A method for controlling settlement of large-diameter riprap subgrade in highways

Abstract

This invention relates to a method for controlling settlement of large-diameter stone-filled roadbeds for highways, specifically including the following steps: S1, conducting foundation bearing capacity testing and elevation re-measurement of the upper embankment base, then filling and compacting sandy soil in layers; S2, laying geogrid, overlapping and fixing it, then covering it with sandy soil and compacting it; S3, spreading and compacting a mixture of large-diameter stones and fine aggregates, then roughening, wetting, and laying cement slurry on the top surface of the mixture layer to form a cement slurry layer, and finally spreading graded crushed stone on the cement slurry layer and compacting it; S4, repeating steps S2 and S3 until the design height of the upper embankment is reached, and performing elevation measurement control and surface cleaning after each layer is completed. This invention forms an upper embankment structure layer with strong integrity and high deformation resistance, effectively controlling differential settlement and post-construction total settlement, improving highway smoothness and driving comfort, reducing pavement structure damage, extending service life, and reducing maintenance costs.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, and in particular to a method for controlling settlement of large-diameter rockfill subgrade for highways. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] With the rapid advancement of my country's transportation infrastructure construction and the continuous expansion of the scale of high-grade highway construction, large-diameter stone-filled roadbeds have become widely used in areas with complex terrain, poor geological conditions, and abundant stone resources due to their advantages such as high strength, good stability, and full utilization of local stone resources.

[0004] However, settlement remains a key challenge in the construction and use of this roadbed. Excessive settlement not only damages the smoothness and driving comfort of the road, but also destroys the pavement structure, shortens the road's lifespan, increases maintenance costs, and even endangers driving safety.

[0005] Currently, the structure of large-diameter stone-filled roadbeds is divided into pavement structure and roadbed structure from top to bottom. The roadbed structure includes the subgrade, embankment, and foundation structure. The laying of large-diameter stones is mainly concentrated in the embankment stage. Existing embankment laying usually adopts different methods depending on the location. The lower embankment, being close to the foundation, needs to meet the requirements of foundation bearing capacity and slope stability, and is mostly filled with larger-diameter stones. The upper embankment is filled and compacted in layers with large-diameter stones of 30-100cm. However, the upper embankment formed by filling and compacting large-diameter stones in layers alone has many internal pores, resulting in reduced density and strength because the gaps between the stones cannot be effectively filled. Under long-term vehicle loads, the pores are compressed, which easily leads to settlement. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings by providing a method for controlling settlement of large-diameter rockfill subgrade in highways.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for controlling the settlement of large-diameter rockfill subgrade in highways, specifically including the following steps: S1, conduct foundation bearing capacity testing and elevation re-measurement on the foundation of the upper embankment, then fill and compact the sandy soil in layers to form a horizontal and dense sandy soil layer; S2, a grid is laid on the sandy soil layer, and after being overlapped and fixed, it is immediately covered with sandy soil and compacted to form a reinforced cushion layer; S3, spread a mixture of large-diameter stone and fine material on the reinforced cushion layer and compact it to form a mixed layer. At the same time, the settlement difference is detected. Then, the top surface of the mixed layer is roughened, moistened with water and cement slurry is laid to form a cement slurry layer. Finally, graded crushed stone is spread on the cement slurry layer and compacted to form a crushed stone layer. S4. Repeat steps S2 and S3 until the design height of the upper embankment is reached, and conduct elevation measurement control and surface cleaning after each layer of construction is completed.

[0008] Furthermore, in step S1, a ground penetration tester is used to detect the bearing capacity of the foundation, and a total station is used to re-measure the elevation of the foundation, with the error controlled within ±10mm; When laying sandy soil, the thickness of each layer should not exceed 20cm. Use a light roller to perform 2-3 passes of static compaction, and the compaction degree should reach more than 93%.

[0009] Furthermore, in step S2, the grid is a bidirectional geogrid, and the overlapping grids are fixed with U-shaped nails. The fixing of the grid and the U-shaped nails, as well as the covering of the sandy soil, are all carried out using an automatic laying device. The automatic paving device includes a mobile frame, and the top of the mobile frame is sequentially provided with a grid paving frame, a power box, a vertical frame, a sandy soil paving frame and a leveling frame along its traveling direction; The mobile frame is also equipped with an array of moving wheels for construction movement, wherein a set of moving wheels located between the grid laying frame and the upright is driven by the frame. A nailing assembly, located on the upright, is used to push and press in U-shaped nails to fix the overlapping grid.

[0010] Furthermore, a workbench is provided at the lower end of the upright frame, and at least one pressure groove is provided on the surface of the workbench. A connected conveying part is provided on one side of each pressure groove, and multiple U-shaped nails are pre-placed in the conveying part. The nail pressing assembly includes an electric telescopic rod horizontally disposed on the upper part and located outside the feeding end of the conveying section, and a pressing frame disposed on the top of the upright frame. The movable end of the electric telescopic rod is provided with a push block slidably connected to the inner wall of the conveying section. The push block abuts against the surface of the outermost U-shaped nail in the conveying section. Under the extension and retraction of the electric telescopic rod, the push block pushes the U-shaped nail in the conveying section to the inlet of the pressing groove. The upper end of the pressure frame is equipped with a hydraulic telescopic cylinder fixed to the top of the upright frame, and the lower end of the pressure frame is equipped with one or more plate-shaped pressure heads. Each plate-shaped pressure head is correspondingly arranged with respect to the pressure groove. Two symmetrically arranged elastic support clips are arranged in the pressure groove and on the side near the conveying part. When the hydraulic telescopic cylinder is activated, the pressure frame is driven to descend smoothly, so that the plate-shaped pressure heads press down the U-shaped nails temporarily positioned by the elastic support clips in the pressure groove into the embankment, thereby fixing the overlapping grid.

[0011] Furthermore, the inside of the grid laying frame has a U-shaped groove structure. Two discs are symmetrically and rotatably arranged at the two straight ends of the U-shaped groove to guide the grid to move smoothly within the grid laying frame. A discharge trough is provided at the bottom of the grid laying frame and on the side facing the power box. A pressure roller is rotatably arranged on the outside of the discharge trough to compact the grid and fit tightly against the laying surface on the sandy soil layer. The axis of the pressure roller is lower than the bottom edge of the discharge trough.

[0012] Furthermore, both ends of the pressure frame extend through the outside of the upright frame and are integrally formed with hinge seats. The hinge seats move vertically on the outer surface of the upright frame along with the pressure frame. Two support rods are symmetrically arranged on the hinge seats. A slide seat is provided on one end of the two support rods away from the hinge seat. The slide seats are located on the top of the mobile frame and are slidably arranged. A rack is provided on each of the two slide seats.

[0013] Furthermore, a notch is provided on the power box at the position where the slide block moves in, and a first drive gear is provided at the notch to engage with the rack. The end face of the first drive gear is provided with a first one-way transmission that extends into the power box and is coaxially connected with the moving wheel. The first one-way transmission is used only to transmit torque when the rack meshes and drives the first drive gear to rotate in the opposite direction.

[0014] Furthermore, the sandy soil laying frame includes an outer frame fixedly mounted on the top of the mobile frame and an inner frame fixedly connected to the inner wall of the outer frame. A discharge roller is rotatably mounted at the lower discharge point of the inner frame. A cylinder seat is provided on the inner frame at a corresponding contact point with one end of the discharge roller. A second one-way transmission device connected to the discharge roller is coaxially mounted inside the cylinder seat. A second drive gear that engages with the rack is provided on the second one-way transmission device extending through the outside of the cylinder seat. The transmission direction of the second one-way drive is opposite to that of the first one-way drive, and the second one-way drive is only used to transmit torque when the rack drives the second drive gear to rotate in the forward direction.

[0015] Furthermore, in step S3, the fine material accounts for 10% to 20% of the mass of the mixture, the maximum particle size of the large-diameter stone does not exceed 2 / 3 of the layer thickness, the loose paving thickness is 45 to 55 cm, and a vibratory roller of 25t or more is used to perform 1 to 2 passes of static compaction, 6 to 8 passes of strong vibration, and 1 to 2 passes of static compaction finishing. During strong vibration, the vibration frequency is 28 to 35 Hz, the amplitude is 0.8 to 1.2 mm, and the settlement difference between two consecutive passes is ≤5 mm. The groove depth of the roughening treatment shall not be less than 3cm and the spacing shall not be greater than 15cm. The groove shall be moistened with water to within ±2% of the optimum moisture content, and the thickness of the cement slurry layer shall be 2-3cm. The graded crushed stone adopts a continuous gradation of 0-31.5mm, with a needle-like and flaky particle content of no more than 15% and a mud content of no more than 5%. The thickness of the crushed stone layer is 22-32cm. A light roller is used to perform 1-2 passes of static compaction, 3-4 passes of weak vibration, and 1-2 passes of static compaction for finishing. During weak vibration, the vibration frequency is 25-30Hz and the amplitude is 0.5-0.8mm.

[0016] Furthermore, in step S4, after the construction of each layer is completed, a total station is used to measure the elevation, and the total filling height error is controlled within ±15mm.

[0017] The beneficial effects of this invention are reflected in: This invention utilizes a multi-layered, cyclical composite structure consisting of a reinforced cushion layer, a mixed layer, a cement slurry bonding layer, and a crushed stone layer sequentially arranged on a sandy soil layer. By leveraging the tensile strength of the geogrid, the interlocking of the mixture, the interfacial bonding of the cement slurry, and the stress diffusion effect of the crushed stone layer, a robust and deformation-resistant upper embankment structure is formed, effectively controlling differential settlement and post-construction total settlement. Furthermore, the innovative process of roughening, watering, and applying cement slurry after compaction of the mixed layer thoroughly improves the roughness and bonding conditions between the fill layer and the upper structure, preventing water infiltration, eliminating slip surfaces, and ensuring the coordinated operation of the multi-layered structure. An automatic laying device automates the laying of the geogrid and the covering of the upper sandy soil layer, eliminating the tediousness of traditional manual laying and allowing for rapid project progress. In the fixing stage, the device automatically completes the fixing of U-shaped nails, effectively ensuring the quality of geogrid overlap and significantly improving construction efficiency and process reliability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the settlement control method for large-diameter rockfill subgrade of highways according to the present invention; Figure 2 This is a simplified flowchart illustrating the method for controlling settlement of large-diameter rockfill subgrade in highways according to the present invention. Figure 3 This is a schematic diagram of the mobile frame structure in the method for controlling settlement of large-diameter rockfill subgrade in this invention. Figure 4 This invention relates to a method for controlling settlement of large-diameter rockfill subgrade in highways. Figure 3 Enlarged structural diagram at point A in the diagram; Figure 5 This invention relates to a method for controlling settlement of large-diameter rockfill subgrade in highways. Figure 3 Enlarged structural diagram at point B in the diagram; Figure 6 This invention relates to a method for controlling settlement of large-diameter rockfill subgrade in highways. Figure 3 Enlarged structural diagram at point C; Figure 7 This is a schematic diagram of the power box structure in the method for controlling settlement of large-diameter rockfill subgrade in highways according to the present invention; Figure 8 This is a schematic diagram of the sandy soil paving frame structure in the method for controlling settlement of large-diameter rockfill subgrade in this invention.

[0019] In the picture: 1. Mobile frame; 2. Grating laying frame; 3. Power box; 4. Vertical frame; 5. Sandy soil laying frame; 6. Leveling frame; 7. Pressing frame; 8. Hydraulic telescopic cylinder; 9. Pressing groove; 10. Conveying unit; 11. Electric telescopic rod; 12. Elastic support clips; 21. Disc body; 22. Discharge chute; 23. Pressure roller; 30. Notch; 31. First drive gear; 32. First one-way transmission; 41. Worktable; 51. Discharge roller; 52. Outer frame; 53. Inner frame; 54. Cylinder seat; 55. Second drive gear; 56. Second one-way transmission; 71. Plate-shaped pressure head; 72. Hinge seat; 73. Support rod; 74. Slide seat; 75. Rack; 111. Push block. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1 , Figure 2 This invention discloses a method for controlling settlement of large-diameter rockfill subgrade in highways, specifically including the following steps: S1, conduct foundation bearing capacity testing and elevation re-measurement on the foundation of the upper embankment, then fill and compact the sandy soil in layers to form a horizontal and dense sandy soil layer; S2, a grid is laid on the sandy soil layer, and after being overlapped and fixed, it is immediately covered with sandy soil and compacted to form a reinforced cushion layer; S3, spread a mixture of large-diameter stone and fine material on the reinforced cushion layer and compact it to form a mixed layer. At the same time, the settlement difference is detected. Then, the top surface of the mixed layer is roughened, moistened with water and cement slurry is laid to form a cement slurry layer. Finally, graded crushed stone is spread on the cement slurry layer and compacted to form a crushed stone layer. S4. Repeat steps S2 and S3 until the design height of the upper embankment is reached, and conduct elevation measurement control and surface cleaning after each layer of construction is completed.

[0022] The following is a detailed explanation of the above steps: S1. Before laying sandy soil on the top of the embankment, a second test is conducted on the foundation. A penetrometer is used to test the bearing capacity of the foundation to ensure that it meets the design requirements and that its bearing capacity is not lower than the design value (e.g., 220 kPa). The foundation elevation is re-measured using a total station, with the error controlled within ±10 mm. Subsequently, sandy soil is filled in layers, with each layer loosely laid to a thickness of 20 cm. A light roller (12-15 t) is used to perform 2-3 passes of static compaction, and the compaction degree must reach more than 93%, making it horizontal and dense, forming a sandy soil layer as a stable foundation for the subsequent reinforced cushion layer.

[0023] S2. On the accepted sandy soil layer, lay a bidirectional geogrid (bidirectional high-strength polyester geogrid with a warp and weft tensile strength ≥80kN / m and an elongation ≤10%). The overlap width between geogrids is ≥30cm. This step is carried out using an automatic laying device (structure described in Example 2 below). This device simultaneously completes: geogrid laying, automatic U-shaped nail pressing and fixing (U-shaped nails are laid at 50cm intervals along the overlap joint, with a nailing depth of not less than 20cm and an embedment depth in the soil layer of not less than 15cm), and then promptly lays sandy soil on top of the geogrid, with a thickness controlled at 10-15cm. Use a vibratory roller (18-20t) for 1-2 passes of weak vibration compaction, followed by 1-2 passes of static pressure leveling to form a reinforced cushion layer, preventing the geogrid from aging due to prolonged exposure.

[0024] S3 involves using a bulldozer to spread the mixture on the reinforced subbase. The mixture is prepared by pre-mixing large-diameter stones and fine aggregates at a quarry, and then turning it over at least three times using a loader to ensure uniform mixing. Simultaneously, random samples of the mixture are taken from the construction site, and the gradation is tested using a sieve analysis method to ensure that the proportion of fine aggregates is within the range of 10%-20%, and that the maximum diameter of the large-diameter stones does not exceed 2 / 3 of the layer thickness (i.e., not exceeding 33cm). The loose paving thickness is 45-55cm (40-50cm after compaction). The thickness is measured using elevation control stakes and a level, with at least 3 points measured per 100㎡. Compaction is performed using a heavy vibratory roller of 25t or more. First, 1-2 passes of static rolling are performed at a speed of 2-3km / h. Then, 6-8 passes of strong vibration are performed at a frequency of 28-35Hz, an amplitude of 0.8-1.2mm, and a speed of 3-4km / h. Finally, 1-2 passes of static rolling are performed to finish the surface and eliminate wheel tracks. After every two passes, the settlement of the top surface of the roadbed is measured using a level. When the settlement difference between two consecutive passes is ≤5mm, the compaction is considered qualified.

[0025] Immediately after compaction, the top surface of the mixed layer is roughened using a bulldozer rake, with grooves at a depth of not less than 3cm and a spacing of not more than 15cm. One to two hours before laying the graded crushed stone layer, a water truck is used to evenly spray water to moisten the top surface of the large-diameter stones, so that the surface moisture content reaches ±2% of the optimal moisture content, which enhances the interlayer bonding strength. At the same time, a 2-3cm thick layer of cement slurry (cement content of 3%-5%) is laid between the layers to further improve the interlayer bonding strength.

[0026] Before the cement slurry initially sets, graded crushed stone is immediately laid. The graded crushed stone adopts a continuous gradation of 0-31.5mm, with a needle-like and flaky particle content not exceeding 15% and a mud content not exceeding 5%. Upon arrival at the site, screening and crushing value tests are conducted every 2000m³. A paver is used for paving, with a paving thickness controlled at 22-32cm (20-30cm after compaction). A light roller (12-15t) is used for compaction, first performing 1-2 passes of static compaction at a speed of 2-3km / h; then performing 3-4 passes of weak vibration compaction at a vibration frequency of 25-30Hz, an amplitude of 0.5-0.8mm, and a speed of 3-4km / h; finally, 1-2 passes of static compaction are performed to ensure the surface flatness is ≤8mm, using a 3m straightedge for inspection, with no fewer than 5 inspections per 100m. This forms a dense and flat crushed stone layer.

[0027] S4. Repeat steps S2 and S3, constructing one or more composite cycles (each cycle includes one layer of reinforced cushion layer, one layer of mixed layer, and one layer of crushed stone) until the design height of the upper embankment in the embankment is reached. When repeating steps S2 and S3, after each layer is completed, use a total station to measure the elevation, strictly control the filling thickness and total filling height of each layer, and ensure that the design height of the upper embankment in the embankment is reached, with the error controlled within ±15mm. At the same time, after each layer is completed, clean up the debris and loose particles on the subgrade surface in a timely manner to create good conditions for the construction of the next layer.

[0028] Specifically, the settlement control method of this invention effectively solves the settlement problem through a series of construction steps. During the treatment of the embankment foundation, the foundation is subjected to secondary testing, and the laying and compaction of sandy soil are strictly controlled to ensure a solid and level foundation, laying a good foundation for subsequent construction and reducing settlement caused by foundation problems. High-strength materials are selected for the laying of geogrids, and automatic laying devices are used for standardized construction. The geogrids enhance the overall integrity of the roadbed and reduce differential settlement. The firm fixing of U-shaped nails ensures a tight connection between the geogrids and the base layer, further improving the stability of the roadbed.

[0029] In the construction of the large-diameter stone layer and the graded crushed stone layer, pre-control of gradation ensures uniform mixing of large-diameter stones and fine aggregates, reducing voids between stones. Standardized paving and compaction processes improve the density and strength of the embankment, reducing the risk of settlement due to pore compression. Interlayer reinforcement, through roughening, wetting with water, and laying cement slurry, enhances interlayer bonding, preventing localized settlement caused by interlayer slippage. Proper construction of the graded crushed stone layer further fills voids, improving the overall deformation resistance of the subgrade. Cyclic construction and elevation control ensure the quality of each layer, strictly controlling the total filling height to guarantee the overall stability of the subgrade.

[0030] In summary, this method can significantly reduce the settlement of large-diameter stone-filled subgrades on high-grade highways, improve highway smoothness and driving comfort, protect the pavement structure, extend highway life, reduce maintenance costs, and ensure driving safety.

[0031] In one embodiment of the present invention, such as Figure 3-8 As shown, the automatic laying device disclosed in this embodiment is used to efficiently implement the grid laying, U-shaped nail fixing and sandy soil covering in step S2.

[0032] Structural components: like Figure 3 As shown, the device includes a mobile frame 1. The top of the mobile frame 1, along its direction of travel, is sequentially fixed with: a grating laying frame 2, a power box 3, a vertical frame 4, a sandy soil laying frame 5, and a leveling frame 6. The bottom of the mobile frame 1 is equipped with an array of wheels, one set of which, located between the grating laying frame 2 and the vertical frame 4, is driven by the power box 3.

[0033] Specifically, the structure and connection relationship of the automatic laying device will be further explained. The automatic laying device of the present invention has the ability to automatically lay grids and sandy soil, eliminating the tediousness of traditional manual laying, greatly improving construction efficiency, and allowing the project progress to proceed quickly. In the fixing stage, the device can automatically complete the fixing work of U-shaped nails, effectively ensuring the tight connection between the grid and the base layer, laying a solid foundation for the quality of the project. At the same time, it also has an automatic leveling function for sandy soil, which can make the laying surface flat and smooth, meeting the strict requirements of various projects for surface flatness.

[0034] Grid laying frame 2 (see Figure 4 The interior features a U-shaped groove, providing reasonable space and guidance for the laying of the geogrid. Discs 21 are rotatably installed at both ends within the geogrid laying frame 2. The rotation of the discs 21 guides the geogrid rolls smoothly out and also limits the geogrid to prevent lateral displacement. A discharge trough 22 is machined and reserved at the bottom, and a pressure roller 23 is rotatably installed at the outlet of the discharge trough 22. The pressure roller 23 is designed to be slightly lower than the bottom edge of the discharge trough 22, so that the pressure roller 23 can effectively compact the geogrid discharged from the discharge trough 22, ensuring that the laid geogrid is lightly pressed and adhered to the surface of the underlying sandy soil.

[0035] Frame 4 and nailing assembly (combined) Figure 3 , Figure 5 , Figure 6 The support frame 4 has a worktable 41 fixed to its lower end. Multiple pressure grooves 9 (e.g., three evenly spaced side-by-side) are machined on the worktable 41. Each pressure groove 9 has a conveying section 10 on one side, pre-installed with U-shaped nails. An electric telescopic rod 11 is horizontally bolted to the worktable 41, and its pusher 111 extends into the conveying section 10, pushing the U-shaped nails one by one into the inlet of the pressure groove 9. The nails are temporarily positioned by two symmetrical elastic support clips 12. During this process, when the elastic support clips 12 are compressed, they quickly retract to the inner wall of the pressure groove 9, cleverly avoiding structural conflict with the downward movement of the U-shaped nails. A hydraulic telescopic cylinder 8 is bolted to the top of the support frame 4, driving the pressure frame 7 below to move vertically. Multiple plate-shaped pressure heads 71 ​​are located at the lower end of the pressure frame 7, corresponding one-to-one with the pressure grooves 9. When the U-shaped nails are in place, the hydraulic telescopic cylinder 8 drives the plate-shaped pressure heads 71 ​​to quickly press down, driving the U-shaped nails into the embankment and fixing the grating.

[0036] Further optimization shows that the length and width of the pressure groove 9 are equal to the length and width of the U-shaped nail, respectively. This precise dimensional correspondence is a key factor in ensuring processing quality. Through this design, when the plate-shaped pressure head 71 applies downward pressure, it can ensure that the U-shaped nail is pressed vertically and accurately into the embankment, avoiding problems such as skewing and deformation caused by size mismatch, thereby improving the processing accuracy and quality stability of the product.

[0037] It should be noted that the hydraulic telescopic cylinder 8 is remotely controlled by an external remote control device, which allows operators to make flexible adjustments according to the actual working conditions. The electric telescopic rod 11 is also controlled by an external remote control device, allowing operators to remotely and precisely control the feeding rhythm and quantity of U-shaped nails to meet different laying needs.

[0038] Linkage drive mechanism (see) Figure 5 , Figure 7 , Figure 8 The pressure frame 7 extends through both ends of the upright frame 4 and is integrally formed and installed with the hinge seat 72. Two support rods 73 are symmetrically hinged to the surface of the hinge seat 72, and the corresponding ends of the two support rods 73 away from the hinge seat 72 are hinged and installed with the slide 74. The slide 74 is horizontally slidably connected to the top of the moving frame 1 via a slide rail, and a rack 75 is welded / integratedly formed on the slide 74.

[0039] The power box 3 has a notch 30 machined on the side near the slide 74. This design provides a reasonable spatial layout for the mating and transmission of subsequent components. Inside the notch, a first drive gear 31 meshes with the rack 75. The first drive gear 31 is connected to the power shaft of the drive wheel through a first one-way transmission 32. In this design, the bottom of the first drive gear 31 extends into the notch 30 and meshes with the rack 75 on the top of the slide 74, thus establishing a reliable transmission path.

[0040] Further optimization explains that the first one-way transmission device 32 has a unique one-way transmission characteristic. It transmits torque only when the rack 75 moves in opposite directions (i.e., the pressure frame 7 rises and resets) and drives the first drive gear 31 meshing with it to rotate in the opposite direction. This design ensures that the wheel moves in one direction and has a good performance.

[0041] The sandy soil laying frame 5 is composed of an outer frame 52 bolted / welded to the top of the mobile frame 1 and an inner frame 53 welded to the inner wall of the outer frame 52. This design provides a stable support frame for the entire sandy soil laying frame 5, ensuring the stability and reliability of the structure during the sandy soil laying process. The discharge roller 51 is rotatably connected to the inner wall of the discharge port of the inner frame 53 (located on the lower side of the inner frame 53) and is the key component for discharging sandy soil. On the inner frame 53, at the end corresponding to the discharge roller 51, a cylindrical seat 54 is installed by a threaded connection. The threaded connection is convenient for installation and disassembly and has high connection strength, which facilitates subsequent maintenance and replacement of the cylindrical seat 54 and related components. A second drive gear 55 is coaxially mounted on the cylindrical seat 54. This gear meshes with the rack 75 on the top of the slide 74, forming a reliable gear and rack transmission mechanism. Through this transmission method, the linear movement of the slide 74 can be converted into the rotation of the second drive gear 55. The second drive gear 55 is connected to the discharge roller 51 through a second one-way transmission 56 inside the cylindrical seat 54.

[0042] Further optimization explains that the transmission direction of the second one-way drive 56 is opposite to that of the first one-way drive 32. This unique design makes the entire power transmission system have more complex control logic. The second one-way drive 56 transmits torque only when the rack 75 drives the second drive gear 55 to rotate in the forward direction, ensuring that the discharge roller 51 can rotate in the predetermined direction and at the predetermined time, thereby achieving the precise laying of sandy soil.

[0043] It should be noted that the first drive gear 31 and the second drive gear 55 are both located on the upper side of the corresponding rack 75, and the second one-way transmission 56 and the first one-way transmission 32 are both ratchet-type one-way transmissions.

[0044] Working principle: After the device is started, the hydraulic telescopic cylinder 8 pushes the pressure frame 7 to descend smoothly until the plate-shaped pressure head 71 accurately presses down the U-shaped nail located in the pressure groove 9 and temporarily positioned by the elastic support clip 12 into the embankment, thus completing the firm fixation of the grid. During this process, the rack 75 on the two disengaged slide blocks 74 will drive the meshing first drive gear 31 to rotate in the forward direction and the second drive gear 55 to rotate in the opposite direction. Although the first drive gear 31 and the second drive gear 55 are driven, the first one-way transmission 32 and the second one-way transmission 56 do not transmit torque at this time (idle), so the moving wheel and the discharge roller 51 do not move.

[0045] After the nailing action is completed, the hydraulic telescopic cylinder 8 is activated, driving the pressure frame 7 to rise and return to its original position. During the rising and resetting process, the hinge seat 72 connected to it will rise simultaneously. Since the hinge seat 72 is hinged to two sets of support rods 73, and the other end of the support rods 73 is hinged to two sets of slides 74 respectively, according to the lever and slider mechanism principle, the rising action of the hinge seat 72 will drive the two sets of slides 74 to move towards each other synchronously through the support rods 73. During this process, the movement of the slide 74 near the power box 3 will cause its top rack 75 to mesh with the first drive gear 31 preset in the power box 3. As the rack 75 moves, according to the gear rack 75 transmission principle and the torque transmitted when the first drive gear 31 rotates in the opposite direction, it will synchronously drive the transmission mechanism inside the power box 3 to operate, transmitting torque. The torque is supplied to the moving wheels, driving the entire device forward a set distance (e.g., the spacing of a U-shaped nail). During the movement, the grid in the grid laying frame 2 is automatically laid by the movement of the frame. At the same time, when the slide 74 on the side of the power box 3 moves, the rack 75 on its top will mesh with the drive component of the discharge roller 51 on the sandy soil laying frame 5. Driven by the rack 75, according to the same gear rack 75 transmission mechanism and the forward rotation of the second one-way transmission device 56, the discharge roller 51 will be driven to rotate around its own axis. At this time, the sandy soil laying frame 5 evenly feeds and lays on the grid that has just been fixed, and the leveling frame 6 performs fine leveling of the sandy soil behind it.

[0046] Once the pressure frame 7 returns to its original position, the wheels and discharge roller 51 stop rotating, and the electric telescopic rod 11 actuates, pushing the next U-shaped nail into the inlet of the pressure groove 9. Subsequently, the pressure frame 7 descends again, repeating the cycle of nailing, discharging, and moving forward, thus achieving automated continuous operation of grid laying, fixing, and covering sandy soil.

[0047] This device ingeniously links the U-shaped nail fixing action with the device's movement and the sandy soil feeding action through a one-way transmission, realizing automatic rhythm control of "pause-nailing and covering with soil-movement", which greatly improves construction efficiency and quality consistency.

[0048] The electrical components described in this article are controlled automatically by a controller. The controller circuit can be implemented by a person skilled in the art through simple programming. The power supply is also common knowledge in the field. Furthermore, since this application is mainly used to protect mechanical devices, the control method and circuit connection will not be explained in detail here.

[0049] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0050] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0051] Additionally, "multiple" refers to two or more.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling settlement of large-diameter riprap subgrade in highways, characterized in that, Specifically, the following steps are included: S1, conduct foundation bearing capacity testing and elevation re-measurement on the foundation of the upper embankment, then fill and compact the sandy soil in layers to form a horizontal and dense sandy soil layer; S2, a grid is laid on the sandy soil layer, and after being overlapped and fixed, it is immediately covered with sandy soil and compacted to form a reinforced cushion layer; S3, spread a mixture of large-diameter stone and fine material on the reinforced cushion layer and compact it to form a mixed layer. At the same time, the settlement difference is detected. Then, the top surface of the mixed layer is roughened, moistened with water and cement slurry is laid to form a cement slurry layer. Finally, graded crushed stone is spread on the cement slurry layer and compacted to form a crushed stone layer. S4. Repeat steps S2 and S3 until the design height of the upper embankment is reached, and conduct elevation measurement control and surface cleaning after each layer of construction is completed.

2. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 1, characterized in that: In step S1, a ground bearing capacity tester is used to detect the foundation bearing capacity, and a total station is used to re-measure the foundation elevation, with the error controlled within ±10mm. When laying sandy soil, the thickness of each layer should not exceed 20cm. Use a light roller to perform 2-3 passes of static compaction, and the compaction degree should reach more than 93%.

3. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 1, characterized in that: In step S2, the grid is a bidirectional geogrid, and the overlapping grids are fixed with U-shaped nails. The fixing of the grid and the U-shaped nails, as well as the covering of the sandy soil, are all carried out using an automatic laying device. The automatic paving device includes a mobile frame (1), and the top of the mobile frame (1) is provided with a grid paving frame (2), a power box (3), a vertical frame (4), a sandy soil paving frame (5) and a leveling frame (6) in sequence along its driving direction. The mobile frame (1) is also provided with an array of moving wheels for construction movement, wherein a set of moving wheels located between the grid laying frame (2) and the upright frame (4) is driven by the (3); The nailing assembly is located on the upright (4) and is used to push and press in U-shaped nails to fix the overlapping grid.

4. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 3, characterized in that: The lower end of the stand (4) is provided with a workbench (41), and the workbench (41) has at least one pressure groove (9) on its surface. Each pressure groove (9) has a connected conveying part (10) on one side, and multiple U-shaped nails are pre-installed in the conveying part (10). The nail pressing assembly includes an electric telescopic rod (11) horizontally disposed on the (41) and located outside the loading end of the conveying section (10) and a pressing frame (7) disposed at the top inside the upright frame (4). The movable end of the electric telescopic rod (11) is provided with a push block (111) slidably connected to the inner wall of the conveying section (10). The push block (111) abuts against the surface of the outermost U-shaped nail inside the conveying section (10). Under the telescopic action of the electric telescopic rod (11), the push block (111) pushes the U-shaped nail in the conveying section (10) to the inlet of the pressing groove (9). The upper end of the pressure frame (7) is provided with a hydraulic telescopic cylinder (8) fixed to the top of the upright frame (4). The lower end of the pressure frame (7) is provided with one or more plate-shaped pressure heads (71). Each plate-shaped pressure head (71) is correspondingly provided with the pressure groove (9). Two symmetrically arranged elastic support clips (12) are provided in the pressure groove (9) and on the side near the conveying part (10). When the hydraulic telescopic cylinder (8) is activated, the pressure frame (7) is driven to descend smoothly, so that the plate-shaped pressure head (71) presses down the U-shaped nail temporarily positioned by the elastic support clips (12) in the pressure groove (9) into the embankment to fix the overlapping grid.

5. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 3, characterized in that: The inside of the grid laying frame (2) has a U-shaped groove structure. Two discs (21) are symmetrically rotated at the two straight ends of the U-shaped groove to guide the grid to move smoothly within the grid laying frame (2). A discharge chute (22) is provided at the bottom of the grid laying frame (2) and on the side facing the power box (3). A pressure roller (23) is rotatably arranged on the outside of the discharge chute (22) to compact the grid and fit tightly against the laying surface on the sandy soil layer. The axis of the pressure roller (23) is lower than the bottom edge of the discharge chute (22).

6. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 4, characterized in that: The two ends of the pressure frame (7) extend through the outside of the upright frame (4) and are integrally formed with a hinge seat (72). The hinge seat (72) moves vertically on the outer surface of the upright frame (4) along with the pressure frame (7). Two support rods (73) are symmetrically arranged on the hinge seat (72). A slide seat (74) is provided on one end of the two support rods (73) away from the hinge seat (72). The slide seat (74) is located on the top of the mobile frame (1) and is slidably arranged. A rack (75) is provided on the two slide seats (74).

7. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 6, characterized in that: The power box (3) is provided with a notch (30) at the position where the slide (74) moves in. A first drive gear (31) is provided at the notch (30) and is connected to the rack (75). A first one-way transmission (32) is provided on the end face of the first drive gear (31) and extends into the power box (3) and is coaxially connected to the moving wheel. The first one-way transmission (32) is used only to transmit torque when the rack (75) meshes and drives the first drive gear (31) to rotate in the opposite direction.

8. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 7, characterized in that: The sandy soil laying frame (5) includes an outer frame (52) fixedly mounted on the top of the mobile frame (1) and an inner frame (53) fixedly connected to the inner wall of the outer frame (52). A discharge roller (51) is rotatably mounted at the lower discharge point of the inner frame (53). A cylinder seat (54) is provided on the inner frame (53) at a corresponding contact point with one end of the discharge roller (51). A second one-way transmission device (56) connected to the discharge roller (51) is coaxially mounted inside the cylinder seat (54). A second drive gear (55) that is engaged with the rack (75) is provided on the second one-way transmission device (56) extending through the outside of the cylinder seat (54). The transmission direction of the second one-way drive (56) is opposite to that of the first one-way drive (32). The second one-way drive (56) is only used to transmit torque when the rack (75) drives the second drive gear (55) to rotate in the forward direction.

9. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 1, characterized in that: In step S3, the fine material accounts for 10% to 20% of the mass of the mixture, the maximum particle size of the large-diameter stone does not exceed 2 / 3 of the layer thickness, the loose paving thickness is 45 to 55 cm, and a vibratory roller of 25t or more is used to perform 1 to 2 passes of static compaction, 6 to 8 passes of strong vibration, and 1 to 2 passes of static compaction finishing. During strong vibration, the vibration frequency is 28 to 35 Hz, the amplitude is 0.8 to 1.2 mm, and the settlement difference between two consecutive passes is ≤5 mm. The groove depth of the roughening treatment shall not be less than 3cm and the spacing shall not be greater than 15cm. The groove shall be moistened with water to within ±2% of the optimum moisture content, and the thickness of the cement slurry layer shall be 2-3cm. The graded crushed stone adopts a continuous gradation of 0-31.5mm, with a needle-like and flaky particle content of no more than 15% and a mud content of no more than 5%. The thickness of the crushed stone layer is 22-32cm. A light roller is used to perform 1-2 passes of static compaction, 3-4 passes of weak vibration, and 1-2 passes of static compaction for finishing. During weak vibration, the vibration frequency is 25-30Hz and the amplitude is 0.5-0.8mm.

10. The method for controlling settlement of large-diameter rockfill subgrade in highways according to claim 1, characterized in that: In step S4, after each layer of construction is completed, a total station is used to measure the elevation, and the total filling height error is controlled within ±15mm.

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