Shear loading device under complex stress state and drainage condition
By using comb plate and folding frame structure in the experimental device to rotate the main stress axis of the loading plate, the problem of uneven boundary effect of the existing device under complex stress and drainage conditions is solved, and the uniform application of shear stress is achieved and Multi-field coupled simulation provides more realistic experimental data on soil behavior.
Patent Information
- Application Number
- CN202411155189.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-21
- Publication Date
- 2025-01-03
AI Technical Summary
Existing experimental devices are difficult to accurately and uniformly simulate the shear stress on the boundary of soil samples in the laboratory, especially under complex stress states and drainage conditions, and cannot effectively control the rotation load of the main stress axis, resulting in uneven boundary effects.
A shear loading device under complex stress states and drainage conditions was designed, using a foldable comb-shaped plate and an articulated folding frame structure, and the main stress axis of the loading plate is rotated by a servo motor drives the force transmission rod, combined with a force sensor and water bath system to achieve precise control and uniform application of shear stress.
The uniform application of shear stress on the boundary of the soil sample is achieved, which alleviates the boundary effect caused by loading plate stiffness and soil particle friction. It also simulates marine environmental conditions through multiple field coupling, providing more realistic soil behavior experimental data.
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Figure CN119246273A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of ultra-gravity loading shear test, in particular to a shear loading device under complex stress state and drainage conditions. Background Art
[0002] Realistic modeling of soil behavior requires the broadest possible experimental data base to fit model parameters or inspire the proposed model. In marine environments, soils are not only subjected to unidirectional but also multidirectional loads, so it is necessary to consider loads with principal stress axis rotations. Loads with principal stress axis rotations are loads applied in one direction that cause the principal stress axes in the soil to rotate, thus causing stress changes in other directions. Currently, most laboratory tests are performed using fixed principal axes in devices such as classical triaxial apparatus and true triaxial apparatus. In these devices, the boundary conditions should be pure pressure (without shear components). Many results on monotonic or cyclic loading, drained or undrained boundary conditions are obtained in this way.
[0003] The main difficulty in studying the behavior of soil under the action of spindle rotation load is the need to control the shear stress on the soil sample boundary. There are some experimental equipment in the laboratory that can control the shear force on the soil sample boundary, such as Casagrande's direct shear box, Roscoe's simple shear device, or the simple shear box of the Swedish Geotechnical Institute (SGI) and the Norwegian Geotechnical Institute (NGI), but the stress and strain state in these equipment is far from uniform and is not suitable for theoretical research on geological materials.
[0004] Based on the above problems, the present invention provides a device which can accurately and evenly simulate the shear stress on the boundary of a soil sample in a laboratory, and is a shear loading device under complex stress states and boundary drainage conditions. Summary of the invention
[0005] The purpose of the present invention is to provide a shear loading device under complex stress states and drainage conditions, in which a fence-shaped folding frame and an overlapping comb-shaped plate are hingedly connected, a force sensor is arranged at the bottom fixed end, and the movable end is connected to a power system. The rotation control of the principal stress axis of the loading plate is realized through the comb-shaped plate and the folding frame, thereby effectively alleviating the boundary effect caused by the different stiffness of the loading plate and the friction between soil particles.
[0006] To achieve the above-mentioned objectives, the present invention provides a shear loading device under complex stress states and drainage conditions, comprising a loading frame and a shear loading device arranged on the loading frame, the shear loading device comprising a loading unit and a power system connected to the loading unit through a force transmission rod, the loading unit comprising a force sensor, a comb plate and a folding frame arranged on the comb plate, and the power system is configured as a servo motor.
[0007] Preferably, the upper end of the force transmission rod is connected to the output end of the servo motor through a coupling, and the lower end of the force transmission rod is connected to the second base, and a fixing flange is provided on the second base, and the bottom end of the force transmission rod is provided on the fixing flange.
[0008] Preferably, the comb plate is composed of a fixed workpiece, four first movable workpieces and a second movable workpiece which are overlapped in sequence, the other side of the fixed workpiece is fixed on the first base, the second movable workpiece is connected to the second base, and the force sensor is arranged at the lower end of the first base.
[0009] Preferably, the folding frame is configured to be fence-shaped, a plurality of connecting blocks are provided on the folding frame, the top and bottom of the folding frame are respectively connected to the second base and the first base, and the folding frame is hinged to the comb plate through the connecting blocks.
[0010] Preferably, the shear loading device is placed in a centrifuge model box and connected to a water bath circulation system through a pipeline.
[0011] Therefore, the shear loading device under complex stress state and drainage conditions of the present invention has the following beneficial effects:
[0012] (1) The present invention uses a comb plate that can be evenly divided into six comb workpieces, and a folding frame is hinged to one side of the six comb workpieces. This special comb plate and folding frame structure enables the servo motor to control the moving distance of each comb plate individually when manipulating the total displacement of the loading plate. The deformation generated by the mechanical power system and transmitted by the mechanical folding frame transmission structure can be adjusted individually by the comb loading plate.
[0013] (2) The device is able to transmit shear stress on the surface while maintaining the possibility of extensive stretching (or compression) to maintain uniformity of strain. These comb-like loading plates are connected to each other by an articulated arm system, which produces proportional displacement transmission at the center of the loading plate. Due to this proportional displacement, an average uniform stretch is applied to the surface, and the uniformity condition is exactly satisfied at the center of each loading plate.
[0014] (3) The shear loading device realizes the rotation control of the principal stress axis of the loading plate through the comb plate and the equal distribution structure, thereby effectively alleviating the boundary effect caused by the different stiffness of the loading plate and the friction between the soil particles. In addition, the shear loading device protected by the present invention realizes multi-field coupling by controlling the temperature of the water bath system, injecting chemical reagents, etc.
[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1It is a structural schematic diagram of a four-axis loading system composed of four shear loading devices according to an embodiment of the present invention;
[0017] Figure 2 It is a schematic structural diagram of a shear loading device according to an embodiment of the present invention;
[0018] Figure 3 A schematic diagram of the structure of a comb plate according to an embodiment of the present invention;
[0019] Figure 4 This is a schematic diagram of the layout inside the centrifuge model box according to an embodiment of the present invention;
[0020] Reference numerals:
[0021] 1. Force sensor; 2. First base; 3. Folding frame; 4. Comb plate; 5. Second base; 6. Force transmission rod; 7. Power system; 8. Shear loading device; 9. Centrifuge model box; 10. Inlet and outlet pipes. DETAILED DESCRIPTION
[0022] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.
[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.
[0024] Example
[0025] The present invention provides a shear loading device under complex stress state and drainage conditions, including a loading frame and a shear loading device 8 arranged on the loading frame, such as Figure 1 As shown, the shear loading device 8 is capable of simultaneously forming a parallelogram-shaped loading frame with four members, the outer structure of which is vertical, the support surface surrounds the specimen, and transmits shear stress on the inner surface while maintaining the possibility of extensive tension (or compression) to maintain uniformity of strain.
[0026] like Figure 2 As shown, the shear loading device 8 includes a loading unit and a power system 7 connected to the loading unit through a force transmission rod 6, the power system 7 is configured as a servo motor, the upper end of the force transmission rod 6 is connected to the output end of the servo motor through a coupling, the lower end of the force transmission rod 6 is connected to the second base 5, the second base 5 is provided with a fixed flange, and the bottom end of the force transmission rod 6 is arranged on the fixed flange.
[0027] The loading unit includes a force sensor 1, a comb plate 4 and a folding frame 3 arranged on the comb plate 4. Figure 3As shown, the comb plate 4 is composed of a fixed workpiece, four first movable workpieces and a second movable workpiece which are overlapped in sequence. The six comb loading plates overlap each other, do not separate from each other, and do not overlap each other. The other side of the fixed workpiece is fixed on the first base 2, and the second movable workpiece is connected to the second base 5. The folding frame 3 is arranged in a grid fence shape, and a plurality of connecting blocks are arranged on the folding frame 3. The top and bottom of the folding frame 3 are respectively connected to the second base 5 and the first base 2. The folding frame 3 is hinged with each comb plate workpiece in the comb plate 4 through the connecting blocks to form a whole. The connecting blocks are used to transmit the control information of the power system 7 to the folding frame 3, so as to realize the control of the folding and unfolding of the folding frame 3. When working, the first movable workpiece and the second movable workpiece can change their positions as the power system 7 controls the extension and contraction of the folding frame 3, thereby realizing the system's principal stress axis rotation shear loading mode for the specimen.
[0028] The force sensor 1 is arranged at the lower end of the first base 2 through a force transmission flange, and the shear force borne by the sample is measured by the force sensor 1, and the data is recorded; the components in the entire device are connected to the controller, and the deformation degree of the folding frame 3 is accurately controlled by setting a servo motor, a force transmission rod 6, a force sensor 1 and a controller.
[0029] like Figure 4 As shown, the shear loading device of the four-axis loading system is placed in the centrifuge model box 9, and connected to the water bath circulation system through the inlet and outlet pipes 10 to realize the simulation of the hypergravity environment; the water bath temperature control system can control the internal water temperature change to simulate the real temperature and its change of the seabed environment. The temperature control liquid used is not water but oil. The specific heat capacity of oil is 4200J / (kg·K), which is smaller than that of water 2000J / (kg·K), and the temperature rises and falls faster. In addition, the oil has a low freezing point and will not freeze when the temperature is less than 0°C, so a wider range of temperature control can be achieved; and different chemical reagents are injected to react chemically with the granular soil to produce cementation to simulate more realistic conditions.
[0030] The device provided by the present invention is a principal stress axis rotation shear loading device controlled by an equal distribution structure. When loading, the comb plate 4 directly contacts the sample to generate a shear force. As the displacement increases, the folding frame 3 of the equal distribution structure connected to the power system 7 moves, so that the comb plates 4 in the shear direction are separated. Figure 2 As shown, the displacement in the shear direction is proportional, and a uniform shear strain is applied to the sample. This comb plate 4 that can apply uniform strain is realized by a clever folding frame 3 structure, and the entire structure has the advantages of simple structure, convenient operation, and strong adaptability. At the same time, by setting a servo motor, a force transmission rod 6, a force sensor 1 and a controller, the deformation degree of the folding frame 3 can be accurately controlled to adapt to different working environments and requirements.
[0031] Therefore, the present invention provides a shear loading device under complex stress states and drainage conditions, in which a fence-shaped folding frame and overlapping comb-shaped plates are hingedly connected, a force sensor is arranged at the bottom fixed end, and the movable end is connected to a power system. The rotation control of the principal stress axis of the loading plate is realized through the comb-shaped plate and the folding frame, thereby effectively alleviating the boundary effect caused by the different stiffness of the loading plate and the friction between soil particles.
[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.
Claims
1. A shear loading device under complex stress state and drainage conditions, characterized in that: It includes a loading frame and a shear loading device arranged on the loading frame, the shear loading device includes a loading unit and a power system connected to the loading unit through a force transmission rod, the loading unit includes a force sensor, a comb plate and a folding frame arranged on the comb plate, and the power system is configured as a servo motor.
2. A shear loading device under complex stress state and drainage conditions according to claim 1, characterized in that: The upper end of the force transmission rod is connected to the output end of the servo motor through a coupling, and the lower end of the force transmission rod is connected to the second base. The second base is provided with a fixing flange, and the bottom end of the force transmission rod is provided on the fixing flange.
3. A shear loading device under complex stress state and drainage conditions according to claim 2, characterized in that: The comb plate is composed of a fixed workpiece, four first movable workpieces and a second movable workpiece which are overlapped in sequence. The other side of the fixed workpiece is fixed on the first base. The second movable workpiece is connected to the second base. The force sensor is arranged at the lower end of the first base.
4. A shear loading device under complex stress state and drainage conditions according to claim 3, characterized in that: The folding frame is configured in a fence shape, a plurality of connecting blocks are provided on the folding frame, the top and the bottom of the folding frame are respectively connected to the second base and the first base, and the folding frame is hinged to the comb plate through the connecting blocks.
5. The shear loading device under complex stress state and drainage condition according to claim 1, characterized in that: The shear loading device is placed in the centrifuge model box and connected to the water bath circulation system through a pipeline.