An automated calibration device and method for three-dimensional earth pressure cells

Abstract

This invention discloses an automated calibration device and method for a three-dimensional earth pressure cell, relating to the field of earth pressure calibration devices. It solves the problems of existing three-dimensional earth pressure cell calibration devices being cumbersome to operate, lacking accuracy, having low automation, and being unable to comprehensively and accurately detect and calibrate triaxial stress. The device includes a base plate, a cylinder, a detection mechanism, a backfilling mechanism, and a positioning mechanism. The detection mechanism includes a three-dimensional earth pressure cell, the backfilling mechanism includes a loading plate with a backfilling groove, and the positioning mechanism includes an electromagnet. This invention calibrates the sand pressure inside the cylinder using the three-dimensional earth pressure cell in the detection mechanism. The backfilling groove on the backfilling mechanism evenly transports the sand from the top to the bottom and allows for sand compaction. The positioning mechanism pre-controls the electromagnet to position the three-dimensional earth pressure cell, and when the backfilling mechanism has reached the required height, the three-dimensional earth pressure cell is placed on top of the sand for detection.

Description

Technical Field

[0001] This invention relates to the field of earth pressure calibration device technology, specifically to an automated calibration device and method for a three-dimensional earth pressure cell. Background Technology

[0002] Soil stress testing is a challenging aspect of geotechnical engineering, particularly under loading and unloading conditions. Currently, soil stress testing primarily utilizes membrane-type earth pressure cells, which generally only measure the normal stress perpendicular to the membrane surface and cannot obtain the triaxial stress state at a specific point.

[0003] Three-dimensional earth pressure cells have been applied in many engineering fields, but the accuracy of the earth pressure measured is questionable because the calibration coefficients used are based on indoor air or water pressure, which differs significantly from the actual soil testing environment in engineering projects. Furthermore, the existing methods of manually placing and burying the three-dimensional earth pressure cells are prone to inaccurate positioning and uneven soil layer distribution, resulting in low automation and affecting the accuracy of subsequent test results. Summary of the Invention

[0004] The purpose of this invention is to provide an automated calibration device and method for three-dimensional earth pressure cells that facilitates improved efficiency and accuracy of soil stress detection operations, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an automated calibration device for a three-dimensional earth pressure cell, comprising a base plate, a detection mechanism, a burial mechanism, and a positioning mechanism. A cylinder is fixedly connected to the base plate. The detection mechanism includes a three-dimensional earth pressure cell installed inside the cylinder, with a wire fixedly connected to the three-dimensional earth pressure cell. The detection mechanism can calibrate the sand pressure inside the cylinder through the three-dimensional earth pressure cell. The burial mechanism includes a loading plate installed inside the cylinder, with a burial groove formed on the loading plate. The burial mechanism can uniformly transport sand from above to below through the burial groove and can perform sand compaction operations, improving the uniformity of burial. The positioning mechanism includes a positioning rod installed inside the cylinder, with an electromagnet fixedly connected to the bottom of the positioning rod. The positioning mechanism can pre-position the three-dimensional earth pressure cell using the electromagnet and place the three-dimensional earth pressure cell above the sand when the burial mechanism has burial to the required height for subsequent burial and detection operations, thereby improving the efficiency and accuracy of soil stress detection.

[0006] Preferably, the detection mechanism further includes a base circular plate that slides against the inner wall of the cylinder. A triangular support is fixedly connected to the bottom surface of the base circular plate. A circular hole is opened on the base circular plate. A side hole is opened on the bottom side of the cylinder. The wire can pass through the circular hole and the side hole. A rubber tube is fixedly connected inside the circular hole to facilitate the calibration of the sand pressure inside the cylinder through the three-dimensional earth pressure box.

[0007] Preferably, the landfill mechanism further includes a drive pipe fixedly installed on the loading plate, a support frame fixedly connected above the cylinder, the outer diameter of the three-dimensional earth pressure box being smaller than the inner diameter of the drive pipe, the drive pipe being able to connect the positioning rod and the electromagnet, and the support frame being provided with a drive component for driving the drive pipe to rotate and lift, so as to facilitate the uniform transportation of sand and soil from above to below through the landfill trough, and to enable the compaction of sand and soil, thereby improving the uniformity of landfilling.

[0008] Preferably, the driving component includes a driving ring rotatably connected to the support frame, a driving tube passing through the driving ring, a driving groove formed on the outer wall of the driving tube, a driving block fixedly connected to the inner wall of the driving ring, the driving block being slidably connected to the inner wall of the driving groove in the vertical direction, a rotating component for driving the driving ring to rotate on the support frame, and a lifting component for driving the driving tube to rise and fall during rotation and to achieve a compaction function, which facilitates driving the driving tube to rotate and rise and fall.

[0009] Preferably, the lifting component includes multiple sets of electric telescopic rods fixedly installed on the support frame. The telescopic end of the electric telescopic rod is fixedly connected to the lifting frame. The drive tube passes through the lifting frame. The outer wall of the drive tube is provided with a threaded groove. The threaded groove is threadedly connected to the inner wall of the lifting frame, which facilitates the lifting and lowering of the drive tube during rotation and achieves the compaction function.

[0010] Preferably, the positioning mechanism further includes a guide frame fixedly installed on the support frame, a guide bracket slidably connected in the vertical direction inside the guide frame, a conductive ring fixedly connected to the guide bracket, a positioning rod passing through the conductive ring, a conductive block electrically connected to the top of the positioning rod, a knob for fixing the guide bracket on the side of the guide frame, and multiple sets of elastic metal plates evenly fixedly connected to the inner wall of the bottom end of the drive tube, which facilitates the pre-positioning of the three-dimensional earth pressure box by the electromagnet, and the placement of the three-dimensional earth pressure box on top of the sand for subsequent burial and testing operations when the burial mechanism burials to the required height.

[0011] Preferably, the rotating component includes a drive motor fixedly mounted on the support frame, a drive gear coaxially fixedly connected to the output end of the drive motor, and an external gear ring coaxially fixedly connected to the drive ring. The external gear ring meshes with the drive gear to facilitate the rotation of the drive ring.

[0012] Preferably, the bottom end of the drive tube is provided with a sealing block, and the side of the sealing block is provided with a plug-in hole. A baffle is slidably connected in the horizontal direction inside the landfill trench, and a plug-in block is fixedly connected to the side of the baffle. The plug-in block can be plugged into the plug-in hole, which facilitates the sealing of the drive tube and the bottom of the landfill trench, and facilitates subsequent pressurization.

[0013] Preferably, the guide frame has a graduated groove on its side, a feed hopper is fixedly connected to the top side of the cylinder, and a Teflon film is fixedly connected to the inner wall of the cylinder, which facilitates the adjustment of the height of the guide frame, improves the sand filling efficiency through the feed hopper, and reduces the friction between the loading plate and the inner wall of the cylinder through the Teflon film.

[0014] A calibration method for an automated calibration device for a three-dimensional earth pressure cell includes the following steps:

[0015] S1. Fix the three-dimensional earth pressure cell with an electromagnet so that the wires pass through the cylinder and the positioning rod is adjusted so that the three-dimensional earth pressure cell reaches the required height.

[0016] S2. By placing sand on the loading plate, driving the landfill mechanism to rotate the loading plate, the sand is evenly distributed into the cylinder through the landfill trough, and the loading plate is raised and lowered to achieve the function of compacting the sand.

[0017] S3. After the sand is filled to the required height, de-energize the electromagnet, place the three-dimensional earth pressure box above the sand, and then continue to control the loading plate to rotate and transport the sand evenly above and around the three-dimensional earth pressure box.

[0018] S4. After the backfilling is completed, control the loading plate to lift and lower and monitor the data of the three-dimensional earth pressure cell to realize the automatic calibration function of the three-dimensional earth pressure cell under repeated loading and unloading conditions.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention provides an automated calibration device and method for a three-dimensional earth pressure cell, which solves the problems of existing three-dimensional earth pressure cell calibration devices being cumbersome to operate, lacking accuracy, having a low degree of automation, and being unable to comprehensively and accurately detect and calibrate triaxial stress. The device calibrates the sand pressure inside a cylinder using a three-dimensional earth pressure cell in the detection mechanism. The filling mechanism uses a filling trough to evenly transport the sand from the top to the bottom and can perform sand compaction, improving the uniformity of the filling. A positioning mechanism pre-controls an electromagnet to position the three-dimensional earth pressure cell, and when the filling mechanism reaches the required height, the three-dimensional earth pressure cell is placed on top of the sand for subsequent filling and detection operations. This device has a simple structure, is convenient and efficient to operate, and provides more accurate positioning of the three-dimensional earth pressure cell, enabling precise automated detection and calibration of triaxial stress. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 This is a partial structural diagram of the driving component of the present invention;

[0023] Figure 3 This is a schematic diagram of the internal structure of the cylinder of the present invention;

[0024] Figure 4 for Figure 3 Enlarged view of region A in the middle;

[0025] Figure 5 This is a partial structural diagram of the rotating component of the present invention;

[0026] Figure 6 for Figure 5 Enlarged view of region B in the middle;

[0027] Figure 7 for Figure 5 Enlarged view of region C;

[0028] Figure 8 This is a partial structural breakdown diagram of the detection mechanism of the present invention;

[0029] Figure 9 for Figure 8 Enlarged view of region D in the middle;

[0030] Figure 10 This is a partial structural diagram of the positioning mechanism of the present invention;

[0031] Figure 11 for Figure 10 Enlarged view of region E in the middle;

[0032] Figure 12 This is a schematic diagram of the baffle assembly state of the present invention.

[0033] In the diagram: 1-Base plate; 2-Cylinder; 3-Three-dimensional earth pressure cell; 4-Wire; 5-Loading plate; 6-Backfill trench; 7-Positioning rod; 8-Electromagnet; 9-Base circular plate; 10-Triangular brace; 11-Circular hole; 12-Side hole; 13-Rubber tube; 14-Drive tube; 15-Support frame; 16-Drive component; 17-Drive ring; 18-Drive groove; 19-Drive block; 20-Rotating component; 21-Lifting component ; 22-Electric telescopic rod; 23-Lifting frame; 24-Threaded groove; 25-Guide frame; 26-Guide bracket; 27-Conductive ring; 28-Conductive block; 29-Knob; 30-Elastic metal sheet; 31-Drive motor; 32-Drive gear; 33-External gear ring; 34-Sealing block; 35-Insertion hole; 36-Baffle; 37-Insertion block; 38-Scale groove; 39-Feed hopper; 40-Teflon film. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Please see Figures 1-12 This invention provides a technical solution: an automated calibration device for a three-dimensional earth pressure cell, comprising a base plate 1, a detection mechanism, a burial mechanism, and a positioning mechanism. A cylinder 2 is fixedly connected to the base plate 1. The detection mechanism includes a three-dimensional earth pressure cell 3 installed inside the cylinder 2, and a wire 4 is fixedly connected to the three-dimensional earth pressure cell 3. The detection mechanism can calibrate the sand pressure inside the cylinder 2 through the three-dimensional earth pressure cell 3. The burial mechanism includes a loading plate 5 installed inside the cylinder 2, and a burial groove 6 is provided on the loading plate 5. The burial mechanism can evenly transport the sand above to the bottom through the burial groove 6 and can perform sand compaction operations to improve the uniformity of burial. The positioning mechanism includes a positioning rod 7 installed inside the cylinder 2, and an electromagnet 8 is fixedly connected to the bottom of the positioning rod 7. The positioning mechanism can pre-position the three-dimensional earth pressure cell 3 using the electromagnet 8, and place the three-dimensional earth pressure cell 3 on top of the sand when the burial mechanism burials to the required height for subsequent burial and detection operations.

[0036] The testing mechanism also includes a base plate 9 that slides against the inner wall of the cylinder 2. A triangular support 10 is fixedly connected to the bottom surface of the base plate 9. A circular hole 11 is opened on the base plate 9. A side hole 12 is opened on the bottom side of the cylinder 2. The wire 4 can pass through the circular hole 11 and the side hole 12. A rubber tube 13 is fixedly connected inside the circular hole 11.

[0037] The landfill mechanism also includes a drive tube 14 fixedly installed on the loading plate 5, a support frame 15 fixedly connected above the cylinder 2, the outer diameter of the three-dimensional earth pressure box 3 is smaller than the inner diameter of the drive tube 14, the drive tube 14 can connect the positioning rod 7 and the electromagnet 8, and the support frame 15 is provided with a drive component 16 for driving the drive tube 14 to rotate and lift.

[0038] The driving component 16 includes a driving ring 17 rotatably connected to the support frame 15, a driving tube 14 passing through the driving ring 17, a driving groove 18 on the outer wall of the driving tube 14, a driving block 19 fixedly connected to the inner wall of the driving ring 17, and the driving block 19 slidingly connected to the inner wall of the driving groove 18 in the vertical direction. The support frame 15 is provided with a rotating component 20 for driving the driving ring 17 to rotate, and a lifting component 21 for driving the driving tube 14 to rise and fall during rotation and to achieve a compaction function. The lifting component 21 includes multiple sets of electric telescopic rods 22 fixedly installed on the support frame 15. The telescopic end of the electric telescopic rod 22 is fixedly connected to a lifting frame 23. The driving tube 14 passes through the lifting frame 23, and a threaded groove 24 is opened on the outer wall of the driving tube 14. The threaded groove 24 is threadedly connected to the inner wall of the lifting frame 23.

[0039] The rotating component 20 includes a drive motor 31 fixedly mounted on the support frame 15. The output end of the drive motor 31 is coaxially fixedly connected to a drive gear 32. An external gear ring 33 is coaxially fixedly connected to the drive ring 17. The external gear ring 33 meshes with the drive gear 32. A sealing block 34 is provided at the bottom end of the drive tube 14. An insertion hole 35 is provided on the side of the sealing block 34. A baffle 36 is slidably connected in the horizontal direction in the landfill 6. An insertion block 37 is fixedly connected to the side of the baffle 36. The insertion block 37 can be inserted into the insertion hole 35.

[0040] The positioning mechanism also includes a guide frame 25 fixedly installed on the support frame 15. A guide frame 26 is slidably connected in the vertical direction inside the guide frame 25. A conductive ring 27 is fixedly connected to the guide frame 26. A positioning rod 7 passes through the conductive ring 27. A conductive block 28 that can be electrically connected to the conductive ring 27 is fixedly connected to the top of the positioning rod 7. A knob 29 for fixing the guide frame 26 is provided on the side of the guide frame 25. Multiple sets of elastic metal sheets 30 are evenly fixedly connected to the inner wall of the bottom end of the drive tube 14. A scale groove 38 is provided on the side of the guide frame 25. A feed hopper 39 is fixedly connected to the top side of the cylinder 2. A Teflon film 40 is fixedly connected to the inner wall of the cylinder 2.

[0041] Please see Figures 1-12 This invention provides a calibration method for an automated calibration device for a three-dimensional earth pressure cell, comprising the following steps:

[0042] S1. Fix the three-dimensional earth pressure box 3 with the electromagnet 8 so that the wire 4 passes out from the cylinder 2, and adjust the positioning rod 7 so that the three-dimensional earth pressure box 3 reaches the required height.

[0043] S2. By placing sand on the loading plate 5, driving the landfill mechanism to rotate the loading plate 5, the sand is evenly distributed into the cylinder 2 through the landfill trough 6, and the loading plate 5 is lifted and lowered to achieve the function of compacting the sand.

[0044] S3. After the sand is filled to the required height, the electromagnet 8 is de-energized, the three-dimensional earth pressure box 3 is placed on top of the sand, and then the loading plate 5 is controlled to rotate and transport the sand evenly to fill the three-dimensional earth pressure box 3 above and around it.

[0045] S4. After the backfilling is completed, control the loading plate 5 to lift and lower and monitor the data of the three-dimensional earth pressure cell 3 to realize the automatic calibration function of the three-dimensional earth pressure cell 3 under repeated loading and unloading conditions.

[0046] Working principle: Calibration test of loading and unloading effect of three-dimensional earth pressure cell during pile driving.

[0047] 1. Test Preparation: Raise the loading plate 5 to its highest position. Adjust the position of the positioning rod 7 to attach the three-dimensional earth pressure cell 3 to the electromagnet 8. Pass the wire 4 through the pre-drilled hole 11 in the lower base plate 9. Use a rubber tube 13 to improve the wrapping of the wire 4's outer wall, preventing sand and gravel from flowing out of the hole 11. Lead the wire 4 out through the lower side hole 12 and connect it to the data acquisition instrument. Adjust the strain acquisition software on the computer to control the guide frame 26 to slide within the guide frame 25, moving the positioning rod 7 down to the desired position. Observe the scale lines to determine the height of the three-dimensional earth pressure cell 3. The guide frame 26 is fixed by the knob 29, and then the drive gear 32 is driven to rotate by the drive motor 31, so that the external gear ring 33 drives the drive ring 17 to rotate. The drive block 19 on the drive ring 17 drives the drive groove 18 to make the drive tube 14 rotate. Guided by the threaded groove 24, the drive tube 14 gradually moves down during the rotation. The drive tube 14 is fitted down along the positioning rod 7 and the outer wall of the three-dimensional earth pressure box 3, while driving the loading plate 5 to move down. During this process, the baffle 36 and the sealing block 34 need to be removed so that the loading plate 5 can move to the lowest position close to the top surface of the base circular plate 9.

[0048] 2. Calibration cylinder drag reduction measures: In order to reduce the friction between the calibration sand and the inner wall of cylinder 2, a Teflon film 40 is installed on the inner wall of cylinder 2 and graphite powder is applied to reduce the load loss caused by the friction between the sand and the inner wall of cylinder 2.

[0049] 3. Layered Sand Filling and Earth Pressure Cell Placement: Sand to be filled is loaded into the hopper 39 and falls above the loading plate 5. Then, the drive motor 31 is controlled to drive the drive gear 32 to rotate in the opposite direction, thereby causing the drive ring 17 to drive the drive tube 14 to rotate in the opposite direction and rise. The rotation speed is kept uniform, so that the sand can be continuously and stably transported from the filling trench 6 to the base circular plate 9. An oscillating structure can be set above the loading plate 5 to improve the falling speed and efficiency of the sand. The test sand is laid in layers with a thickness of 30mm in the cylinder 2. Due to the stiffness mismatch between the three-dimensional earth pressure cell 3 and the surrounding sand medium, stress concentration problems are prone to occur. In order to reduce the measurement error caused by this effect, the bottom test sand is fully compacted to the design density. When the loading plate 5 moves up a set distance, the electric telescopic rod 22 is controlled to drive the lifting mechanism. The lowering frame 23 reciprocates multiple times, allowing the loading plate 5 to be driven by the drive tube 14 to rise and fall, compacting the sand at the bottom. During the rising and falling process, the rotation of the loading plate 5 ensures that the filling trench 6 is compacted. When the layered filling reaches the height where the three-dimensional earth pressure box 3 is placed, the protruding part in the middle of the elastic metal sheet 30 will abut against the outer edge of the bottom of the electromagnet 8, lifting the electromagnet 8. The electromagnet 8 pushes the positioning rod 7 and the conductive block 28 upward. The conductive block 28 releases the conductive state from the conductive ring 27, and the electromagnet 8 is de-energized, allowing the three-dimensional earth pressure box 3 to be placed at this position. At the same time, the stability of the three-dimensional earth pressure box 3 is ensured under the guidance of the drive tube 14. Afterward, the loading plate 5 continues to rotate and rise, while driving the positioning rod 7 to move upward synchronously to continue layering the test sand to the top of the cylinder. In the experiment, the filling density of sand was controlled at 1.78 g / cm³, with a relative density of about 70%. A horizontally retractable block can be set on the loading plate 5 to extend under the drive pipe 14 to assist in compaction when compaction is required at the position directly below the drive pipe 14. After compaction, the block is retracted laterally to avoid obstructing the transmission of the conductor 4 and the three-dimensional earth pressure box 3.

[0050] 4. Preloading: After the filling is completed, the loading plate 5 moves up and removes the sand and soil above it. The sealing block 34 is inserted into the bottom of the drive pipe 14, and the baffle 36 is inserted horizontally to seal the position of the filling trench 6. The plug block 37 is inserted into the plug hole 35 to limit the sealing block 34 and the baffle 36. After the loading plate 5 moves down into the cylinder 2, one end of the baffle 36 is abutted by the inner wall of the cylinder 2 to achieve fixation. Then, the loading plate 5 is controlled to rotate and move down to the top of the soil layer. The through hole electric telescopic rod 22 controls the drive pipe 14 and the loading plate 5 to lift and lower, applying preload to the loading plate 5. After 10 minutes of preload, the load is unloaded. After debugging the data acquisition equipment and reading the initial value, the loading is started in stages. The level of the loading plate 5 is checked with a level to ensure that the load can be evenly transferred into the cylinder.

[0051] 5. Loading and Unloading Calibration: After debugging the loading system and data acquisition system and completing the preparation, loading and unloading will begin. To reflect the loading and unloading effect, the loading system will be reciprocated during calibration, with a total of six loading levels and a loading / unloading rate of 60 kPa / min. After each loading level, the load will be maintained for 2 minutes before unloading, and the loading and unloading will be carried out step by step until the test is completed.

[0052] 6. Data Acquisition and Processing: During the loading process, a static strain gauge is used to collect voltage values. Once the voltage value stabilizes under each load level, the voltage value under the current load is read. The unloading curve is fitted using the following formula:

[0053]

[0054] In the formula: and These are the current stress and the maximum stress before unloading, respectively. and They are respectively the corresponding and Earth pressure cell voltage reading at that time; , , , , , 3. The three-dimensional earth pressure cell has 6 undetermined coefficients for each unloading curve.

[0055] Using the above formula for curve fitting, for an earth pressure cell with a pressure of 3 MPa, a unified normalized unloading curve can be used to determine the soil stress under unloading conditions, such as the maximum unloading corresponding to the first unloading curve of the three-dimensional earth pressure cell 3. =200kPa, =-0.15, =1.98, =1.53, =0.483, =0.518. After obtaining the above 6 parameters, the soil stress at the time of unloading can be obtained.

[0056] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for automated calibration of a three-dimensional earth pressure cell, characterized in that include: A base plate (1) is fixedly connected to a cylinder (2); Also includes: The testing mechanism includes a three-dimensional earth pressure box (3) installed inside the cylinder (2), and a wire (4) is fixedly connected to the three-dimensional earth pressure box (3). The testing mechanism can calibrate the sand pressure inside the cylinder (2) through the three-dimensional earth pressure box (3). The landfill mechanism includes a loading plate (5) installed inside the cylinder (2), and a landfill groove (6) is provided on the loading plate (5). The landfill mechanism can uniformly transport the sand and soil above to the bottom through the landfill groove (6) and can perform the compaction operation of the sand and soil to improve the uniformity of landfilling. The positioning mechanism includes a positioning rod (7) installed inside the cylinder (2), and an electromagnet (8) is fixedly connected to the bottom of the positioning rod (7). The positioning mechanism can pre-position the position of the three-dimensional earth pressure box (3) by means of the electromagnet (8), and place the three-dimensional earth pressure box (3) on top of the sand when the burial mechanism burials to the required height for subsequent burial and detection operations.

2. The device for automatic calibration of a three-dimensional earth pressure cell according to claim 1, characterized in that: The detection mechanism also includes a base plate (9) that slides against the inner wall of the cylinder (2). A triangular support (10) is fixedly connected to the bottom surface of the base plate (9). A circular hole (11) is opened on the base plate (9). A side hole (12) is opened on the bottom side of the cylinder (2). The wire (4) can pass through the circular hole (11) and the side hole (12). A rubber tube (13) is fixedly connected inside the circular hole (11).

3. The automated calibration device for a three-dimensional earth pressure cell according to claim 2, characterized in that: The landfill mechanism also includes a drive tube (14) fixedly installed on the loading plate (5), a support frame (15) fixedly connected above the cylinder (2), the outer diameter of the three-dimensional earth pressure box (3) is smaller than the inner diameter of the drive tube (14), the drive tube (14) can connect the positioning rod (7) and the electromagnet (8), and the support frame (15) is provided with a drive component (16) for driving the drive tube (14) to rotate and lift.

4. The automated calibration device for a three-dimensional earth pressure cell according to claim 3, characterized in that: The driving component (16) includes a driving ring (17) rotatably connected to the support frame (15), a driving tube (14) passing through the driving ring (17), a driving groove (18) being provided on the outer wall of the driving tube (14), a driving block (19) being fixedly connected to the inner wall of the driving ring (17), the driving block (19) being slidably connected to the inner wall of the driving groove (18) in the vertical direction, a rotating component (20) being provided on the support frame (15) for driving the driving ring (17) to rotate, and a lifting component (21) being provided on the support frame (15) for driving the driving tube (14) to rise and fall during rotation and to achieve the compaction function.

5. The automated calibration device for a three-dimensional earth pressure cell according to claim 4, characterized in that: The lifting component (21) includes multiple sets of electric telescopic rods (22) fixedly installed on the support frame (15). The telescopic end of the electric telescopic rod (22) is fixedly connected to the lifting frame (23). The drive pipe (14) passes through the lifting frame (23). The outer wall of the drive pipe (14) is provided with a threaded groove (24). The threaded groove (24) is threadedly connected to the inner wall of the lifting frame (23).

6. The automated calibration device for a three-dimensional earth pressure cell according to claim 3, characterized in that: The positioning mechanism also includes a guide frame (25) fixedly installed on the support frame (15). A guide frame (26) is slidably connected in the vertical direction inside the guide frame (25). A conductive ring (27) is fixedly connected on the guide frame (26). The positioning rod (7) passes through the conductive ring (27). A conductive block (28) that can be electrically connected to the conductive ring (27) is fixedly connected to the top of the positioning rod (7). A knob (29) for fixing the guide frame (26) is provided on the side of the guide frame (25). Multiple sets of elastic metal sheets (30) are evenly fixedly connected to the inner wall of the bottom end of the drive tube (14).

7. The automated calibration device for a three-dimensional earth pressure cell according to claim 4, characterized in that: The rotating component (20) includes a drive motor (31) fixedly mounted on the support frame (15). The output end of the drive motor (31) is coaxially fixedly connected to a drive gear (32). An external gear ring (33) is coaxially fixedly connected to the drive ring (17). The external gear ring (33) meshes with the drive gear (32).

8. The automated calibration device for a three-dimensional earth pressure cell according to claim 3, characterized in that: The bottom end of the drive tube (14) is provided with a sealing block (34), and the side of the sealing block (34) is provided with a plug hole (35). A baffle (36) is slidably connected in the horizontal direction inside the landfill groove (6), and a plug block (37) is fixedly connected to the side of the baffle (36). The plug block (37) can be plugged into the plug hole (35).

9. The automated calibration device for a three-dimensional earth pressure cell according to claim 6, characterized in that: The guide frame (25) has a scale groove (38) on its side, the top side of the cylinder (2) is fixedly connected to a feed hopper (39), and the inner wall of the cylinder (2) is fixedly connected to a Teflon film (40).

10. A calibration method for an automated calibration device for a three-dimensional earth pressure cell based on any one of claims 1-9, characterized in that, Includes the following steps: S1. Fix the three-dimensional earth pressure box (3) with an electromagnet (8) so that the wire (4) passes through the cylinder (2) and adjust the positioning rod (7) so that the three-dimensional earth pressure box (3) reaches the required height; S2. By placing sand on the loading plate (5), driving the landfill mechanism to rotate the loading plate (5), the sand is evenly dispersed into the cylinder (2) through the landfill trough (6), and the loading plate (5) is lifted up and down to achieve the function of compacting sand. S3. After the sand is filled to the required height, the electromagnet (8) is de-energized, the three-dimensional earth pressure box (3) is placed on top of the sand, and then the loading plate (5) is controlled to rotate and transport the sand evenly to fill the three-dimensional earth pressure box (3) above and around it. S4. After the backfilling is completed, control the loading plate (5) to lift and lower and monitor the data of the three-dimensional earth pressure cell (3) to realize the automatic calibration function of the three-dimensional earth pressure cell (3) under repeated loading and unloading conditions.

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