Loading device and loading method for on-site soil matrix rebound modulus test

Abstract

The invention provides a loading device and a loading method for on-site soil matrix rebound modulus testing, and belongs to the technical field of roadbed engineering detection. The loading device for the on-site soil matrix rebound modulus test comprises a reaction frame, a hydraulic cylinder, a spherical hinge seat, a loading plate and a bearing plate, a cushion connecting cylinder is fixedly mounted at the bottom of the spherical hinge seat, a mounting plate is fixedly mounted at the bottom of the cushion connecting cylinder, two toothed plates are slidably mounted on the mounting plate in a penetrating manner, and the two toothed plates are fixedly mounted on the bearing plate. And two first circular shafts are rotatably mounted at the top of the mounting plate, and first gears fixedly sleeve the two first circular shafts. The loading device for the on-site soil matrix rebound modulus test has the advantages that the loading distance can be greatly adjusted to adapt to a low-position soil matrix test scene, the comprehensive protection function is achieved, operation is convenient and efficient, the integrated pressing roller mechanism can assist fine sand leveling, and the on-site soil matrix rebound modulus test efficiency can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of roadbed engineering testing technology, and in particular to a loading device and loading method for on-site testing of the resilient modulus of subgrade. Background Technology

[0002] The resilient modulus of subgrade is a core indicator for road engineering design and quality assessment, directly reflecting the elastic deformation capacity of the subgrade under vehicle loads. The accuracy of its field test results directly affects the design thickness and service life of road structural layers. Currently, the mainstream method in the industry is the bearing plate method for field testing of subgrade resilient modulus. The core equipment is a loading device, mainly composed of a reaction frame, hydraulic jacks (or hydraulic cylinders), a bearing plate, and a loading plate. The reaction frame provides reverse support, and the hydraulic jacks output graded loads, which are transferred to the bearing plate through the loading plate and finally act on the subgrade test points. The resilient modulus is then calculated by combining the settlement data.

[0003] In actual engineering testing, some subgrade test points are located at lower elevations due to site limitations (such as road pits, low-lying road sections, and excavated subgrade surfaces). Traditional loading devices rely on the piston stroke of hydraulic jacks or simple manual telescopic structures for adjusting the distance between the loading plate and the reaction frame. This adjustment stroke is limited. When the subgrade surface is significantly lower than the preset height at the bottom of the reaction frame, the loading plate cannot effectively adhere to the bearing plate placed on the subgrade surface, resulting in unstable load transfer and even making testing impossible. Even if some devices can extend the distance by adding shims, problems such as cumbersome installation, poor stability, and excessive load eccentricity during transfer persist, severely impacting testing efficiency and data accuracy.

[0004] Therefore, it is necessary to provide a new loading device and loading method for on-site testing of the resilient modulus of subgrade to solve the above problems. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a hydraulic tensioning instrument and its usage method that can significantly adjust the loading distance to adapt to low-position soil foundation testing scenarios, has comprehensive protection functions, is easy and efficient to operate, integrates a pressure roller mechanism to assist in fine sand leveling, and can effectively improve the efficiency of on-site soil foundation rebound modulus testing.

[0006] To solve the above-mentioned technical problems, the present invention provides a loading device for on-site soil resilient modulus testing, comprising a reaction frame, a hydraulic cylinder, a ball joint seat, a loading plate, and a bearing plate. The hydraulic cylinder is fixedly installed at the bottom of the reaction frame, the top of the ball joint seat is fixedly installed on the output end of the hydraulic cylinder, the loading plate is disposed below the ball joint seat, the bearing plate is disposed below the loading plate, a pad is fixedly installed at the bottom of the ball joint seat, and an mounting plate is fixedly installed at the bottom of the pad. Two toothed plates are slidably mounted through the mounting plate, and the loading plate is fixedly installed at the bottom of the two toothed plates. Two first round shafts are rotatably mounted on the top of the mounting plate. A first gear is fixedly sleeved on each of the two first round shafts, and the two first gears mesh with the corresponding gear plates. A worm gear is fixedly sleeved on one end of each of the two first round shafts. A second round shaft is rotatably mounted on the top of the mounting plate. A worm is fixedly mounted on both ends of the second round shaft, and the two worms mesh with the corresponding worm gears. A first motor is fixedly mounted on the top of the mounting plate, and the output end of the first motor is fixedly connected to the end of the corresponding worm that is away from the second round shaft.

[0007] Furthermore, a guide telescopic slide rod is provided inside the padding cylinder. The guide telescopic slide rod includes an outer cylinder and an inner rod. The outer cylinder is slidably installed inside the padding cylinder, and the inner rod is slidably installed inside the outer cylinder. The bottom end of the inner rod extends to the bottom of the mounting plate and is fixedly connected to the loading plate.

[0008] Furthermore, two suspension rods are fixedly installed at the bottom of the reaction frame, and an axially retractable protective curtain is fixedly installed at the bottom of the two suspension rods. A fixed frame is fixedly installed at the bottom of the protective curtain, and the bottom of the fixed frame is in contact with the mounting plate. Circular insertion holes are provided at the four corners of the fixed frame, and locking mechanisms are provided at the four corners of the top of the mounting plate. The locking mechanisms are used to cooperate with the circular insertion holes to fix the fixed frame.

[0009] Preferably, the locking mechanism includes a corner block, a screw, and a pin. The corner block is fixedly installed on the top of the mounting plate, the screw is threaded onto the corner block, the pin is disposed at one end of the screw and is integrally formed with the screw, and the end of the pin away from the screw extends into the circular insertion hole.

[0010] Furthermore, a protective frame is fixedly installed on the top of the mounting plate. The fixed frame is located between the protective frame and the four corner blocks. The first motor, two worm gears, two worm wheels, and two first gears are all located inside the protective frame. A frustum-shaped guide frame is provided on the top of the protective frame. The connection between the two inner sides of the corner blocks and the top is chamfered.

[0011] Furthermore, an annular groove is formed on the outer wall of the screw, and a ring is rotatably installed in the annular groove. A connecting rod is fixedly installed on the top of the ring, and a limiting rod is fixedly installed on the corner block. The limiting rod passes through the connecting rod and is movably connected to the connecting rod. A first limiting end plate is fixedly installed on the end of the limiting rod away from the pressure plate.

[0012] Furthermore, the loading plate is also equipped with a pressure roller mechanism, which is used to level the fine sand layer after the fine sand is laid at the soil test point; The pressure roller mechanism includes two elongated boxes, two sliders, two follower round shafts, two horizontal plates, two vertical plates, a round roller, a lead screw, and a second motor. The two elongated boxes are fixedly installed on the top of the loading plate and located on both sides of the guide telescopic slide rod. The two sliders are slidably installed inside the two elongated boxes. The two follower round shafts are respectively installed on the outer walls of the two sliders on opposite sides. The two horizontal plates are fixedly installed on opposite ends of the two follower round shafts. The two vertical plates are respectively installed at the bottom of the two horizontal plates. The round roller is rotatably installed between the two vertical plates. The lead screw is rotatably installed inside one of the elongated boxes, with both ends extending beyond the ends of the elongated box. The lead screw passes through the corresponding slider and is threadedly connected to the corresponding slider. The second motor is fixedly installed at one end of the corresponding elongated box, and the output end of the second motor is fixedly connected to one end of the corresponding lead screw.

[0013] Preferably, both follower circular shafts are rotatably mounted on the corresponding sliders. A second gear is fixedly sleeved on the outer wall of one of the follower circular shafts, and a third motor is fixedly mounted on the corresponding slider. A third gear is fixedly sleeved on the output end of the third motor, and the third gear meshes with the second gear.

[0014] Preferably, two limiting slide rods are slidably installed through the horizontal plate, and the vertical plate is fixedly installed at the bottom end of the two limiting slide rods. A spring is sleeved on the limiting slide rod, the top end of the spring is in contact with the horizontal plate, and the bottom end is in contact with the vertical plate. A second limiting end plate is fixedly installed at the top end of the two limiting slide rods, and the bottom of the second limiting end plate is in contact with the horizontal plate.

[0015] To address the above problems, the present invention also provides a method for using a loading device for on-site soil resilient modulus testing, comprising the following steps: T1: Clean the surface of the soil test point and ensure that the diameter of the test area is not less than 50cm; place the bearing plate stably in the center of the test point and ensure that it is horizontally aligned; T2: Move the reaction frame above the test point so that the center of the loading plate projection coincides with the center of the bearing plate, and fix the reaction frame base; check the equipment wiring, hydraulic station status and settlement sensor to ensure normal operation; T3: Start the first motor to drive the loading plate to descend, so that the lower surface of the loading plate gently contacts the upper surface of the pre-placed bearing plate. Then, turn off the first motor and the worm gear self-locks and fixes the position. T4: Start the hydraulic station and control the hydraulic cylinder to load gradually from 0.05MPa, with each load increasing by 0.05MPa. Maintain the load at each level for 1 minute and record the rebound deformation and load data. During the loading process, the ball joint seat self-adjusts and the guide telescopic slide rod ensures that the loading plate and the pressure plate are in close contact. T5: After loading is completed, unload step by step and record the residual deformation data; start the first motor to drive the loading plate to reset, remove the reaction frame, and complete the test.

[0016] Compared with related technologies, the loading device and loading method for on-site soil resilient modulus testing provided by the present invention have the following advantages: This invention, through the arrangement of components such as a toothed plate, a first gear, a worm gear, a worm, a first motor, and a guide telescopic slide, achieves a significant adjustment of the distance between the loading plate and the reaction frame, solving the problem of limited adjustment range in traditional devices. In the core transmission mechanism, the motor converts rotational motion into gear rotation via the worm gear, and then drives the loading plate to rise and fall smoothly through the meshing of the gear and the toothed plate. The worm gear transmission has a reliable self-locking function, which can prevent the loading plate from settling under load. Even when stationary for a long time, it can maintain a stable fit, solving the problems of traditional devices that rely on shims to extend the distance, are cumbersome to install, and are prone to load transfer eccentricity. This invention employs a retractable protective curtain installed at the bottom of the reaction frame, in conjunction with a bottom fixed frame and a protective frame at the top of the mounting plate, to completely protect the core transmission components inside, effectively isolating them from dust, sand, and other debris, preventing component wear, jamming, or corrosion, and extending their service life; the locking mechanism, through a combination design of corner blocks, screws, and pins, allows for quick locking and unlocking of the fixed frame simply by turning the screw with a wrench, making operation convenient and fast; To address the standard requirement of leveling minor pits and depressions on the soil surface with fine sand, this invention integrates a pressure roller mechanism on the loading plate. This solves the problems of traditional testing methods, which require additional tools and involve uneven thickness and low efficiency in manual leveling. The mechanism is compact and integrated with the loading plate, requiring no additional testing space. During leveling, a third motor, via gear transmission, drives a follower shaft to rotate, adjusting the roller initially positioned above the loading plate downwards to contact the fine sand layer, accommodating different sand thicknesses. A second motor drives a lead screw to rotate, which, through the lead screw and nut pair, moves a slider along a long box, thereby causing the roller to roll and level the fine sand layer at a stable speed. This effectively ensures uniform contact between the pressure plate and the soil surface, laying a solid foundation for the stability of subsequent load transfer and the accuracy of test data. It also eliminates the need for tools and cumbersome manual leveling, further improving the continuity and efficiency of the testing process. Attached Figure Description

[0017] Figure 1 A schematic diagram of the loading device for on-site soil resilient modulus testing provided by the present invention; Figure 2 for Figure 1 The diagram shown is a structural schematic of the protective curtain and the reaction frame in a separated state. Figure 3 for Figure 2 An enlarged schematic diagram of part A shown; Figure 4 for Figure 2 The diagram shows the structural schematic of the components mounted on the mounting plate. Figure 5 for Figure 1 A partial front view of the loading device used for on-site soil resilient modulus testing; Figure 6 for Figure 4 A cross-sectional view of the guide telescopic slide rod shown; Figure 7 for Figure 4 The diagram shows the structure of the corner piece; Figure 8 for Figure 7 The diagram shows the structure of the screw. Figure 9 for Figure 4 The diagram shows the connection structure between the circular roller and the long box. Figure 10 for Figure 9 The enlarged schematic diagram of section B is shown below; Figure 11 for Figure 9 The diagram shows the connection between the horizontal and vertical plates.

[0018] Numbering on the map: 1. Reaction frame; 2. Hydraulic cylinder; 3. Ball joint seat; 4. Pad sleeve; 5. Mounting plate; 6. Gear plate; 7. Loading plate; 8. Bearing plate; 9. First round shaft; 10. Worm gear; 11. First gear; 12. Worm; 13. First motor; 14. Guide telescopic slide bar; 15. Protective curtain; 16. Fixed frame; 17. Protective frame; 18. Corner block; 19. Screw; 20. Pin; 21. Long box; 22. Slider; 23. Follower round shaft; 24. Horizontal plate; 25. Vertical plate; 26. Round roller; 27. Lead screw; 28. Second motor; 29. ​​Second gear; 30. Third motor; 31. Third gear; 161. Round insertion hole. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] First embodiment: Please refer to the following: Figures 1-11 In the first embodiment of the present invention, a loading device for on-site soil resilient modulus testing is proposed, comprising: a reaction frame 1, a hydraulic cylinder 2, a ball joint seat 3, a loading plate 7, and a bearing plate 8. The reaction frame 1 provides core reaction support for the entire device and is welded from high-strength alloy steel. The hydraulic cylinder 2 is fixedly installed at the bottom of the reaction frame 1, and the hydraulic cylinder 2 achieves graded loading control through a matching hydraulic station. The top of the ball joint seat 3 is fixedly installed on the output end of the hydraulic cylinder 2, and the ball joint seat 3 can achieve adaptive angle adjustment within a range of ±5°, which can counteract the hydraulic cylinder. 2. Load eccentricity caused by installation deviation, slight tilt of reaction frame 1 or initial unevenness of soil surface. Ensure that the output force of hydraulic cylinder 2 is always transmitted to bearing plate 8 in the vertical direction. Loading plate 7 is set below ball joint seat 3 and bearing plate 8 is set below loading plate 7. Bearing plate 8 is forged from high-strength alloy steel with a diameter of 30cm and a thickness of not less than 20mm. The bottom is machined into a smooth surface (roughness Ra≤1.6μm) to ensure uniform contact with the soil surface and uniformly spread the load to the soil test area to avoid local stress concentration. A pad cylinder 4 is fixedly installed at the bottom of the ball joint seat 3, and an mounting plate 5 is fixedly installed at the bottom of the pad cylinder 4. The pad cylinder 4 is a hollow cylindrical structure with an inner diameter matching the outer cylinder size of the guide telescopic slide rod 14 mentioned below. Its top is bolted to the ball joint seat 3 via a flange, and its bottom is welded to the mounting plate 5. Two toothed plates 6 are slidably installed through the mounting plate 5. A loading plate 7 is fixedly installed at the bottom of the two toothed plates 6. The two toothed plates 6 are symmetrically arranged, and their sliding direction is consistent with the force direction of the pressure plate 8. Two first round shafts 9 are rotatably installed on the top of the mounting plate 5. The first round shafts 9 are rotatably installed on the top of the mounting plate 5 via bearing seats. A first round shaft 9 is fixedly sleeved on each of the two first round shafts 9. One gear 11, two first gears 11 mesh with corresponding tooth plates 6, and one end of each of the two first round shafts 9 is fixedly fitted with a worm gear 10. A second round shaft is rotatably mounted on the top of the mounting plate 5. The second round shaft is also rotatably mounted on the top of the mounting plate 5 through a bearing seat. Worms 12 are fixedly mounted on both ends of the second round shaft. Both worms 12 mesh with corresponding worm gears 10. The worms 12 and worm gears 10 form a worm gear transmission pair, which has a self-locking function and can prevent the loading plate 7 from settling on its own under load. A first motor 13 is fixedly mounted on the top of the mounting plate 5. The output end of the first motor 13 is fixedly connected to the end of the corresponding worm 12 away from the second round shaft.

[0021] The first motor 13 is started, and its output torque is reduced by the reducer and transmitted to the second circular shaft, driving the worm gears 12 at both ends to rotate synchronously. The worm gears 12 mesh with the worm wheel 10, converting the horizontal rotational motion into the rotational motion of the first circular shaft 9. The first circular shaft 9 drives the first gear 11 to rotate, and the first gear 11 meshes with the gear plate 6, converting the rotational motion into the axial linear motion of the gear plate 6, ultimately driving the loading plate 7 to rise and fall. Since the two worm gears 12 rotate in opposite directions and the worm wheel 10 has the same number of teeth, the movement directions of the two gear plates 6 are completely synchronized, ensuring that the loading plate 7 remains horizontal during the rising and falling process. Combined with the leveling function of the ball joint seat 3, this achieves precise contact between the pressure plate 8 and the soil surface. In this embodiment, a guide telescopic slide rod 14 is provided inside the pad cylinder 4. The guide telescopic slide rod 14 includes an outer cylinder and an inner rod. The outer cylinder is slidably installed inside the pad cylinder 4, and the inner rod is slidably installed inside the outer cylinder. The bottom end of the inner rod extends to the bottom of the mounting plate 5 and is fixedly connected to the loading plate 7. The function of the guide telescopic slide rod 14 is to provide precise guidance for the lifting and lowering movement of the loading plate 7, limit its lateral displacement, ensure the stable meshing clearance between the toothed plate 6 and the first gear 11, and avoid load transmission deviation caused by the offset of the loading plate 7.

[0022] In this embodiment, two hanging rods are fixedly installed at the bottom of the reaction frame 1. An axially retractable protective curtain 15 is fixedly installed at the bottom of the two hanging rods. The main body of the protective curtain 15 is composed of a cloth cover and a square frame connected at intervals. It can be extended and retracted within a certain range. A fixed frame 16 is fixedly installed at the bottom of the protective curtain 15. The bottom of the fixed frame 16 is in contact with the mounting plate 5. A round insertion hole 161 is provided at each of the four corners of the fixed frame 16. A locking mechanism is provided at each of the four corners of the top of the mounting plate 5. The locking mechanism is used to cooperate with the round insertion hole 161 to fix the fixed frame 16.

[0023] Preferably, the locking mechanism includes a corner block 18, a screw 19, and a pin 20. The corner block 18 is fixedly installed on the top of the mounting plate 5. The corner block 18 is a right-angled triangular steel structure and is fixed to the mounting plate 5 by welding. The screw 19 is threaded onto the corner block 18. The pin 20 is located at one end of the screw 19 and is integrally formed with the screw 19. The end of the pin 20 is machined into a hemispherical chamfer to facilitate insertion into the round insertion hole 161. The end of the pin 20 away from the screw 19 extends into the round insertion hole 161. When the fixing frame 16 is attached to the mounting plate 5, the screw 19 is rotated with a wrench, and the pin 20 is pushed axially through the threaded transmission to insert into the round insertion hole 161 of the fixing frame 16, thereby achieving a rigid connection between the fixing frame 16 and the mounting plate 5. By rotating the screw 19 in the opposite direction, the pin 20 can be pulled out to release the fixation. The operation is convenient and the fixation is reliable.

[0024] In this embodiment, a protective frame 17 is fixedly installed on the top of the mounting plate 5. The inner dimension of the protective frame 17 is larger than the outline dimensions of components such as the first motor 13, worm gear 10, and worm 12, ensuring that the components do not interfere with each other. At the same time, it provides physical protection for the transmission components, preventing the fixed frame 16 from touching the relevant components when it is lowered. The fixed frame 16 is located between the protective frame 17 and the four corner blocks 18. The first motor 13, the two worms 12, the two worm gears 10, and the two first gears 11 are all located inside the protective frame 17. A frustum-shaped guide frame is provided on the top of the protective frame 17. Its function is to provide guidance for the installation of the fixed frame 16, so that the fixed frame 16 can be quickly aligned with the protective frame 17, reducing the installation difficulty. The connection between the two inner sides of the corner blocks 18 and the top is chamfered. The chamfer design can prevent the fixed frame 16 from colliding with the corner blocks 18 during installation, and at the same time guide the fixed frame 16 to be accurately positioned.

[0025] In this embodiment, an annular groove is provided on the outer wall of the screw 19, and a ring is rotatably installed in the annular groove. A connecting rod is fixedly installed on the top of the ring, and a limiting rod is fixedly installed on the corner block 18. The limiting rod passes through the connecting rod and is movably connected to the connecting rod. A first limiting end plate is fixedly installed on the end of the limiting rod away from the pressure plate 8. With this design, the screw 19 can be prevented from detaching from the corner block 18 and lost.

[0026] In this embodiment, a pressure roller mechanism is also provided on the loading plate 7. In some test scenarios (e.g., the surface of the soil has small pits or unevenness), it is necessary to lay a layer of fine sand. The pressure roller mechanism is used to level the fine sand layer after laying the fine sand at the soil test point. The pressure roller mechanism includes two elongated boxes 21, two sliders 22, two follower circular shafts 23, two horizontal plates 24, two vertical plates 25, a circular roller 26, a lead screw 27, and a second motor 28. The two elongated boxes 21 are fixedly installed on the top of the loading plate 7 and located on both sides of the guide telescopic slide rod 14. The two sliders 22 are slidably installed inside the two elongated boxes 21. The two follower circular shafts 23 are respectively installed on the outer walls of the two sliders 22 on opposite sides. The two horizontal plates 24 are respectively fixedly installed on the opposite ends of the two follower circular shafts 23. The two vertical plates 25 are respectively installed on the outer walls of the two sliders 22. At the bottom of the horizontal plate 24, a circular roller 26 is rotatably mounted between two vertical plates 25. The circular roller 26 is made of seamless steel pipe with a rubber coating. A lead screw 27 is rotatably mounted inside one of the elongated boxes 21, with both ends extending beyond the ends of the elongated box 21. The lead screw 27 passes through the corresponding slider 22 and is threadedly connected to the corresponding slider 22. The slider 22 has threaded holes that match the lead screw 27, forming a lead screw and nut pair. A second motor 28 is fixedly mounted on one end of the corresponding elongated box 21, and the output end of the second motor 28 is fixedly connected to one end of the corresponding lead screw 27. When the second motor 28 is started, its output torque drives the lead screw 27 to rotate. The lead screw 27 meshes with the threaded hole of the slider 22, converting the rotational motion into linear motion of the slider 22 along the elongated box 21. The slider 22 drives the circular roller 26 to move synchronously through the follower circular shaft 23, the horizontal plate 24, and the vertical plates 25. The circular roller 26 rolls on the surface of the fine sand layer, achieving leveling of the fine sand layer.

[0027] In this embodiment, two follower circular shafts 23 are rotatably mounted on corresponding sliders 22. A second gear 29 is fixedly sleeved on the outer wall of one of the follower circular shafts 23, and a third motor 30 is fixedly mounted on the corresponding slider 22. A third gear 31 is fixedly sleeved on the output end of the third motor 30, and the third gear 31 meshes with the second gear 29. When the third motor 30 is started, its output torque is reduced by a reducer and drives the third gear 31 to rotate. The third gear 31 meshes with the second gear 29, driving the follower circular shaft 23 to rotate. The follower circular shaft 23 drives the roller 26 to rotate around the axis of the follower circular shaft 23 through the horizontal plate 24 and the vertical plate 25, thereby adjusting the working angle of the roller 26. The ultimate goal is to adjust the height position of the roller 26. In the initial state, the vertical plate 25 is in a horizontal state. In this state, the axis of the roller 26 and the follower circular shaft 23 are on the same horizontal plane, and the roller 26 is located above the loading plate 7. When it is necessary to level the fine sand, the roller 26 is adjusted downward.

[0028] Preferably, two limiting slide rods are slidably installed through the horizontal plate 24, and the vertical plate 25 is fixedly installed at the bottom end of the two limiting slide rods. Springs are sleeved on the limiting slide rods, with the top end of the spring contacting the horizontal plate 24 and the bottom end contacting the vertical plate 25. A second limiting end plate is fixedly installed at the top end of the two limiting slide rods, and the bottom of the second limiting end plate contacts the horizontal plate 24. The function of this spring buffer mechanism is to enable the roller 26 to adapt during the leveling process. When the roller 26 encounters a small protrusion in the fine sand layer, the protrusion pushes the roller 26 upward, compressing the spring on the vertical plate 25, and causing the limiting slide rod to slide upward along the through hole in the horizontal plate 24. When the protrusion disappears, the spring returns to its original shape, pushing the roller 26 downward to reset, ensuring that the roller 26 is always in contact with the fine sand layer and that the contact pressure is stable, preventing the fine sand layer from being compacted or scratched due to localized protrusions.

[0029] Working principle: First, clear away weeds, gravel, loose soil, and other debris from the surface of the soil test point, ensuring that the test area has a diameter of not less than 50cm and no obvious large protrusions or depressions. Place the bearing plate 8 stably in the center of the test point, ensuring that the bearing plate 8 is horizontal and its bottom is fully in contact with the soil surface (or the subsequent fine sand layer), without any gaps or tilting. Move the reaction frame 1 above the test point and adjust its position so that the projection center of the loading plate 7 coincides with the center of the bearing plate 8. Fix the base of the reaction frame 1 to the surrounding stable soil using expansion bolts or ground anchors, and tighten all connecting bolts to ensure that the reaction frame 1 is firmly installed and not loose. The first motor 13 is started, and its output torque is transmitted to the second round shaft through the reducer, driving the worm gears 12 at both ends to rotate synchronously. The worm gears 12 mesh with the worm wheel 10, driving the first round shaft 9 and the first gear 11 to rotate. The first gear 11 meshes with the toothed plate 6, converting the rotational motion into the axial linear motion of the toothed plate 6, which drives the loading plate 7 to descend synchronously, lowering the loading plate 7 to a height that is aligned with the upper surface of the pre-placed pressure plate 8. During the descent, the outer cylinder and inner rod of the guide telescopic slide rod 14 extend and retract synchronously, providing precise guidance for the loading plate 7, limiting its lateral displacement, and ensuring that the loading plate 7 always remains horizontal, avoiding misalignment with the pressure plate 8. When the lower surface of the loading plate 7 gently touches the upper surface of the pressure plate 8, the first motor 13 is turned off. At this time, the self-locking function of the worm gear transmission pair can prevent the loading plate 7 from sinking on its own, ensuring a stable contact state. If the soil surface is flat and the bearing plate 8 is directly attached to the soil, the fine sand laying step can be skipped. If there are small pits on the soil surface, a 3-5mm thick layer of fine sand should be evenly laid on the surface of the soil test point first. Start the third motor 30, adjust the angle of the roller 26 so that it rotates downwards to contact the fine sand layer, and then turn off the third motor 30. Start the second motor 28 to drive the roller 26 to move horizontally along the long box 21, and level it back and forth 2-3 times. The spring buffer mechanism ensures that the contact pressure between the roller 26 and the fine sand layer is stable. After leveling, turn off the second motor 28, and then place the bearing plate 8 back in the center of the fine sand layer to ensure that the bearing plate 8 is horizontally attached. Check the horizontality and attachment of the bearing plate 8 again. Start the hydraulic station and control hydraulic cylinder 2 to apply the load step by step according to the test procedure. The initial load is 0.05 MPa, and the load increases by 0.05 MPa for each subsequent level until it reaches 0.3 MPa (or the soil settlement reaches the specified value). After each load level is applied, maintain the load stable for 1 minute. During this time, the ball joint seat 3 can adaptively adjust its angle within ±5° to counteract any possible load eccentricity and ensure that the output force of hydraulic cylinder 2 is transmitted vertically to loading plate 7. Loading plate 7 evenly transfers the load to bearing plate 8, which then evenly distributes the load to the soil test area to avoid local stress concentration. At the same time, the rebound deformation data of bearing plate 8 is recorded by settlement sensor, and the actual applied load value is recorded by load sensor to ensure accurate data acquisition. After all load levels are tested, control hydraulic cylinder 2 to unload step by step, maintaining the load for 1 minute after each unloading and recording the residual deformation data. When it is necessary to inspect the components inside the protective frame 17, turn the screw 19 in the reverse direction, pull out the pin 20, release the lock of the fixed frame 16, and then raise the protective curtain 15 to carry out the inspection. After the inspection is completed, lower the protective curtain 15 at the bottom of the reaction frame 1, and guide the fixed frame 16 to accurately fall into place through the four-sided frustum guide frame at the top of the protective frame 17, so that the bottom of the fixed frame 16 fits against the mounting plate 5; use a wrench to turn the screw 19 on the four corner blocks 18, push the pin 20 into the round insertion hole 161 of the fixed frame 16, and complete the sealing of the protective cavity to prevent external dust and sand from interfering with the transmission components.

[0030] Second embodiment: In a second embodiment of the present invention, a loading method for on-site soil resilient modulus testing is provided, comprising the following steps: T1: Clean the surface of the soil test point and ensure that the diameter of the test area is not less than 50cm; place the bearing plate 8 stably in the center of the test point and ensure that it is horizontally attached; T2: Move the reaction frame 1 above the test point so that the center of the projection of the loading plate 7 coincides with the center of the bearing plate 8, and fix the base of the reaction frame 1; check the equipment wiring, hydraulic station status and settlement sensor to ensure normal operation. T3: Start the first motor 13 to drive the loading plate 7 to descend, so that the lower surface of the loading plate 7 gently contacts the upper surface of the pre-placed pressure plate 8. Then, turn off the first motor 13 and the worm gear self-locks and fixes the position. T4: Start the hydraulic station and control the hydraulic cylinder 2 to load gradually from 0.05MPa, with each load increasing by 0.05MPa. Maintain the load at each level for 1 minute and record the rebound deformation and load data. During the loading process, the ball joint seat 3 self-adjusts and the guide telescopic slide rod ensures that the loading plate 7 and the pressure plate 8 fit tightly. T5: After loading is completed, unload step by step and record the residual deformation data; start the first motor 13 to drive the loading plate 7 to reset, remove the reaction frame 1, and complete the test.

[0031] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A loading device for on-site testing of the resilient modulus of subgrade, comprising a reaction frame, a hydraulic cylinder, a ball joint seat, a loading plate, and a bearing plate, wherein the hydraulic cylinder is fixedly installed at the bottom of the reaction frame, the top end of the ball joint seat is fixedly installed on the output end of the hydraulic cylinder, the loading plate is disposed below the ball joint seat, and the bearing plate is disposed below the loading plate, characterized in that, A pad is fixedly installed at the bottom of the ball joint seat, and a mounting plate is fixedly installed at the bottom of the pad. Two toothed plates are slidably installed through the mounting plate. A loading plate is fixedly installed at the bottom of the two toothed plates. Two first round shafts are rotatably installed at the top of the mounting plate. A first gear is fixedly sleeved on each of the two first round shafts. The two first gears mesh with the corresponding toothed plates. A worm gear is fixedly sleeved at one end of each of the two first round shafts. A second round shaft is rotatably installed at the top of the mounting plate. Worms are fixedly installed at both ends of the second round shaft. The two worms mesh with the corresponding worm gears. A first motor is fixedly installed at the top of the mounting plate. The output end of the first motor is fixedly connected to the end of the corresponding worm away from the second round shaft.

2. The loading device for on-site soil resilient modulus testing according to claim 1, characterized in that, The pad cylinder is provided with a guide telescopic slide rod, which includes an outer cylinder and an inner rod. The outer cylinder is slidably installed inside the pad cylinder, and the inner rod is slidably installed inside the outer cylinder. The bottom end of the inner rod extends to the bottom of the mounting plate and is fixedly connected to the loading plate.

3. The loading device for on-site soil resilient modulus testing according to claim 1, characterized in that, Two suspension rods are fixedly installed at the bottom of the reaction frame. An axially retractable protective curtain is fixedly installed at the bottom of the two suspension rods. A fixed frame is fixedly installed at the bottom of the protective curtain. The bottom of the fixed frame is in contact with the mounting plate. Circular insertion holes are provided at the four corners of the fixed frame. Locking mechanisms are provided at the four corners of the top of the mounting plate. The locking mechanisms are used to cooperate with the circular insertion holes to fix the fixed frame.

4. The loading device for on-site soil resilient modulus testing according to claim 3, characterized in that, The locking mechanism includes a corner block, a screw, and a pin. The corner block is fixedly installed on the top of the mounting plate. The screw is threaded onto the corner block. The pin is located at one end of the screw and is integrally formed with the screw. The end of the pin away from the screw extends into the circular insertion hole.

5. The loading device for on-site soil resilient modulus testing according to claim 4, characterized in that, A protective frame is fixedly installed on the top of the mounting plate. The fixed frame is located between the protective frame and the four corner blocks. The first motor, two worm gears, two worm wheels and two first gears are all located inside the protective frame. A frustum-shaped guide frame is provided on the top of the protective frame. The connection between the two inner sides of the corner blocks and the top is chamfered.

6. The loading device for on-site soil resilient modulus testing according to claim 5, characterized in that, An annular groove is formed on the outer wall of the screw, and a ring is rotatably installed in the annular groove. A connecting rod is fixedly installed on the top of the ring, and a limiting rod is fixedly installed on the corner block. The limiting rod passes through the connecting rod and is movably connected to the connecting rod. A first limiting end plate is fixedly installed on the end of the limiting rod away from the pressure plate.

7. The loading device for on-site soil resilient modulus testing according to claim 2, characterized in that, The loading plate is also equipped with a pressure roller mechanism, which is used to level the fine sand layer after the fine sand is laid at the soil test point. The pressure roller mechanism includes two elongated boxes, two sliders, two follower round shafts, two horizontal plates, two vertical plates, a round roller, a lead screw, and a second motor. The two elongated boxes are fixedly installed on the top of the loading plate and located on both sides of the guide telescopic slide rod. The two sliders are slidably installed inside the two elongated boxes. The two follower round shafts are respectively installed on the outer walls of the two sliders on opposite sides. The two horizontal plates are fixedly installed on opposite ends of the two follower round shafts. The two vertical plates are respectively installed at the bottom of the two horizontal plates. The round roller is rotatably installed between the two vertical plates. The lead screw is rotatably installed inside one of the elongated boxes, with both ends extending beyond the ends of the elongated box. The lead screw passes through the corresponding slider and is threadedly connected to the corresponding slider. The second motor is fixedly installed at one end of the corresponding elongated box, and the output end of the second motor is fixedly connected to one end of the corresponding lead screw.

8. The loading device for on-site soil resilient modulus testing according to claim 7, characterized in that, Both of the following circular shafts are rotatably mounted on the corresponding sliders. A second gear is fixedly sleeved on the outer wall of one of the following circular shafts, and a third motor is fixedly mounted on the corresponding slider. A third gear is fixedly sleeved on the output end of the third motor, and the third gear meshes with the second gear.

9. The loading device for on-site soil resilient modulus testing according to claim 7, characterized in that, Two limiting slide rods are slidably installed through the horizontal plate. The vertical plate is fixedly installed at the bottom end of the two limiting slide rods. A spring is sleeved on the limiting slide rod. The top end of the spring contacts the horizontal plate and the bottom end contacts the vertical plate. A second limiting end plate is fixedly installed at the top end of the two limiting slide rods. The bottom of the second limiting end plate contacts the horizontal plate.

10. A loading method for in-situ soil resilient modulus testing using a loading device as described in any one of claims 1-9, characterized in that, Includes the following steps: T1: Clean the surface of the soil test point and ensure that the diameter of the test area is not less than 50cm; place the bearing plate stably in the center of the test point and ensure that it is horizontally aligned; T2: Move the reaction frame above the test point so that the center of the loading plate projection coincides with the center of the bearing plate, and fix the reaction frame base; check the equipment wiring, hydraulic station status and settlement sensor to ensure normal operation; T3: Start the first motor to drive the loading plate to descend, so that the lower surface of the loading plate gently contacts the upper surface of the pre-placed bearing plate. Then, turn off the first motor and the worm gear self-locks and fixes the position. T4: Start the hydraulic station and control the hydraulic cylinder to load gradually from 0.05MPa, with each load increasing by 0.05MPa. Maintain the load at each level for 1 minute and record the rebound deformation and load data. During the loading process, the ball joint seat self-adjusts and the guide telescopic slide rod ensures that the loading plate and the pressure plate are in close contact. T5: After loading is completed, unload step by step and record the residual deformation data; start the first motor to drive the loading plate to reset, remove the reaction frame, and complete the test.

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