A loading device and loading method for in-situ soil base modulus test

Abstract

The application provides a loading device and a loading method for field soil base resilience modulus testing, and belongs to the technical field of roadbed engineering detection. The loading device for field soil base resilience modulus testing comprises a counterforce frame, a hydraulic cylinder, a spherical hinge base, a loading plate and a pressure bearing plate. The bottom of the spherical hinge base is fixedly provided with a cushioning sleeve. The bottom of the cushioning sleeve is fixedly provided with a mounting plate. Two toothed plates are slidably installed through the mounting plate. The top of the mounting plate is rotatably provided with two first circular shafts. First gears are fixedly arranged on the two first circular shafts. The loading device for field soil base resilience modulus testing has the advantages that the loading distance can be greatly adjusted to adapt to low-position soil base testing scenes, the device is convenient and efficient to operate and has comprehensive protection functions, the integrated pressure roller mechanism can assist fine sand leveling, and the efficiency of field soil base resilience modulus testing can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of subgrade engineering detection, and particularly relates to a loading device and a loading method for testing the modulus of resilience of a soil base in situ. BACKGROUND

[0002] The modulus of resilience of a soil base is a core index for road engineering design and quality evaluation, and directly reflects the elastic deformation capacity of the soil base under vehicle load. The accuracy of the in-situ test results directly affects the design of the thickness of the road structure layer and the service life. At present, the bearing plate method is mainly used in the industry for in-situ testing of the modulus of resilience of a soil base. The core equipment is a loading device, which mainly consists of a counterforce frame, a hydraulic jack (or a hydraulic cylinder), a pressure plate, a loading plate and the like. The counterforce frame provides a counterforce support, the hydraulic jack outputs a graded load, the load is transmitted to the pressure plate through the loading plate, and finally acts on the test point of the soil base. The modulus of resilience is calculated in combination with the settlement data.

[0003] In actual engineering testing, some test points of the soil base are located at a low position due to site conditions (such as road excavation, low-lying sections, and soil base surface layers treated by excavation). The traditional loading device adjusts the distance between the loading plate and the counterforce frame by means of the piston stroke of the hydraulic jack or a simple manual telescopic structure. The adjustment stroke is limited. When the soil base surface position is too low below the preset height of the bottom of the counterforce frame, the loading plate cannot effectively fit the pressure plate placed on the soil base surface in advance, resulting in unstable load transmission or even failure to test. Even if some devices can extend the distance by adding shims and the like, there are problems such as complicated installation, poor stability, easy load transmission eccentricity and the like, which seriously affect the testing efficiency and data accuracy.

[0004] Therefore, it is necessary to provide a new loading device and a loading method for testing the modulus of resilience of a soil base in situ to solve the above problems. SUMMARY

[0005] The technical problem solved by the present application is to provide a hydraulic tensioning instrument capable of greatly adjusting the loading distance to adapt to the low-position soil base testing scene, having comprehensive protection function and being convenient and efficient to operate, integrating a pressing roller mechanism to assist fine sand leveling, and effectively improving the efficiency of in-situ testing of the modulus of resilience of a soil base.

[0006] To solve the above technical problems, the loading device for in-situ soil base resilience modulus test is provided, which comprises a counterforce frame, a hydraulic cylinder, a spherical hinge base, a loading plate and a pressure bearing plate, the hydraulic cylinder is fixedly installed at the bottom of the counterforce frame, the top end of the spherical hinge base is fixedly installed on the output end of the hydraulic cylinder, the loading plate is arranged below the spherical hinge base, the pressure bearing plate is arranged below the loading plate, the bottom of the spherical hinge base is fixedly installed with a pad connecting barrel, the bottom of the pad connecting barrel is fixedly installed with a mounting plate, two tooth plates are slidably installed through the mounting plate, the loading plate is fixedly installed at the bottom of the two tooth plates, two first circular shafts are rotatably installed at the top of the mounting plate, first gears are fixedly sleeved on the two first circular shafts, the two first gears are engaged with the corresponding tooth plates, a worm wheel is fixedly sleeved on one end of the two first circular shafts, a second circular shaft is rotatably installed at the top of the mounting plate, worm gears are fixedly installed at the two ends of the second circular shaft, the two worm gears are engaged with the corresponding worm wheels, a first motor is fixedly installed at the top of the mounting plate, and the output end of the first motor is fixedly connected with the end of the corresponding worm gear away from the second circular shaft.

[0007] Further, a guide telescopic slide rod is arranged in the pad connecting barrel, the guide telescopic slide rod comprises an outer barrel and an inner rod, the outer barrel is slidably installed in the pad connecting barrel, and the inner rod is slidably installed in the outer barrel, the bottom end of the inner rod extends below the mounting plate and is fixedly connected with the loading plate.

[0008] Further, two hanging rods are fixedly installed at the bottom of the counterforce frame, an axially telescopic protective curtain is fixedly installed at the bottom of the two hanging 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 formed at the positions of the four corners of the fixed frame, and locking mechanisms are arranged at the positions of the four corners of the top of the mounting plate, the locking mechanisms are used for fixing the fixed frame in cooperation with the circular insertion holes.

[0009] Preferably, the locking mechanism comprises an angle block, a screw rod and a bolt, the angle block is fixedly installed at the top of the mounting plate, the screw rod is threadedly installed on the angle block, the bolt is arranged at one end of the screw rod and is integrally formed with the screw rod, and the end of the bolt away from the screw rod extends into the circular insertion hole.

[0010] Further, a protective frame is fixedly installed at the top of the mounting plate, the fixed frame is located between the protective frame and the four angle blocks, the first motor, the two worm gears, the two worm wheels and the two first gears are located in the protective frame, a four-prism-taip-shaped guide frame is arranged at the top of the protective frame, and the connection positions of the two inner sides and the top of the angle block are designed as chamfers.

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

[0012] Further, the loading plate is further provided with a pressure roller mechanism, which is used for flattening the fine sand layer after the fine sand is laid on the soil foundation test point.

[0013] The pressure roller mechanism comprises two long boxes, two sliding blocks, two follow-up circular shafts, two cross plates, two vertical plates, a circular roller, a lead screw and a second motor, both of the long boxes are fixedly installed on the top of the loading plate and are located on the two sides of the guide telescopic slide rod, both of the sliding blocks are slidably installed in the two long boxes, both of the follow-up circular shafts are installed on the outer walls of the two sliding blocks away from each other, both of the cross plates are fixedly installed on the ends of the two follow-up circular shafts away from each other, both of the vertical plates are installed on the bottoms of the two cross plates, the circular roller is rotatably installed between the two vertical plates, the lead screw is rotatably installed in one of the long boxes and extends out of the two ends of the long box, the lead screw penetrates through the corresponding sliding block and is threadedly connected with the corresponding sliding block, and the second motor is fixedly installed on one end of the corresponding long box and is fixedly connected with one end of the corresponding lead screw.

[0014] Preferably, both of the follow-up circular shafts are rotatably installed on the corresponding sliding blocks, a second gear is fixedly sleeved on the outer wall of one of the follow-up circular shafts, a third motor is fixedly installed on the corresponding sliding block, a third gear is fixedly sleeved on the output end of the third motor, and the third gear is engaged with the second gear.

[0015] Preferably, two limiting slide rods are penetratively and slidably installed on the cross plate, the vertical plate is fixedly installed on 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 cross plate, the bottom end of the spring is in contact with the vertical plate, a second limiting end plate is fixedly installed on the top end of the two limiting slide rods, and the bottom of the second limiting end plate is in contact with the cross plate.

[0016] To solve the above problems, the application further provides a use method of the loading device for the field soil foundation resilience modulus test.

[0017] T1: clean the surface of the soil foundation test point of sundries, ensure that the diameter of the test area is not less than 50 cm, place the pressure plate stably at the center of the test point, and ensure that the pressure plate is horizontally attached;

[0018] T2: Move the counterforce frame to above the test point, make the loading plate projection center coincide with the bearing plate center, fix the counterforce frame base; check the equipment wiring, hydraulic station state and settlement sensor, and ensure normal operation;

[0019] T3: Start the first motor to drive the loading plate to descend, make the lower surface of the loading plate lightly adhere to the upper surface of the bearing plate placed in advance, turn off the first motor, and the worm gear self-locking fixes the position;

[0020] T4: Start the hydraulic station, control the hydraulic cylinder to start loading from 0.05MPa, each load increment is 0.05MPa, each load is kept stable for 1 minute, and the rebound deformation and load data are recorded; the ball hinge base self-adapts to level, and the guide telescopic slide rod ensures that the loading plate and the bearing plate are closely adhered;

[0021] T5: After loading is completed, unload step by step, record the residual deformation data; start the first motor to drive the loading plate to reset, remove the counterforce frame, and complete the test.

[0022] Compared with the related art, the loading device and the loading method for testing the rebound modulus of the soil base on site provided by the present application have the following beneficial effects:

[0023] The present application realizes the large adjustment of the distance between the loading plate and the counterforce frame through the setting of the tooth plate, the first gear, the worm gear, the worm, the first motor and the guide telescopic slide rod, and solves the problem of limited adjustment range of the traditional device. In the core transmission mechanism, the motor converts the rotary motion into the rotation of the gear through the worm gear, and then drives the loading plate to stably ascend and descend through the meshing of the gear and the tooth plate. The worm gear transmission has reliable self-locking function, can prevent the loading plate from self-settling under the action of load, can keep the adhering state stable even if it is left for a long time, and solves the problems of the traditional device, such as relying on gaskets to extend the distance, complicated installation and easy eccentricity of load transmission;

[0024] The present application adopts the telescopic protective curtain installed at the bottom of the counterforce frame, cooperates with the bottom fixed frame and the protective frame at the top of the mounting plate, can completely protect the core transmission components inside, effectively isolates the dust, sand and other sundries on site, avoids the wear, jamming or rust of the components, and prolongs the service life; the lock holding mechanism is designed by combining the angle block, the screw rod and the bolt, only needs to rotate the screw rod by a wrench to realize the quick locking and unlocking of the fixed frame, and is convenient and fast to operate;

[0025] 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

[0026] Figure 1 A schematic diagram of the loading device for on-site soil resilient modulus testing provided by the present invention;

[0027] Figure 2 for Figure 1 The diagram shown is a structural schematic of the protective curtain and the reaction frame in a separated state.

[0028] Figure 3 for Figure 2 An enlarged schematic diagram of part A shown;

[0029] Figure 4 for Figure 2 The diagram shows the structural schematic of the components mounted on the mounting plate.

[0030] Figure 5 for Figure 1 A partial front view of the loading device used for on-site soil resilient modulus testing;

[0031] Figure 6 for Figure 4 A cross-sectional view of the guide telescopic slide rod shown;

[0032] Figure 7 for Figure 4 The diagram shows the structure of the corner piece;

[0033] Figure 8 for Figure 7 The diagram shows the structure of the screw.

[0034] Figure 9 for Figure 4 The diagram shows the connection structure between the circular roller and the long box.

[0035] Figure 10 forFigure 9 B part enlarged view shown in the figure;

[0036] Figure 11 For Figure 9 The connection diagram of the cross plate and the vertical plate shown.

[0037] Figure mark:

[0038] 1, counterforce frame; 2, hydraulic cylinder; 3, spherical hinge base; 4, pad connecting tube; 5, mounting plate; 6, toothed plate; 7, loading plate; 8, pressure bearing plate; 9, first circular shaft; 10, worm gear; 11, first gear; 12, worm; 13, first motor; 14, guide telescopic slide rod; 15, protective curtain; 16, fixed frame; 17, protective frame; 18, angle block; 19, screw rod; 20, bolt; 21, long box; 22, sliding block; 23, follow-up circular shaft; 24, cross plate; 25, vertical plate; 26, circular roller; 27, lead screw; 28, second motor; 29, second gear; 30, third motor; 31, third gear; 161, circular insertion hole. DETAILED DESCRIPTION

[0039] The application will be further described below in conjunction with the drawings and embodiments.

[0040] First embodiment:

[0041] Please refer to Figures 1-11 In the first embodiment of the application, a loading device for field soil base resilience modulus testing is provided, which comprises: a counterforce frame 1, a hydraulic cylinder 2, a spherical hinge base 3, a loading plate 7 and a pressure bearing plate 8. The counterforce frame 1 provides core counterforce support for the overall device and is formed by welding high-strength alloy steel. The hydraulic cylinder 2 is fixedly installed at the bottom of the counterforce frame 1. The hydraulic cylinder 2 realizes stepwise loading control through a matching hydraulic station. The top end of the spherical hinge base 3 is fixedly installed on the output end of the hydraulic cylinder 2. The spherical hinge base 3 can realize angle self-adaptive adjustment within a range of ±5°, can offset load eccentricity caused by installation deviation of the hydraulic cylinder 2, slight inclination of the counterforce frame 1 or initial unevenness of the soil base surface, and can ensure that the output force of the hydraulic cylinder 2 is always transmitted to the pressure bearing plate 8 along the vertical direction. The loading plate 7 is arranged below the spherical hinge base 3, and the pressure bearing plate 8 is arranged below the loading plate 7. The pressure bearing plate 8 is forged by high-strength alloy steel, has a diameter of 30 cm, a plate thickness not less than 20 mm, and a bottom processed into a smooth plane (roughness Ra≤1.6 μm), so as to ensure uniform contact with the surface of the soil base, uniformly diffuse the load to the soil testing area, and avoid local stress concentration.

[0042] The bottom of the ball hinge base 3 is fixedly provided with a cushioning sleeve 4, the bottom of the cushioning sleeve 4 is fixedly provided with a mounting plate 5, the cushioning sleeve 4 is a hollow cylindrical structure, the inner diameter of which matches the outer diameter of the guide telescopic slide rod 14 to be mentioned below, the top of the cushioning sleeve 4 is bolted to the ball hinge base 3 through a flange, the bottom of the cushioning sleeve 4 is welded to the mounting plate 5, two toothed plates 6 are slidably installed on the mounting plate 5, a loading plate 7 is fixedly installed on the bottom of the two toothed plates 6, the two toothed plates 6 are symmetrically arranged, the sliding direction of the two toothed plates 6 is consistent with the stress direction of the bearing plate 8, the top of the mounting plate 5 is rotatably provided with two first circular shafts 9, the first circular shafts 9 are rotatably installed on the top of the mounting plate 5 through bearing seats, a first gear 11 is fixedly sleeved on each of the two first circular shafts 9, the two first gears 11 are engaged with the corresponding toothed plates 6, a worm wheel 10 is fixedly sleeved on one end of each of the two first circular shafts 9, a second circular shaft is rotatably installed on the top of the mounting plate 5, the second circular shaft is also rotatably installed on the top of the mounting plate 5 through a bearing seat, a worm 12 is fixedly installed on each end of the second circular shaft, the two worms 12 are engaged with the corresponding worm wheels 10, the worm 12 and the worm wheel 10 form a worm and gear transmission pair, have a self-locking function, and can prevent the loading plate 7 from self-settling under the action of the load, a first motor 13 is fixedly installed on the top of the mounting plate 5, and the output end of the first motor 13 is fixedly connected to one end of the corresponding worm 12 away from the second circular shaft.

[0043] The first motor 13 is started, the output torque of the first motor 13 is transmitted to the second circular shaft after being decelerated by a reducer, the two ends of the worm 12 are driven to rotate synchronously, the worm 12 is engaged with the worm wheel 10 to convert the horizontal rotation into the rotation of the first circular shaft 9; the first circular shaft 9 drives the first gear 11 to rotate, the first gear 11 is engaged with the toothed plate 6 to convert the rotation into the axial linear motion of the toothed plate 6, and finally drives the loading plate 7 to ascend and descend. Since the two worms 12 rotate in opposite directions and the worm wheels 10 have the same number of teeth, the movement directions of the two toothed plates 6 are completely synchronized, so that the loading plate 7 always remains horizontal during the ascending and descending process, and the precise fitting of the bearing plate 8 and the surface of the soil base is realized in cooperation with the leveling function of the ball hinge base 3.

[0044] In the embodiment, the guide telescopic slide rod 14 is arranged in the cushioning sleeve 4, the guide telescopic slide rod 14 includes an outer sleeve and an inner rod, the outer sleeve is slidably installed in the cushioning sleeve 4, and the inner rod is slidably installed in the outer sleeve, the bottom end of the inner rod extends below the mounting plate 5 and is fixedly connected to the loading plate 7, the guide telescopic slide rod 14 provides precise guidance for the ascending and descending motion of the loading plate 7, limits the lateral displacement of the loading plate 7, ensures the stability of the meshing gap between the toothed plate 6 and the first gear 11, and avoids the load transmission deviation caused by the deviation of the loading plate 7.

[0045] In this embodiment, the bottom of the counterforce frame 1 is fixedly provided with two hangers, the bottom of each hanger is fixedly provided with an axially retractable protective curtain 15, the main body of the protective curtain 15 is connected by cloth sleeves and square boxes, and the protective curtain 15 can be extended and retracted within a certain range, the bottom of the protective curtain 15 is fixedly provided with a fixed frame 16, the bottom of the fixed frame 16 is in contact with the mounting plate 5, circular insertion holes 161 are formed at the four corners of the fixed frame 16, and the top of the mounting plate 5 is provided with a locking mechanism at each corner.

[0046] Preferably, the locking mechanism comprises an angle block 18, a screw rod 19 and a bolt 20, the angle block 18 is fixedly installed on the top of the mounting plate 5, the angle block 18 is a right-angled triangular steel structure and is fixed to the mounting plate 5 by welding, the screw rod 19 is threadedly installed on the angle block 18, the bolt 20 is arranged at one end of the screw rod 19 and is integrally formed with the screw rod 19, the end of the bolt 20 is processed into a semispherical chamfer, the bolt 20 is convenient to insert into the circular insertion hole 161, and the end of the bolt 20 away from the screw rod 19 extends into the circular insertion hole 161; when the fixed frame 16 is attached to the mounting plate 5, the screw rod 19 is rotated by using a wrench, the bolt 20 is axially moved by thread transmission, the bolt 20 is inserted into the circular insertion hole 161 of the fixed frame 16, and the rigid connection between the fixed frame 16 and the mounting plate 5 is achieved; the screw rod 19 is reversely rotated, the bolt 20 can be pulled out, the fixed frame 16 is released, the operation is convenient and the fixing is reliable.

[0047] In this embodiment, the top of the mounting plate 5 is fixedly provided with a protective frame 17, the inner side of the protective frame 17 is larger than the contour size of the first motor 13, the worm wheel 10, the worm 12 and other components, the components are ensured to be free from interference, the physical protection is provided for the transmission components, the related components are avoided from being touched when the fixed frame 16 is lowered, the fixed frame 16 is located between the protective frame 17 and the four angle blocks 18, the first motor 13, the two worms 12, the two worm wheels 10 and the two first gears 11 are located in the protective frame 17, the top of the protective frame 17 is provided with a four-prism-taip guide frame, the guide frame is used for guiding the installation of the fixed frame 16, the fixed frame 16 can be quickly aligned with the protective frame 17, the installation difficulty is reduced, and the connection between the two inner sides and the top of the angle block 18 is chamfered, the chamfered design can avoid the knocking between the fixed frame 16 and the angle block 18 during the installation of the fixed frame 16 and guide the accurate positioning of the fixed frame 16.

[0048] In this embodiment, an annular groove is formed in the outer wall of the screw rod 19, a circular ring is rotatably installed in the annular groove, a connecting rod is fixedly installed on the top of the circular ring, a limiting rod is fixedly installed on the angle block 18, the limiting rod penetrates through the connecting rod and is movably connected with the connecting rod, a first limiting end plate is fixedly installed on the end of the limiting rod away from the pressure receiving plate 8, and the screw rod 19 can be avoided from being separated from the angle block 18 and lost.

[0049] In this embodiment, the loading plate 7 is also provided with a pressure roller mechanism. In some test scenarios (for example, the surface of the soil base has small pits or unevenness), a layer of fine sand needs to be laid, and the pressure roller mechanism is used to flatten the fine sand layer after laying the fine sand on the soil base test point;

[0050] The pressure roller mechanism comprises two long boxes 21, two sliding blocks 22, two follow-up round shafts 23, two cross plates 24, two vertical plates 25, a round roller 26, a lead screw 27 and a second motor 28. The two long 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 sliding blocks 22 are slidably installed in the two long boxes 21 respectively. The two follow-up round shafts 23 are installed on the outer walls of the two sliding blocks 22 respectively. The two cross plates 24 are fixedly installed on the ends of the two follow-up round shafts 23 respectively. The two vertical plates 25 are installed on the bottoms of the two cross plates 24 respectively. The round roller 26 is rotatably installed between the two vertical plates 25. The round roller 26 is made of seamless steel pipe and is wrapped with a rubber layer on the surface. The lead screw 27 is rotatably installed in one of the long boxes 21 and extends out of the two ends of the long box 21. The lead screw 27 penetrates through the corresponding sliding block 22 and is threadedly connected with the corresponding sliding block 22. The sliding block 22 is provided with a threaded hole matched with the lead screw 27, forming a lead screw nut pair. The second motor 28 is fixedly installed on one end of the corresponding long box 21. The output end of the second motor 28 is fixedly connected with one end of the corresponding lead screw 27. Starting the second motor 28, the output torque drives the lead screw 27 to rotate. The lead screw 27 is engaged with the threaded hole of the sliding block 22, converting the rotary motion into the linear motion of the sliding block 22 along the long box 21. The sliding block 22 drives the round roller 26 to move synchronously through the follow-up round shaft 23, the cross plate 24 and the vertical plate 25. The round roller 26 rolls on the surface of the fine sand layer, achieving the flattening of the fine sand layer.

[0051] In this embodiment, the two follow-up round shafts 23 are rotatably installed on the corresponding sliding blocks 22. A second gear 29 is fixedly sleeved on the outer wall of one of the follow-up round shafts 23. A third motor 30 is fixedly installed on the corresponding sliding block 22. A third gear 31 is fixedly sleeved on the output end of the third motor 30. The third gear 31 is engaged with the second gear 29. Starting the third motor 30, the output torque drives the third gear 31 to rotate after being decelerated by the speed reducer. The third gear 31 is engaged with the second gear 29 for transmission, driving the follow-up round shaft 23 to rotate. The follow-up round shaft 23 drives the round roller 26 to rotate around the axis of the follow-up round shaft 23 through the cross plate 24 and the vertical plate 25, achieving the adjustment of the working angle of the round roller 26. The final purpose is to adjust the height position of the round roller 26. In the initial state, the vertical plate 25 is in the horizontal state. In this state, the axis of the round roller 26 is located in the same horizontal plane as the follow-up round shaft 23. The round roller 26 is located above the loading plate 7 as a whole. When it is necessary to flatten the fine sand, the round roller 26 is adjusted downward.

[0052] Preferably, two limiting slide rods are installed on the horizontal plate 24 and slide through the horizontal plate 24, the vertical plate 25 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 24, the bottom end of the spring is in contact with the vertical plate 25, the top end of the two limiting slide rods is fixedly installed with a second limiting end plate, and the bottom of the second limiting end plate is in contact with the horizontal plate 24. The function of the spring buffer mechanism is to make the round roller 26 have self-adaptive ability during the leveling process. When the round roller 26 encounters a small protrusion of the fine sand layer, the protrusion will push the round roller 26 to move upward, the vertical plate 25 compresses the spring, and the limiting slide rod slides upward along the through hole of the horizontal plate 24; when the protrusion disappears, the spring restores the deformation and pushes the round roller 26 to reset downward, so that the round roller 26 is always in contact with the fine sand layer and the contact pressure is stable, and the fine sand layer is prevented from being compacted or scratched due to local protrusions.

[0053] Working principle:

[0054] First, clean the weeds, gravel, floating soil and other sundries on the surface of the test point of the soil foundation, ensure that the diameter of the test area is not less than 50 cm, there is no obvious large protrusion or depression, place the pressure plate 8 stably at the center position of the test point, ensure that the pressure plate 8 is horizontal, the bottom is fully attached to the surface of the soil foundation (or the fine sand layer subsequently laid), and there is no suspension or inclination; move the counterforce frame 1 above the test point, adjust the position of the counterforce frame 1, so that the projection center of the loading plate 7 coincides with the center of the pressure plate 8; fix the base of the counterforce frame 1 to the surrounding stable soil body through the expansion bolts or ground anchors, tighten all the connecting bolts, and ensure that the counterforce frame 1 is firmly installed and has no looseness;

[0055] Start the first motor 13, the output torque of which is transmitted to the second circular shaft through the reducer, so as to drive the two ends of the worm 12 to rotate synchronously; the worm 12 is in meshing transmission with the worm gear 10, so as to drive the first circular shaft 9 and the first gear 11 to rotate; the first gear 11 is in meshing transmission with the toothed plate 6, so as to convert the rotary motion into the axial linear motion of the toothed plate 6, and drive the loading plate 7 to descend synchronously; in the descending process, the outer cylinder of the guide telescopic slide rod 14 and the inner rod are synchronously telescopic, so as to provide accurate guidance for the loading plate 7, limit the transverse displacement of the loading plate 7, ensure that the loading plate 7 always remains horizontal, and avoid misalignment with the pressure plate 8; when the lower surface of the loading plate 7 is lightly attached to 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 by itself, and ensure that the attachment state is stable;

[0056] If the soil base surface is flat, the bearing plate 8 has been directly attached to the soil base, and the fine sand laying step can be skipped; if the soil base surface has small pits and bumps, a 3-5mm thick layer of fine sand needs to be uniformly laid on the surface of the soil base test point; start the third motor 30, adjust the angle of the round roller 26, make it rotate downward to contact the fine sand layer, and turn off the third motor 30; start the second motor 28 to drive the round roller 26 to translate along the long box 21, and flatten 2-3 times back and forth, the spring buffer mechanism ensures that the contact pressure of the round roller 26 with the fine sand layer is stable, and after flattening, the second motor 28 is turned off, and the bearing plate 8 is placed again in the center of the fine sand layer to ensure that the bearing plate 8 is horizontally attached, and the horizontal and attached state of the bearing plate 8 is checked again;

[0057] Start the hydraulic station, control the hydraulic cylinder 2 to apply load step by step according to the test procedure, the initial load is 0.05MPa, then each load is increased by 0.05MPa, until 0.3MPa (or the soil base settlement reaches the specified value); after each load is applied, the load is kept stable for 1 minute, during which the spherical hinge seat 3 can be self-adaptively adjusted within an angle range of ±5° to offset possible load eccentricity, and ensure that the output force of the hydraulic cylinder 2 is transmitted to the loading plate 7 along the vertical direction; the loading plate 7 uniformly transmits the load to the bearing plate 8, and the bearing plate 8 uniformly diffuses the load to the soil base test area to avoid local stress concentration; at the same time, the rebound deformation data of the bearing plate 8 is recorded by the settlement sensor, and the actual applied load value is recorded by the load sensor to ensure accurate data collection. After all load level tests are completed, the hydraulic cylinder 2 is controlled to unload step by step, and the residual deformation data is recorded after each unloading step for 1 minute;

[0058] When the components in the protective frame 17 need to be maintained, the screw rod 19 is reversed, the bolt 20 is pulled out, the locking of the fixed frame 16 is released, the protective curtain 15 is retracted upward, and then the maintenance can be carried out. After the maintenance is completed, the protective curtain 15 at the bottom of the counterforce frame 1 is lowered, the four prismatic guide frames at the top of the protective frame 17 are guided to accurately position the fixed frame 16, and the bottom of the fixed frame 16 is attached to the mounting plate 5. The screw rod 19 on the four corner blocks 18 is turned by a wrench, the bolt 20 is inserted into the circular insertion hole 161 of the fixed frame 16, and the protective cavity is closed to avoid external dust and sand interfering with the transmission components.

[0059] Second embodiment:

[0060] In the second embodiment of the present application, a loading method for in-situ soil base rebound modulus test is provided, comprising the following steps:

[0061] T1: clean the surface of the soil base test point of sundries, ensure that the test area diameter is not less than 50cm; place the bearing plate 8 stably in the center of the test point to ensure horizontal attachment;

[0062] T2: move the counter-force frame 1 to above the test point, so that the projection center of the loading plate 7 coincides with the center of the bearing plate 8, and fix the base of the counter-force frame 1; check the equipment wiring, the hydraulic station state and the settlement sensor, and ensure normal operation;

[0063] T3: start the first motor 13 to drive the loading plate 7 to descend, so that the lower surface of the loading plate 7 lightly adheres to the upper surface of the bearing plate 8 placed in advance, turn off the first motor 13, and the worm gear self-locking fixes the position;

[0064] T4: start the hydraulic station, control the hydraulic cylinder 2 to start loading step by step from 0.05 MPa, each load increment is 0.05 MPa, each load is kept stable for 1 minute, record the rebound deformation and load data; the ball hinge base 3 self-adapts to level during the loading process, and the guide telescopic slide rod ensures that the loading plate 7 and the bearing plate 8 are closely adhered;

[0065] T5: after the loading is completed, unload step by step, record the residual deformation data; start the first motor 13 to drive the loading plate 7 to reset, remove the counter-force frame 1, and complete the test.

[0066] The above is only an embodiment of the present application, and does not limit the patent range of the present application, and any equivalent structure or equivalent process transformation using the content of the specification and the drawings, or direct or indirect application in other related technical fields, are also included in the patent protection range of the present application.

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 an 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. The pad is provided with a guide telescopic slide rod, which includes an outer cylinder and an inner rod. The outer cylinder is slidably installed in the pad, and the inner rod is slidably installed in 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. 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 circular shafts, two horizontal plates, two vertical plates, a circular 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 circular 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 circular shafts. The two vertical plates are respectively installed at the bottom of the two horizontal plates. The circular 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.

2. 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.

3. The loading device for on-site soil resilient modulus testing according to claim 2, 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.

4. The loading device for on-site soil resilient modulus testing according to claim 3, 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.

5. The loading device for on-site soil resilient modulus testing according to claim 4, 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.

6. The loading device for on-site soil resilient modulus testing according to claim 1, 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.

7. The loading device for on-site soil resilient modulus testing according to claim 1, 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.

8. A loading method for in-situ soil resilient modulus testing using a loading device as described in any one of claims 1-7, 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 and worm self-lock to fix 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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