A visual observation device for transparent soil root pulling test

Abstract

The application discloses a visual observation device for transparent soil root system pulling test, which comprises an external bearing box, an internal sample box, a cover plate, a normal stress loading mechanism, a camera system and a laser system. The internal sample box is fixed in the external bearing box, and the internal sample box cavity is filled with transparent soil samples and pore liquid. The cover plate is located in the cavity of the internal sample box and closely adheres to the top surface of the transparent soil sample, and a pulling hole is formed in the center of the cover plate to simulate the root system and the soil. The normal stress loading mechanism is arranged above the cover plate to apply stable normal stress to the sample during the test. The camera system and the laser system are arranged outside the external bearing box to observe the particle image velocimetry of the transparent soil sample in the internal sample box. The normal stress loading mechanism can apply stable and controllable normal stress to the sample during the root system pulling test, thereby improving the accuracy and repeatability of the test results.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, specifically a visualization observation device for root pull-out tests in transparent soil. Background Technology

[0002] Plant roots can significantly improve the shear strength and overall stability of soil through friction, interlocking, and interlocking with the soil, playing an important role in slope protection, ecological restoration, and engineering reinforcement.

[0003] To study the mechanical behavior of the root-soil interface, indoor root pull-out tests are widely used. Existing root pull-out test apparatuses mostly employ unconstrained or simple overloading conditions to pull out roots, making it difficult to stably and accurately control the normal stress on the specimen during the test. Furthermore, some loading methods are significantly affected by factors such as friction and eccentric loading, and the loading path is unclear, thus the repeatability and reliability of the test results need improvement.

[0004] In recent years, transparent soil technology combined with particle image velocimetry (PIV) has been increasingly applied in geotechnical engineering tests, enabling the visualization of soil displacement and deformation. However, in root pull-out tests, transparent soil tests often only focus on changes in pull-out force, lacking a dedicated device for simultaneous observation of soil deformation fields under controllable normal stress conditions.

[0005] Meanwhile, in existing transparent soil testing devices, cameras and lasers are usually arranged using temporary supports or external methods, which makes position adjustment inconvenient and lacks a unified structural constraint with the loading device. This makes them prone to relative displacement during the test, affecting the observation accuracy and test stability. Summary of the Invention

[0006] The purpose of this invention is to provide a visualization observation device for root pull-out tests in transparent soil, including an external bearing box, an internal sample box, a cover plate, a normal stress loading mechanism, a camera system, and a laser system.

[0007] The external support box is a hollow box structure with one open end and the other closed. The internal sample box is fixedly assembled inside the external support box and is also a box structure with both ends open. The bottom of the internal sample box near the closed end of the external support box has a drainage hole, and the internal sample box also contains a transparent soil sample and pore fluid.

[0008] Plant roots are pre-embedded in the transparent soil sample, with one end of the plant roots located in the transparent soil sample and the other end extending out of the transparent soil sample.

[0009] The cover plate is placed inside the cavity of the built-in sample box, and is positioned above and in close contact with the transparent soil sample. A pull-out hole is provided at the center of the cover plate, through which plant roots pre-embedded in the transparent soil sample pass, so that an external pull-out device can pull out the plant roots.

[0010] The cover plate is equipped with a normal stress loading mechanism for applying normal stress to the transparent soil sample. The normal stress loading mechanism includes several lever groups, each group comprising two primary levers, two fulcrum structures, two roller structures, and weights. The two fulcrum structures within each group are fixed at intervals to the external support box and are located on the same side. The two primary levers within each group are arranged in parallel and mounted on different fulcrum structures. One end of each of the two primary levers within the group is rotatably mounted on the fulcrum structure, while the other end is suspended for mounting the weights.

[0011] A roller structure is provided on one side of each of the two primary levers, near the fulcrum structure. The roller structure is located between the primary levers and the cover plate and is used to apply the load transmitted by the primary levers to the cover plate.

[0012] The camera system and laser system are respectively located on the outside of the external support box, and are used to perform particle image velocity measurement observation on the transparent soil sample inside the built-in sample box.

[0013] Furthermore, the visualization observation device also includes a limiting block for limiting the lateral displacement of the built-in sample box and a limiting rod for limiting the vertical displacement of the built-in sample box.

[0014] The limiting blocks are L-shaped and located at the four corners of the bottom of the outer bearing box. When the inner sample box is placed, the outer wall of the inner sample box contacts the inner corners of the four L-shaped limiting blocks, thereby restricting the lateral displacement of the inner sample box.

[0015] The four sides of the external carrier box are designated as side wall I, side wall II, side wall III, and side wall IV. Each of side wall I and side wall III has two through holes for the external carrier box; these two through holes on side wall I are designated as external carrier box through holes I, and the two through holes on side wall III are designated as external carrier box through holes II. The two side walls of the internal sample box each have a through hole penetrating through the side wall of the internal sample box.

[0016] The limiting rod passes through the external bearing box through hole I, the internal sample box through hole and the external bearing box through hole II in sequence, thereby limiting the vertical displacement of the internal sample box.

[0017] Furthermore, the four sides of the external carrier box are respectively labeled as side wall I, side wall II, side wall III, and side wall IV.

[0018] The top of the side walls II and IV of the external carrier box extends outward with protrusions. The protrusions are integrally formed with the external carrier box, and the top surface of the protrusions is flush with the top surface of the external carrier box.

[0019] The fulcrum structures within the same lever group are fixed on the same side boss, and the positions of the two fulcrum structures are symmetrical about the top surface of the external bearing box.

[0020] Furthermore, the fulcrum structure includes a hinge shaft and two hinge lugs, which are respectively referred to as hinge lug I and hinge lug II.

[0021] The end of the primary lever is embedded between hinge lug I and hinge lug II. Hinges I and II are respectively provided with through holes I and II. One end of the primary lever connected to the fulcrum structure has a through hole III. Through hole III is coaxial with through holes I and II, allowing the hinge shaft to pass through through holes I, III, and II sequentially. Elastic retaining rings are fitted at both ends of the hinge shaft.

[0022] After assembly, the first-stage lever can rotate around the hinge axis.

[0023] Furthermore, the normal stress loading mechanism includes a connecting rod. A through hole IV is provided on the mounting end of the primary lever. The through holes IV of the two primary levers within the same lever group are coaxially arranged, allowing the connecting rod to pass through the two through holes IV and be fixed to the two primary levers.

[0024] The weights are hung on the connecting rod. By hanging different numbers or weights of weights on the connecting rod, the primary lever rotates around the fulcrum structure, thereby using the weight of the weights as an input load. After being transmitted through the primary lever, the load is applied to the cover plate through the roller structure.

[0025] Furthermore, the roller structure includes a roller, a rotating shaft, and a support base.

[0026] The primary lever is fixed to the top surface of the support base.

[0027] The roller is rotatably mounted in the support base via a pivot, and the roller is positioned on a cover plate gasket. The cover plate gasket is mounted on the cover plate, with two cover plate gaskets located on opposite sides of the pull-out hole. The length of the cover plate gasket is equal to the length of the cover plate, and it is used to distribute the local load applied by the normal stress loading mechanism.

[0028] Furthermore, the camera system includes a camera guide rail, a camera mounting plate, a camera vertical rod, and a camera. The four sides of the external support box are designated as side wall I, side wall II, side wall III, and side wall IV.

[0029] The camera mounting plate is fixedly installed on the bottom of the side wall I of the external support box. A camera guide rail is vertically connected to each end of the camera mounting plate, and a vertical camera rod is slidably connected to the end of each camera guide rail away from the camera mounting plate. The vertical camera rod has a T-shaped structure, with its horizontal section located in the grooves of different camera guide rails, and a camera slidably connected to its vertical section.

[0030] Furthermore, the laser system includes a laser guide rail, a laser mounting plate, a laser vertical rod, and a laser.

[0031] The four sides of the external carrier box are designated as side wall I, side wall II, side wall III, and side wall IV. Laser systems are installed on side wall II and side wall IV.

[0032] The laser mounting plate is fixedly installed at the bottom of side walls II and IV. A laser guide rail is vertically connected to each end of the laser mounting plate, and a vertical laser rod is slidably connected to the end of each laser guide rail furthest from the laser mounting plate. The vertical laser rod has a T-shaped structure, with its horizontal section located in the grooves of different laser guide rails, and a laser slidably connected to its vertical section.

[0033] Furthermore, the outer contour of the cover plate is adapted to the inner contour of the built-in sample box cavity.

[0034] Furthermore, both the external carrier box and the internal sample box are made of transparent material.

[0035] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0036] A. This invention, through the setting of a normal stress loading mechanism, can apply stable and controllable normal stress to the specimen during the root pull-out test, thereby improving the accuracy and repeatability of the test results;

[0037] B. This invention integrates the camera system and laser system with the main body of the device in the form of guide rails and vertical rods, realizing multi-degree-of-freedom adjustment of the position of the observation equipment and avoiding observation errors caused by the instability of traditional external supports;

[0038] C. Under transparent soil conditions, this invention enables full-field particle image velocity measurement and observation of soil deformation field during root pull-out by coordinating the arrangement of lasers on the left and right sides and a camera in front.

[0039] D. The present invention has a high degree of structural integration and compact layout, and can achieve simultaneous loading and observation without affecting the normal loading function, making it suitable for refined research on root pull-out tests in transparent soil. Attached Figure Description

[0040] Figure 1This is a schematic diagram of the overall structure of the visualization observation device of the present invention;

[0041] Figure 2 This is a schematic diagram showing the assembly relationship between the external carrier box and the internal sample box;

[0042] Figure 3 This is a schematic diagram showing the contact position between the roller and the cover plate of the normal stress loading mechanism;

[0043] Figure 4 This is a schematic diagram of the structure and symmetrical arrangement of the first-stage levers of the normal stress loading mechanism.

[0044] In the diagram: 1. External bearing box; 2. Internal sample box; 3. Cover plate; 4. Normal stress loading mechanism; 5. Limiting rod; 6. Camera system; 7. Laser system.

[0045] Limiting block 11, external bearing box through hole 12, external bearing box through hole I121, external bearing box through hole II122, boss 13; internal sample box drainage hole 21, internal sample box through hole 22; pull-out hole 31, cover plate gasket 32; first-level lever 41, fulcrum structure 42, connecting rod 43, roller structure 44, roller 441, support seat 442, weight 45; camera guide rail 61, camera mounting plate 62, camera vertical rod 63, camera 64; laser guide rail 71, laser mounting plate 72, laser vertical rod 73, laser 74. Detailed Implementation

[0046] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0047] Example 1:

[0048] A visualization observation device for root pull-out tests in transparent soil includes an external bearing box 1, an internal sample box 2, a cover plate 3, a normal stress loading mechanism 4, a camera system 6, and a laser system 7.

[0049] The external support box 1 is a hollow box structure with one open end and the other closed. The internal sample box 2 is fixedly assembled inside the external support box 1 and is a box structure with both ends open. The bottom of the internal sample box 2 near the closed end of the external support box 1 is provided with an internal sample box drainage hole 21, and the internal sample box 2 also contains transparent soil samples and pore fluid.

[0050] Plant roots are pre-embedded in the transparent soil sample, with one end of the plant roots located in the transparent soil sample and the other end extending out of the transparent soil sample.

[0051] The cover plate 3 is placed in the cavity of the built-in sample box 2, and is located above and in close contact with the transparent soil sample. A pull-out hole 31 is provided at the center of the cover plate 3, through which the plant roots pre-embedded in the transparent soil sample pass, so that an external pull-out device can pull out the plant roots.

[0052] The cover plate 3 is equipped with a normal stress loading mechanism 4 for applying normal stress to the transparent soil sample. The normal stress loading mechanism 4 includes several lever groups, each group comprising two primary levers 41, two fulcrum structures 42, two roller structures 44, and weights 45. The two fulcrum structures 42 within each group are fixed at intervals to the external bearing box 1 and are located on the same side. The two primary levers 41 within each group are arranged in parallel and are respectively mounted on different fulcrum structures 42. One end of each primary lever 41 is rotatably mounted on the fulcrum structure 42, while the other end is suspended in the air for mounting the weights 45.

[0053] Roller structures 44 are provided on the two primary levers 41, near the fulcrum structure 42. The roller structures 44 are located between the primary levers 41 and the cover plate 3, and are used to apply the load transmitted by the primary levers 41 to the cover plate 3.

[0054] The camera system 6 and the laser system 7 are respectively located on the outside of the external carrier box 1, and are used to perform particle image velocity measurement observation on the transparent soil sample inside the built-in sample box 2.

[0055] Example 2:

[0056] The main structure of this embodiment is the same as that of Embodiment 1. Furthermore, the visualization observation device also includes a limiting block 11 for limiting the lateral displacement of the built-in sample box 2 and a limiting rod 5 for limiting the vertical displacement of the built-in sample box 2.

[0057] The limiting blocks 11 are L-shaped and are located at the four corners of the bottom of the inner cavity of the outer bearing box 1. When the inner sample box 2 is placed, the outer wall of the inner sample box 2 contacts the inner corners of the four L-shaped limiting blocks 11, thereby limiting the lateral displacement of the inner sample box 2.

[0058] The four sides of the external carrier box 1 are designated as side wall I, side wall II, side wall III, and side wall IV. Each of side wall I and side wall III has two external carrier box through holes 12. The two external carrier box through holes 12 on side wall I are designated as external carrier box through holes I121, and the two external carrier box through holes 12 on side wall III are designated as external carrier box through holes II122. The two side walls of the internal sample box 2 each have an internal sample box through hole 22 penetrating through the side wall of the internal sample box 2.

[0059] The limiting rod 5 passes through the external bearing box through hole I121, the internal sample box through hole 22 and the external bearing box through hole II122 in sequence, thereby limiting the vertical displacement of the internal sample box 2.

[0060] Example 3:

[0061] The main structure of this embodiment is the same as any one of embodiments 1 to 2. Furthermore, the four sides of the external carrier box 1 are respectively referred to as side wall I, side wall II, side wall III and side wall IV.

[0062] The top of the side walls II and IV of the external bearing box 1 extends outward with a boss 13. The boss 13 and the external bearing box 1 are integrally formed, and the top surface of the boss 13 is flush with the top surface of the external bearing box 1.

[0063] The fulcrum structure 42 within the same lever group is fixed on the same side boss 13, and the positions of the two fulcrum structures 42 are symmetrical about the top surface of the external bearing box 1.

[0064] Example 4:

[0065] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Furthermore, the fulcrum structure 42 includes a hinge shaft and two hinge lugs, which are respectively referred to as hinge lug I and hinge lug II.

[0066] The end of the primary lever 41 is embedded between hinge lug I and hinge lug II. Hinges I and II are respectively provided with through holes I and II. One end of the primary lever 41 connected to the fulcrum structure 42 has a through hole III. Through hole III is coaxial with through holes I and II, allowing the hinge shaft to pass through through holes I, III, and II sequentially. Elastic retaining rings are fitted at both ends of the hinge shaft.

[0067] After assembly, the first-stage lever 41 can rotate around the hinge axis.

[0068] Example 5:

[0069] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Furthermore, the normal stress loading mechanism 4 includes a connecting rod 43.

[0070] The mounting end of the first-level lever 41 is provided with a through hole IV. The through holes IV of the two first-level levers 41 in the same lever group are coaxially arranged so that the connecting rod 43 passes through the two through holes IV and is fixed on the two first-level levers 41.

[0071] The weight 45 is hung on the connecting rod 43.

[0072] Before the experiment, the normal load applied to the cover plate 3 is determined based on the torque balance relationship of the primary lever 41 at the fulcrum structure 42. Specifically, by hanging different numbers or weights of weights 45 on the connecting rod 43, the primary lever 41 rotates around the fulcrum structure 42, thereby using the weight of the weights 45 (including the weights 45 themselves, the connecting rod, the weight pan, etc.) as the input load. This load is transmitted and converted by the primary lever 41 according to the lever arm ratio between its hanging end and the output end, and then applied to the cover plate 3 through the roller structure 44. This allows for the quantitative adjustment and setting of the normal load on the cover plate 3.

[0073] Example 6:

[0074] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Furthermore, the roller structure 44 includes a roller 441, a rotating shaft, and a support base 442.

[0075] The primary lever 41 is fixed to the top surface of the support base 442.

[0076] The roller 441 is rotatably mounted in the support base 442 via a rotating shaft, and the roller 441 is disposed on the cover plate gasket 32. The cover plate gasket 32 ​​is disposed on the cover plate 3, and the two cover plate gaskets 32 are respectively located on both sides of the pull-out hole 31. The length of the cover plate gasket 32 ​​is equal to the length of the cover plate 3, and it is used to distribute the local load applied by the normal stress loading mechanism 4.

[0077] The support base 442 includes two ear plates and a fixed plate. One side of the fixed plate is connected to the first-stage lever 41, and the other side is connected to the two parallel ear plates. The roller 441 is embedded between the two ear plates, so that the center hole of the roller 441 is aligned with the connecting hole on the two ear plates. The rotating shaft passes through the center hole and the connecting hole to fix the roller 441 on the ear plates.

[0078] Example 7:

[0079] The main structure of this embodiment is the same as any one of embodiments 1 to 6. Furthermore, the camera system 6 includes a camera guide rail 61, a camera mounting plate 62, a camera vertical rod 63, and a camera 64.

[0080] The four sides of the external bearing box 1 are respectively labeled as side wall I, side wall II, side wall III and side wall IV.

[0081] The camera mounting plate 62 is fixedly installed on the bottom of the side wall I of the external support box 1. A camera guide rail 61 is vertically connected to each end of the camera mounting plate 62, and a vertical camera rod 63 is slidably connected to the end of each camera guide rail 61 away from the camera mounting plate 62. The vertical camera rod 63 has a T-shaped structure, with its horizontal section located in the grooves of different camera guide rails 61, and a camera 64 slidably connected to its vertical section.

[0082] During the imaging process, the sliding position of the camera vertical rod 63 on the camera guide rail 61 and the sliding position of the camera 64 on the vertical section of the camera vertical rod 63 can be manually adjusted according to imaging needs, so as to adjust the front-back and up-down position of the camera 64. A locking bolt is provided between the camera 64 and the camera vertical rod 63 to lock the relative position after adjustment, thereby ensuring the stability of the installation and connection of the camera 64.

[0083] Example 8:

[0084] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Further, the laser system 7 includes a laser guide rail 71, a laser mounting plate 72, a laser vertical rod 73, and a laser 74.

[0085] The four sides of the external carrier box 1 are designated as side wall I, side wall II, side wall III, and side wall IV. Laser systems 7 are installed on both side wall II and side wall IV.

[0086] The laser mounting plate 72 is fixedly installed at the bottom of side wall II and side wall IV. A laser guide rail 71 is vertically connected to each end of the laser mounting plate 72, and a vertical laser rod 73 is slidably connected to the end of each laser guide rail 71 away from the laser mounting plate 72. The vertical laser rod 73 has a T-shaped structure, with its horizontal section located in the grooves of different laser guide rails 71, and a laser 74 slidably connected to its vertical section.

[0087] During the imaging process, the sliding position of the laser vertical rod 73 on the laser guide rail 71 and the sliding position of the laser 74 on the vertical section of the laser vertical rod 73 can be manually adjusted according to imaging needs, so as to adjust the front-back and up-down position of the laser 74. A locking bolt is provided between the laser 74 and the laser vertical rod 73 to lock the relative position after adjustment, thereby ensuring the stability of the laser 74 installation and connection.

[0088] Example 9:

[0089] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Furthermore, the outer contour of the cover plate 3 is adapted to the inner contour of the cavity of the built-in sample box 2.

[0090] Example 10:

[0091] The main structure of this embodiment is the same as any one of embodiments 1 to 9. Furthermore, both the external carrier box 1 and the internal sample box 2 are made of transparent material.

[0092] Example 11:

[0093] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Further, an integrated device for controllable normal stress loading and PIV observation for root pull-out test of transparent soil includes: an external bearing box 1, an internal sample box 2 set in the external bearing box 1, a cover plate 3 covering the top of the internal sample box 2, a normal stress loading mechanism 4 set above the cover plate 3, a limiting rod 5, a camera system 6, and a laser system 7.

[0094] Both the external support box 1 and the internal sample box 2 are made of transparent material to facilitate optical observation under transparent soil conditions.

[0095] The inner wall of the outer support box 1 is provided with a limiting block for lateral limiting of the inner sample box 2. The limiting rod 5 passes through the corresponding through holes of the outer support box 1 and the inner sample box 2 to limit the vertical displacement of the inner sample box 2.

[0096] The normal stress loading mechanism 4 is used to apply normal stress to the cover plate 3 during the test.

[0097] The camera system 6 and the laser system 7 are respectively located on the outside of the external carrier box 1, and are used to perform particle image velocity measurement observation on the transparent soil sample inside the built-in sample box 2.

[0098] The camera system 6 includes two parallel camera guide rails 61 located in front of the external support box 1, a vertical camera rod 63 cooperating with the camera guide rails 61, and a camera 64 mounted on the vertical camera rod 63. The vertical camera rod 63 can move back and forth along the camera guide rails 61 and is fixed on the camera guide rails 61, and the camera 64 can be adjusted up and down along the vertical camera rod 63. A camera mounting plate 62 is provided at one end of the camera guide rails 61 near the external support box 1. The camera mounting plate 62 is integrated with the camera guide rails 61 and is fixed to the bottom of the external support box 1 by bolts to enable the disassembly and replacement of the camera system 6.

[0099] The laser system 7 includes laser guide rails 71 respectively disposed on the left and right sides of the external support box 1, a laser vertical rod 73 cooperating with the laser guide rails 71, and a laser 74 mounted on the laser vertical rod 73. The laser vertical rod 73 can move left and right along the laser guide rails 71 and be fixed, and the laser 74 can be adjusted up and down along the laser vertical rod 73 to adjust the spatial position of the laser beam in the transparent soil sample.

[0100] The normal stress loading mechanism 4 includes multiple symmetrically arranged primary levers. Each primary lever is mounted on the external bearing box 1 through a fulcrum structure, and its output end contacts the cover plate 3 through rollers.

[0101] Example 12:

[0102] The main structure of this embodiment is the same as any one of embodiments 1 to 11. Furthermore, the purpose of this invention is to provide an integrated device for controllable normal stress loading and PIV observation for root pull-out tests in transparent soil. By structurally integrating the normal stress loading mechanism 4 with the camera system 6 and the laser system 7, stable normal stress application and particle image velocity measurement observation of the root pull-out process are achieved during the test, thereby overcoming the problems of difficult control of normal stress and unstable arrangement of the observation system in the prior art.

[0103] To achieve the above objectives, the present invention adopts the following technical solution: an integrated device for controllable normal stress loading and PIV observation for root pull-out tests in transparent soil, comprising an external bearing box 1, an internal sample box 2, a cover plate 3, a normal stress loading mechanism 4, a limiting rod 5, a camera system 6, and a laser system 7.

[0104] The external support box 1 provides structural support and reaction conditions for the entire test apparatus, and its internal space is used to accommodate the internal sample box 2. The internal sample box 2 is located inside the external support box 1 and is used to hold transparent soil samples and their pore fluid.

[0105] The inner wall of the external carrier box 1 is provided with a limiting block, which is used to contact the outer wall of the built-in sample box 2 to limit the lateral movement and position the built-in sample box 2.

[0106] The side wall of the built-in sample box 2 and the side wall of the external bearing box 1 are respectively provided with a through hole 22 for the built-in sample box and a through hole 12 for the external bearing box at corresponding positions. The limiting rod 5 passes through the through hole 22 for the built-in sample box and the through hole 12 for the external bearing box, and is used to limit the vertical displacement of the built-in sample box 2 during the test, thereby preventing the built-in sample box 2 from being lifted as a whole when normal stress is applied and root pull-out is performed.

[0107] By using the combination of the limiting block and the limiting rod 5, the internal sample box 2 is positioned laterally and limited vertically within the external bearing box 1, so that the internal sample box 2 maintains a stable position during loading and testing.

[0108] The cover plate 3 covers the top of the built-in sample box 2 and is used to apply normal stress to the transparent soil sample during the test. The cover plate 3 is a detachable structure to facilitate sample loading, root arrangement, and disassembly and replacement after the test.

[0109] The cover plate 3 has a pull-out hole at its center, which is used for the roots to pass through during the test, so that the roots can be pulled out under normal stress.

[0110] The cover plate 3 is provided with a contact structure at the position where it contacts the normal stress loading mechanism 4 to distribute the load and avoid local stress concentration.

[0111] The normal stress loading mechanism 4 is disposed above the cover plate 3 and is used to apply stable and controllable normal stress to the cover plate 3 during the test.

[0112] The normal stress loading mechanism 4 includes multiple primary levers, which are mounted on the external bearing box 1 via a fulcrum structure and can rotate around the fulcrum structure.

[0113] The multiple primary levers are symmetrically arranged on both sides of the built-in sample box 2 so that the normal force applied to the cover plate 3 remains symmetrical and balanced.

[0114] Each of the primary levers includes an input end (mounting end) and an output end. The output end contacts the cover plate 3 via a roller structure 44 to apply the load transmitted by the primary lever to the cover plate 3.

[0115] The roller structure 44 can roll with the vertical displacement of the cover plate 3 during loading, thereby avoiding the impact of friction caused by relative sliding on the stability of normal stress.

[0116] The camera system 6 is located in front of the external support box 1 and is used to acquire images of the transparent soil sample inside the built-in sample box 2.

[0117] The camera system 6 includes two parallel camera guide rails 61 fixedly installed below the external support box 1, a camera vertical rod 63 that cooperates with the camera guide rails 61, and a camera 64 installed on the camera vertical rod 63.

[0118] The camera guide rail 61 provides a forward and backward movement path for the camera vertical rod 63, which can move forward and backward along the camera guide rail 61 and be fixed at the desired position.

[0119] The camera 64 is mounted on the camera vertical rod 63 and can be adjusted up and down along the camera vertical rod 63, thereby realizing the spatial adjustment of the camera 64 in the front-back and up-down directions to meet the needs of different observation areas and imaging fields of view.

[0120] The above structural design allows the camera system 6 and the external support box 1 to be installed as an integrated unit, preventing changes in camera position due to instability of the external support during the test.

[0121] The laser system 7 is respectively set on the left and right sides of the external carrier box 1, and is used to provide sheet light illumination required for particle image velocimetry to the transparent soil sample in the built-in sample box 2.

[0122] Each side of the laser system 7 includes a laser guide rail 71 fixedly installed below the external support box 1, a laser vertical rod 73 that cooperates with the laser guide rail 71, and a laser 74 installed on the laser vertical rod 73.

[0123] The vertical laser rod 73 can move left and right along the laser guide rail 71 and be fixed, and the laser 74 can adjust its position up and down along the vertical laser rod 73, thereby adjusting the spatial position of the laser beam in the transparent soil sample.

[0124] The laser systems 7 on the left and right sides enable the laser sheet light to stably penetrate the transparent box and form the optical conditions for PIV observation.

[0125] Both the external support box 1 and the internal sample box 2 are made of transparent material, which allows the laser sheet light to penetrate the box and illuminate the inside of the transparent soil sample, while facilitating the imaging observation of the transparent soil sample by the camera system 6.

[0126] Example 13:

[0127] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Further, see [link to embodiment 1]. Figure 1 This embodiment provides an integrated device for controllable normal stress loading and PIV observation for root pull-out tests in transparent soil, including an external bearing box 1, an internal sample box 2, a cover plate 3, a normal stress loading mechanism 4, a limiting rod 5, a camera system 6, and a laser system 7.

[0128] The camera system 6 is located in front of the external support box 1, and the laser system 7 is located on the left and right sides of the external support box 1 respectively. The above systems and the external support box 1 are arranged in an integrated manner to achieve the coordinated normal loading and optical observation during the root pull-out test of transparent soil.

[0129] See Figure 2 The external support box 1 is a transparent box structure, which is used to provide load and reaction support for the entire device. The internal sample box 2 is set inside the external support box 1 and is used to hold transparent soil samples and their pore fluid. The bottom and lower part of the side wall of the internal sample box are provided with drainage holes 21 for drainage or pore fluid control during the test.

[0130] A limiting block 11 is fixedly installed on the inner wall of the external bearing box 1. The limiting block 11 is used to contact the outer wall of the built-in sample box 2 to limit and position the built-in sample box 2 laterally, preventing it from lateral displacement during loading and testing.

[0131] The side wall of the external bearing box 1 has an external bearing box through hole 12 at a corresponding position, and the side wall of the internal sample box 2 has an internal sample box through hole 22 at a corresponding position. The limiting rod 5 passes through the external bearing box through hole 12 and the internal sample box through hole 22 in sequence, thereby forming a vertical limit on the internal sample box 2 during the test, preventing it from being lifted as a whole when normal stress is applied or when root pulling is performed.

[0132] By using the combination of the limiting block 11 and the limiting rod 5, the internal sample box 2 is positioned laterally and limited vertically within the external bearing box 1, ensuring the stability of the test process.

[0133] The cover plate 3 covers the top of the built-in sample box 2 and is used to apply normal stress to the transparent soil sample during the test. The cover plate 3 is a detachable structure, which facilitates sample loading and disassembly after the test. See also Figure 3 The cover plate 3 has a pull-out hole 31 at its center for the roots to pass through during the test. The cover plate 3 is provided with a cover plate gasket 32 ​​at the position where it contacts the normal stress loading mechanism 4, which is used to disperse the local load applied by the loading mechanism and avoid local stress concentration on the cover plate.

[0134] See Figure 1 and Figure 4 The normal stress loading mechanism 4 is located above the cover plate 3 and is used to apply stable and controllable normal stress to the cover plate 3 during the test.

[0135] The normal stress loading mechanism 4 includes multiple primary levers 41, each of which is rotatably mounted on the external bearing box 1 via a fulcrum structure 42. Each primary lever 41 includes an input end and an output end. The input end is equipped with a connecting rod 43 for suspending weights 45. By placing weights 45 of different numbers or weights at the connecting rod 43, the primary lever 41 rotates at the fulcrum structure 42, thereby transmitting and amplifying the gravity of the weights 45 through the primary lever 41 and applying it to the cover plate 3. The output end contacts the cover plate gasket 32 ​​via a roller structure 44, used to apply the load transmitted by the primary lever 41 to the cover plate 3.

[0136] Multiple primary levers 41 are symmetrically arranged on both sides of the built-in sample box 2, so that the normal load generated by the weights 45 is kept symmetrical and balanced in space.

[0137] See Figure 3 The roller structure 44 is fixed on the first-stage lever 41, and its roller 441 makes rolling contact with the cover plate gasket 32. When the cover plate 3 undergoes vertical displacement during loading, the roller 441 rolls with the relative movement, thereby reducing friction and improving the stability of the normal stress.

[0138] See Figure 1The camera system 6 includes a camera guide rail 61, a camera mounting plate 62, a camera vertical rod 63, and a camera 64. The camera guide rail 61 is located in front of the external support box 1, with one end integrated with the camera mounting plate 62. The camera mounting plate 62 is bolted to the bottom of the external support box 1 to facilitate disassembly and replacement of the camera system 6. The camera vertical rod 63 is engaged between the two camera guide rails 61 and can move back and forth along the camera guide rails 61 and be fixed in the desired position. The camera 64 is mounted on the camera vertical rod 63 and can be adjusted up and down along the camera vertical rod 63, thereby achieving spatial adjustment of the camera in the back-and-forth and up-and-down directions to meet the imaging needs of different observation areas of the transparent soil sample.

[0139] See Figure 1 The laser system 7 is respectively installed on the left and right sides of the external support box 1. Each side of the laser system 7 includes a laser guide rail 71, a laser mounting plate 72, a laser vertical rod 73, and a laser 74. The laser vertical rod 73 is engaged with the corresponding laser guide rail 71 and can move left and right along the laser guide rail 71 and be fixed in the desired position. The laser 74 is installed on the laser vertical rod 73 and can be adjusted up and down along the laser vertical rod 73 to adjust the spatial position of the laser beam in the transparent soil sample, thereby providing stable optical conditions for particle image velocity measurement observation.

[0140] Before a pull-out test of the roots in transparent soil, the built-in sample box 2 is first placed inside the outer bearing box 1, with its outer wall in contact with the limiting block 11 to complete the lateral positioning. Then, the limiting rod 5 is inserted into the through hole 12 of the outer bearing box and the through hole 22 of the built-in sample box to vertically limit the built-in sample box 2.

[0141] After fixation is completed, the transparent soil sample and its pore fluid are filled into the built-in sample box 2, and drainage or consolidation treatment is carried out as needed for the test.

[0142] After the sample preparation is completed, cover the top of the built-in sample box 2 with the cover plate 3 so that the root system can emerge from the pull-out hole 31.

[0143] Subsequently, a predetermined normal stress is applied to the cover plate 3 through the normal stress loading mechanism 4.

[0144] According to the experimental observation requirements, the positions of camera system 6 and laser system 7 are adjusted so that the laser sheet light forms a stable light sheet in the transparent soil sample, and the camera 64 obtains a clear field of view, thereby conducting particle image velocity measurement observation of the internal deformation of the transparent soil during the root pull-out process.

Claims

1. A visualization observation device for root pull-out tests in transparent soil, characterized in that: It includes an external bearing box (1), an internal sample box (2), a cover plate (3), a normal stress loading mechanism (4), a camera system (6), and a laser system (7). The external carrier box (1) is a box structure with a hollow interior, one open end and the other closed end; the internal sample box (2) is fixedly assembled inside the external carrier box (1) and is a box structure with open ends; the internal sample box (2) has a drainage hole (21) at the bottom of the side of the external carrier box (1) near the closed end, and the internal sample box (2) also contains transparent soil samples and pore liquid. The transparent soil sample contains plant roots, with one end of the plant roots inside the transparent soil sample and the other end extending out of the transparent soil sample. The cover plate (3) is placed in the cavity of the built-in sample box (2) and is located above and close to the transparent soil sample; a pull-out hole (31) is provided at the center of the cover plate (3), and the plant roots pre-embedded in the transparent soil sample pass through the pull-out hole (31) so that the external pull-out device can pull out the plant roots. The cover plate (3) is equipped with a normal stress loading mechanism (4) for applying normal stress to the transparent soil sample; the normal stress loading mechanism (4) includes several lever groups, each lever group including two primary levers (41), two fulcrum structures (42), two roller structures (44) and weights (45); the two fulcrum structures (42) in the group are fixed at intervals on the external bearing box (1) and located on the same side; the two primary levers (41) in the group are arranged in parallel and installed on different fulcrum structures (42); one end of the two primary levers (41) in the group is rotatably installed on the fulcrum structure (42), and the other end is suspended for hanging weights (45). Roller structures (44) are provided on the two primary levers (41) on the side near the fulcrum structure (42); the roller structures (44) are located between the primary levers (41) and the cover plate (3) and are used to apply the load transmitted by the primary levers (41) to the cover plate (3); The camera system (6) and laser system (7) are respectively located on the outside of the external carrier box (1) for particle image velocity measurement observation of the transparent soil sample in the built-in sample box (2).

2. The visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The visualization observation device also includes a limiting block (11) for limiting the lateral displacement of the built-in sample box (2) and a limiting rod (5) for limiting the vertical displacement of the built-in sample box (2). The limiting block (11) is L-shaped and is located at the four corners of the bottom of the inner cavity of the outer bearing box (1). When the inner sample box (2) is placed, the outer wall of the inner sample box (2) contacts the inner corners of the four L-shaped limiting blocks (11), thereby limiting the lateral displacement of the inner sample box (2). The four sides of the external carrier box (1) are respectively labeled as side wall I, side wall II, side wall III and side wall IV; two external carrier box through holes (12) are opened on side wall I and side wall III, and the two external carrier box through holes (12) on side wall I are labeled as external carrier box through holes I (121), and the two external carrier box through holes (12) on side wall III are labeled as external carrier box through holes II (122); the two side walls of the internal sample box (2) are respectively provided with an internal sample box through hole (22) penetrating the side wall of the internal sample box (2). The limiting rod (5) passes through the external bearing box through hole I (121), the internal sample box through hole (22) and the external bearing box through hole II (122) in sequence, thereby limiting the vertical displacement of the internal sample box (2).

3. The visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The four sides of the external bearing box (1) are respectively labeled as side wall I, side wall II, side wall III and side wall IV; The top of the side wall II and side wall IV of the external carrier box (1) extends outward with a boss (13). The boss (13) and the external carrier box (1) are integrally formed, and the top surface of the boss (13) is flush with the top surface of the external carrier box (1). The fulcrum structure (42) within the same lever group is fixed on the same side boss (13), and the positions of the two fulcrum structures (42) are symmetrical about the top surface of the external bearing box (1).

4. The visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The fulcrum structure (42) includes a hinge shaft and two hinge lugs, which are respectively referred to as hinge lug I and hinge lug II; The end of the first-stage lever (41) is embedded between the hinge lug I and the hinge lug II; the hinge lug I and the hinge lug II are respectively provided with through holes I and II; the end of the first-stage lever (41) connected to the fulcrum structure (42) is provided with through hole III; the through hole III is coaxially arranged with through hole I and through hole II, so that the hinge shaft passes through through hole I, through hole III and through hole II in sequence; elastic limiting retaining rings are sleeved at both ends of the hinge shaft; After assembly, the first-stage lever (41) can rotate around the hinge axis.

5. A visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The normal stress loading mechanism (4) includes a connecting rod (43); The mounting end of the first-level lever (41) is provided with a through hole IV. The through holes IV of the two first-level levers (41) in the same lever group are coaxially arranged so that the connecting rod (43) passes through the two through holes IV and is fixed on the two first-level levers (41). The weight (45) is hung on the connecting rod (43); By hanging different numbers or weights of weights (45) on the connecting rod (43), the first-stage lever (41) rotates around the fulcrum structure (42), thereby using the gravity of the weights (45) as the input load. After being transmitted through the first-stage lever (41), the load is applied to the cover plate (3) through the roller structure (44).

6. A visualization observation device for root pull-out tests in transparent soil according to claim 1 or 5, characterized in that: The roller structure (44) includes a roller (441), a rotating shaft, and a support base (442). The primary lever (41) is fixed to the top surface of the support base (442); The roller (441) is rotatably mounted in the support base (442) via a rotating shaft, and the roller (441) is mounted on the cover plate gasket (32); The cover plate gasket (32) is disposed on the cover plate (3), and the two cover plate gaskets (32) are respectively located on both sides of the pull hole (31); The length of the cover plate gasket (32) is equal to the length of the cover plate (3), and it is used to distribute the local load applied by the normal stress loading mechanism (4).

7. A visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The camera system (6) includes a camera rail (61), a camera mounting plate (62), a camera vertical rod (63), and a camera (64). The four sides of the external bearing box (1) are respectively labeled as side wall I, side wall II, side wall III and side wall IV; The camera mounting plate (62) is fixedly installed on the bottom of the side wall I of the external carrier box (1); a camera guide rail (61) is vertically connected to each end of the camera mounting plate (62), and a camera vertical rod (63) is slidably connected to the end of the two camera guide rails (61) away from the camera mounting plate (62); the camera vertical rod (63) has a T-shaped structure, with the two ends of the horizontal section located in the grooves of different camera guide rails (61), and a camera (64) is slidably connected to the vertical section.

8. A visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The laser system (7) includes a laser guide rail (71), a laser mounting plate (72), a laser vertical rod (73), and a laser (74). The four sides of the external carrier box (1) are respectively labeled as side wall I, side wall II, side wall III and side wall IV; a laser system (7) is provided on both side wall II and side wall IV. The laser mounting plate (72) is fixedly installed at the bottom of side wall II and side wall IV; a laser guide rail (71) is vertically connected to each end of the laser mounting plate (72), and a laser vertical rod (73) is slidably connected to the end of the two laser guide rails (71) away from the laser mounting plate (72); the laser vertical rod (73) has a T-shaped structure, with the two ends of the horizontal section located in the grooves of different laser guide rails (71), and a laser (74) is slidably connected to the vertical section.

9. A visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: The outer contour of the cover plate (3) is adapted to the inner contour of the cavity of the built-in sample box (2).

10. A visualization observation device for root pull-out tests in transparent soil according to claim 1, characterized in that: Both the external carrier box (1) and the internal sample box (2) are made of transparent material.

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