensional drainage system.

[0046] The present invention also provides a construction method for the roadbed structure of the highway reconstruction and expansion project in arid desert areas, comprising the following steps: S1: Excavation steps of the original roadbed: According to the design drawings, the boundary line and excavation line of the roadbed to be reconstructed and expanded are determined. Along the slope of the original roadbed 1, the steps 12 are excavated from top to bottom according to the design parameters, and the overlapping grooves 11 are chiseled on the side of the steps close to the original roadbed. S2: Construction of Grouting Waterproof Curtain and Subgrade Retaining Wall: Based on the design drawings of the reconstructed and expanded subgrade, the grouting waterproof curtain 7 is positioned and constructed using high-pressure grouting machinery to form the grouting waterproof curtain 7; then, on the outside of the subgrade, the foundation trench of the subgrade retaining wall is excavated and leveled according to the design position, and the prefabricated subgrade retaining wall 5 is installed to ensure its smooth alignment and accurate elevation; the steel-plastic geogrid 22 at the base of the reconstructed and expanded subgrade is inserted into the bottom of the foot plate 52 of the subgrade retaining wall 5; S3: Preparation of subgrade fill material: Take undisturbed soil from the project site, screen it, and test its moisture content; according to the mix proportion determined by the test, mix the undisturbed soil, geopolymer cementitious material, admixture, and an appropriate amount of water to prepare a uniform modified subgrade fill material; the key control indicators are the uniformity of the mixture and the elastic modulus after molding. E g , E g Compared with the original roadbed elastic modulus E y Consistent; S4: Roadbed reconstruction and expansion construction: On the treated original roadbed step 12 surface and overlapping groove 11 area, first lay steel-plastic geogrid 22, then quickly fill and compact the prepared improved roadbed fill layer 21, and roll it to the designed compaction degree. S5: Construct roadbed slope protection 6: Construct slope functional layer, slope block layer, slope protection layer and vertical drainage ditch on the side of the roadbed respectively, so that the road surface intercepting ditch, vertical drainage ditch, retaining wall intercepting ditch, horizontal drainage ditch and grouting water-proof curtain form a three-dimensional waterproof and drainage system. S6: Construction of the reconstructed and expanded pavement layer: After the top surface of the subgrade has passed the acceptance inspection, the pavement functional layer is laid; on the pavement functional layer, each layer of asphalt mixture is spread and compacted according to the conventional asphalt pavement construction process to form the asphalt pavement layer, namely the reconstructed and expanded pavement 4. The newly laid reconstructed and expanded pavement 4 should be smoothly overlapped with the original pavement.

[0047] In step S3, the preparation of the improved roadbed fill material includes: The original roadbed was tested using a falling weight deflectometer or a dynamic cone penetrator to obtain the target elastic modulus. E y ; Different amounts of geopolymer were determined through experiments. α elastic modulus below E And based on the experimental data, a mathematical model of geopolymer content-elastic modulus was obtained; Based on the target elastic modulus E y The required geopolymer content is calculated using the mathematical model described above. α ; According to the dosage α Modified filler was prepared by mixing geopolymer cementitious materials with undisturbed soil.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A roadbed structure for the reconstruction and expansion of highways in arid desert areas, characterized in that, This includes the original roadbed (1), the reconstructed and expanded roadbed (2), the original pavement (3), the reconstructed and expanded pavement (4), the roadbed retaining wall (5), the roadbed slope protection (6), and the grouting water-tight curtain (7); among which: The original roadbed (1) and the reconstructed and expanded roadbed (2) are connected by steps (12); The reconstructed and expanded roadbed (2) includes an improved roadbed fill layer (21), a steel-plastic geogrid (22), and a roadbed functional layer (23). The steel-plastic geogrid (22) is laid between the layers of the improved roadbed fill layer (21), and the roadbed functional layer (23) is set at the bottom and top of the improved roadbed fill layer (21). The original road surface (3) is located on the original roadbed (1); The reconstructed and expanded road surface (4) is located on the reconstructed and expanded roadbed (2) and overlaps with the original road surface (3); The roadbed retaining wall (5) is located on the outside of the roadbed (2) being renovated and expanded. The roadbed retaining wall (5) includes a vertical wall (51), a footboard (52), a horizontal drainage ditch (53), and a one-way drainage pipe (54). The footboard (52) and the drainage ditch (53) are both connected to the vertical wall (51), and the one-way drainage pipe (54) is located inside the vertical wall (51). The roadbed slope protection (6) is located on the slope side of the reconstructed and expanded roadbed (2); The grouting waterproof curtain (7) is located on the outside of the roadbed slope protection (6).

2. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 1, characterized in that, The original roadbed (1) has multiple overlapping grooves (11) on the steps (12). The overlapping grooves (11) are semi-circular grooves with a diameter of 0.15m to 0.25m and the spacing between adjacent overlapping grooves (11) is 0.3m to 0.5m.

3. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 1, characterized in that, The improved subgrade fill layer (21) is made of geopolymer-modified desert undisturbed soil, wherein the amount of geopolymer is based on increasing the elastic modulus of the layer. E g The elastic modulus of the original roadbed (1) E y The principle of matching is determined.

4. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 1, characterized in that, The subgrade functional layer (23) is formed by spraying aerogel material with a thickness of 3mm to 5mm.

5. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 1, characterized in that, The roadbed retaining wall (5) is a precast steel fiber concrete structure, including a low-density steel fiber concrete pouring area (511) and a high-density steel fiber concrete pouring area (512); the one-way drainage pipe (54) is high on the inside and low on the outside, with a downward inclination angle of 15° to 30°.

6. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 5, characterized in that, The one-way drain pipe (54) includes a variable diameter outlet pipe (541) and a one-way valve plate (542). The one-way valve plate (542) is movably located at the variable diameter of the outlet pipe (541) and is used to close the pipe when the water flow impacts.

7. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 1, characterized in that, The grouting water-proof curtain (7) is formed by high-pressure grouting of geopolymer grout, with a depth of 2.5m to 3m and a width of 0.3m to 0.5m.

8. The roadbed structure for highway reconstruction and expansion in arid desert areas according to claim 1, characterized in that, The roadbed slope protection (6) includes a slope functional layer (61), a slope block layer (62), and a slope protection layer (63); the slope functional layer (61) is an aerogel coating with a thickness of 2mm to 3mm; the slope block layer (62) includes multi-cell blocks (621) and planting soil (622); the slope protection layer (63) is a W-OH solution curing layer.

9. A construction method for the subgrade structure of a highway reconstruction and expansion project in arid desert areas as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Excavate steps (12) on the slope of the original roadbed (1) and chisel out overlapping grooves (11) on the surface of the steps. S2: Construct the grouting water-blocking curtain (7) and the roadbed retaining wall (5), and insert the steel-plastic geogrid (22) into the bottom of the footboard (52) of the roadbed retaining wall (5); S3: Prepare improved roadbed fill material to improve its elastic modulus. E g Compared with the original roadbed elastic modulus E y Consistent; S4: Lay the steel-plastic geogrid (22) in the area of ​​the step (12) and the overlap groove (11), and then fill the improved subgrade fill layer (21) in layers on the steel-plastic geogrid (22) and compact it to the designed compaction degree; S5: Construction of roadbed slope protection (6), forming a three-dimensional drainage system; S6: Lay the reconstructed and expanded road surface on the top surface of the roadbed (4).

10. The construction method according to claim 9, characterized in that, In step S3, the preparation of the improved roadbed fill material includes: The original roadbed was tested using a falling weight deflectometer or a dynamic cone penetrator to obtain the target elastic modulus. E y ; Different amounts of geopolymer were determined through experiments. α elastic modulus below E And based on the experimental data, a mathematical model of geopolymer content-elastic modulus was obtained; Based on the target elastic modulus E y The required geopolymer content is calculated using the mathematical model described above. α ; According to the dosage α Modified filler was prepared by mixing geopolymer cementitious materials with undisturbed soil.

Images