Construction method for roadbed penetrating through V-shaped valley area

Abstract

The invention relates to a construction method for a roadbed penetrating through a V-shaped valley area, and belongs to the technical field of foundation engineering and foundation treatment. The problems of low foundation drainage efficiency, filling side slope instability and differential settlement control in V-shaped valley roadbed construction are solved. According to the technical scheme, a groove is dug along the bottom of a valley, a gravel drainage blind ditch wrapped by permeable geotextile is laid, and a foundation drainage system is formed; during layered filling, a vibratory roller with a piezoelectric sensor embedded into a steel wheel is adopted; after every two layers are filled, one-way geogrids are laid along the slope and vertically anchored into the compaction layer through U-shaped anchoring parts; a transverse drainage pipe is pre-buried when filling is conducted to a foundation bearing capacity sudden change point threshold value; and after filling is completed, a settlement monitoring array is arranged. According to the method, through system integration of foundation drainage structure optimization, filling body intelligent compaction and differential settlement dynamic treatment, the bearing stability of the fill roadbed under the complex terrain is remarkably improved, and the method is suitable for foundation construction and disaster prevention and control of the V-shaped canyon section of the mountain road.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation engineering and ground treatment. More specifically, the present invention relates to a subgrade construction method for crossing a V-shaped valley area. Background Art

[0002] When implementing subgrade filling projects in V-shaped valley areas, the special terrain conditions pose multiple challenges to construction techniques. In the prior art, the drainage system design usually adopts a single drainage blind ditch structure. The gravel filling layer is prone to local accumulation density differences due to the irregular terrain at the bottom of the valley. The contact interface between the permeable geotextile and the filling body is prone to dislocation, resulting in discontinuous drainage paths. This phenomenon is due to the significant lateral slope change in the V-shaped valley bottom. Conventional straight blind ditches are difficult to adapt to the longitudinal undulations, and there is a lack of coordinated control of the gravel particle size and the extension length of the permeable geotextile during construction, resulting in a significant decrease in the permeability coefficient of the blind ditch during the filling process. In addition, the covering layer on the top of the blind ditch is prone to structural deformation during the operation of heavy compaction equipment, causing blockage of the drainage channel, and the effective water passing area of the blind ditch is significantly reduced after the filling is completed.

[0003] Regarding the control of slope stability, the laying interval of geogrids in the traditional layered filling process is too large, resulting in the distance between the stress-bearing layers of the grids exceeding the reasonable range. The lateral earth pressure of the V-shaped valley fill slope increases non-linearly with the increase of the filling height, but the existing anchoring spacing cannot effectively disperse the stress concentration area. Especially in the area where the foundation bearing capacity changes suddenly, the anti-pulling force of the anchor bolts shows a significant loss. At the same time, when the vertical insertion angle deviation of the U-shaped steel anchor bolts is large, the co-deformation ability with the geogrid nodes is reduced, resulting in a decrease in the utilization rate of the tensile strength of the geogrid.

[0004] In terms of differential settlement control, the traditional method relies on the surface settlement observation after the subgrade is formed. However, hidden uneven settlements are often caused by sudden changes in the foundation bearing capacity inside the V-shaped valley filling body. In the prior art, the identification of the sudden change points of the foundation bearing capacity mostly relies on the static analysis of geological exploration data, without considering the dynamic response during the filling loading process. When the change rate of the foundation compression modulus accelerates, the traditional method is difficult to capture the critical state in time, resulting in an increase in the design deviation of the subsequent filling layer thickness. In addition, the paving thickness control of the graded gravel layer is affected by the longitudinal slope change, and the paving thickness deviation caused by the slope change gradually increases, directly affecting the surface drainage performance.

[0005] In the link of compaction quality control, the operation of conventional vibratory rollers relies on the experience of operators to adjust the compaction parameters, and the response to the non-uniformity of the filler is lagging. When the moisture content of the filler changes, the coefficient of variation of the compaction degree increases significantly, and weak zones are easily formed in the overlapping areas of adjacent compaction sections, and the compaction degree in these areas is lower than that in the normal areas. In the prior art, the compaction degree detection adopts sampling point detection, which cannot effectively identify local compaction defects, resulting in a high omission ratio of non-compliant areas.

[0006] For internal drainage of the filling body, the elevation of traditional horizontal drainage pipes is mostly determined based on fixed elevations, without considering the dynamic influence of foundation settlement during the filling process. When the filling body continuously compresses and deforms, the pre-buried drainage pipes are prone to longitudinal displacement, resulting in the failure of their connection with the blind ditch. At the same time, there is a lack of continuous guarantee measures for the lap treatment of the drainage geotextile of the drainage pipe and the permeable geotextile of the blind ditch. When the interface permeability coefficient difference is significant, a drainage barrier will be formed, causing a reduction in drainage efficiency.

[0007] In terms of the reinforcement treatment in the differential settlement area, the existing technologies mostly adopt unified grouting parameters without considering the spatial variation characteristics of the soil permeability coefficient. When there are significant differences in the soil permeability coefficient in the reinforcement area, the conventional grouting pressure setting will lead to insufficient slurry diffusion in the low-permeability area and serious slurry loss in the high-permeability area. In addition, the interpretation accuracy of ground penetrating radar scanning data is interfered by the reflection of the filler stratification interface. When the interface misalignment is large, the porosity detection error will expand, directly affecting the accuracy of the reinforcement plan formulation.

[0008] The coupled action of the above technical problems often leads to problems such as high late maintenance costs and shortened service life in the V-shaped valley subgrade project. Especially in rainy mountainous areas, the risk of slope sliding caused by internal water accumulation in the fill body increases significantly. The improvements in existing technologies mostly focus on the optimization of a single subsystem, lacking the research on the synergistic action mechanism of the drainage structure, filling technology, and settlement control, which has become a bottleneck problem for improving the quality of subgrade projects in complex terrains. Summary of the Invention

[0009] An object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0010] To achieve these objects and other advantages according to the present invention, a subgrade construction method for crossing a V-shaped valley area is provided, including the following steps: Step 1: Excavate a trench along the longitudinal direction of the subgrade at the bottom of the V-shaped valley and lay a permeable geotextile, and then fill it with gravel to form a drainage blind ditch. The top of the drainage blind ditch is covered with a permeable geotextile, and both side edges extend to the subgrade filling boundary; On the top and both sides of the drainage blind ditch, the subgrade filler is laid layer by layer using the layered filling method to cover the entire subgrade cross-section. After each layer of filling, it is rolled by a vibratory roller according to a preset compaction path. The traveling direction of the vibratory roller is parallel to the longitudinal axis of the subgrade, and the overlapping width of adjacent rolling wheel tracks is 1 / 3 - 1 / 2 of the wheel width; Step 2: After every two layers of subgrade filling layers are completed, a unidirectional geogrid is unfolded longitudinally on the slope surface of the subgrade. The laying direction of the unidirectional geogrid is consistent with the longitudinal direction of the subgrade, and U-shaped steel anchor bolts are vertically inserted into the compacted filling layer. The horizontal spacing of the U-shaped steel anchor bolts is 1.5 - 2 m and is aligned with the overlapping area of the geogrid; Step 3: When the subgrade filling height reaches the preset threshold, a plurality of drain pipes are horizontally embedded below the subgrade top surface. The inlet end of the drain pipe communicates with the drainage blind ditch through an inclined connecting pipe, and the outlet end extends to the outside of the subgrade slope. Moreover, the filter geotextile wrapped outside the drain pipe and the permeable geotextile of the drainage blind ditch form a continuous drainage interface; Step 4: After the subgrade is filled to the design elevation, a graded gravel layer is evenly spread and leveled on the subgrade surface. The spreading thickness of the graded gravel layer is dynamically adjusted by elevation control piles; After spreading and static curing, catch basins are simultaneously excavated at the toe of the side slopes on both sides of the subgrade. A concrete cushion is laid at the bottom of the catch basin, and the longitudinal slope of the catch basin is consistent with the subgrade drainage direction; Step 5: Since the completion of filling, a settlement monitoring point array is arranged on the subgrade surface. The monitoring points are distributed in a grid along the longitudinal and transverse directions of the subgrade, and elevation data is collected by a total station at fixed intervals. When the elevation difference between adjacent monitoring points exceeds the set threshold, reinforcement treatment is carried out in the corresponding area.

[0011] Preferably, piezoelectric dynamic compaction sensors are arranged at intervals of 200 - 300 mm inside the steel wheels of the vibratory roller to collect the reaction force waveform data of the filler during the rolling process in real time; The waveform data is subjected to spectral analysis through an Internet of Things control platform to extract the energy proportion of the characteristic frequency band. When the energy proportion is lower than the set threshold range of 65% - 75%, it is determined that the compaction degree is insufficient; If the compaction degree data of three consecutive rolling sections are all lower than the threshold lower limit, the control roller automatically increases the vibration frequency of the current rolling section by 2 - 4 Hz and adds 1 - 2 additional passes of rolling; If the energy proportion exceeds the threshold upper limit, the vibration frequency is reduced by 1 - 2 Hz, and the number of rolling passes in the subsequent rolling section is reduced by 1 pass.

[0012] Preferably, in the adjacent rolling section junction area, the differential positioning technology is used to control the overlap width of the roller tracks of the roller to increase by 50 - 100 mm, and the vibration frequency in this area is synchronously increased by 1 - 3 Hz; After every 100 - 150 m of rolling operation is completed, the Internet of Things platform generates a compaction degree heat map, and the area with a compaction degree coefficient of variation greater than 0.15 is marked as the recompaction area. During recompaction, a fan-shaped path is used for densifying rolling; The densifying rolling of the fan-shaped path includes rolling in concentric circular arc trajectories with a radius of 1 - 3 m centered on the center of the recompaction area, and the distance between adjacent arcs is 1 / 2 - 2 / 3 of the roller width.

[0013] Preferably, the method for determining the preset threshold of the subgrade filling height in Step 3 includes the following steps: Obtain the foundation bearing capacity data at different depths in the V-shaped valley section through geological exploration. When the cumulative thickness of the subgrade filling layer reaches 70% - 80% of the depth corresponding to the mutation point of the foundation bearing capacity, it is determined as the preset threshold trigger point; During the filling process, use a settlement monitoring device to measure the compression deformation rate of the filled layer in real time. When the deformation rate is less than 0.5 mm / d for 3 consecutive days, the preset threshold determination condition is triggered synchronously; If both the mutation point of the foundation bearing capacity and the stable condition of the deformation rate are satisfied, locate the burial elevation of the horizontal drain pipe at 1.2 - 1.8 m downward from the top of the current filling layer; If the two conditions are not satisfied simultaneously, continue filling until the thickness of the next layer reaches the incremental threshold corresponding to the depth of the mutation point of the foundation bearing capacity. The incremental threshold is 1.2 - 1.5 times the single-layer filling thickness.

[0014] Preferably, the specific method for dynamically adjusting the paving thickness of the graded sand and gravel layer is as follows: Set elevation control piles along the longitudinal axis of the subgrade surface at intervals of 5 - 8 m. The top elevation of the elevation control piles is the same as the designed elevation of the graded sand and gravel layer; During the progress of the paver, use a laser rangefinder to measure the vertical distance between the surface of the paved sand and gravel layer and the top of the elevation control pile in real time; When the measured vertical distance exceeds the range of -10 mm to +15 mm of the designed paving thickness, synchronously adjust the scraper opening and the traveling speed through the hydraulic control system of the paver; After the dynamic adjustment is completed, a continuous elevation control reference surface is formed on the surface of the graded sand and gravel layer, and its longitudinal flatness error is controlled within the range of ±5 mm / 10 m.

[0015] Preferably, it further includes: setting elevation re-measurement points behind the paver, and using a dynamic compaction degree detector to obtain the compaction degree data of the adjusted area; When the compaction degree data is lower than 95% of the design value, control the vibratory roller to roll the corresponding area 1 - 2 more times; When adding rolling, the exciting force of the vibratory roller is increased by 10% - 15%, and the rolling path intersects with the original path at an intersection angle of 30° - 45°.

[0016] Preferably, the specific method for reinforcement treatment in step five includes: When the elevation difference between adjacent monitoring points exceeds 10 - 15 mm, demarcate a circular difference area with a radius of 2 - 3 m centered on the point with the largest elevation difference; Use ground penetrating radar to scan the internal structure of the subgrade within the difference area. If the detected porosity is greater than 20% or the dislocation of the filler stratification interface exceeds 50 mm, use the high-pressure jet grouting method for reinforcement, and control the grouting pressure to be 0.8 - 1.2 MPa; If it is detected that the compactness of the filler is 5% - 8% lower than the design value, the surface filler in the differential area shall be removed to the stable layer, and then re-filled in layers and compacted with a vibratory roller with the exciting force increased by 10% - 15%, and the number of compaction passes is 3 - 4 times; After the treatment is completed, monitoring points shall be densely arranged in the differential area to 1 / 2 of the original spacing, and the monitoring period shall be shortened to 1 / 3 of the original period until the fluctuation range of the monitoring data is less than 2 mm for 3 consecutive times.

[0017] Preferably, it further includes: If there are signs of slope slip in the differential area, a biaxial geogrid shall be paved on the slope surface. The tensile strength of the biaxial geogrid is 100 - 150 kN / m, and it is fixed to the deep stable layer of the slope through L-shaped anchor rods, and the embedding depth of the anchor rods is 1.5 - 2 m; The installation sequence of the L-shaped anchor rods is to construct row by row from top to bottom. The installation interval distance of the anchor rods in the same row is 1.2 - 1.5 times the length of the anchor rods, and the minimum spacing shall not be less than 1.8 m, and the nodes of the anchor rod tails and the geogrid are locked through fasteners.

[0018] Preferably, the grouting pressure of the high-pressure jet grouting method is dynamically adjusted according to the soil permeability coefficient of the differential area: When the soil permeability coefficient k ≥ 1×10 -4 cm / s, the grouting pressure is controlled at 0.8 - 1.0 MPa, the grouting hole spacing is 0.8 m × 0.8 m to 1 m × 1 m, and the grouting speed is 15 - 20 L / min; When the soil permeability coefficient 1×10 -6 cm / s ≤ k < 1×10 -4 cm / s, the grouting pressure is controlled at 1.0 - 1.2 MPa, the grouting hole spacing is 0.6 m × 0.6 m to 0.8 m × 0.8 m, and the grouting speed is 10 - 15 L / min; When the soil permeability coefficient k < 1×10 -6 cm / s, a pre-cracking process shall be adopted before grouting. The pre-cracking hole spacing is 0.5 - 0.7 times the grouting hole spacing, and the pre-cracking pressure is applied in stages. The initial pressure is 0.8 - 1.0 times the grouting pressure, and it is stabilized for 2 minutes for each increase of 0.2 MPa. The final pressure does not exceed 1.2 times the grouting pressure; After the grouting is completed, the consolidation state of the grout is monitored through a pore water pressure sensor. If the dissipation rate of the pore water pressure within 24 hours after grouting is less than 30% of the initial value, grout shall be supplemented at adjacent hole positions, and the supplementary grouting pressure is 80% - 90% of the original pressure.

[0019] The present invention has at least the following beneficial effects: Through the continuous interface design of the crushed stone blind ditch and the permeable geotextile combined with the layered filling process, the present invention effectively maintains the continuity of the drainage path and reduces the seepage attenuation. At the same time, the interval anchoring of the geogrid significantly improves the anti-slip ability of the slope; The intelligent compaction system based on piezoelectric sensing and Internet of Things feedback dynamically adjusts the vibration parameters to eliminate the weak compaction areas caused by the non-uniformity of the filler; The double-threshold determination method of the sudden change point of the foundation bearing capacity and the deformation rate realizes the early warning of differential settlement, combined with the ground penetrating radar to accurately identify internal defects, improving the pertinence of reinforcement treatment; The dynamic positioning technology of the drain pipe elevation adapts to the settlement change of the filling body, ensuring the interface seepage matching of the three-dimensional drainage system; The paving control technology of laser ranging and hydraulic linkage optimizes the thickness and flatness of the graded gravel layer, enhancing the surface drainage efficiency; The grouting parameter control strategy with graded permeability coefficients improves the uniformity of slurry diffusion, ensuring the balanced improvement of the bearing capacity of the reinforced area; The synergistic effect of the biaxial geogrid and the deep anchor rod strengthens the shear strength of the potential slip surface, and combined with high-frequency monitoring, realizes the dynamic control of the slope stability; The fan-shaped re-rolling path guided by differential positioning improves the compaction degree of the rolling joint area and reduces the equipment energy consumption; The closed-loop mechanism of the pore water pressure monitoring and supplementary grouting linkage ensures the long-term stability of the reinforcement effect, significantly extending the service life of the roadbed.

[0020] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. Detailed implementation manners

[0021] The following further elaborates on the present invention in conjunction with the specific implementation manners, so that those skilled in the art can implement it according to the text of the specification.

[0022] It should be understood that the terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0023] It should be noted that the experimental methods described in the following implementation schemes are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0024] The present invention provides a roadbed construction method for crossing a V-shaped valley area, including the following steps: Step 1: Excavate a trench along the longitudinal direction of the roadbed at the bottom of the V-shaped valley and lay a permeable geotextile, and then fill it with crushed stones to form a drainage blind ditch. The top of the drainage blind ditch is covered with a permeable geotextile, and both sides extend to the roadbed filling boundary. The roadbed filler is laid layer by layer on the top and both sides of the blind drainage ditch to cover the entire roadbed cross section. After each layer is filled, it is rolled by a vibratory roller according to a preset compaction path. The moving direction of the vibratory roller is parallel to the longitudinal axis of the roadbed, and the overlapping width of adjacent rolling wheel tracks is 1 / 3 to 1 / 2 of the wheel width. Step 2: After completing two layers of roadbed filling, a one-way geogrid is deployed longitudinally on the slope surface of the roadbed. The laying direction of the one-way geogrid is consistent with the longitudinal direction of the roadbed, and is vertically inserted into the compacted filling layer through U-shaped steel bar anchors. The horizontal spacing of the U-shaped steel bar anchors is 1.5-2m, and they are aligned with the overlap area of ​​the geogrid. Step 3: When the roadbed filling height reaches a preset threshold, multiple drainage pipes are pre-buried transversely below the top surface of the roadbed. The inlet end of the drainage pipe is connected to the drainage blind ditch through an inclined connecting pipe, and the outlet end extends to the outside of the roadbed slope. The water-filtering geotextile wrapped outside the drainage pipe and the permeable geotextile of the drainage blind ditch form a continuous drainage interface; Step 4: After the roadbed is filled to the designed elevation, a graded gravel layer is evenly spread on the roadbed surface and leveled. The spreading thickness of the graded gravel layer is dynamically adjusted by the elevation control piles. After paving is completed and static curing is performed, intercepting ditches are excavated at the foot of the slopes on both sides of the roadbed. A concrete cushion is laid at the bottom of the intercepting ditch, and the longitudinal slope of the intercepting ditch is consistent with the drainage direction of the roadbed; Step 5: After the self-filling is completed, an array of settlement monitoring points is arranged on the roadbed surface. The monitoring points are distributed in a grid along the longitudinal and transverse directions of the roadbed, and elevation data is collected at a fixed period by a total station. When the elevation difference between adjacent monitoring points exceeds the set threshold, reinforcement treatment is carried out in the corresponding area.

[0025] In this technical solution, when implementing the subgrade construction for crossing the V-shaped valley area, first, a trench is excavated longitudinally along the subgrade at the bottom of the V-shaped valley. The depth of the trench can be determined according to the actual geological conditions, generally ranging from 1 to 2 meters. A permeable geotextile can be selected for laying, and its material can be polyester fiber. This permeable geotextile has good water permeability and durability. Subsequently, crushed stones are filled to form a drainage blind ditch. The particle size of the crushed stones can be selected from 2 to 5 centimeters to ensure good drainage performance. The top of the drainage blind ditch is covered with the same polyester fiber permeable geotextile, and the two side edges extend to the subgrade filling boundary. Above and on both sides of the drainage blind ditch, the subgrade filler is laid layer by layer using the layered filling method to cover the entire cross-section of the subgrade. The thickness of each filling layer can be controlled within 20 to 30 centimeters. After each filling layer, a selectable vibratory roller is used for compaction. The traveling direction of the vibratory roller is parallel to the longitudinal axis of the subgrade. The overlapping width of adjacent roller tracks can be selected as 1 / 3 of the roller width. For example, when the roller width is 2 meters, the overlapping width is approximately 0.67 meters. Here, a vibratory roller with a self-weight of 15 to 20 tons can be selected, and its compaction effect is better and can meet the construction requirements. In step two, after every two subgrade filling layers are completed, a unidirectional geogrid is unfolded longitudinally at the slope surface of the subgrade. The unidirectional geogrid can be made of high-strength polypropylene material, and its tensile strength is relatively high, which can effectively enhance the slope stability. The U-shaped steel anchor is vertically inserted into the compacted filling layer. The horizontal spacing of the U-shaped steel anchor can be selected as 1.5 meters. The U-shaped steel anchor should be aligned with the overlapping area of the geogrid. The U-shaped steel anchor can be made of steel bars with a diameter of 12 to 16 millimeters. During installation, the U-shaped steel anchor needs to be vertically inserted into the filling layer, and the insertion depth should ensure effective anchoring of the geogrid, generally ranging from 30 to 50 centimeters. In step three, when the subgrade filling height reaches the preset threshold, the horizontal drainage pipes are pre-embedded. The preset threshold can be determined by obtaining the foundation bearing capacity data at different depths in the V-shaped valley section through geological exploration. When the cumulative thickness of the subgrade filling layer reaches 70% of the depth corresponding to the mutation point of the foundation bearing capacity, it is determined as the preset threshold trigger point. Multiple drainage pipes are pre-embedded horizontally below the subgrade top surface. The drainage pipes can be made of polyvinyl chloride (PVC) material, which has strong corrosion resistance. The inlet end of the drainage pipe is connected to the drainage blind ditch through an inclined connecting pipe, and the inclined connecting pipe can also be made of PVC material. The outlet end extends to the outside of the subgrade slope. The filter geotextile wrapped outside the drainage pipe can be selected as the same polyester fiber permeable geotextile as the drainage blind ditch to form a continuous drainage interface. In step four, after the subgrade is filled to the design elevation, a graded gravel layer is evenly spread and leveled on the subgrade surface. The spreading thickness of the graded gravel layer is dynamically adjusted through elevation control piles. Elevation control piles are set at intervals of 5 meters along the longitudinal axis on the subgrade surface. The elevation control piles can be made of reinforced concrete, and the top elevation is the same as the design elevation of the graded gravel layer. During the traveling process of the paver, the vertical distance between the surface of the already spread gravel layer and the top of the elevation control pile is measured in real time through a selectable laser rangefinder.When the measured vertical distance exceeds the range of -10 mm to +15 mm of the designed paving thickness, synchronously adjust the scraper opening and the traveling speed through the hydraulic control system of the paver. After the dynamic adjustment is completed, a continuous elevation control reference plane is formed on the surface of the graded gravel layer, and the longitudinal flatness error is controlled within the range of ±5 mm / 1 m. After the paving is completed and left for curing, intercepting ditches are synchronously excavated at the toe of the side slopes on both sides of the subgrade. A concrete cushion is laid at the bottom of the intercepting ditch, and the concrete can be selected as commercial concrete with a strength grade of C20. The longitudinal slope of the intercepting ditch is consistent with the drainage direction of the subgrade to ensure smooth drainage. Step Five, after the filling is completed, a settlement monitoring point array is arranged on the surface of the subgrade, and the monitoring points are distributed in a grid along the longitudinal and transverse directions of the subgrade. Use a total station that can be selected to collect elevation data at fixed intervals, and the fixed interval can be selected as 7 days. When the elevation difference between adjacent monitoring points exceeds 10 mm, reinforcement treatment is carried out in the corresponding area.

[0026] Through the above construction steps, problems such as foundation drainage, slope stability and differential settlement control in the construction of V-shaped valley subgrades can be effectively solved, and the bearing stability of the filled subgrade can be improved. In terms of drainage, the drainage blind ditch at the bottom of the valley, combined with permeable geotextiles, and the continuous drainage interface formed by the drain pipe and the blind ditch can efficiently drain the accumulated water in the foundation and reduce the subgrade diseases caused by the accumulated water. In terms of slope stability, unidirectional geogrids are combined with U-shaped steel bar anchors to enhance the connection between the slope soil masses and effectively prevent slope sliding. In the compaction link, the specified compaction method and the overlapping width of wheel tracks ensure the compaction uniformity and improve the subgrade density. For differential settlement, through the settlement monitoring point array and timely reinforcement treatment, the uneven settlement of the subgrade can be controlled. With the improvement of the drainage system and the coordination of each construction link, the bearing capacity of the subgrade is improved, the stability of the subgrade under the complex terrain of the V-shaped valley is ensured, the later maintenance is reduced, and the service life of the subgrade is extended. In another technical solution, piezoelectric dynamic compaction sensors are arranged at intervals of 200 - 300 mm inside the steel wheel of the vibratory roller to collect the reaction force waveform data of the filler during the compaction process in real time; Perform spectral analysis on the waveform data through the Internet of Things control platform, extract the energy proportion of the characteristic frequency band, and when the energy proportion is lower than the set threshold range of 65% - 75%, it is determined that the compaction degree is insufficient; If the compaction degree data of three consecutive compaction sections are all lower than the lower limit of the threshold, control the roller to automatically increase the vibration frequency of the current compaction section by 2 - 4 Hz and add 1 - 2 additional compaction passes; If the energy proportion exceeds the upper limit of the threshold, reduce the vibration frequency by 1 - 2 Hz and reduce the number of compaction passes in the subsequent compaction section by 1 pass.

[0027] In this technical solution, a vibratory roller of a type with a structure capable of installing sensors can be selected. A piezoelectric dynamic compaction degree sensor can choose a product on the market with an accuracy meeting the engineering requirements and install it inside the steel wheel of the vibratory roller. The installation interval of the sensors can be selected as 250 mm. Such a spacing can not only ensure effective data collection but also not affect the sensor performance due to excessive density. During the rolling process, the piezoelectric dynamic compaction degree sensor starts to work and real-time collects the reaction force waveform data of the filler. These data are transmitted to the Internet of Things control platform through a selectable wireless transmission module. The Internet of Things control platform can choose an off-the-shelf system with a spectrum analysis function. This system performs spectrum analysis on the collected waveform data and extracts the energy proportion of the characteristic frequency band. The set threshold range here is 65% - 75%. In actual operation, 65% is used as the lower limit of insufficient compaction degree, and 75% is used as the upper limit. When the energy proportion data analyzed by the Internet of Things control platform is lower than 65%, the system will make a judgment. If the compaction degree data of three consecutive rolling sections are all lower than this lower limit, an instruction will be sent to the vibratory roller. The vibratory roller can receive the instruction through the internal intelligent control system and automatically increase the vibration frequency of the current rolling section. The frequency increase amount can be selected as 3 Hz. At the same time, an additional pass of rolling is added. This is because a lower energy proportion means insufficient compaction degree, and increasing the vibration frequency and the number of rolling passes can improve the compaction effect. On the contrary, when the energy proportion exceeds 75%, it indicates that the current rolling parameters may result in too high compaction degree. At this time, the system will control the vibratory roller to reduce the vibration frequency. The reduction amount can be selected as 1 Hz, and the number of rolling passes in the subsequent rolling sections is reduced by 1 pass to avoid over-rolling and ensure the construction efficiency and quality. In terms of functional testing, a representative subgrade area can be selected as the experimental object. Use the above construction method to perform rolling operations in this area, and at the same time use professional compaction degree detection equipment, such as the sand replacement method or nuclear densitometer, etc., to detect the compaction degree of the rolled subgrade. Compare the detection results with the compaction degree judgment results obtained by the Internet of Things control platform based on the sensor data to verify the accuracy of the entire system. In terms of structural design, focus on the installation stability of the piezoelectric dynamic compaction degree sensor inside the steel wheel to ensure its normal operation in a vibrating environment. Sort out the data analysis process of the Internet of Things control platform to ensure the accuracy and timeliness of data processing. Through such a construction method and related operations, areas with insufficient or excessive compaction degree can be discovered in a timely manner, and corresponding measures can be taken for adjustment, thereby improving the uniformity and stability of the subgrade compaction quality.

[0028] By arranging piezoelectric dynamic compaction sensors inside the steel wheels of a vibratory roller and combining with an Internet of Things control platform for compaction control, the sensors can collect the reaction force waveform data in real time. The Internet of Things platform analyzes the energy ratio to judge the compaction situation. When the energy ratio is lower than the threshold range of 65% - 75%, it can timely detect the under-compacted areas, avoiding problems such as insufficient subgrade compaction and subsequent settlement caused by under-compaction. When it is higher than the upper threshold, it can prevent over-rolling, ensuring stable and uniform compaction quality. In terms of improving construction efficiency, when the compaction degree of three consecutive rolling sections is lower than the lower threshold, the vibration frequency is automatically increased by 2 - 4 Hz and additional rolling is carried out to quickly improve the compaction degree, avoiding the cumbersome process of repeated detection and manual adjustment. When the energy ratio exceeds the upper limit, the vibration frequency is reduced and the number of rolling passes is decreased, reducing unnecessary construction operations, reasonably allocating construction resources, and shortening the overall construction time. In addition, precise compaction control reduces the rework cost caused by compaction problems. By timely adjusting the rolling parameters, the one-time compaction compliance rate is increased, reducing additional material, equipment, and labor inputs, avoiding resource waste, achieving economic benefits improvement, and at the same time ensuring the quality of the subgrade project, laying a foundation for long-term stable use in the future.

[0029] In another technical solution, in the adjacent rolling section junction area, the differential positioning technology is used to control the overlap width of the roller tracks to increase by 50 - 100 mm, and the vibration frequency in this area is synchronously increased by 1 - 3 Hz; After every 100 - 150 m of rolling operation is completed, the Internet of Things platform generates a compaction degree heat map, and the areas with a compaction degree coefficient of variation greater than 0.15 are marked as recompaction areas. During recompaction, a fan-shaped path is used for denser rolling; The denser rolling of the fan-shaped path includes rolling in concentric circular arc trajectories with a radius of 1 - 3 m centered on the center of the recompaction area, and the distance between adjacent arcs is 1 / 2 - 2 / 3 of the roller width.

[0030] In the actual construction of this technical solution, when operating in the adjacent rolling section junction area, a roller with differential positioning function can be selected. Through differential positioning technology, the overlap width of the roller tracks is controlled to increase by 75 mm, and the vibration frequency in this area is simultaneously increased by 2 Hz. The differential positioning system can choose existing high-precision products on the market. It accurately determines the position of the roller by receiving satellite signals and comparing with the data of the reference station, so as to achieve precise control of the overlap width of the roller tracks and the vibration frequency. After every 120 m of rolling operation is completed, the Internet of Things platform starts to generate a compaction degree heat map. The Internet of Things platform can choose an off-the-shelf system with data processing and visualization functions. This system analyzes and processes the data from various sensors to generate an intuitive compaction degree heat map. In the generated heat map, for the area where the coefficient of variation of compaction degree is greater than 0.15, the system will automatically mark it as the recompaction area for subsequent targeted treatment. For the marked recompaction area, rolling is carried out with a fan-shaped path encryption. The specific operation of the fan-shaped path encryption rolling is to roll in concentric circular arc trajectories with a radius of 2 m centered on the center of the recompaction area. The distance between adjacent arcs is 2 / 3 of the roller width. Such a distance setting can not only ensure the rolling effect but also improve the construction efficiency. During the rolling process, the roller starts from the center of the circle and gradually expands outward along the concentric circular arc trajectory according to the pre-set program. Through this fan-shaped path encryption rolling method, the recompaction area can be more comprehensively and carefully compacted to ensure that the compaction degree of this area meets the requirements. In terms of functional testing, a section of subgrade area with different compaction conditions can be selected as the experimental object. Carry out rolling operations in this area according to the above construction method, and use professional compaction degree detection equipment, such as sand replacement method or nuclear densitometer, etc., to detect the compaction degree of the rolled subgrade. Compare the detection results with the compaction degree heat map generated by the Internet of Things platform to verify the accuracy of the heat map and the reliability of marking the recompaction area. In terms of structural design, focus on the integration stability of the differential positioning system and the roller to ensure that the overlap width of the roller tracks and the vibration frequency can be accurately controlled during the construction process. Optimize the program of the fan-shaped path encryption rolling to ensure that the roller can operate efficiently according to the set trajectory and parameters. Through such a construction method and related operations, the compaction problem in the adjacent rolling section junction area can be effectively solved, the overall quality and uniformity of subgrade compaction can be improved, and subgrade diseases caused by uneven compaction can be reduced.

[0031] This technical solution has significant beneficial effects in the aspect of subgrade compaction quality control through measures such as differential positioning technology, compaction degree heat map marking, and fan-shaped path recompaction. In the adjacent rolling section junction area, by using differential positioning technology to increase the wheel track overlap width and enhance the vibration frequency, the problem of low compaction degree caused by insufficient rolling connection in the junction area during traditional construction can be effectively solved, significantly reducing the density difference between the junction area and the adjacent rolling section, enhancing the continuity and uniformity of the overall subgrade structure, and avoiding local settlement or cracking caused by weak zones in the later stage. The Internet of Things platform generates a compaction degree heat map and marks the recompaction area, which can accurately identify areas with large discreteness of compaction degree, changing the defect of high missed inspection rate in traditional sampling inspection. For these areas, fan-shaped path densification rolling is adopted, and the concentric arc trajectory centered on the center of the recompaction area can ensure that each part is effectively covered. The reasonable ratio of the distance between adjacent arcs and the wheel width makes the rolling without dead angles, further improving the compaction quality of the recompaction area and reducing local compaction defects caused by non-uniformity of the filler. The above technical means work together, avoiding the energy waste caused by over-rolling and solving the quality hidden danger of insufficient compaction, significantly improving the overall uniformity of subgrade compaction under complex terrain, providing a stable support foundation for the subsequent filling layer, effectively reducing the disease risk caused by uneven compaction during the service period of the subgrade, and ensuring the long-term stability of the project.

[0032] In another technical solution, the method for determining the preset threshold of the subgrade filling height in step three includes the following steps: Obtain the foundation bearing capacity data at different depths in the V-shaped valley section through geological exploration. When the cumulative thickness of the subgrade filling layer reaches 70% - 80% of the depth corresponding to the foundation bearing capacity mutation point, it is determined as the preset threshold trigger point; During the filling process, use a settlement monitoring device to continuously measure the compression deformation rate of the filled layer. When the deformation rate is less than 0.5 mm / d for 3 consecutive days, the preset threshold determination condition is triggered synchronously; If both the foundation bearing capacity mutation point and the stable condition of the deformation rate are met, locate the burial elevation of the horizontal drainage pipe 1.2 - 1.8 m downward from the top of the current filling layer; If the two conditions are not met simultaneously, continue filling until the thickness of the next layer reaches the increment threshold of the depth corresponding to the foundation bearing capacity mutation point. The increment threshold is 1.2 - 1.5 times the single-layer filling thickness.

[0033] In this technical solution, before construction, when obtaining the foundation bearing capacity data of the V-shaped valley section through geological exploration, a static cone penetrometer or drilling and sampling equipment can be selected. Exploration points are arranged at intervals of 20 - 30 m along the longitudinal direction of the roadbed, and the foundation bearing capacity at different depths is tested in layers. When processing the exploration data, by plotting the bearing capacity - depth curve, the depth corresponding to the sudden change point of the foundation bearing capacity is identified. For example, if there is a significant change in the foundation bearing capacity of a certain exploration point at a depth of 8 m, then this depth is determined as the sudden change point. When the cumulative thickness of the roadbed filling layer reaches 75% (i.e., 6 m) of the depth corresponding to the sudden change point, the preliminary determination condition of the preset threshold is triggered. This value is selected in the middle range of 70% - 80%, which can balance safety and construction efficiency. During the filling process, a high-precision electronic level or an automated displacement sensor can be selected as the settlement monitoring device. It is installed on the surface of the filled layer, and a monitoring point is arranged every 10 - 15 m along the longitudinal direction of the roadbed to measure the soil layer compression deformation rate in real time. When the deformation rate is monitored to be less than 0.5 mm / d for 3 consecutive days, it indicates that the foundation consolidation tends to be stable, and the preset threshold determination condition is triggered synchronously. If both the triggering condition of the foundation bearing capacity sudden change point and the deformation rate stability condition are met at this time, the embedding elevation of the horizontal drainage pipe is located 1.5 m downward from the top of the current filling layer. This depth is within the recommended range of 1.2 - 1.8 m, which can effectively avoid the surface load concentration area. The horizontal drainage pipe can be a high-density polyethylene (HDPE) corrugated pipe, and the wall hole rate and the specification of the outer filter geotextile need to meet the drainage design requirements. If the two conditions are not met simultaneously, for example, only the triggering depth of the bearing capacity sudden change point is reached but the deformation rate is still greater than 0.5 mm / d, then continue filling, and the next layer filling thickness is controlled to be 1.3 times the single-layer filling thickness (for example, when the single-layer thickness is 0.5 m, the next layer is filled with 0.65 m). This increment threshold is within the reasonable range of 1.2 - 1.5 times, ensuring a gradual approach to the foundation stable state. In the functional test link, a V-shaped valley section with representative geological conditions is selected as the experimental object, and the comparison between manual detection and automatic monitoring data is carried out synchronously. The compaction degree of the filled layer is detected by the sand replacement method, and the settlement data is manually measured with a level and calibrated with the automated data of the settlement monitoring device to ensure the measurement accuracy of the deformation rate. In terms of structural design, the drilling hole positions of the geological exploration equipment need to avoid the drainage blind ditch and the subsequent filling area, and the sensors of the settlement monitoring device need to be fixed on the concrete pedestal on the surface of the compacted layer to avoid mechanical disturbance during the filling process. Through the above construction method, the embedding time of the drainage pipe can be dynamically determined according to the actual bearing capacity and deformation state of the foundation, which not only prevents the drainage pipe from being damaged due to excessive load caused by premature embedding, but also avoids the drainage system failure caused by too late embedding, effectively improving the reliability and adaptability of the roadbed drainage structure under complex terrain.

[0034] This method for determining the preset threshold significantly improves the accuracy and rationality of the buried elevation of the drainage pipe through dual-index judgment. The threshold setting of 70% - 80% of the sudden change point of the foundation bearing capacity not only avoids the problem of insufficient foundation bearing caused by premature burial of the drainage pipe but also prevents the defects of too long drainage path and reduced drainage efficiency caused by late burial. By continuously monitoring the deformation rate and combining with the stability condition for judgment, the consolidation state of the foundation can be dynamically captured. When the deformation rate is continuously less than 0.5 mm / d, it indicates that the initial settlement of the foundation has been basically completed. At this time, burying the drainage pipe can effectively reduce the impact of subsequent settlement on the drainage system and avoid the fracture or blockage of the drainage pipe due to uneven settlement. The setting of the incremental threshold ensures that the optimal burial time can still be gradually approached under complex geological conditions. Through layered filling and dynamic adjustment, the buried elevation of the drainage pipe better conforms to the actual bearing capacity and deformation characteristics of the foundation. This method effectively improves the reliability and durability of the subgrade drainage system, reduces the risk of subgrade diseases caused by poor drainage, extends the service life of the road, and reduces the subsequent maintenance cost.

[0035] In another technical solution, the specific method for dynamically adjusting the paving thickness of the graded gravel layer by elevation control piles is as follows: Elevation control piles are set at intervals of 5 - 8 m along the longitudinal axis on the subgrade surface, and the top elevation of the elevation control piles is the same as the designed elevation of the graded gravel layer; During the progress of the paver, the vertical distance between the surface of the paved gravel layer and the top of the elevation control pile is measured in real time by a laser rangefinder; When the measured vertical distance exceeds the range of -10 mm to +15 mm of the designed paving thickness, the scraper opening and the traveling speed are synchronously adjusted through the hydraulic control system of the paver; After the dynamic adjustment is completed, a continuous elevation control reference surface is formed on the surface of the graded gravel layer, and its longitudinal flatness error is controlled within the range of ±5 mm / 10 m.

[0036] In this technical solution, elevation control piles are set every 6 m along the longitudinal axis on the subgrade surface. The elevation control piles can be steel pipes with a diameter of 25 mm or reinforced concrete piles, and the elevation of their tops is consistent with the designed elevation of the graded sand and gravel layer. The elevation control piles are accurately measured and positioned using a total station to ensure that the elevation error of their tops does not exceed ±3 mm. During the progress of the paver, the laser rangefinder installed in front of the screed of the paver measures the vertical distance between the surface of the paved sand and gravel layer and the top of the elevation control pile in real time. The laser rangefinder can be a model with a measurement accuracy of ±2 mm, and the measurement frequency is set to 5 times per second to ensure the real-time nature of the data. When the measured vertical distance exceeds the range of -8 mm to +12 mm of the designed paving thickness, the hydraulic control system of the paver synchronously adjusts the opening of the scraper and the traveling speed. For example, when the measured distance is 8 mm less than the designed thickness, the hydraulic control system increases the opening of the scraper by 5 mm and reduces the traveling speed of the paver by 0.3 m / min; when the measured distance is 12 mm greater than the designed thickness, the opening of the scraper is reduced by 6 mm and the traveling speed is increased by 0.4 m / min. This dynamic adjustment process is achieved through a PID controller, and the parameters of the controller can be optimized according to the on-site test data. The proportional coefficient is set to 0.8, the integral coefficient is set to 0.2, and the derivative coefficient is set to 0.1. After the dynamic adjustment is completed, a continuous elevation control reference surface is formed on the surface of the graded sand and gravel layer. A section is measured every 10 m using a level, and 5 points are measured for each section to detect the longitudinal flatness error. After detection, the longitudinal flatness error of the elevation control reference surface is controlled within the range of ±5 mm / 10 m. In terms of functional testing, a test section with a length of 200 m is selected, and the paving thickness is measured before and after the dynamic adjustment respectively, and the thickness uniformity is analyzed by comparison. In terms of structural design, the elevation control piles need to be buried at least 500 mm into the subgrade soil to ensure their stability; the laser rangefinder needs to be installed on the rigid support of the paver to avoid the influence of vibration on the measurement accuracy. Through this method of dynamically adjusting the paving thickness, the flatness and thickness uniformity of the graded sand and gravel layer can be effectively improved, providing a good foundation for the subsequent construction of the pavement structural layer.

[0037] This technical solution can significantly improve the paving accuracy and surface quality by setting elevation control piles on the subgrade surface and combining laser ranging with a hydraulic control system for dynamic adjustment of the paving thickness of the graded sand-gravel layer. The elevation control piles are arranged at intervals of 5 - 8 m and the elevation is accurately positioned, providing a continuous reference for the paving operation, avoiding the discrete errors of traditional manual measurement, and ensuring that the elevations of each cross-section of the graded sand-gravel layer meet the design requirements. The laser rangefinder monitors the paving thickness in real time. When the measured vertical distance exceeds the range of -10 mm to +15 mm, the hydraulic system synchronously adjusts the opening of the scraper and the traveling speed of the paver. This dynamic feedback mechanism effectively offsets the thickness deviation caused by factors such as longitudinal slope changes and uneven distribution of filler particles, greatly improving the uniformity of the paving thickness. The longitudinal flatness error of the elevation control reference surface formed after adjustment is controlled within ±5 mm / 10 m, providing a stable support foundation for the pavement structural layer. The uniform graded sand-gravel layer not only enhances the surface drainage efficiency, reduces the risk of subgrade softening caused by rainwater retention, but also reduces the impact of differential settlement on the upper structure by optimizing the stress distribution. This method avoids the lag of relying on manual experience adjustment in the traditional paving process, realizes the automatic precise control of the paving process, effectively improves the construction quality of the subgrade surface under complex terrain, and lays a foundation for the long-term stable operation of subsequent projects.

[0038] In another technical solution, it further includes: setting elevation re-measurement points behind the paver and obtaining the compaction data of the adjusted area by using a dynamic compaction detector; When the compaction data is lower than 95% of the design value, control the vibratory roller to roll the corresponding area one to two additional times; During the additional rolling, the exciting force of the vibratory roller is increased by 10% - 15%, and the rolling path intersects with the original path at an angle of 30° - 45°.

[0039] In this technical solution, an elevation re-measurement point is set 3 to 5 meters behind the paver, and a detection section is arranged every 10 to 15 meters along the longitudinal direction of the roadbed. Each section has a measurement point at the center line and 20 cm from the edges on both sides. A portable dynamic compaction detector, such as a drop hammer compaction meter or a nuclear density meter, can be used at the re-measurement point. It is fixed on a movable detection bracket. The height of the bracket is flush with the bottom surface of the paver screed. Ensure that the detector probe is vertically aligned with the surface of the paved graded gravel layer to obtain compaction data in real time. The detector is connected to the on-site control system via a data cable or a wireless transmission module, and the measured compaction value is fed back to the control terminal in real time. When the dynamic compaction detector shows that the compaction data of a certain area is lower than 95% of the design value, the control terminal automatically marks the area and dispatches a vibratory roller for additional rolling. Vibratory rollers can be selected with models that have the function of adjusting the exciting force. After receiving the command, the operator manually or automatically increases the exciting force by 12% (in the middle range of 10%~15%). For example, when the original exciting force is 250kN, it is adjusted to 280kN. At the same time, the rolling path is adjusted to a 40° cross angle with the original rolling direction (in the range of 30°~45°) to ensure that the weak areas of the original rolling are covered. The number of additional rolling passes is controlled to 1 pass. If the compaction degree is still not up to standard after the first rolling, another pass is added. In the functional test, a test section with a length of 150m was selected, and 5 test points were randomly selected in the dynamic adjustment area and the non-adjustment area, and the compaction degree was compared and tested using the sand filling method. The results show that the compaction degree of the area after the additional rolling meets the design requirements. In terms of structural design, the bracket of the dynamic compaction tester must have a shock-absorbing function to avoid the influence of the paver vibration on the detection accuracy; the steering system of the vibratory roller must support precise angle control to ensure that the cross-rolling path meets the set requirements. Through this construction method, it is possible to promptly discover and deal with the problem of insufficient compaction that may occur during the paving process, effectively improve the overall density of the graded gravel layer, provide a uniform and stable bearing foundation for the roadbed surface, and reduce the risk of later settlement caused by local compaction defects.

[0040] This technical solution sets elevation re-measurement points behind the paver and combines dynamic compaction degree detection and additional rolling, which can effectively improve the construction quality of the graded gravel layer. By arranging re-measurement points 3 to 5 m behind the paver and using a dynamic compaction degree detector to obtain data in real time, local under-compacted areas caused by paving adjustment or filler characteristics can be detected in time, avoiding the missed detection problem of traditional sampling detection and ensuring the comprehensiveness and real-time nature of compaction degree detection. When the detected compaction degree is lower than 95% of the design value, the vibrating roller is controlled to perform additional rolling with an excitation force increased by 10% to 15% and a cross angle of 30° to 45°, which can specifically enhance the density of the weak area. The cross-rolling path can cover the wheel track gaps of the original rolling, solving the compaction blind area problem at the connection of adjacent rolling sections. The increase in the excitation force adapts to the compaction requirements of different fillers, ensuring a significant additional rolling effect. This dynamic feedback mechanism avoids the blindness of supplementary compaction based on experience and realizes the precise repair of compaction defects. The above measures work together synergistically to effectively improve the overall compaction uniformity of the graded gravel layer, provide a stable bearing foundation for the subgrade surface layer, reduce the risk of differential settlement caused by local under-compaction, ensure the cooperative stress-bearing performance of the subgrade and the subsequent pavement structural layer, and extend the service life of the road project.

[0041] In another technical solution, the specific method of reinforcement treatment in step five includes: When the elevation difference between adjacent monitoring points exceeds 10 to 15 mm, a circular difference area with a radius of 2 to 3 m is demarcated with the point with the largest elevation difference as the center; The ground penetrating radar is used to scan the internal structure of the subgrade within the difference area. If the detected porosity is greater than 20% or the dislocation of the filler stratification interface exceeds 50 mm, the high-pressure jet grouting method is used for reinforcement, and the grouting pressure is controlled at 0.8 to 1.2 MPa; If the detected filler density is 5% to 8% lower than the design value, the surface filler in the difference area is removed to the stable layer, re-layered filling is carried out, and a vibrating roller with an excitation force increased by 10% to 15% is used for supplementary compaction, and the number of supplementary compaction passes is 3 to 4; After the treatment is completed, the monitoring points are densely arranged in the difference area to 1 / 2 of the original spacing, and the monitoring period is shortened to 1 / 3 of the original period until the fluctuation range of the continuous 3 monitoring data is less than 2 mm.

[0042] In this technical solution, when the elevation difference between adjacent monitoring points exceeds 12 mm (in the range of 10 - 15 mm), a circular difference area with a radius of 2.5 m (in the range of 2 - 3 m) is demarcated with the point having the largest elevation difference as the center. Within the difference area, a ground penetrating radar device that can be selected is used to scan the internal structure of the subgrade. The antenna of the ground penetrating radar moves uniformly along the surface of the subgrade, and the scanning frequency is set at 200 MHz, which can penetrate the filler layer to detect the porosity and the state of the layered interface. If the detected porosity is 22% (exceeding the threshold of 20%) or the misalignment of the filler layered interface is 60 mm (exceeding the threshold of 50 mm), it is determined as a structural defect, and the high-pressure jet grouting method is used for reinforcement. A double-tube jet grouting rig can be selected as the grouting equipment, and the grouting pressure is controlled at 1.0 MPa (in the range of 0.8 - 1.2 MPa) to ensure that the slurry penetrates evenly into the defect area. If the ground penetrating radar detects that the filler density is 6% lower than the design value (in the range of 5% - 8%), the surface filler in the difference area is manually removed to the stable layer, and the removal depth is determined according to the density test results, generally 30 - 50 cm. After removal, the subgrade filler is re-laid in layers, with the thickness of each layer controlled at 20 - 30 cm, and a vibrating roller that can be selected is used for supplementary compaction. During supplementary compaction, the excitation force of the vibrating roller is increased by 12% (in the range of 10% - 15%). For example, when the original excitation force is 200 kN, it is adjusted to 224 kN. The rolling path intersects with the original laying direction at an angle of 40° (in the range of 30° - 45°), and the number of supplementary compaction passes is 3 (in the range of 3 - 4) to ensure that the filler density meets the standard. After the reinforcement treatment is completed, settlement monitoring points are densely arranged in the difference area. The original monitoring spacing of 10 m longitudinally and 8 m transversely is shortened to 5 m longitudinally and 4 m transversely (1 / 2 of the original spacing), and the monitoring period is shortened from 7 days to 2 days (1 / 3 of the original period). The total station is used to collect elevation data according to the new period until the fluctuation range of the monitoring data is less than 2 mm for three consecutive times. In the functional test, the density is re-measured by the sand replacement method and the internal structure is re-inspected by the ground penetrating radar for the treated area to ensure the reinforcement effect. In terms of structural design, the ground penetrating radar antenna needs to maintain a height of 5 - 10 cm from the subgrade surface to avoid contact damage; the verticality error of the high-pressure jet grouting pipe is controlled within 1% to ensure the uniformity of grouting. Through this reinforcement treatment method, it is possible to take precise measures for different types of subgrade defects, effectively improve the bearing capacity of the differential settlement area, and ensure the overall stability of the subgrade.

[0043] The reinforcement treatment method of this technical solution effectively improves the repair effect of the subgrade differential settlement area through hierarchical determination and targeted measures. When the elevation difference between adjacent monitoring points exceeds 10 - 15 mm, a circular area with a radius of 2 - 3 m is demarcated with the point with the largest elevation difference as the center, which can accurately locate the core influence range of differential settlement, avoid large-area blind reinforcement, and improve the treatment efficiency. The ground-penetrating radar scanning technology can penetrate the surface layer of the subgrade and clearly identify defects such as excessive internal porosity, misalignment of filler layers, or insufficient compactness, providing an intuitive basis for selecting a reinforcement plan. For structural defects with a porosity greater than 20% or a misalignment of the layered interface exceeding 50 mm, the high-pressure jet grouting method controls the pressure at 0.8 - 1.2 MPa, enabling the slurry to evenly fill the pores and cement the misaligned interface, effectively enhancing the local bearing capacity; for compaction defects with a compactness 5% - 8% lower than the design value, after removing the surface filler, it is re-layered and filled, and the vibration force is increased to supplement the compaction, which can fundamentally solve the problem of insufficient filler compactness and avoid subsequent settlement. After reinforcement, the monitoring points are densified to 1 / 2 of the original spacing and the monitoring period is shortened, which can track the settlement dynamics of the treated area in real time. When the fluctuation of the monitoring data is less than 2 mm for three consecutive times, the conventional monitoring is restored, forming a closed-loop quality control. The above method avoids the blindness of traditional unified reinforcement, realizes the precise treatment process of "detection - diagnosis - repair - monitoring", significantly improves the bearing stability of the differential settlement area, reduces the risk of recurrence of subgrade diseases, ensures the long-term uniform stress performance of the entire filling body, and effectively extends the safe service life of the subgrade under complex mountainous terrain.

[0044] In another technical solution, it further includes: If there are signs of slope slip in the differential area, a biaxial geogrid is laid on the slope surface. The tensile strength of the biaxial geogrid is 100 - 150 kN / m, and it is fixed to the deep stable layer of the slope through L-shaped anchor bolts. The burial depth of the anchor bolts is 1.5 - 2 m; The installation sequence of the L-shaped anchor bolts is row-by-row construction from top to bottom. The installation interval distance of the anchor bolts in the same row is 1.2 - 1.5 times the length of the anchor bolts, and the minimum spacing shall not be less than 1.8 m. The node between the tail of the anchor bolt and the geogrid is locked through a fastener.

[0045] In this technical solution, if signs of slope sliding appear in the differential area, such as fine cracks on the slope surface or local bulging of the soil mass, first clean the slope surface in the sliding area, remove the floating soil, loose fillers and vegetation, and expose the solid soil layer. Subsequently, horizontally lay out lines along the longitudinal direction of the slope surface every 1.8 - 2.5 m (determined in combination with the buried depth of the anchor rod) to mark the installation positions of the L-shaped anchor rods. The two-way geogrid can be selected as a finished product made of polypropylene material, with a tensile strength of 120 kN / m (within the range of 100 - 150 kN / m), which can effectively resist the lateral tensile force of the slope soil mass. The L-shaped anchor rod can be processed from threaded steel with a diameter of 20 - 25 mm. The buried depth of the vertical section of the anchor rod is 1.8 m (within the range of 1.5 - 2 m), and the horizontal section length is 30 - 50 cm, forming a stable "L"-shaped anchoring structure. The installation of the anchor rods is carried out row by row in the order from top to bottom. The spacing between the anchor rods in the same row is 1.2 times the length of the anchor rod (for example, for an anchor rod with a buried depth of 1.8 m, the spacing is 2.16 m), and it shall not be less than the minimum spacing requirement of 1.8 m. Use a drilling rig to vertically drill holes at the marked positions. The hole depth is slightly greater than the length of the vertical section of the anchor rod (about 1.85 m). After clearing the holes, insert the L-shaped anchor rods into the holes and fix them by pouring M20 cement mortar at the hole openings. After the anchor rods are consolidated, unfold the two-way geogrid along the longitudinal direction of the slope, align the nodes of the geogrid with the tails of the anchor rods, and lock the nodes of the geogrid and the tails of the anchor rods through metal U-shaped fasteners to ensure a reliable connection between the geogrid and the anchor rods. Keep the geogrid flat and moderately tensioned during laying to avoid wrinkles or slack. In the functional test, conduct a pull-out test on the installed L-shaped anchor rods to detect whether their pull-out resistance meets the design requirements (not less than 80 kN), and check the connection firmness between the U-shaped fasteners and the geogrid nodes. In terms of structural design, the horizontal section of the anchor rod needs to face the inner side of the slope and maintain an inclination angle of 10 - 15° with the slope surface to enhance the anchoring effect on the deep stable layer; the overlapping width of the two-way geogrid is not less than 20 cm to ensure continuous force transmission between adjacent geogrids. Through this reinforcement method, the two-way geogrid and the L-shaped anchor rod act synergistically to transfer the shallow slope sliding force to the deep stable soil layer, effectively improve the shear strength of the potential slip surface, and cooperate with the construction sequence of layered anchoring to gradually enhance the overall stability of the slope, reduce the sliding risk caused by differential settlement, and ensure the safety performance of the subgrade slope under long-term load.

[0046] When signs of slope slip appear in the differential area, the reinforcement method of combining bidirectional geogrid with L-shaped anchor bolts can effectively improve the slope stability. The bidirectional geogrid is made of materials with a tensile strength of 100-150 kN / m, which can withstand the lateral tension of the slope soil, inhibit the shallow slip trend, and enhance the integrity of the slope soil. The L-shaped anchor bolts are buried to a depth of 1.5-2 m, and the anchoring end is located in the deep stable layer of the slope, which can transfer the tension borne by the geogrid to the deep soil, significantly improve the shear strength of the potential slip surface, and prevent the expansion of the slip range. The anchor bolts are constructed row by row from top to bottom, and the spacing in the same row is 1.2-1.5 times the length of the anchor bolt and not less than 1.8 m to ensure uniform distribution of the anchoring force and avoid uneven stress caused by too dense or too sparse spacing. The tail of the anchor bolt is locked with the geogrid node through a fastener to form a reliable mechanical connection, enabling the geogrid and the slope soil to deform synergistically and effectively dispersing the stress concentration area. This reinforcement method targets the slip signs precisely, and through the combination of deep anchoring and surface strengthening, it fundamentally improves the anti-sliding ability of the slope, reduces the risk of secondary disasters caused by differential settlement, and ensures the long-term stability of the subgrade slope under complex loads and environmental conditions.

[0047] In another technical solution, the grouting pressure of the high-pressure jet grouting method is dynamically adjusted according to the soil permeability coefficient in the differential area: When the soil permeability coefficient k≥1×10 -4 cm / s, the grouting pressure is controlled at 0.8-1.0 MPa, the grouting hole spacing is 0.8 m×0.8 m to 1 m×1 m, and the grouting speed is 15-20 L / min; When the soil permeability coefficient 1×10 -6 cm / s≤k<1×10 -4 cm / s, the grouting pressure is controlled at 1.0-1.2 MPa, the grouting hole spacing is 0.6 m×0.6 m to 0.8 m×0.8 m, and the grouting speed is 10-15 L / min; When the soil permeability coefficient k<1×10 -6 cm / s, a pre-cracking process is adopted before grouting. The pre-cracking hole spacing is 0.5-0.7 times the grouting hole spacing, and the pre-cracking pressure is applied in stages. The initial pressure is 0.8-1.0 times the grouting pressure, and it is stabilized for 2 minutes every time it increases by 0.2 MPa. The final pressure does not exceed 1.2 times the grouting pressure; After grouting is completed, the consolidation state of the grout is monitored through a pore water pressure sensor. If the dissipation rate of the pore water pressure within 24 hours after grouting is less than 30% of the initial value, additional grout is injected at the adjacent hole positions, and the additional injection pressure is 80%-90% of the original pressure.

[0048] In this technical solution, before reinforcing the differential area, the soil permeability coefficient k is first measured through an indoor permeability test or a field pumping test. When k≥1×10-4 When the permeability coefficient k is 1×10 -6 cm / s≤k<1×10 - 4 cm / s, adjust the grouting equipment pressure to 1.1 MPa (in the range of 1.0 - 1.2 MPa), reduce the grouting hole spacing to 0.7 m×0.7 m (in the range of 0.6 m×0.6 m to 0.8 m×0.8 m), and reduce the grouting speed to 12 L / min (in the range of 10 - 15 L / min). If k<1×10 -6 cm / s, a pre - cracking process needs to be carried out first: the pre - cracking hole spacing is set to 0.6 times the grouting hole spacing (in the range of 0.5 - 0.7 times), the initial pre - cracking pressure is 80% of the grouting pressure (for example, when the grouting pressure is 1.0 MPa, the initial pressure is 0.8 MPa), then it increases by 0.2 MPa every 2 minutes and stabilizes the pressure, and the final pressure does not exceed 1.2 times the grouting pressure. During the pre - cracking process, the pre - cracking pipes and grouting pipes are arranged at intervals to ensure that the pre - cracking holes form a penetration channel for subsequent grouting. After grouting, pore water pressure sensors are buried between adjacent grouting holes, and the installation depth of the sensors is the same as the grouting section. They are connected to the on - site data acquisition instrument through data lines to monitor the consolidation state of the grout in real time. If the dissipation rate of pore water pressure within 24 hours after grouting is less than 30% of the initial value, the supplementary grouting procedure is started, and the supplementary grouting pressure is controlled at 85% of the original grouting pressure (in the range of 80% - 90%). The materials of the supplementary grout are the same as those of the first grouting to ensure that the grout fills the reinforcement area densely. In the functional test, a typical geological area can be selected for on - site grouting tests. By taking cores to detect the strength and uniformity of the reinforced soil mass, the grouting parameters are adjusted to meet the design requirements. In terms of structural design, the grouting pipes need to be kept vertical, and the verticality error is controlled within 1%. The pressure sensors need to be calibrated regularly to ensure accurate data. Through the above construction method, the grouting process can be dynamically adjusted according to the soil permeability characteristics, improving the uniformity of grout diffusion and ensuring the reinforcement effect under different geological conditions.

[0049] In this technical solution, the high-pressure jet grouting method regulates the grouting parameters by grading the soil permeability coefficient, significantly improving the reinforcement effect under different geological conditions. For soils with high permeability coefficients, lower pressure and larger hole spacing avoid excessive loss of grout, ensuring the formation of continuous solidified bodies in the permeable layer; for soils with medium and low permeability coefficients, increasing the pressure and reducing the hole spacing enhance the grout penetration ability and improve the soil density. For soils with extremely low permeability coefficients, the pre-cracking process breaks the compactness of the soil structure by applying pressure in stages, creating channels for grout diffusion and avoiding reinforcement blind spots caused by insufficient pressure. The monitoring of pore water pressure after grouting and the supplementary grouting mechanism ensure that the grout fully fills the pores and consolidates, avoiding the influence of local grout deficiency on the reinforcement effect. This dynamic adjustment method reduces the blindness of traditional grouting with unified parameters, significantly improves the uniformity of grout diffusion, makes the bearing capacity of the reinforced area more balanced, effectively reduces the recurrence risk of differential settlement of the subgrade, and ensures the long-term reliability of the reinforcement project under complex stratum conditions.

[0050] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the examples shown and described herein.

Claims

1. A subgrade construction method for crossing a V-shaped valley area, characterized in that The following steps are involved: Step 1: dig a trench longitudinally along the roadbed at the bottom of the V-shaped valley and lay a permeable geotextile, then fill it with gravel to form a drainage blind ditch, the top of the drainage blind ditch is covered with permeable geotextile and the edges on both sides extend to the roadbed filling boundary; The roadbed filler is laid layer by layer on the top and both sides of the blind drainage ditch to cover the entire roadbed cross section. After each layer is filled, it is rolled by a vibratory roller according to a preset compaction path. The moving direction of the vibratory roller is parallel to the longitudinal axis of the roadbed, and the overlapping width of adjacent rolling wheel tracks is 1 / 3 to 1 / 2 of the wheel width. Step 2: After completing two layers of roadbed filling, a one-way geogrid is deployed longitudinally on the slope surface of the roadbed. The laying direction of the one-way geogrid is consistent with the longitudinal direction of the roadbed, and is vertically inserted into the compacted filling layer through U-shaped steel bar anchors. The horizontal spacing of the U-shaped steel bar anchors is 1.5-2m, and they are aligned with the overlap area of ​​the geogrid. Step 3: When the roadbed filling height reaches a preset threshold, multiple drainage pipes are pre-buried transversely below the top surface of the roadbed. The inlet end of the drainage pipe is connected to the drainage blind ditch through an inclined connecting pipe, and the outlet end extends to the outside of the roadbed slope. The water-filtering geotextile wrapped outside the drainage pipe and the permeable geotextile of the drainage blind ditch form a continuous drainage interface; Step 4: After the roadbed is filled to the designed elevation, a graded gravel layer is evenly spread on the roadbed surface and leveled. The spreading thickness of the graded gravel layer is dynamically adjusted by the elevation control piles. After paving is completed and static curing is performed, intercepting ditches are excavated at the foot of the slopes on both sides of the roadbed. A concrete cushion is laid at the bottom of the intercepting ditch, and the longitudinal slope of the intercepting ditch is consistent with the drainage direction of the roadbed; Step 5: After the self-filling is completed, an array of settlement monitoring points is arranged on the roadbed surface. The monitoring points are distributed in a grid along the longitudinal and transverse directions of the roadbed, and elevation data is collected at a fixed period by a total station. When the elevation difference between adjacent monitoring points exceeds the set threshold, reinforcement treatment is carried out in the corresponding area.

2. The subgrade construction method for crossing the V-shaped valley area according to claim 1, characterized in that, Piezoelectric dynamic compaction sensors are arranged inside the steel wheel of the vibratory roller at intervals of 200 to 300 mm to collect the reaction force waveform data of the filler during the rolling process in real time; The waveform data is analyzed spectrally through the IoT control platform to extract the energy proportion of the characteristic frequency band. When the energy proportion is lower than the set threshold range of 65% to 75%, it is judged as insufficient compaction. If the compaction data of three consecutive rolling sections are all below the lower threshold, the roller is controlled to automatically increase the vibration frequency of the current rolling section by 2~4Hz and add 1~2 rolling passes; If the energy ratio exceeds the upper threshold, the vibration frequency will be reduced by 1~2Hz, and the number of rolling times in the subsequent rolling section will be reduced by 1.

3. The subgrade construction method for crossing the V-shaped valley area according to claim 2, characterized in that, At the junction of adjacent rolling sections, the roller wheel track overlap width is controlled by differential positioning technology to increase by 50-100 mm, and the vibration frequency in this area is simultaneously increased by 1-3 Hz. After each 100-150m rolling operation, the IoT platform generates a compaction degree heat map, and marks the area with a compaction degree dispersion coefficient greater than 0.15 as a re-compacting area. During re-compacting, a fan-shaped path is used for dense rolling. The encrypted rolling of the fan-shaped path includes rolling in concentric circular arc trajectories with a radius of 1 to 3 m centered on the center of the recompaction area, and the distance between adjacent circular arcs is 1 / 2 to 2 / 3 of the width of the roller wheel.

4. The subgrade construction method for crossing the V-shaped valley area as described in claim 1, characterized in that, The method for determining the preset threshold of the subgrade filling height in Step 3 includes the following steps: Obtain the foundation bearing capacity data at different depths in the V-shaped valley section through geological exploration. When the cumulative thickness of the subgrade filling layer reaches 70% to 80% of the depth corresponding to the mutation point of the foundation bearing capacity, it is determined as the preset threshold trigger point; During the filling process, use a settlement monitoring device to measure the compression deformation rate of the filled layer in real time. When the deformation rate is less than 0.5 mm / d for 3 consecutive days, the preset threshold determination condition is triggered synchronously; If both the mutation point of the foundation bearing capacity and the stable condition of the deformation rate are satisfied, locate the burial elevation of the horizontal drainage pipe 1.2 to 1.8 m downward from the top of the current filling layer; If the two conditions are not satisfied simultaneously, continue filling until the incremental threshold of the next layer's filling thickness reaches the depth corresponding to the mutation point of the foundation bearing capacity. The incremental threshold is 1.2 to 1.5 times the single-layer filling thickness.

5. The subgrade construction method for crossing the V-shaped valley area according to claim 1, characterized in that The specific method for dynamically adjusting the paving thickness of the graded gravel layer is as follows: Set elevation control piles along the longitudinal axis of the subgrade surface at intervals of 5 to 8 m. The top elevation of the elevation control piles is the same as the designed elevation of the graded gravel layer; During the progress of the paver, use a laser rangefinder to measure the vertical distance between the surface of the paved gravel layer and the top of the elevation control pile in real time; When the measured vertical distance exceeds the range of -10 mm to +15 mm of the designed paving thickness, synchronously adjust the scraper opening and the traveling speed through the hydraulic control system of the paver; After the dynamic adjustment is completed, a continuous elevation control reference surface is formed on the surface of the graded gravel layer, and its longitudinal flatness error is controlled within the range of ±5 mm / 10 m.

6. The subgrade construction method for crossing the V-shaped valley area according to claim 5, characterized in that, Further includes: Set elevation re-measurement points behind the paver, and use a dynamic compaction degree detector to obtain the compaction degree data of the adjusted area; When the compaction degree data is lower than 95% of the design value, control the vibratory roller to roll the corresponding area 1 to 2 more times; When adding rolling, the exciting force of the vibratory roller is increased by 10% to 15%, and the rolling path intersects the original path at an angle of 30° to 45°.

7. The subgrade construction method for crossing the V-shaped valley area according to claim 1, characterized in that, The specific method for reinforcement treatment in Step 5 includes: When the elevation difference between adjacent monitoring points exceeds 10 to 15 mm, delimit a circular difference area with a radius of 2 to 3 m centered on the point with the largest elevation difference; Use a ground penetrating radar to scan the internal structure of the subgrade within the difference area. If the detected porosity is greater than 20% or the misalignment of the filler stratification interface exceeds 50 mm, use the high-pressure jet grouting method for reinforcement, and control the grouting pressure to be 0.8 to 1.2 MPa; If the detected filler density is 5% to 8% lower than the design value, remove the surface filler in the difference area to the stable layer, re-layer the filling and use a vibratory roller with an increased exciting force of 10% to 15% to supplement the compaction, and the number of supplementary compaction passes is 3 to 4 times; After the treatment is completed, densely arrange monitoring points in the difference area to 1 / 2 of the original spacing, and shorten the monitoring period to 1 / 3 of the original period until the fluctuation range of the continuous 3 monitoring data is less than 2 mm.

8. The subgrade construction method for crossing the V-shaped valley area according to claim 7, characterized in that Further includes: If there are signs of slope slip in the differential area, a biaxial geogrid is laid on the slope surface. The tensile strength of the biaxial geogrid is 100 - 150 kN / m, and it is fixed to the deep stable layer of the slope by L-shaped anchor rods. The embedding depth of the anchor rods is 1.5 - 2 m. The installation sequence of the L-shaped anchor rods is to construct row by row from top to bottom. The installation interval distance of the anchor rods in the same row is 1.2 - 1.5 times the length of the anchor rods, and the minimum spacing shall not be less than 1.8 m. The nodes between the tails of the anchor rods and the geogrid are locked by fasteners.

9. The subgrade construction method for crossing the V-shaped valley area according to claim 7, characterized in that, The grouting pressure of the high-pressure jet grouting method is dynamically adjusted according to the soil permeability coefficient of the differential area: When the permeability coefficient k of the soil mass is ≥ 1×10 -4 cm / s, the grouting pressure is controlled at 0.8 - 1.0 MPa, the spacing of grouting holes is 0.8 m × 0.8 m to 1 m × 1 m, and the grouting speed is 15 - 20 L / min; When the permeability coefficient of the soil mass is 1×10 -6 cm / s ≤ k < 1×10 -4 cm / s, the grouting pressure is controlled at 1.0 - 1.2 MPa, the spacing between grouting holes is 0.6 m × 0.6 m to 0.8 m × 0.8 m, and the grouting speed is 10 - 15 L / min; When the soil permeability coefficient k < 1×10 -6 cm / s, a pre-cracking process is adopted before grouting. The spacing of the pre-cracking holes is 0.5 to 0.7 times the spacing of the grouting holes. The pre-cracking pressure is applied in stages. The initial pressure is 0.8 to 1.0 times the grouting pressure. It is stabilized for 2 minutes every time it increases by 0.2 MPa, and the final pressure does not exceed 1.2 times the grouting pressure; After grouting, the consolidation state of the grout is monitored by a pore water pressure sensor. If the dissipation rate of the pore water pressure within 24 hours after grouting is less than 30% of the initial value, grout is supplemented at adjacent hole positions, and the supplementary grouting pressure is 80% - 90% of the original pressure.