A flexible road suitable for use in a subsidence area of a high groundwater level mine and a method of construction thereof

Abstract

The application discloses a flexible road suitable for a collapse area of a high water level mine area and a construction method thereof, and relates to the technical field of foundation treatment. The flexible road is sequentially provided with a drainage base layer, a self-adaptive cushion layer, an integrated anti-seepage and drainage layer, a flexible stable layer and a surface layer from bottom to top. The construction method divides a risk area through digital twinning, adopts foundation three-in-one control pre-disposal, is matched with factory prefabrication, on-site quick insertion installation and intelligent construction of unmanned aerial vehicles, AGVs and the like, and forms a whole-cycle closed loop through completion detection and intelligent monitoring. The application realizes three-dimensional seepage control and deformation self-adaptation, solves the problems of seepage and subsidence in the collapse area, is efficient and controllable in construction, and improves long-term stability of the road.

Description

Technical Field

[0001] This invention relates to the field of foundation treatment technology, specifically to a flexible road suitable for subsidence areas in mining areas with high groundwater levels and its construction method. Background Technology

[0002] In coal mining subsidence areas with high groundwater levels, surface collapse, high groundwater levels, and high soil saturation often lead to road structural cracking, localized subsidence, and leakage failure. Traditional construction methods often employ a step-by-step process: first the foundation, then the roadbed, then seepage prevention, and finally drainage. This approach has the following drawbacks: 1) Construction fragmentation: The lack of coordinated design between foundation reinforcement and roadbed filling makes it easy for stress concentration to form at the interface, resulting in significant uneven settlement in the later stage; 2) Delayed seepage control: The drainage system often lags behind the main construction, making it difficult to guarantee saturation soaking and compaction during construction; 3) Manual laying: The manual laying and overlapping sealing of the seepage prevention layer is unstable, which easily forms seepage channels; 4) Invisible quality: Key indicators such as compaction, moisture content, and weld quality rely on experience for control, and the process is not traceable; 5) Lack of closed loop: Construction and monitoring are disconnected, there is a lack of real-time control mechanism, and the ability to cope with sudden deformation is weak.

[0003] Existing technologies (such as relying solely on reinforced layers or rigid frames) tend to be more "passive" and struggle to simultaneously address the coordinated control of seepage, deformation, and construction quality. Therefore, a closed-loop construction methodology covering the entire lifecycle from surveying, design, construction to operation and maintenance is needed. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, it proposes a flexible road suitable for subsidence areas in mining areas with high groundwater levels and its construction method.

[0005] The technical solution of this invention to solve the technical problem is as follows: Firstly, this technical solution proposes a flexible road suitable for subsidence areas in mining areas with high groundwater levels, comprising, from bottom to top, a drainage base layer, an adaptive subbase layer, an integrated seepage-proof and drainage layer, a flexible stabilizing layer, and a surface layer, wherein: The drainage base layer uses graded crushed stone, with permeable corrugated pipes embedded inside. The outer wall of the permeable corrugated pipes is wrapped with a three-dimensional drainage net to form a pipe-net composite structure. The pipe-net composite structure integrates sensors for seepage pressure, flow rate, and conductivity. The end of the permeable corrugated pipe is connected to a water collection well with a water level sensor. The adaptive subbase uses lightweight foamed concrete; The integrated seepage prevention and drainage layer uses a nano-modified HDPE membrane, with non-woven fabric laid under the membrane and a three-dimensional drainage grid laid on top of the membrane to form a composite structure. The flexible stabilizing layer uses bio-enzyme-stabilized soil as the load-bearing layer, with dispersed fibers mixed inside; the upper surface of the load-bearing layer is covered with geotextile to form a synergistic load-bearing structure.

[0006] Preferably, the surface layer is an intelligent self-healing surface layer or a prefabricated replaceable surface layer. The intelligent self-healing surface layer includes modified asphalt concrete with 3% to 6% microcapsules and 0.2% to 0.5% nanofibers. The prefabricated replaceable surface layer is assembled from several interlocking permeable modular bricks.

[0007] Preferably, the enzyme content in the bio-enzyme-stabilized soil is 0.3% to 0.5%, and the content of dispersed fibers is 0.2% to 0.4%.

[0008] Preferably, the particle size of the graded crushed stone is 5–31.5 mm.

[0009] Secondly, this technical solution proposes a method for constructing flexible roads suitable for subsidence areas in mining areas with high groundwater levels. The specific steps are as follows: S1. Risk Zoning: Collect the foundation database of the construction area, establish a digital twin field, divide high, medium and low risk zones, and output risk zoning map, construction parameters and early warning thresholds; S2. Foundation Tri-control Pre-treatment The foundation is pretreated by a combination of vacuum preloading, intermittent air extraction and pulsating load. For the high-risk areas in S1, CFG pile construction and sleeve valve pipe micro-grouting reinforcement are also required to form a reinforced foundation. S3. Construction of base course drainage: S31. In the factory, the three-dimensional drainage net, the perforated permeable corrugated pipe, and the pressure sensor, flow sensor, and conductivity sensor are integrated and fixed to form a pre-assembled component. The pre-assembled component is equipped with quick-connect interfaces at both ends. S32. On-site, a traction plow or trenching machine is used to form trenches in one go. Pre-installed components are embedded into the trenches and connected to adjacent pre-installed components through quick-connect interfaces to form a continuous guide and discharge system. S33. After the water collection wells are prefabricated in the factory, they are reasonably arranged on the site, and the positions for subsequent interfaces are reserved. The end of the pre-installed component is connected to the water collection wells on both sides. The water collection wells are pre-installed with water level sensors. The surface of the component is backfilled and compacted with graded crushed stone to complete the drainage base construction. S4. Adaptive Subbase Construction Mix the substrate, foaming agent and curing agent according to the preset formula, pump and spread in sections and layers, and cure to the preset strength after laser leveling; S5. Integrated seepage prevention and drainage layer construction The drone performs a 3D scan of the adaptive underlayment in S3 to generate a digital twin model and optimize the operation path. The drone transports the materials, and the AGV and welding robot work together to lay non-woven fabric and nano-modified HDPE membrane. A 3D drainage net is laid on the membrane and welding is carried out to form a seepage-proof and drainage-guiding composite layer. The drone is used to inspect the welds and composite layer and guide personnel to carry out targeted repairs. S6. Construction of Flexible Stabilizing Layer Soil is thoroughly mixed with fly ash, coal gangue, bio-enzyme solidifying agent and fiber using mixing equipment to obtain bio-enzyme solidified soil; then it is spread in layers, and the compaction degree is controlled by intelligent compaction equipment. After compaction, geotextile is laid and covered with a membrane for curing until the standard strength is reached. S7. Surface Layer Construction Choose a self-healing asphalt surface layer or a prefabricated replaceable surface layer according to functional requirements, and complete the paving, compaction or assembly according to the corresponding process. S8. Completion Inspection: Core sampling was conducted to verify the thickness of each structural layer, FWD deflection tests were performed, surface permeability coefficient tests were conducted, and GPR testing was carried out.

[0010] S9. Intelligent Monitoring: After the quality verification is completed, all monitoring data and construction records are uploaded to the cloud, automated handling rules are set, routine operation and maintenance configurations are completed, and intelligent monitoring is achieved.

[0011] Preferably, the negative pressure value of the vacuum pre-compression in S2 is -60 to -80 kPa, and the maintenance time is 48 to 96 h; the pressure of the intermittent air extraction is 0.05 to 0.1 MPa, the extraction is 10 to 20 min / cycle, and the intermittent operation is 40 to 60 min; the pressure of the pulsating load is 10 to 20 kPa, and the frequency is 0.5 to 1 Hz.

[0012] Preferably, the CFG piles in S2 have a pile length of 8 to 12 m and a diameter of 500 mm, and are arranged in a triangular pattern at intervals of 1.5 to 2.0 m; the sleeve valve pipe micro-grouting adopts a 0.8% to 1.2% micro-expansion cement system, and the grouting pressure and grout volume are controlled according to real-time monitoring feedback.

[0013] Preferably, the substrate is sand or lime-soil, and the target density after foaming is stable at 600-800 kg / m³; the construction temperature is controlled at 10-35℃, and the time for pouring into the mold is ≤10 min; the thickness of each layer is 150-220 mm, the flatness after laser leveling is ≤5 mm / 3 m, 0.3-0.6 kg / m² of cement paste is sprayed to enhance the interlayer bonding, and the strength after 24 h of curing is ≥0.8 MPa and the strength after 72 h is ≥1.0 MPa.

[0014] Preferably, the risk zoning criteria in S1 are as follows: annual deformation >10mm in high-risk areas, 5–10mm in medium-risk areas, and <5mm in low-risk areas; the warning thresholds are: settlement ≥3mm or pore pressure rises to 70% of the initial value in high-risk areas, settlement ≥5mm or pore pressure ≥50% of the initial value in medium-risk areas, and settlement ≥10mm in low-risk areas.

[0015] Preferably, the specific method in S1 is as follows: S11. Collect the topography, soil layer distribution, groundwater level and mechanical parameters of the construction area to generate a three-dimensional geological initial dataset; S12. Import the initial dataset into the numerical simulation software in the controller to construct a digital twin model, i.e., a twin field, that is consistent with the physical properties of the construction area; S1.3 Based on the digital twin model, the settlement rate and seepage pressure distribution under different construction conditions are simulated. Settlement rate threshold and seepage pressure threshold are set, high, medium and low risk zones are divided, and risk zoning map and recommended construction parameters and early warning thresholds for each zone are output as input conditions for subsequent construction.

[0016] The above technical solution has the following advantages or beneficial effects: 1. The flexible road in this invention comprises a drainage base layer, an adaptive subbase layer, an integrated seepage-proof and drainage layer, a flexible stabilizing layer, and a surface layer, forming a multi-layered synergistic structure. The pipe-network composite structure of the drainage base layer, together with the integrated seepage-proof and drainage layer and the adaptive subbase layer, forms a three-dimensional seepage control system. This system can quickly drain groundwater and block seepage channels, while the adaptive subbase layer buffers deformation, structurally solving the problems of seepage failure and local subsidence caused by high water levels in the collapse area. Furthermore, the flexible stabilizing layer uses bio-enzyme-stabilized soil mixed with dispersed fibers and covered with geotextiles to form a synergistic stress-bearing structure, which can actively adapt to uneven settlement in the collapse area and avoid structural cracking. Compared with traditional rigid structures, this significantly improves the road's adaptability to deformation.

[0017] 2. The drainage base layer is equipped with built-in sensors for seepage pressure and flow rate, and the water collection well is equipped with a water level sensor. The integrated design of the structural layer and monitoring elements breaks through the traditional limitation of invisible quality, provides real-time data support for construction control and operation and maintenance, and ensures the long-term stability of the structure.

[0018] 3. By constructing a geological model using digital twins, high, medium and low risk zones are divided according to annual deformation. Targeted pretreatment of the foundation using a three-pronged approach is adopted, and CFG piles and sleeve valve pipe grouting reinforcement are additionally used in high-risk zones to avoid insufficient reinforcement or waste of resources caused by the one-size-fits-all approach of traditional construction, thus solving the problem of fragmented construction.

[0019] 4. Prefabricated components and water collection wells in the drainage base layer are prefabricated in the factory and quickly connected on site; the integrated seepage prevention and drainage layer is laid by AGV and welding robots in collaboration, replacing manual laying, which not only solves the problem of unstable sealing of the seepage prevention layer overlap, but also shortens the on-site construction cycle and improves construction efficiency and reliability.

[0020] 5. The drone's 3D scanning optimizes the path and detects weld defects without contact. The intelligent compaction equipment controls the compaction degree, and the indicators are collected and uploaded in real time, replacing the traditional experience-based control. This enables the construction process to be visualized and traceable, solving problems such as insufficient compaction degree and potential weld quality issues. The intelligent construction process ensures that the process quality is controllable and traceable.

[0021] 6. This construction method adopts a full-cycle closed-loop process, which breaks through the limitation of the disconnect between monitoring and construction. From digital twin risk zoning and dynamic optimization of construction parameters to multi-dimensional detection after completion and intelligent monitoring of operation and maintenance, it forms a closed loop of the entire process of surveying, design, construction and operation and maintenance. It can quickly respond to sudden deformation and improve the long-term service stability of the road. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0023] Figure 1 This is a cross-sectional view of the flexible road proposed in this invention, suitable for subsidence areas in mining areas with high groundwater levels.

[0024] Figure 2 This is a schematic diagram of the split structure of the integrated seepage prevention and drainage layer.

[0025] Figure 3 This is a simulation result of the total deformation of the static structure of the flexible road (without the pretreatment of the three-way control of the foundation).

[0026] Figure 4 This is a simulation result diagram of the total deformation of the static structure of a flexible road (under the condition of pretreatment of the foundation with three-way control).

[0027] Explanation of reference numerals in the attached figures: 1. Drainage base layer; 11. Permeable corrugated pipe; 2. Adaptive subbase; 3. Integrated seepage prevention and drainage layer; 31. Non-woven fabric; 32. Nano-modified HDPE membrane; 33. Three-dimensional drainage grid; 4. Flexible stabilizing layer; 41. Load-bearing layer; 42. Geotextile; 5. Surface layer; 6. Collection well. Detailed Implementation

[0028] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. 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.

[0029] Example 1: like Figure 1 - Figure 2 As shown, this embodiment proposes a flexible road suitable for subsidence areas in mining areas with high groundwater levels, comprising, from bottom to top, a drainage base layer 1, an adaptive cushion layer 2, an integrated seepage-proof and drainage layer 3, a flexible stabilizing layer 4, and a surface layer 5, wherein: The drainage base layer 1 is used to quickly drain groundwater and stabilize the road base. It solves the problem of groundwater retention in mining areas with high water table, which leads to base softening and increased settlement. It achieves functions such as rapid groundwater drainage, base stress dispersion, and real-time seepage monitoring, providing a stable working surface for the superstructure.

[0030] The drainage base layer 1 uses graded crushed stone with a particle size of 5-31.5mm. The graded crushed stone forms a skeleton porous structure, which not only ensures bearing capacity but also provides vertical / horizontal infiltration channels for groundwater. Permeable corrugated pipes 11 are buried inside the graded crushed stone. The outer wall of the permeable corrugated pipes 11 is wrapped with a three-dimensional drainage net to form a pipe-net composite structure. The three-dimensional drainage net is made of high-density polyethylene. The corrugated pipes serve as the main drainage channels. The three-dimensional drainage net expands the groundwater collection range and is adapted to the dispersed seepage characteristics of the mining area. The permeable corrugated pipes 11 can be made of HDPE material, which is resistant to acids and alkalis and can resist corrosive ions that may be contained in the groundwater in the mining area.

[0031] The pipe-network composite structure integrates sensors for seepage pressure, flow rate, and conductivity. The end of the permeable corrugated pipe 11 is connected to the collection well 6, which is equipped with a water level sensor. Each sensor is prefabricated as an integrated unit with the pipe-network composite structure, avoiding damage to the base structure during later installation. It can transmit data in real time to a cloud platform, enabling functions such as detecting seepage anomalies and providing timely early warnings, adapting to the long-term operation and maintenance needs of the mining area. The collection well 6 is prefabricated for rapid on-site installation; its denser deployment in high-risk areas addresses localized concentrated seepage in subsidence zones.

[0032] The adaptive subbase layer 2 uses lightweight foamed concrete to buffer settlement stress and adjust elevation deviations. Its lightweight properties reduce the additional load on the subgrade, and its porous structure adapts to the deformation, buffering continuous minor settlement in the subsidence area while achieving precise adjustment of road elevation, preventing cracking of the upper structure due to differential settlement. The lightweight foamed concrete base material is sand / lime-soil, mixed with foaming agents and 42.5 grade ordinary Portland cement curing agents. The density of lightweight foamed concrete is 600–800 kg / m³, only 1 / 3 to 1 / 2 that of ordinary concrete, significantly reducing the subgrade load and preventing further compression of the soil in the subsidence area. Its elastic modulus is 150–250 MPa, much lower than that of ordinary concrete, exhibiting strong deformation adaptability and capable of absorbing ±3 mm of settlement deformation without cracking.

[0033] The integrated seepage prevention and drainage layer 3 is used to block the rise of groundwater and drain surface seepage. It can solve the two-way leakage problem of groundwater seepage softening the base layer and surface water seepage aggravating the collapse in the mining area. It realizes the dual functions of blocking groundwater seepage and draining surface water seepage, while protecting the lower adaptive cushion layer 2 from surface water erosion.

[0034] The integrated seepage-proof and drainage layer 3 uses a nano-modified HDPE membrane 32, with a non-woven fabric 31 laid underneath and a three-dimensional drainage grid 33 laid on top, forming a composite structure. The non-woven fabric 31 serves as a protective and buffer layer for the nano-modified HDPE membrane, preventing sharp particles from the underlying adaptive pad layer 2 from puncturing the membrane. The three-dimensional drainage grid 33 and the non-woven fabric 31 under the membrane form a synergistic system of upper drainage and lower protection: surface rainwater or snowmelt is quickly drained through the drainage grid to the side ditches on both sides of the road, preventing water from seeping into the membrane; the three-dimensional drainage grid 33 has a lightweight structure and does not add excessive load.

[0035] The flexible stabilizing layer 4 is used to transfer loads and adapt to settlement deformation. It uses bio-enzyme-stabilized soil as the load-bearing layer 41, with dispersed fibers mixed inside. The upper surface of the load-bearing layer 41 is covered with geotextile 42 to form a synergistic load-bearing structure. As the load-bearing core layer of the road, the flexible stabilizing layer 4 receives the traffic load transferred from the surface layer 5 and evenly distributes it to the lower layers. At the same time, through the flexible design of bio-enzyme solidification and dispersed fiber reinforcement, it adapts to the continuous small uneven settlement in the subsidence area and avoids structural cracking.

[0036] In some embodiments, the enzyme content in the bio-enzyme-stabilized soil is 0.3%–0.5%, and the content of dispersed fibers is 0.2%–0.4%. The mix proportion of the bio-enzyme-stabilized soil is: 60%–70% silty clay, 20%–25% fly ash, and 10%–15% coal gangue. Bio-enzyme-stabilized soil utilizes solid waste resources, which can reduce costs. At the same time, fly ash improves soil gradation, and coal gangue enhances strength. The dispersed fibers are made of polypropylene short fibers, which are acid and alkali resistant and anti-aging, with a length of 12–18 mm and a diameter of 20–30 μm.

[0037] Geotextile 42 can be made of polyester filament woven geotextile, which serves to disperse surface load, prevent the loss of solidified soil particles, and further enhance the integrity between layers.

[0038] Surface layer 5, designed for skid resistance, wear resistance, and bearing traffic loads, offers two differentiated surface layer 5 solutions to address the challenges of maintenance and high post-settlement repair costs in mining subsidence areas. These solutions are tailored to different road section needs. The surface layer can be either an intelligent self-healing layer or a prefabricated replaceable layer. The intelligent self-healing layer comprises modified asphalt concrete, such as SBS modified asphalt concrete, incorporating 3%–6% microcapsules and 0.2%–0.5% nanofibers. The microcapsules have a particle size of 50–100 μm, with an epoxy curing agent as the core material, enabling self-healing of cracks ≤0.5 mm in width. The nanofibers are carbon fiber nanofibers with a diameter of 50–100 nm, enhancing the tensile strength and thermal conductivity of the asphalt concrete. The advantages of the intelligent self-healing layer are: self-repair of micro-cracks, reducing the frequency of manual maintenance; and enhanced crack resistance and wear resistance by nanofibers, extending service life. Applicable scenarios: suitable for main roads in mining areas, high-traffic areas, and sections with high maintenance difficulty.

[0039] The prefabricated, replaceable surface layer is assembled from several interlocking permeable modular bricks. The modular bricks are made of permeable concrete, measuring 500×500×80mm, and feature an interlocking structure at the edges. Advantages: After settlement, modules can be replaced locally without overall milling, resulting in low repair costs; the permeable design guides and drains surface rainwater, preventing road surface flooding. Applicable scenarios: Secondary arterial roads in mining areas, sections with high settlement risk (annual deformation ≥8mm), and sections requiring frequent localized repairs.

[0040] The flexible road proposed in this embodiment includes a drainage base layer 1, an adaptive subbase layer 2, an integrated seepage-proof and drainage layer 3, a flexible stabilizing layer 4, and a surface layer 5, forming a multi-layered synergistic structure. The pipe-network composite structure of the drainage base layer 1, together with the integrated seepage-proof and drainage layer 3 and the adaptive subbase layer 2, forms a three-dimensional seepage control system. This system can quickly drain groundwater and block seepage channels, while the adaptive subbase layer 2 can buffer deformation, structurally solving the problems of seepage failure and local subsidence caused by high water levels in the collapse area. In addition, the flexible stabilizing layer 4 uses bio-enzyme-stabilized soil mixed with dispersed fibers and covered with geotextile 42 to form a synergistic stress-bearing structure, which can actively adapt to uneven settlement in the collapse area and avoid structural cracking. Compared with traditional rigid structures, this significantly improves the road's adaptability to deformation.

[0041] In addition, the drainage base layer 1 is equipped with sensors for seepage pressure and flow rate, and the water collection well 6 is equipped with a water level sensor. The integrated design of the structural layer and monitoring elements breaks through the traditional limitation of invisible quality, provides real-time data support for construction control and operation and maintenance, and ensures the long-term stability of the structure.

[0042] Example 2: This embodiment proposes a method for constructing flexible roads suitable for subsidence areas in mining areas with high groundwater levels. The specific steps are as follows: S1. Risk Zoning: Collect the foundation database of the construction area, establish a digital twin field, divide high, medium and low risk zones, and output risk zoning map, construction parameters and early warning thresholds; The specific method in S1 is as follows: S11. Collect topography, soil layer distribution, groundwater level and mechanical parameters of the construction area to generate a three-dimensional geological initial dataset; specifically, use UAV aerial photography to obtain topography data, analyze soil layer distribution through drilling sampling, determine soil mechanical parameters through static penetration test, monitor groundwater level continuously for 72 hours using water level monitoring well, and finally generate a three-dimensional geological initial dataset containing topography, soil layers, water level and mechanical parameters.

[0043] S12. Import the initial dataset into the numerical simulation software in the controller to construct a digital twin model, i.e., a twin field, that is consistent with the physical properties of the construction area.

[0044] S1.3 Based on the digital twin model, the settlement rate and seepage pressure distribution under different construction conditions are simulated. Settlement rate threshold and seepage pressure threshold are set, high, medium and low risk zones are divided, and risk zoning map and recommended construction parameters and early warning thresholds for each zone are output as input conditions for subsequent construction.

[0045] The risk zoning standard in S1 is as follows: high-risk area with annual deformation >10mm, medium-risk area with annual deformation 5-10mm, and low-risk area with annual deformation <5mm. High-risk areas (annual deformation >10mm) are mainly concentrated in the original coal mining subsidence core area, medium-risk areas (annual deformation 5-10mm) are distributed in the transition zone around high-risk areas, and low-risk areas (annual deformation <5mm) are far away from the subsidence impact area.

[0046] The warning thresholds are: settlement ≥3mm or pore pressure rises to 70% of the initial value in high-risk areas; settlement ≥5mm or pore pressure ≥50% of the initial value in medium-risk areas; and settlement ≥10mm in low-risk areas.

[0047] Additionally, it should be noted that the risk zoning map includes GIS coordinates, zoning boundaries, and risk level labels.

[0048] This step utilizes 3D geological modeling and working condition simulation to accurately identify construction risks, providing a scientific basis for subsequent foundation treatment and structural layer design, and avoiding insufficient reinforcement or waste of resources caused by a one-size-fits-all approach to construction.

[0049] S2. Foundation Tri-control Pre-treatment The foundation is pretreated by a combination of vacuum preloading, intermittent air extraction and pulsating load. For the high-risk areas designated in S1, CFG pile construction and sleeve valve pipe micro-grouting reinforcement are also required to form a reinforced foundation.

[0050] In S2, the negative pressure value of vacuum pre-compression is -60 to -80 kPa, and the maintenance time is 48 to 96 hours; the pressure of intermittent air extraction is 0.05 to 0.1 MPa, the extraction is 10 to 20 min / cycle, and the intermittent operation is 40 to 60 min; the pressure of pulsating load is 10 to 20 kPa, and the frequency is 0.5 to 1 Hz.

[0051] The CFG piles are 8-12m long and 500mm in diameter, arranged in a triangular pattern at 1.5-2.0m intervals; the sleeve valve pipe micro-grouting uses a 0.8%-1.2% micro-expansion cement system, and the grouting pressure and grout volume are controlled based on real-time monitoring feedback.

[0052] Specific examples include: General handling measures: Vacuum preloading: A vacuum jet pump set is used, a sealing membrane is laid, the negative pressure value is stabilized at -70kPa and maintained for 72 hours to drain the pore water in the soil. Intermittent air extraction: An air compressor is configured to pressurize the underground soil with air through a pre-buried air pipe. The pressure is controlled at 0.08 MPa. The extraction cycle is 15 minutes, with an interval of 50 minutes, and the operation is repeated for a total of 15 days. Pulsating load: A vibratory roller is used to apply a pulsating pressure of 15 kPa and a frequency of 0.8 Hz, and the roller is rolled back and forth 8 times along the road axis to enhance the compaction of the soil.

[0053] Strengthened measures in high-risk areas: CFG pile construction: Long spiral drilling rigs are used, with piles 10m long and 500mm in diameter, arranged in a triangular pattern at 1.8m intervals, using C30 concrete strength grade, and cured for 28 days after pile completion. Sleeve valve pipe micro-grouting: Φ42mm sleeve valve pipes are used, arranged at 2.0m intervals. The grouting material is 1.0% micro-expansion cement slurry (cement:water:expansion agent=100:45:5). Based on real-time feedback from the pore pressure sensor, the grouting pressure is controlled at 0.3-0.5MPa, and the grouting volume per hole is 1.2m³, to ensure soil compaction.

[0054] This step reduces soil moisture content and increases density through the synergistic effects of vacuum preloading, airlift extraction, and pulsating load; additional reinforcement treatment is applied to high-risk areas to address the problems of foundation softening and uneven settlement at the source, providing a stable base for the superstructure.

[0055] S3. Construction of Base Layer 1: S31. The three-dimensional drainage net, the perforated permeable corrugated pipe 11, and the pressure sensor, flow sensor, and conductivity sensor are integrated and fixed in the factory to form a pre-assembled component. The pre-assembled component is equipped with quick-connect interfaces at both ends, such as socket-type rubber-sealed quick-connect interfaces, to ensure the connection is sealed.

[0056] S32. On-site, a traction plow or trenching machine is used to form trenches in one go. Pre-installed components are embedded into the trenches and connected to adjacent pre-installed components through quick-connect interfaces to form a continuous guide and discharge system. S33. After the water collection wells 6 are prefabricated in the factory, they are reasonably arranged on the site, with reserved positions for subsequent interfaces; the ends of the pre-assembled components are connected to the water collection wells 6 on both sides, and water level sensors are preset inside the water collection wells 6. The surface of the pre-assembled components is backfilled and compacted with graded crushed stone to complete the construction of the drainage base layer 1. During backfilling, layered backfilling is adopted, and compaction is carried out with a small vibratory rammer.

[0057] This step can build a coordinated drainage system of "pipe-network-well" to achieve rapid drainage of groundwater, while integrating sensors to monitor the seepage status in real time and provide data support for operation and maintenance.

[0058] S4. Adaptive Subbase 2 Construction: The substrate, foaming agent, and curing agent are mixed according to the preset formula, pumped in sections and laid in layers, and then cured to the preset strength after laser leveling. The substrate is sand or lime-soil, and the target density after foaming is stable at 600-800 kg / m³; the construction temperature is controlled at 10-35℃, and the time for pouring into the mold is ≤10 min; the thickness of each layer is 150-220 mm, the flatness after laser leveling is ≤5 mm / 3 m, and 0.3-0.6 kg / m² of cement slurry is sprayed to enhance the interlayer bonding. The strength is ≥0.8 MPa after 24 h and ≥1.0 MPa after 72 h.

[0059] Specifically: Material mixing: If sand is used as the base material, 42.5 grade ordinary Portland cement is used as the curing agent, and animal protein foaming agent is used as the foaming agent. The mixing ratio is sand: cement: foaming agent: water = 100:15:0.8:35. A forced mixer is used for mixing for 3 minutes to ensure that the mixture is uniform and free of lumps.

[0060] Paving and leveling: The construction temperature is controlled at 25℃, the mixing time is 8 minutes, the paving is carried out in sections using pumping equipment, the thickness of each layer is 200mm, and the paving is leveled using a laser screed machine. The flatness after leveling is ≤5mm / 3m.

[0061] Interlayer bonding and curing: After paving, immediately spray 0.5kg / m² cement slurry to enhance interlayer bonding; then cover and cure, keeping the ambient temperature at 20-25℃. After 24 hours of curing, the strength is ≥0.9MPa, and after 72 hours, the strength is ≥1.1MPa, meeting the preset strength requirements.

[0062] In this step, the low elasticity of lightweight foamed concrete buffers settlement stress and simultaneously achieves precise elevation adjustment, preventing the upper structure from cracking due to differential settlement.

[0063] S5. Construction of Integrated Seepage Prevention and Drainage Layer 3: A drone performs a 3D scan of the adaptive underlayment 2 in S3 to generate a digital twin model and optimize the operation path. The drone then transports the materials. An AGV and a welding robot collaboratively lay nonwoven fabric 31 and nano-modified HDPE membrane 32. A 3D drainage net is laid on the membrane and welded to form a seepage-proof and drainage-guiding composite layer. The drone is used to inspect the welds and composite layer and guide personnel in targeted repairs. Specifically: Digital twin model construction and path optimization: A drone is used to perform a 3D scan of the surface of the adaptive subbase 2 to generate a digital twin model. The material transfer and laying path is optimized by path planning software to avoid construction blind spots.

[0064] Material laying and welding: The drone transports nonwoven fabric 31, 1.5mm thick nano-modified HDPE film and 15mm thick three-dimensional drainage net; the AGV cooperates with the welding robot to lay nonwoven fabric 31, the nonwoven fabric 31 is laid flat and the overlap width is ≥100mm; the nano-modified HDPE film is covered on nonwoven fabric 31 with an overlap width of 100mm, and the welding robot uses hot air welding method; the three-dimensional drainage net is laid on HDPE film and fixed by hot melt spot welding with a weld point spacing of 300mm.

[0065] Inspection and Repair: The UAV is equipped with a thermal imager to conduct non-contact inspection of the weld and composite layer. The weld is inspected by the air inflation method with an inflation pressure of 0.2MPa. It is considered qualified if there is no pressure drop after 5 minutes. For the missing welds and poor welds found during the inspection, they are repaired manually with a repair welding machine. After repair, they are re-inspected until they are qualified.

[0066] This step can block the infiltration of groundwater upwards and surface water downwards, forming a two-way seepage prevention system of "upward guidance and downward defense". At the same time, intelligent construction can improve the quality and efficiency of laying.

[0067] S6. Construction of Flexible Stabilizing Layer 4 Soil is thoroughly mixed with fly ash, coal gangue, bio-enzyme solidifying agent, and fiber using mixing equipment to obtain bio-enzyme solidified soil. This soil is then spread in layers, with intelligent compaction equipment controlling the compaction degree. After compaction, geotextile 42 is laid and cured under a membrane until the required strength is achieved. Specifically: Preparation of bio-enzyme-stabilized soil: Select on-site silty clay, mix in 20% fly ash, 15% coal gangue, add 0.4% bio-enzyme solidifying agent and 0.3% polypropylene dispersion fiber; use a forced mixer to mix thoroughly for 4 minutes to ensure uniform fiber dispersion and no agglomeration.

[0068] Spreading and compaction: The bio-enzyme-stabilized soil is spread in layers, with each layer being 250mm thick. It is compacted using intelligent compaction equipment with GPS positioning at a speed of 2km / h and 6 passes. The compaction degree is controlled at 96%, and the surface flatness after compaction is ≤8mm / 3m.

[0069] Geotextile 42 laying and curing: After compaction, lay 300g / m² nonwoven fabric 31, with the overlap width of geotextile 42 ≥150mm, and use sewing connection; cover with plastic film for curing for 7 days, keep the film moist during the curing period, and the soil strength ≥2.5MPa after curing.

[0070] S7. Surface Layer 5 Construction Choose either self-healing asphalt surface layer 5 or prefabricated replaceable surface layer according to functional requirements, and complete the paving, compaction or assembly according to the corresponding process.

[0071] S8. Completion Inspection: Core sampling was conducted to verify the thickness of each structural layer, FWD deflection test was performed, surface layer permeability coefficient test was conducted, and GPR test was performed.

[0072] Core sampling and testing: Take one set of core samples every 200m along the road axis, with 3 samples in each set, to test the thickness of the drainage base layer 1, adaptive subbase layer 2, integrated seepage prevention-drainage layer, flexible stabilization layer 4 and surface layer 5. The thickness deviation of each layer is ≤±5mm, which meets the design requirements.

[0073] FWD deflection test: A falling weight deflectometer was used, with a test interval of 10m. Each test point was measured 3 times, and the average value was taken. The deflection value was ≤200 (0.01mm), which meets the road load-bearing requirements.

[0074] Permeability coefficient test of surface layer 5: Using a pavement permeability meter, three test points were randomly selected on surface layer 5, and each point was tested three times. The average permeability coefficient was ≤100mL / min, indicating that surface layer 5 has good impermeability performance.

[0075] GPR inspection: Using 1GHz ground penetrating radar, bidirectional scanning was performed along the road to a depth of 5m. No obvious voids, gaps, or interlayer separation defects were found, and the structural integrity was good.

[0076] S9. Intelligent Monitoring: After quality verification is completed, all monitoring data and construction records are uploaded to the cloud, automated handling rules are set, routine operation and maintenance configurations are completed, and intelligent monitoring is achieved. Specifically: Data Upload and Storage: The seepage pressure, flow rate, and conductivity sensors of the drainage base layer 1, the water level sensor of the collection well 6, the compaction, temperature, and strength data during the construction process, and the completion inspection results are all uploaded to the Alibaba Cloud platform to establish a database and realize permanent data storage and traceability.

[0077] Automated handling rule settings: Set early warning rules: When the settlement in the high-risk area is ≥3mm or the pore pressure rises to 70% of the initial value, the settlement in the medium-risk area is ≥5mm or the pore pressure is ≥50% of the initial value, and the settlement in the low-risk area is ≥10mm, the platform will automatically send SMS and APP early warning information to the operation and maintenance personnel; Set operation and maintenance rules: Automatically generate weekly monitoring data reports every week and remind sensor calibration every six months.

[0078] Intelligent operation and maintenance: Operation and maintenance personnel can view monitoring data in real time through computers or mobile phones, grasp the status of road structure, respond to early warning information in a timely manner, and take targeted measures to achieve intelligent monitoring and operation and maintenance throughout the entire life cycle.

[0079] It should be noted that experimental analysis was conducted regarding the pretreatment of the foundation using a three-pronged approach, such as... Figure 3 - Figure 4 As shown, Figure 3 The figure shows the simulation results of the total deformation of the static structure of the flexible road (without the pretreatment of the foundation three-linkage control). As can be seen from the figure, the simulation time is 0.515s, the maximum deformation is 11.34mm, and the minimum deformation is 0mm. Figure 4 This is a simulation result diagram of the total deformation of the static structure of the flexible road (with the foundation pretreatment under three-way control). The simulation time was 0.516s, the maximum deformation was 5.6522mm, and the minimum deformation was 0mm. Figure 3 The comparison shows that the maximum deformation is relatively... Figure 3 The significant reduction indicates that the overall performance of the flexible road is better after the pretreatment of the foundation with three-way control.

[0080] Specific application case 1: The construction site of this case is located in a reclamation channel in a district of a city in a certain province. This is a typical remediation project for a coal mining subsidence area with a high groundwater level. The geological and hydrological characteristics of the area are as follows: the groundwater depth is between 0.8 and 1.6 m, the soil saturation is greater than 85%, the weak interlayers are distributed in the depth range of -2.5 to -5.0 m, the Young's modulus of the foundation soil is 20 MPa, the Poisson's ratio is 0.279, and the density is 1.8 g / cm³, indicating a significant risk of leakage and uneven settlement.

[0081] This project adopts the flexible road structure described above. After the project is completed, a 90-day early operation monitoring period will be conducted, and the data is shown in Table 1: Table 1 shows the early operational monitoring data for the flexible road 90 days after completion. As can be seen from the table above, the maximum settlement within 90 days was 2.3 mm, which is far below the warning threshold. The seepage pressure control is stable and suitable for the environment of high groundwater level subsidence areas.

[0082] Comparative example: A traditional rigid road structure, consisting of a cement-stabilized crushed stone surface layer and a coal gangue subbase, was used as a comparison. The measured data after 28 days of construction were compared with Case 1 as follows: Table 2 compares the evaluation indicators of the flexible road structure of the present invention with those of the traditional rigid road structure. Engineering practice has shown that, in high groundwater level subsidence areas, this flexible road effectively reduces settlement and crack rate compared to traditional rigid structures, and its overall performance is effectively improved.

[0083] It should be noted that in the description of this invention, the terms "upper," "lower," "left," "right," "inner," and "outer," etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is merely for ease of description and does not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0084] Although the specific embodiments of the invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the invention. Based on the technical solutions of the invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the invention.

Claims

1. A flexible road suitable for subsidence areas in mining areas with high groundwater levels, characterized in that, It includes, from bottom to top, a drainage base layer, an adaptive subbase layer, an integrated seepage-proof and drainage layer, a flexible stabilizing layer, and a surface layer, wherein: The drainage base layer uses graded crushed stone, with permeable corrugated pipes embedded inside. The outer wall of the permeable corrugated pipes is wrapped with a three-dimensional drainage net to form a pipe-net composite structure. The pipe-net composite structure integrates sensors for seepage pressure, flow rate, and conductivity. The end of the permeable corrugated pipe is connected to a water collection well with a water level sensor. The adaptive subbase uses lightweight foamed concrete; The integrated seepage prevention and drainage layer uses a nano-modified HDPE membrane, with non-woven fabric laid under the membrane and a three-dimensional drainage grid laid on top of the membrane to form a composite structure. The flexible stabilizing layer uses bio-enzyme-stabilized soil as the load-bearing layer, with dispersed fibers mixed inside; the upper surface of the load-bearing layer is covered with geotextile to form a synergistic load-bearing structure.

2. A flexible road suitable for subsidence areas in high-water-level mining areas according to claim 1, characterized in that, The surface layer is either an intelligent self-healing surface layer or a prefabricated replaceable surface layer. The intelligent self-healing surface layer includes modified asphalt concrete with 3% to 6% microcapsules and 0.2% to 0.5% nanofibers. The prefabricated replaceable surface layer is assembled from several interlocking permeable modular bricks.

3. A flexible road suitable for subsidence areas in high-water-level mining areas according to claim 1, characterized in that, The enzyme content in the bio-enzyme-stabilized soil is 0.3% to 0.5%, and the content of dispersed fibers is 0.2% to 0.4%.

4. A flexible road suitable for subsidence areas in high-water-level mining areas according to claim 1, characterized in that, The particle size of graded crushed stone is 5–31.5 mm.

5. A method for constructing a flexible road suitable for subsidence areas in high-water-level mining areas according to any one of claims 2-4, characterized in that, The specific steps are as follows: S1. Risk Zoning: Collect the foundation database of the construction area, establish a digital twin field, divide high, medium and low risk zones, and output risk zoning map, construction parameters and early warning thresholds; S2. Foundation Tri-control Pre-treatment The foundation is pretreated by a combination of vacuum preloading, intermittent air extraction and pulsating load. For the high-risk areas in S1, CFG pile construction and sleeve valve pipe micro-grouting reinforcement are also required to form a reinforced foundation. S3. Construction of base course drainage: S31. In the factory, the three-dimensional drainage net, the perforated permeable corrugated pipe, and the pressure sensor, flow sensor, and conductivity sensor are integrated and fixed to form a pre-assembled component. The pre-assembled component is equipped with quick-connect interfaces at both ends. S32. On-site, a traction plow or trenching machine is used to form trenches in one go. Pre-installed components are embedded into the trenches and connected to adjacent pre-installed components through quick-connect interfaces to form a continuous guide and discharge system. S33. After the water collection wells are prefabricated in the factory, they are reasonably arranged on the site, and the positions for subsequent interfaces are reserved. The end of the pre-installed component is connected to the water collection wells on both sides. The water collection wells are pre-installed with water level sensors. The surface of the component is backfilled and compacted with graded crushed stone to complete the drainage base construction. S4. Adaptive Subbase Construction Mix the substrate, foaming agent and curing agent according to the preset formula, pump and spread in sections and layers, and cure to the preset strength after laser leveling; S5. Integrated seepage prevention and drainage layer construction The drone performs a 3D scan of the adaptive underlayment in S3 to generate a digital twin model and optimize the operation path. The drone transports the materials, and the AGV and welding robot work together to lay non-woven fabric and nano-modified HDPE membrane. A 3D drainage net is laid on the membrane and welding is carried out to form a seepage-proof and drainage-guiding composite layer. The drone is used to inspect the welds and composite layer and guide personnel to carry out targeted repairs. S6. Construction of Flexible Stabilizing Layer Soil is thoroughly mixed with fly ash, coal gangue, bio-enzyme solidifying agent and fiber using mixing equipment to obtain bio-enzyme solidified soil; then it is spread in layers, and the compaction degree is controlled by intelligent compaction equipment. After compaction, geotextile is laid and covered with a membrane for curing until the standard strength is reached. S7. Surface Layer Construction Choose a self-healing asphalt surface layer or a prefabricated replaceable surface layer according to functional requirements, and complete the paving, compaction or assembly according to the corresponding process. S8. Completion Inspection: Core sampling was conducted to verify the thickness of each structural layer, FWD deflection tests were performed, surface permeability coefficient tests were conducted, and GPR testing was carried out. S9. Intelligent Monitoring: After the quality verification is completed, all monitoring data and construction records are uploaded to the cloud, automated handling rules are set, routine operation and maintenance configurations are completed, and intelligent monitoring is achieved.

6. A method for constructing a flexible road suitable for subsidence areas in high-water-level mining areas according to claim 5, characterized in that, The vacuum pre-compression described in S2 has a negative pressure value of -60 to -80 kPa and a maintenance time of 48 to 96 hours; the pressure of intermittent air extraction is 0.05 to 0.1 MPa, the extraction is 10 to 20 min / cycle, and the intermittent operation is 40 to 60 min; the pressure of the pulsating load is 10 to 20 kPa and the frequency is 0.5 to 1 Hz.

7. A method for constructing a flexible road suitable for subsidence areas in high-water-level mining areas according to claim 5, characterized in that, The CFG piles described in S2 have a length of 8-12m and a diameter of 500mm, and are arranged in a triangular pattern at intervals of 1.5-2.0m. The sleeve valve pipe micro-grouting uses a 0.8%-1.2% micro-expansion cement system, and the grouting pressure and grout volume are controlled based on real-time monitoring feedback.

8. A method for constructing a flexible road suitable for subsidence areas in high-water-level mining areas according to claim 5, characterized in that, The substrate is sand or lime-soil, and the target density after foaming is stable at 600-800 kg / m³; the construction temperature is controlled at 10-35℃, and the time for pouring into the mold is ≤10 min; the thickness of each layer is 150-220 mm, the flatness after laser leveling is ≤5 mm / 3 m, and 0.3-0.6 kg / m² of cement paste is sprayed to enhance the interlayer bonding. The strength is ≥0.8 MPa after 24 h of curing and ≥1.0 MPa after 72 h of curing.

9. A method for constructing a flexible road suitable for subsidence areas in high-water-level mining areas according to claim 5, characterized in that, The risk zoning criteria for S1 are as follows: annual deformation >10mm in high-risk areas, 5–10mm in medium-risk areas, and <5mm in low-risk areas. The warning thresholds are: settlement ≥3mm or pore pressure rises to 70% of the initial value in high-risk areas, settlement ≥5mm or pore pressure ≥50% of the initial value in medium-risk areas, and settlement ≥10mm in low-risk areas.

10. A method for constructing a flexible road suitable for subsidence areas in high-water-level mining areas according to claim 5, characterized in that, The specific method in S1 is as follows: S11. Collect the topography, soil layer distribution, groundwater level and mechanical parameters of the construction area to generate a three-dimensional geological initial dataset; S12. Import the initial dataset into the numerical simulation software in the controller to construct a digital twin model, i.e., a twin field, that is consistent with the physical properties of the construction area; S1.3 Based on the digital twin model, the settlement rate and seepage pressure distribution under different construction conditions are simulated. Settlement rate threshold and seepage pressure threshold are set, high, medium and low risk zones are divided, and risk zoning map and recommended construction parameters and early warning thresholds for each zone are output as input conditions for subsequent construction.

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