A true triaxial apparatus with multiple loading boundaries and a test method

Abstract

The present invention provides a multi-loading boundary true triaxial apparatus, comprising a device arranged at a large principal stress of a specimen s 1 direction s 1-way rigid loading system (1) and / or s 1. Semi-rigid force transmission device (2) in the direction of the main stress s 2-way s 2-way rigid loading system (3) and / or s 2-direction semi-rigid force transmission device (4), set at the minimum principal stress of the specimen s Flexible loading system in 3 directions (5) and / or application of confining pressure stress s c The pressure chamber structure (6) s The present invention also provides a method for testing a true triaxial test apparatus with multiple loading boundaries. The present invention uses a replaceable loading device and is suitable for studying the influence of different boundary conditions on the test results under three-dimensional stress. It can realize true triaxial testing under complex stress paths and study the constitutive relationship and microstructural evolution of geotechnical materials.

Description

Technical Field

[0001] The invention relates to a multi-loading boundary true triaxial instrument and a test method, belonging to the technical field of indoor geotechnical test equipment. Background Art

[0002] The true triaxial apparatus can apply three different principal stress components σ1, σ2, and σ3 to a cubic soil specimen, simulating the actual stress state of the soil. It is an important instrument for studying the constitutive relationship of the soil. The development and improvement of the true triaxial testing apparatus has a history of nearly a hundred years. According to different loading methods, it can be divided into: (1) rigid loading; (2) flexible loading; (3) mixed loading. Existing studies have pointed out that rigid loading has problems such as large friction and top support between plates, while flexible loading has problems such as unclear force at the corners of the specimen and limited loading range. Currently, the more widely recognized loading method is "mixed loading".

[0003] In the true triaxial apparatus with mixed loading, according to different loading methods, it can be divided into: (1) σ1 rigid plate + σ2 rigid plate + σ c Confining pressure chamber; (2) σ1 rigid plate + σ2 water bag + σ c Confining pressure chamber; (3) σ1 rigid plate + σ2 compressible force transmission block + σ c Confining pressure chamber; (4) σ1 rigid plate + σ2 compressible force transmission block + σ3 water bag. It can be seen that the loading methods of the hybrid loading true triaxial apparatus are quite diverse, covering rigid, semi-rigid, flexible, and confining pressure chamber loading, a total of 4 different combinations of loading methods.

[0004] However, due to the limitation of the single loading mode of each type of true triaxial apparatus, the study on the influence of different loading boundaries on the true triaxial test results is relatively rare. In fact, there is always an unclear issue in indoor geotechnical tests: the influence of boundary conditions on test results, that is, the test results of the same soil obtained on different instruments may be very different. Especially for the true triaxial apparatus with 4 different combined loading modes, the discreteness of the test results and the influencing factors will be further amplified.

[0005] In addition, one of the key points in geotechnical material research is to establish multi-scale connections, that is, macro- and micro-reference research. However, most of the micro- and micro-studies on soil are concentrated in conventional triaxial and plane strain tests, and the micro- and micro-studies on soil in true triaxial tests are very rare. However, the micro- and micro-structures in true triaxial tests can better reflect the real structural state of the soil.

[0006] Studying the influence of different loading boundaries on test results is of great practical significance for geotechnical testing, especially for true triaxial tests with more complex boundaries. It is currently difficult to evaluate the accuracy of test results under different boundaries. At the same time, establishing multi-scale connections under general stress states can effectively reveal the deformation mechanism of soil. Therefore, it is of practical value to develop a true triaxial apparatus with multiple loading boundary conditions that can realize the solidification of discrete specimens and provide a test method. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a multi-loading boundary true triaxial apparatus, which can apply three-dimensional stresses of different loading boundary combinations to the sample, and provide a basis for studying the influence of different loading boundary conditions on the test results.

[0008] At the same time, the present invention provides a test method of a multi-loading boundary true triaxial apparatus, which is suitable for studying the influence of different boundary conditions on the test results under three-dimensional stress; it can realize true triaxial tests under complex stress paths, prepare samples with different deposition angles, realize the solidification of discrete granular samples, and study the constitutive relationship of rock and soil materials and the evolution of microstructures.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A multi-loading boundary true triaxial apparatus, comprising a σ1 direction rigid loading system and / or a σ1 direction semi-rigid force transmission device arranged in the direction of the large principal stress σ1 of the specimen, a σ2 direction rigid loading system and / or a σ2 direction semi-rigid force transmission device arranged in the direction of the medium principal stress σ2 of the specimen, a flexible loading system and / or a σ3 direction for applying a confining pressure stress σ c A pressure chamber structure, a displacement measurement system in the σ3 direction, a sample preparation device and / or a sample curing system;

[0011] The displacement measurement system is used to detect the local deformation of the specimen;

[0012] The sample solidification system is used for solidification of discrete particle samples;

[0013] The sample preparation device is used to prepare samples with different deposition angles.

[0014] The rigid loading system in the σ1 direction includes an upper loading system arranged at the top of the sample and a lower loading system arranged at the bottom of the sample; the upper loading system includes an upper servo motor and a first piston rod that are movably connected, the first piston rod is connected to a first force sensor, the first force sensor is connected to a first rigid plate, and a synchronous deformation rod is also provided on the first piston rod; the first force sensor and the synchronous deformation rod are independent of each other; the synchronous deformation rod includes a fixing ring connected to the first piston rod, a connecting plate is horizontally and symmetrically extended outward on the fixing ring, the lower surfaces of the two connecting plates are connected to connecting rods, and the bottom end of the connecting rod is provided with a pad for contacting the upper surface of the semi-rigid force transmission device in the σ2 direction;

[0015] The lower loading system includes a loading base, the upper surface of which is provided with an outward convex disc for connecting to the sample preparation device or the sample curing system, and the loading base is symmetrically provided with two wedge teeth along the σ2 direction for connecting to the bottom surface of the semi-rigid force transmission device in the σ2 direction.

[0016] The semi-rigid force transmission device in the σ1 direction includes a plurality of dispersion blocks, a positioning grid and a magnetic adsorption device;

[0017] The dispersion block includes a universal ball and a rectangular block;

[0018] The rectangular block is provided with a threaded hole;

[0019] The universal ball comprises a rectangular base, the lower surface of the rectangular base is provided with a threaded column adapted to the threaded hole, the upper surface of the rectangular base is provided with a hemispherical groove, a plurality of balls arranged in a single layer are provided in the hemispherical groove, a universal ball body is provided on the balls, and the top surface opening diameter of the hemispherical groove is smaller than the diameter of the universal ball body;

[0020] The positioning grid comprises a square grid and a top surface coating;

[0021] The square grid is divided into a plurality of squares adapted to the dispersed blocks;

[0022] The top surface of the grid is provided with the top surface coating;

[0023] The magnetic adsorption device comprises a magnetic seat and a cast iron plate;

[0024] The top surface of the top surface coating is provided with the cast iron plate, and the cast iron plate is provided with the magnetic seat for adsorbing and desorbing the dispersion block.

[0025] Preferably, the σ2 direction rigid loading system includes a front loading system arranged on the front side of the specimen and a rear loading system arranged on the rear side of the specimen, and the rear loading system has the same structure as the front loading system; the front loading system includes a front servo motor, a second piston rod, a second sensor, a connecting flange and a second rigid plate; the front servo motor is connected to the load frame in the pressure chamber structure; the front servo motor is movably connected to the second piston rod, the second piston rod is connected to the second sensor, and the second sensor is connected to the connecting flange by bolts; the connecting flange is connected to the second rigid plate by bolts.

[0026] Preferably, the semi-rigid force transmission device in the σ2 direction comprises a compressible force transmission block and a force transmission block base;

[0027] The compressible force transmission block comprises a special-shaped steel plate, a first roller, a first optical axis, balsa wood and a steel ball;

[0028] The special-shaped steel plate is a square plate with a plurality of first grooves formed on one side; a through hole for penetrating the first optical axis is formed on the side wall of the first groove;

[0029] The first roller is sleeved outside the first optical axis;

[0030] The steel ball is placed in the second groove on the top surface of the top-layer special-shaped steel plate;

[0031] The bottom surface of the special-shaped steel plate is connected to the cubic protrusion of the balsa wood top surface through the third groove;

[0032] The special-shaped steel plates and the balsa wood are arranged in layers and at intervals;

[0033] The force transmission block base comprises a seat, a wing plate, a second roller, a second optical axis and a fourth groove;

[0034] The lower surface of the seat is provided with the fourth groove for matching with the wedge tooth;

[0035] The base is a flat plate, and vertical wing plates extend upward from both ends of the base;

[0036] A plurality of second optical axes at the same height are connected between the two wing plates;

[0037] A plurality of second rollers are sleeved on the second optical axis;

[0038] The bottom of the second roller is higher than the upper surface of the base;

[0039] The compressible force transmission block is carried on the second roller.

[0040] Preferably, the flexible loading system comprises a left flexible loading system arranged on the left side of the sample, a right flexible loading system arranged on the right side of the sample and a connecting and positioning device, the left flexible loading system and the right flexible loading system have the same structure, and the connecting and positioning device connects the left flexible loading system and the right flexible loading system;

[0041] The left side flexible loading system includes a rubber membrane water bag, a rectangular steel plate, a third piston rod, a water bag frame, an optical axis sleeve, a square thin plate and bolts;

[0042] The rubber membrane water bag is embedded in the water bag frame, and the rubber membrane water bag is clamped between the water bag frame and the rectangular steel plate through the bolts;

[0043] The inner side of the rubber membrane water bag is adhered to the square thin plate, and the third piston rod is connected to the square thin plate through threads;

[0044] The rectangular steel plate is symmetrically provided with two piston holes for passing the third piston rod;

[0045] A water injection hole for injecting water into the rubber membrane water bag is provided at the lower left corner of the rectangular steel plate;

[0046] An exhaust hole is provided at the upper right corner of the rectangular steel plate;

[0047] The optical axis sleeve is sealed and connected to the piston hole via an O-ring;

[0048] The connection and positioning device comprises an L-shaped base, a screw rod and a hexagonal nut;

[0049] The L-shaped base is respectively connected to the left flexible loading system and the right flexible loading system through threads, and the left flexible loading system and the right flexible loading system are connected through the screw rod 1 and the hexagonal nut;

[0050] The bottom surface of the L-shaped base is connected to a hole on the loading base that matches the bottom surface of the L-shaped base by bolt 1;

[0051] The side of the L-shaped base is connected to the rectangular steel plate by bolt 2. Preferably, the pressure chamber structure includes a pressure chamber body and a plurality of load frames; the pressure chamber body includes a cubic pressure chamber, a left pressure chamber door and a right pressure chamber door; the cubic pressure chamber is connected to the left pressure chamber door by a damping hinge, and the cubic pressure chamber and the left pressure chamber door are sealed by a rubber ring; a window is opened at the center of the left pressure chamber door, and an acrylic plate is embedded; the right pressure chamber door has the same structure as the left pressure chamber door; the load frame includes a column and a loading pier, and the loading pier is threadedly connected to the pressure chamber body through the column.

[0052] Preferably, the sample preparation device comprises a sample rubber membrane, a membrane holding tube, a sample cap, a first sample base and a sample preparation angle adjustment device;

[0053] The bottom end of the sample rubber membrane is sleeved on the first sample base;

[0054] The membrane-bearing cylinder is sleeved on the outer side of the middle part of the sample rubber membrane;

[0055] The film bearing cylinder comprises a left split mold and a right split mold connected by three bolts;

[0056] The top of the sample rubber membrane is turned outward and sleeved on the upper edge of the membrane-bearing cylinder, and the sample is added into the sample rubber membrane and compacted;

[0057] The sample preparation angle adjustment device comprises two adjustable angle gauges and angle steels, the model specification of the adjustable angle gauges is NYN-906, the angle steels are unequal angle steels, and the length of the long side of the angle steels is equal to the height of the sample;

[0058] When preparing samples with different deposition angles, the adjustable angle gauge is adjusted to a preset angle, the angle steel is placed on two adjustable angle gauges, and the first sample base together with the sample rubber membrane and the membrane-bearing cylinder are fixed on the angle steel as a whole, and the sample is added into the sample rubber membrane and compacted;

[0059] Then, the sample cap is placed on the top of the sample, and the top of the sample rubber membrane is turned back and put on the outside of the sample cap, and the upper O-ring fixes the sample rubber membrane and the sample cap through the upper lateral groove;

[0060] The lower O-ring fixes the sample rubber membrane to the first sample base through the lower lateral groove;

[0061] A hemispherical groove is arranged on the top of the sample cap, a second steel ball is placed in the hemispherical groove, and the first rigid plate of the upper loading system transfers the load to the sample cap through the second steel ball;

[0062] The top surface of the sample cap is provided with a sample extraction pipe;

[0063] The bottom surface of the first sample base is provided with a first disc groove adapted to match the outer convex disc;

[0064] The first sample base is connected with a first saturation hole.

[0065] Preferably, the first specimen base is replaced by a specimen curing system;

[0066] The sample curing system comprises a second sample base and a curing device;

[0067] The second sample base comprises a second disc groove adapted to fit with the outer convex disc;

[0068] A curing hole is arranged inside the second sample base, the curing hole is arranged obliquely from bottom to top and passes through the second sample base;

[0069] The second sample base is also provided with an L-shaped second saturation hole penetrating the top surface and the side surface of the second sample base; the second saturation hole is movably provided with a plug at the opening of the top surface of the second sample base;

[0070] The curing device includes a rubber hose for inserting into the curing hole;

[0071] The rubber hose is connected to the separatory funnel through a valve.

[0072] A test method of a true triaxial apparatus with multiple loading boundaries comprises the following steps:

[0073] For the σ1 rigidity + σ2 rigidity + σ3 confining pressure loading boundary combination: first, select the σ1 direction rigid loading system, the σ2 direction rigid loading system, the pressure chamber structure and the displacement measurement system; prepare the sample using the sample preparation device, and then take the sealed sample out of the film bearing cylinder; place the prepared and sealed sample on the loading base; close the left pressure chamber door and ensure a good seal; control the upper servo motor, the front servo motor and the rear servo motor to rotate through the computer, so that the first rigid plate and the steel ball are in contact, and the second rigid plate and the sample surface are in contact; the above completes the sample preparation and installation of the σ1 rigidity + σ2 rigidity + σ3 confining pressure loading boundary combination; σ1 rigidity + σ2 rigidity + σ3 confining pressure is referred to as the basic combination below;

[0074] For the σ1 rigid + σ2 rigid + σ3 water bag loading boundary combination, on the basis of the basic combination operation, a flexible loading system is installed to control the pressure of the rubber membrane water bag through the motor to control the water pressure;

[0075] For the σ1 rigid + σ2 semi-rigid + σ3 confining pressure loading boundary combination, on the basis of the basic combination operation, a force transfer block base is installed on the loading base, compressible force transfer blocks are arranged on the front and rear sides of the specimen, and the front loading system and the rear loading system are controlled to make the second rigid plate contact the compressible force transfer block;

[0076] For the σ1 rigid + σ2 semi-rigid + σ3 water bag loading boundary combination, on the basis of the σ1 rigid + σ2 rigid + σ3 water bag combination operation, a σ2 direction semi-rigid force transmission device is arranged on the front and rear sides of the specimen;

[0077] For the σ1 semi-rigid + σ2 rigid + σ3 confining pressure loading boundary combination, on the basis of the basic combination operation, a σ1 direction semi-rigid force transmission device is arranged at the top and bottom of the specimen;

[0078] For the σ1 semi-rigid + σ2 rigid + σ3 water bag loading boundary combination, on the basis of the "σ1 rigid + σ2 rigid + σ3 water bag" combination operation, a σ1 direction semi-rigid force transmission device is arranged at the top and bottom of the specimen;

[0079] For the σ1 semi-rigid + σ2 semi-rigid + σ3 confining pressure loading boundary combination, on the basis of the σ1 rigid + σ2 semi-rigid + σ3 confining pressure combination operation, a σ1 direction semi-rigid force transmission device is arranged at the top and bottom of the specimen;

[0080] For the σ1 semi-rigid + σ2 semi-rigid + σ3 water bag loading boundary combination, on the basis of the σ1 rigid + σ2 semi-rigid + σ3 water bag operation, a σ1 direction semi-rigid force transmission device is arranged at the top and bottom of the specimen.

[0081] Beneficial effects of the present invention:

[0082] The present invention provides a multi-loading boundary true triaxial apparatus and a test method, which can be replaced by a variety of loading modes and is suitable for different test conditions and boundary effect research. The true triaxial apparatus can realize a total of 8 loading boundary combinations: "σ1 rigidity + σ2 rigidity + σ3 confining pressure", "σ1 rigidity + σ2 rigidity + σ3 water bag", "σ1 rigidity + σ2 semi-rigidity + σ3 confining pressure", "σ1 rigidity + σ2 semi-rigidity + σ3 water bag", "σ1 semi-rigidity + σ2 rigidity + σ3 confining pressure", "σ1 semi-rigidity + σ2 rigidity + σ3 water bag", "σ1 semi-rigidity + σ2 rigidity + σ3 water bag", "σ1 semi-rigidity + σ2 semi-rigidity + σ3 confining pressure", and "σ1 semi-rigidity + σ2 semi-rigidity + σ3 water bag".

[0083] The present invention provides a multi-loading boundary true triaxial apparatus, which can solidify discrete particle samples under a three-dimensional stress state, and analyze the internal microstructure of the soil body by means of slicing, X-ray scanning, CT scanning and other technical means.

[0084] The present invention provides a multi-loading boundary true triaxial apparatus, which adopts a wedge-tooth embedding method, and different loading devices can be easily replaced. The true triaxial apparatus adopts a decentralized design in the direction of the major principal stress σ1 by replacing the permeable plate with a semi-rigid force transmission device, which realizes decentralized loading while also having permeability; the loading in the direction of the medium principal stress σ2 is a stacked combination of a rigid plate and balsa wood, which realizes decentralized loading while avoiding the jacking problem of the loading plate in the σ1 and σ2 directions, and the rigid plate and balsa wood are embedded and connected to ensure the integrity of the loading block, which facilitates the installation process.

[0085] Therefore, the multi-loading boundary true triaxial apparatus and test method provided by the present invention can effectively complete three-dimensional stress loading, study the influence of boundary effect on test results, and realize the solidification of discrete samples, which is convenient for further analysis of microstructure.

[0086] The present invention adopts a replaceable loading device, and rigid loading or semi-rigid loading can be adopted in the σ1 and σ2 directions, and flexible loading or confining pressure chamber loading can be adopted in the σ3 loading system, which is suitable for studying the influence of different boundary conditions on the test results under three-dimensional stress; the present invention includes a sample solidification device design, which is suitable for studying the evolution process of the sample microstructure. The multi-loading boundary true triaxial apparatus provided by the present invention can realize true triaxial tests under complex stress paths and study the constitutive relationship of geotechnical materials and the evolution of microstructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 It is a stereogram of the present invention using the combination of σ1 rigidity + σ2 semi-rigidity + σ3 confining pressure loading boundaries;

[0088] Figure 2 It is a structural schematic diagram of the present invention using a combination of σ1 rigidity + σ2 semi-rigidity + σ3 confining pressure loading boundaries to carry out a curing test;

[0089] Figure 3 It is a schematic diagram of the structure of the present invention using a combination of σ1 rigidity + σ2 semi-rigidity + σ3 water bag loading boundaries;

[0090] Figure 4 It is a structural schematic diagram of the rigid loading system in the σ1 direction of the present invention;

[0091] Figure 5 It is a structural schematic diagram of the semi-rigid force transmission device in the σ1 direction of the present invention;

[0092] Figure 6 It is a structural schematic diagram of the rigid loading system in the σ2 direction of the present invention;

[0093] Figure 7 It is a schematic structural diagram of a compressible force transmission block in a semi-rigid force transmission device in the σ2 direction of the present invention;

[0094] Figure 8 It is a structural schematic diagram of the force transmission block base in the semi-rigid force transmission device in the σ2 direction of the present invention;

[0095] Fig. 9 It is a structural schematic diagram of the flexible loading system in the present invention;

[0096] Fig.10 It is a structural schematic diagram of the pressure chamber structure in the present invention;

[0097] Fig.11 It is a structural schematic diagram of the displacement measurement system in the present invention;

[0098] Fig.12 It is a schematic diagram of the structure of the sample preparation device in the present invention;

[0099] Fig.13 It is a schematic diagram of the structure of the sample curing system in the present invention. DETAILED DESCRIPTION

[0100] The following is a further detailed description of a multi-loading boundary true triaxial apparatus and a test method of the present invention in conjunction with the accompanying drawings and specific embodiments.

[0101] Example 1

[0102] like Figure 1-2 As shown, a multi-loading boundary true triaxial apparatus comprises a rigid loading system 1 in the direction of the large principal stress σ1 of the specimen and a semi-rigid force transmission device 2 in the direction of the σ1, a rigid loading system 3 in the direction of the σ2 and a semi-rigid force transmission device 4 in the direction of the medium principal stress σ2, and a flexible loading system 5 in the direction of the small principal stress σ3, applying a confining compressive stress σ c The pressure chamber structure 6, the displacement measurement system 7 in the σ3 direction, the sample preparation device 8 and the sample curing system 9.

[0103] The cubic specimen of this embodiment is placed at the center of the true triaxial apparatus, and a large principal stress σ1 and a medium principal stress σ2 are applied to the specimen through the rigid loading system 1 in the σ1 direction and the rigid loading system 3 in the σ2 direction, a small principal stress σ3 is applied to the specimen through the flexible loading system 5 in the σ3 direction, and a confining pressure stress σ is applied to the specimen through the pressure chamber structure 6. c .

[0104] like Figure 4 As shown, the σ1 direction rigid loading system 1 includes an upper loading system 110 and a lower loading system 120. The upper loading system 110 includes an upper servo motor 111 and a first piston rod 112, the first piston rod 112 is connected to a first force sensor 113, the first force sensor 113 is embedded and connected to a first rigid plate 114, and a synchronous deformation rod 115 is provided on the first piston rod 112; the first force sensor 113 and the synchronous deformation rod 115 are independent of each other; the bottom surface of the first piston rod 112 contacts the top surface of the sample cap 830 through a steel ball 835 to uniformly transfer the load; the bottom surface of the synchronous deformation rod 115 ... The top surface of the cap 830 is aligned horizontally; the loading base 121 is embedded and connected with the first sample base 840 through the convex disc 122 and the first disc groove 841; the loading base 121 is embedded and connected with the force transmission block base 420 through the wedge teeth 123 and the fourth groove 425; when the σ2 direction adopts the σ2 direction semi-rigid force transmission device 4, the loading base 121 is embedded and connected with the force transmission block base 420 through the wedge teeth 123 and the fourth groove 425; when the σ2 direction adopts the σ2 direction rigid loading system 3, the force transmission block base 420 is taken out. The top surface of the force transmission block base 420 is provided with a first roller 412, and wing plates 422 are provided on both sides.

[0105] like Figure 5 As shown, the semi-rigid force transmission device 2 in the σ1 direction includes a dispersion block 210, a positioning grid 220 and a magnetic adsorption device 230; the dispersion block 210 includes a universal ball 211 and a rectangular block 212; the positioning grid 220 includes a grid 221 and a top surface coating 222; the magnetic adsorption device 230 includes a magnetic seat 231 and a cast iron plate 232; the dispersion block 210 is connected by the universal ball 211 and the rectangular block 212 through threads; the positioning grid 220 is made of liquid silicone, and the thickness of the positioning grid 220 is the same as that of the rectangular block 212; the magnetic seat 231 of the magnetic adsorption device 230 can be adjusted to be magnetized or demagnetized by turning the handle, the magnetic seat 231 is fixedly connected to the cast iron plate 232, the size of the cast iron plate 232 is the same as that of the positioning grid 220, and the base can be adjusted to be magnetized or demagnetized by turning the handle.

[0106] Specifically, the dispersion block 210 is connected by a universal ball 211 and a rectangular block 212 through threads; one end of the universal ball 211 is a threaded column 214, the length and width of the rectangular block 212 are not equal, the size along the σ3 direction is slightly smaller than the size along the σ2 direction, and a threaded hole 213 is provided at the center of the rectangular block 212; the outer diameter of the universal ball 211 is less than or equal to the size of the rectangular block 212 along the σ3 direction; the positioning grid 220 is made of liquid silicone, and the thickness of the positioning grid 220 is the same as the thickness of the rectangular block 212; the square grid 221 of the positioning grid 220 is square, and the size of the square is the same as the size of the rectangular block 212 along the σ2 direction; the top surface coating 222 is the same size as the square grid 221; the magnetic seat 231 of the magnetic adsorption device 230 can adjust the magnetization or demagnetization by turning the handle, and the magnetic seat 231 is fixedly connected to the cast iron plate 232, and the size of the cast iron plate 232 is the same as the size of the positioning grid 220.

[0107] The detailed implementation is as follows: When the σ1 direction adopts semi-rigid, confining pressure chamber loading σ c When installing, first place the dispersion block 210 in the positioning grid 220, place the cast iron plate 232 on the positioning grid 220, and then place the magnetic seat 231 on the cast iron plate 232; after the installation is completed, adjust the button of the rotating magnetic seat 231 to magnetization, at this time, the magnetic force of the magnetic seat 231 is transmitted to the dispersion block 210 through the cast iron plate 232, and the dispersion block 210 and the positioning grid 220 are fixed as a whole; place the semi-rigid force transmission device 2 in the σ1 direction as a whole on the top and bottom of the sample rubber film 810, then adjust the magnetic adsorption device 230 to demagnetize, take out the magnetic seat 231 and the cast iron plate 232, and the installation of the semi-rigid force transmission device 2 can be completed.

[0108] The magnetic base in this embodiment is a common commercial product.

[0109] like Figure 6As shown, the σ2 direction rigid loading system 3 includes a front loading system 310 and a rear loading system 320, and the rear loading system 320 has the same structure as the front loading system 310; the front loading system 310 includes a front servo motor 311, a second piston rod 312, a second sensor 313, a connecting flange 314 and a second rigid plate 315; the second piston rod 312 is connected to the second rigid plate 315 through the second sensor 313 and the connecting flange 314; the front servo motor 311 in the front loading system 310 is connected to the load frame 620 in the pressure chamber structure 6; the second piston rod 312 is connected to the second sensor 313, and the second sensor 313 is connected to the connecting flange 314 by bolts; the connecting flange 314 is connected to the second rigid plate 315 by bolts, and the second rigid plate 315 can be replaced according to the sample size.

[0110] like Figure 7-8 As shown, the σ2 direction semi-rigid force transmission device 4 includes a compressible force transmission block 410 and a force transmission block base 420; the compressible force transmission block 410 includes a special-shaped steel plate 411, a first roller 412, a first optical axis 413, balsa wood 414 and a steel ball 415; the balsa wood 414 is preferably balsa wood; the first roller 412 is embedded in the first groove 416 of the special-shaped steel plate 411 through the first optical axis 413 and connected; the steel ball 415 is placed in the second groove 417 of the top special-shaped steel plate 411; the special-shaped steel plate 411 is connected to the balsa wood through the third groove 419; the force transmission block base 420 includes a seat 421, a wing plate 422, The second roller 423, the second optical axis 424 and the fourth groove 425; the compressible force transmission block 410 in the σ2 direction is formed by stacking a special-shaped steel plate 411 and balsa wood; a hole is opened on one side of the special-shaped steel plate 411 and two first grooves 416 are set, and the first optical axis 413 and the first roller 412 are placed respectively. The first roller 412 is connected with the special-shaped steel plate 411 through the first optical axis 413; the steel ball 415 is placed in the second groove 417, and preferably, the coverage area of ​​the steel ball 415 is 1 / 2 to 2 / 3 of the top surface area of ​​the second groove 417; the special-shaped steel plate 411 and the balsa wood are embedded and connected through the third groove 419 and the cubic protrusion 418. The size of the cubic protrusion 418 is slightly smaller than that of the third groove 419; the length and width of the balsa wood are the same as those of the special-shaped steel plate 411.

[0111] In this embodiment, the compression of the semi-rigid force transmission device 4 in the σ2 direction is achieved by compressing the balsa wood through the synchronous deformation rod 115. The top surface of the steel ball 415 is in contact with the bottom surface of the synchronous deformation rod 115. The steel ball 415 can roll freely in the second groove 417 to achieve the purpose of synchronous compression and free sliding; preferably, the total thickness of the balsa wood is 30%-40% of the total height of the sample.

[0112] The force transmission block base 420 includes a base 421, a wing plate 422, a second roller 423, a second optical axis 424 and a fourth groove 425; the lower surface of the base 421 is provided with the fourth groove 425 for matching with the wedge tooth 123; the base 421 is a flat plate, and vertical wing plates 422 extend upward from both ends of the base 421; a plurality of second optical axes 424 at the same height are connected between the two wing plates 422; a plurality of second rollers 423 are sleeved on the second optical axis 424; the bottom of the second roller 423 is slightly higher than the upper surface of the base 421; the compressible force transmission block 410 is carried on the second roller 423.

[0113] like Figure 3 , Fig. 9 As shown, the flexible loading system 5 in the σ3 direction includes a left flexible loading system 510, a right flexible loading system 520 and a connection positioning device 530, wherein the left flexible loading system 510 is the same as the right flexible loading system 520; the left flexible loading system 510 includes a rubber membrane water bag 511, a rectangular steel plate 512, a third piston rod 513, a water bag frame 514, an optical axis sleeve 515, a square thin plate 516 and a bolt 517; the rubber membrane water bag 511 is embedded in the water bag frame 514, and the rubber membrane water bag 511 is clamped between the water bag frame 514 and the rectangular steel plate 512 by bolts 517 The inner side of the rubber membrane water bag 511 is adhered to the square thin plate 516, and the third piston rod 504 is connected to the square thin plate 516 by threads; the L-shaped base 531 is respectively connected to the left flexible loading system 510 and the right flexible loading system 520 by threads, and the left flexible loading system 510 and the right flexible loading system 528 are connected by screw rod 1 532 and hexagonal nut 533; the L-shaped base 531 of the connection positioning device 530 is fixedly connected to the loading base 121 by bolt 1 534; the rectangular steel plate 512 is fixedly connected to the L-shaped base 531 by bolt 2 535;

[0114] The left flexible loading system 510 and the right flexible loading system 520 are connected at the top through a screw 532 and a hexagonal nut 533; the rectangular steel plate 512 is connected to the water bag frame 514 through a bolt 517, and the flange of the rubber membrane water bag 511 is clamped between the rectangular steel plate 512 and the water bag frame 514; the rectangular steel plate 512 has two symmetrical piston holes 5121 for passing the third piston rod 513; the optical axis sleeve 515 is sealed with the piston hole 5121 through an O-ring 5124; the third piston rod 513 is threadedly connected to the square thin plate 516; the axis of the third piston rod 513 corresponds to a position of 1 / 4 of the sample height from the top and bottom ends of the sample; the square thin plate 516 is adhered to the rubber membrane water bag 511 through waterproof soft glue; the size of the square thin plate 516 is 1 / 4 of the sample height.

[0115] Specifically, the water bag frame 514 is a metal square frame with a step, the inner wall size of the water bag frame 514 is equal to the outer wall size of the rubber membrane water bag 511, the outer wall size of the rubber membrane water bag 511 is the same as the sample size along the vertical direction, and is larger than the sample size along the σ2 direction; the flange size of the rubber membrane water bag 511 is slightly larger than the wall thickness of the water bag frame 514; the flange of the rubber membrane water bag 511 is clamped between the rectangular steel plate 512 and the water bag frame 514; a water injection hole 5122 is opened at the lower left corner of the rectangular steel plate 512 for injecting water into the water bag; and an exhaust hole 5123 is opened at the upper right corner of the rectangular steel plate 512.

[0116] like Fig.10 As shown, the pressure chamber structure 6 includes a pressure chamber body 610 and a load frame 620; the pressure chamber body 610 includes a cubic pressure chamber 611, a left pressure chamber door 612, and a right pressure chamber door 613; the cubic pressure chamber 611 is connected to the left pressure chamber door 612 through a damping hinge 614, and the cubic pressure chamber 611 and the left pressure chamber door 612 are sealed by a rubber ring 615; the left pressure chamber door 612 has a window at the center, and an acrylic plate 616 is embedded; the right pressure chamber door 613 has the same structure as the left pressure chamber door 612; the load frame 620 includes a column 621 and a loading pier 622, and the loading pier 622 is threadedly connected to the pressure chamber body 610 through the column 621; when the confining pressure chamber loading σ c When the pressure chamber door on one side is kept closed, the pressure chamber door on the other side is used for sample loading. When the σ3 direction flexible loading system 5 is used, the pressure chamber doors on both sides are opened to install the σ3 direction flexible loading system 5.

[0117] Specifically, the pressure chamber body 610 includes two pressure chamber doors, namely a left pressure chamber door 612 and a right pressure chamber door 613; the left pressure chamber door 612 and the right pressure chamber door 613 have windows at the center of the sample and are equipped with a high-transmittance acrylic plate 616, and the size of the acrylic plate 616 is larger than the size of the sample.

[0118] like Fig.11 As shown, the σ3 direction displacement measurement system 7 includes 4 micro laser displacement sensors 701, 2 sensor holders 702, and 4 reflective sheets 703; there are 4 micro laser displacement sensors 701 in total, and the micro laser displacement sensors 701 are symmetrically arranged in two layers along the σ3 direction and fixed on the sensor holders 702; the measurement target points of the micro laser displacement sensors 701 are respectively located at 1 / 4 of the sample height from the top and bottom ends of the sample; the reflective sheets 703 are attached to the center axis of the sample rubber film 810 at a position 1 / 4 of the sample top and bottom ends. When the confining pressure chamber is used to load σ cWhen the micro laser displacement sensor 701 monitors the displacement of the reflective sheet 703 through the acrylic plate 616, when the σ3 direction flexible loading system 5 is used, the micro laser displacement sensor 701 monitors the displacement of the center of the third piston rod 513.

[0119] like Fig.12 As shown, the sample preparation device 8 includes a sample rubber membrane 810, a membrane tube 820, a sample cap 830, a first sample base 840 and a sample preparation angle adjustment device 850; the sample rubber membrane 810 is a disc-shaped and rectangular special-shaped body; the membrane tube 820 includes a left split mold 821, a right split mold 822, a bolt three 823, and a sample preparation exhaust pipe 832; the sample cap 830 includes a hemispherical groove 831, a sample preparation exhaust pipe 832, an upper lateral groove 833 and an upper O-ring 834; the first sample base 840 includes a first disc groove 841, a first saturation hole 842, a lower lateral groove 843 and a lower O-ring 844; the upper O-ring 834 can be embedded in the upper lateral groove 833; the first sample base 840 is suitable for Used for true triaxial test without curing requirement; the sample rubber membrane 810 is put on the first sample base 840, and then the left split mold 821 and the right split mold 822 are respectively put on the outside of the sample rubber membrane 810, and tightened and fixed by bolt three 823; the top of the sample rubber membrane 810 is turned outward and put on the upper edge of the membrane tube 820; after the soil sample is poured into the sample rubber membrane 810 and compacted, the sample cap 830 is placed on the top of the sample, and the top of the sample rubber membrane 810 is turned back, and the sample rubber membrane 810 and the sample cap 830 are fixed by the upper O-ring 834; the steel ball 835 is put into the hemispherical groove 831, and the first rigid plate 114 of the upper loading system 110 transfers the load to the sample cap 830 through the steel ball 835.

[0120] Specifically, the top and bottom of the sample rubber membrane 810 are in the shape of uncovered discs, and the middle is a hollow cube; the outer shape of the film tube 820 is consistent with that of the sample rubber membrane 810, and the outer edge size of the sample rubber membrane 810 is the same as the inner edge size of the film tube 820; the depth of the upper and lower discs of the film tube 820 is less than the depth of the upper and lower discs of the sample rubber membrane 810; the film tube 820 is provided with an exhaust hole in the left split mold 821 and the right split mold 822; the sample cap 830 is in the shape of a disc, and a hemispherical groove 831 is provided on the top of the sample cap 830, and the radius of the hemispherical groove 831 is slightly larger than the radius of the second steel ball 835; the sample cap 830 is provided with a sample preparation exhaust pipe 832, and the sample preparation exhaust pipe 832 passes through the bottom center of the sample cap 830; the depth of the first disc groove 841 is less than the height of the outer convex disc 122.

[0121] Specifically, the sample preparation angle adjustment device 850 includes two adjustable angle gauges 851 and an angle steel 852. The model specification of the adjustable angle gauge 851 is NYN-906, and the angle steel 852 is an unequal angle steel, and the length of the long side of the unequal angle steel is equal to the height dimension of the sample. When preparing samples with different deposition angles, the adjustable angle gauge 851 is adjusted to a preset angle, the angle steel 852 is placed on the two adjustable angle gauges 851, and then the first sample base 840, the sample rubber film 810 and the film bearing cylinder 820 are fixed on the angle steel 852 as a whole, and the sample is added to the sample rubber film 810 and compacted.

[0122] like Fig.13 As shown, the sample curing system 9 includes a second sample base 910 and a curing device 920; the second sample base 910 includes a second disc groove 911, a second saturated hole 912, a curing hole 913 and a plug 914; the curing device 920 includes a separatory funnel 921, a valve 922 and a rubber hose 923; the second sample base 910 is suitable for true triaxial tests with curing requirements; the plug 914 is suitable for air-drying unsaturated samples, and is used to prevent the curing material from flowing into the second saturated hole 912; the rubber hose 923 is inserted into the curing hole 913; the rubber hose 923 is connected to the separatory funnel 921 through a valve 922; the installation method of the second sample base 910 is consistent with that of the first sample base 840.

[0123] Specifically, the second sample base 910 has the same external dimension structure as the first sample base 840 , and its internal structure is different from that of the first sample base 840 . The second sample base 910 is provided with a straight curing hole 913 ; the curing device 920 includes a rubber hose 923 , and the outer diameter of the rubber hose 923 is the same as the inner diameter of the curing hole 913 .

[0124] This embodiment provides a test method of a true triaxial apparatus with multiple loading boundaries, and the specific operation steps are as follows:

[0125] 1. According to the setting scheme, select a predetermined loading boundary combination from the following 8 loading boundary combinations: "σ1 rigid + σ2 rigid + σ3 confining pressure", "σ1 rigid + σ2 rigid + σ3 water bag", "σ1 rigid + σ2 semi-rigid + σ3 confining pressure", "σ1 rigid + σ2 semi-rigid + σ3 water bag", "σ1 semi-rigid + σ2 rigid + σ3 confining pressure", "σ1 semi-rigid + σ2 rigid + σ3 water bag", "σ1 semi-rigid + σ2 semi-rigid + σ3 confining pressure", and "σ1 semi-rigid + σ2 semi-rigid + σ3 water bag";

[0126] 2. For the loading boundary combination of “σ1 rigidity + σ2 rigidity + σ3 confining pressure”, firstly, the rigid loading system 1 in the σ1 direction and the rigid loading system 3 in the σ2 direction of the principal stress σ2 are applied with the confining pressure stress σ cThe pressure chamber structure 6 and the displacement measurement system 7 in the σ3 direction are installed; the sample is prepared by the sample preparation device 8, and then the sealed sample is taken out from the film bearing cylinder 820; the prepared and sealed sample is placed on the loading base 121; the left pressure chamber door 612 is closed and a good seal is ensured; the upper servo motor 111 and the front and rear servo motors are controlled by a computer to rotate so that the first rigid plate 114 contacts the steel ball 835, and the second rigid plate 315 contacts the sample surface; the above completes the sample preparation and installation of the "σ1 rigidity + σ2 rigidity + σ3 confining pressure" loading boundary combination; hereinafter, "σ1 rigidity + σ2 rigidity + σ3 confining pressure" is referred to as the basic combination;

[0127] 3. For the loading boundary combination of "σ1 rigidity + σ2 rigidity + σ3 water bag", on the basis of the basic combination operation, the σ3 direction flexible loading system (5) is installed to control the pressure of the rubber membrane water bag through the motor to control the water pressure;

[0128] 4. For the loading boundary combination of “σ1 rigidity + σ2 semi-rigidity + σ3 confining pressure”, on the basis of the basic combination operation, the force transmission block base 420 is installed on the loading base 121, and the compressible force transmission blocks 410 are arranged on the front and rear sides of the specimen, and the front loading system 310 and the rear loading system 320 are controlled, and the second rigid plate 315 is in contact with the compressive force transmission block 410;

[0129] 5. For the loading boundary combination of "σ1 rigid + σ2 semi-rigid + σ3 water bag", on the basis of the combined operation of "σ1 rigid + σ2 rigid + σ3 water bag", a semi-rigid force transmission device 4 in the σ2 direction is arranged on the front and rear sides of the specimen;

[0130] 6. For the loading boundary combination of "σ1 semi-rigid + σ2 rigid + σ3 confining pressure", on the basis of the basic combination operation, a semi-rigid force transmission device 2 in the σ1 direction is arranged at the top and bottom of the specimen;

[0131] 7. For the loading boundary combination of "σ1 semi-rigid + σ2 rigid + σ3 water bag", on the basis of the combined operation of "σ1 rigid + σ2 rigid + σ3 water bag", a semi-rigid force transmission device 2 in the σ1 direction is arranged at the top and bottom of the specimen;

[0132] 8. For the loading boundary combination of "σ1 semi-rigid + σ2 semi-rigid + σ3 confining pressure", on the basis of the combined operation of "σ1 rigid + σ2 semi-rigid + σ3 confining pressure", a semi-rigid force transmission device 2 in the σ1 direction is arranged at the top and bottom of the specimen;

[0133] 9. For the loading boundary combination of “σ1 semi-rigid + σ2 semi-rigid + σ3 water bag”, on the basis of the “σ1 rigid + σ2 semi-rigid + σ3 water bag” operation, a semi-rigid force transmission device 2 in the σ1 direction is arranged at the top and bottom of the specimen.

[0134] Example 2

[0135] For the test of the loading boundary combination of "σ1 rigidity + σ2 rigidity + σ3 confining pressure" and without the need for specimen curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 set in the direction of the major principal stress σ1 of the specimen, a σ2 direction rigid loading system 3 set in the direction of the principal stress σ2 of the specimen, and a confining pressure stress σ c The pressure chamber structure 6, the displacement measurement system 7 in the σ3 direction and the sample preparation device 8; the specific structures of the above components are the same as those in the first embodiment.

[0136] Example 3

[0137] like Figure 3 As shown, for the test of "σ1 rigid + σ2 semi-rigid + σ3 water bag" loading boundary combination and the need for sample curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 set in the direction of the large principal stress σ1 of the sample, a σ2 direction rigid loading system 3 and a σ2 direction semi-rigid force transmission device 4 set in the direction of the medium principal stress σ2 of the sample, a flexible loading system 5 set in the direction of the small principal stress σ3 of the sample, a displacement measurement system 7 in the σ3 direction, a sample preparation device 8 and a sample curing system 9, and the second sample base 910 in the sample curing system 9 replaces the first sample base 840 in the sample preparation device 8. The specific structure of the above components is the same as that of the first embodiment.

[0138] Example 4

[0139] For the test of "σ1 rigid + σ2 rigid + σ3 water bag" loading boundary combination and no need for sample solidification, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 arranged in the direction of the large principal stress σ1 of the sample, a σ2 direction rigid loading system 3 arranged in the direction of the medium principal stress σ2 of the sample, a flexible loading system 5 arranged in the direction of the small principal stress σ3 of the sample, a displacement measurement system 7 in the σ3 direction and a sample preparation device 8. The specific structure of the above components is the same as that of Example 1.

[0140] Example 5

[0141] For the test of "σ1 rigid + σ2 semi-rigid + σ3 confining pressure" loading boundary combination and the need for specimen curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 set in the direction of the specimen's major principal stress σ1, a σ2 direction rigid loading system 3 set in the direction of the specimen's main principal stress σ2, and a σ2 direction semi-rigid force transmission device 4, applying a confining pressure stress σ cThe pressure chamber structure 6, the displacement measuring system 7 in the σ3 direction, the sample preparation device 8 and the sample curing system 9, the second sample base 910 in the sample curing system 9 replaces the first sample base 840 in the sample preparation device 8. The specific structure of the above components is the same as that of the first embodiment.

[0142] Example 6

[0143] For the test of "σ1 semi-rigid + σ2 rigid + σ3 confining pressure" loading boundary combination and no need for specimen curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 and a σ1 direction semi-rigid force transmission device 2 arranged in the direction of the specimen's major principal stress σ1, a σ2 direction rigid loading system 3 arranged in the direction of the specimen's main principal stress σ2, and a confining pressure stress σ c The pressure chamber structure 6, the displacement measurement system 7 in the σ3 direction and the sample preparation device 8; the specific structures of the above components are the same as those in the first embodiment.

[0144] Example 7

[0145] For the test of "σ1 semi-rigid + σ2 rigid + σ3 water bag" loading boundary combination and the need for sample curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 and a σ1 direction semi-rigid force transmission device 2 set in the direction of the large principal stress σ1 of the sample, a σ2 direction rigid loading system 3 set in the direction of the principal stress σ2 of the sample, a flexible loading system 5 set in the direction of the small principal stress σ3 of the sample, a σ3 direction displacement measurement system 7, a sample preparation device 8 and a sample curing system 9, and the second sample base 910 in the sample curing system 9 replaces the first sample base 840 in the sample preparation device 8. The specific structure of the above components is the same as that of the first embodiment.

[0146] Example 8

[0147] For the test of the "σ1 semi-rigid + σ2 semi-rigid + σ3 confining pressure" loading boundary combination and without the need for specimen curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 and a σ1 direction semi-rigid force transmission device 2 arranged in the direction of the large principal stress σ1 of the specimen, a σ2 direction rigid loading system 3 and a σ2 direction semi-rigid force transmission device 4 arranged in the direction of the principal stress σ2 of the specimen, and applying a confining pressure stress σ c The pressure chamber structure 6, the displacement measurement system 7 in the σ3 direction and the sample preparation device 8; the specific structures of the above components are the same as those in the first embodiment.

[0148] Example 9

[0149] For the test of "σ1 semi-rigid + σ2 semi-rigid + σ3 water bag" loading boundary combination and the need for sample curing, this embodiment provides a multi-loading boundary true triaxial apparatus, including a σ1 direction rigid loading system 1 and a σ1 direction semi-rigid force transmission device 2 arranged in the direction of the large principal stress σ1 of the sample, a σ2 direction rigid loading system 3 and a σ2 direction semi-rigid force transmission device 4 arranged in the direction of the medium principal stress σ2 of the sample, a flexible loading system 5 arranged in the direction of the small principal stress σ3 of the sample, a displacement measurement system 7 in the σ3 direction, a sample preparation device 8 and a sample curing system 9; the second sample base 910 in the sample curing system 9 replaces the first sample base 840 in the sample preparation device 8. The specific structure of the above components is the same as that of the first embodiment.

[0150] Various loading systems in the present invention are all controlled by the existing controller, and various electrical components in the present invention are all powered by a power supply.

[0151] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0152] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0153] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the individual embodiments previously disclosed. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0154] As used herein, unless otherwise specified, the use of ordinal numbers "first," "second," "third," etc. to describe common objects merely indicates that different instances of similar objects are involved, and is not intended to imply that the objects so described must have a given order in time, space, order, or in any other manner.

[0155] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

[0156] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A true triaxial apparatus with multiple loading boundaries, characterized in that: Including setting the maximum principal stress σ 1 direction σ 1-way rigid loading system (1) and / or σ 1. Semi-rigid force transmission device (2) in the direction of the main stress σ 2-way σ 2-way rigid loading system (3) and / or σ 2-direction semi-rigid force transmission device (4), set at the minimum principal stress of the specimen σ Flexible loading system in 3 directions (5) and / or application of confining pressure stress σ c The pressure chamber structure (6) σ A three-dimensional displacement measurement system (7), a sample preparation device (8) and / or a sample curing system (9); The displacement measurement system (7) is used to detect the local deformation of the specimen; The sample preparation device (8) is used for preparing samples with different deposition angles; The sample solidification system (9) is used for solidifying discrete particle samples; Said σ The 1-direction rigid loading system (1) comprises an upper loading system (110) arranged at the top of the sample and a lower loading system (120) arranged at the bottom of the sample; Said σ The 1-direction semi-rigid force transmission device (2) comprises a plurality of dispersion blocks (210), a positioning grid (220) and a magnetic adsorption device (230); The dispersion block (210) comprises a universal ball (211) and a rectangular block (212); Said σ The 2-direction rigid loading system (3) comprises a front loading system (310) arranged at the front side of the sample and a rear loading system (320) arranged at the rear side of the sample, wherein the rear loading system (320) has the same structure as the front loading system (310); Said σ The two-way semi-rigid force transmission device (4) comprises a compressible force transmission block (410) and a force transmission block base (420); The flexible loading system (5) comprises a left-side flexible loading system (510) arranged on the left side of the sample, a right-side flexible loading system (520) arranged on the right side of the sample, and a connecting and positioning device (530); the left-side flexible loading system (510) and the right-side flexible loading system (520) have the same structure; and the connecting and positioning device (530) connects the left-side flexible loading system (510) and the right-side flexible loading system (520).

2. A multi-loading boundary true triaxial apparatus according to claim 1, characterized in that: The upper loading system (110) comprises an upper servo motor (111) and a first piston rod (112) which are movably connected. The first piston rod (112) is connected to a first force sensor (113), and the first force sensor (113) is connected to a first rigid plate (114). A synchronous deformation rod (115) is also provided on the first piston rod (112). The first force sensor (113) and the synchronous deformation rod (115) are independent of each other. The synchronous deformation rod (115) comprises a fixing ring for connecting to the first piston rod (112), and connecting plates are horizontally and symmetrically extended outward on the fixing ring. The lower surfaces of the two connecting plates are connected to connecting rods, and the bottom ends of the connecting rods are provided with connecting rods for connecting to the first piston rod (112). σ A pad in contact with the upper surface of the 2-way semi-rigid force transmission device (4); The lower loading system (120) comprises a loading base (121), the upper surface of which is provided with an outer convex disc (122) for connecting to the sample preparation device (8) or the sample curing system (9), and the loading base (121) is provided with a σ 2. Two symmetrically arranged σ The wedge teeth (123) are connected to the bottom surface of the 2-way semi-rigid force transmission device (4).

3. The multi-loading boundary true triaxial apparatus according to claim 1, characterized in that: The rectangular block (212) is provided with a threaded hole (213); The universal ball (211) comprises a rectangular base, the lower surface of the rectangular base is provided with a threaded column (214) adapted to match the threaded hole (213), the upper surface of the rectangular base is provided with a hemispherical groove, a plurality of balls arranged in a single layer are arranged in the hemispherical groove, a universal ball body is arranged on the balls, and the top surface opening diameter of the hemispherical groove is smaller than the diameter of the universal ball body; The positioning grid (220) comprises a square grid (221) and a top surface coating (222); The square grid (221) is divided into a plurality of square grids adapted to match the dispersed blocks (210); The top surface of the square grid (221) is provided with the top surface coating (222); The magnetic adsorption device (230) comprises a magnetic seat (231) and a cast iron plate (232); The cast iron plate (232) is provided on the top surface of the top surface coating (222), and the magnetic seat (231) for adsorbing and desorbing the dispersion block (210) is provided on the cast iron plate (232).

4. The multi-loading boundary true triaxial apparatus according to claim 1, characterized in that: The front loading system (310) comprises a front servo motor (311), a second piston rod (312), a second sensor (313), a connecting flange (314) and a second rigid plate (315); the front servo motor (311) is connected to a load frame (620) in a pressure chamber structure (6); the front servo motor (311) is movably connected to the second piston rod (312), the second piston rod (312) is connected to the second sensor (313), the second sensor (313) is connected to the connecting flange (314) by bolts; the connecting flange (314) is connected to the second rigid plate (315) by bolts.

5. The multi-loading boundary true triaxial apparatus according to claim 2, characterized in that: The compressible force transmission block (410) comprises a special-shaped steel plate (411), a first roller (412), a first optical axis (413), balsa wood (414) and a steel ball (415); The special-shaped steel plate (411) is a square plate with a plurality of first grooves (416) formed on one side; a through hole for penetrating the first optical axis (413) is formed on the side wall of the first groove (416); The first roller (412) is sleeved outside the first optical axis (413); The steel ball 1 (415) is placed in the second groove (417) on the top surface of the top-layer special-shaped steel plate (411); The bottom surface of the special-shaped steel plate (411) is connected to the cubic protrusion (418) on the top surface of the balsa wood (414) via a third groove (419); The special-shaped steel plates (411) and the balsa wood (414) are arranged in layers and at intervals; The force transmission block base (420) comprises a base (421), a wing plate (422), a second roller (423), a second optical axis (424) and a fourth groove (425); The lower surface of the seat (421) is provided with the fourth groove (425) for matching with the wedge tooth (123); The base (421) is a flat plate, and vertical wing plates (422) extend upward from both ends of the base (421); A plurality of second optical axes (424) at the same height are connected between the two wing plates (422); A plurality of second rollers (423) are sleeved on the second optical axis (424); The bottom of the second roller (423) is higher than the upper surface of the base (421); The compressible force transmission block (410) is carried on the second roller (423).

6. The multi-loading boundary true triaxial apparatus according to claim 2, characterized in that: The left-side flexible loading system (510) comprises a rubber membrane water bag (511), a rectangular steel plate (512), a third piston rod (513), a water bag frame (514), an optical axis sleeve (515), a square thin plate (516), and a bolt (517); The rubber membrane water bag (511) is embedded in the water bag frame (514), and the rubber membrane water bag (511) is clamped between the water bag frame (514) and the rectangular steel plate (512) via the bolts (517); The inner side of the rubber membrane water bag (511) is adhered to the square thin plate (516), and the third piston rod (513) is connected to the square thin plate (516) via threads; Two piston holes (5121) for passing the third piston rod (513) are symmetrically formed on the rectangular steel plate (512); A water injection hole (5122) for injecting water into the rubber membrane water bag (511) is provided at the lower left corner of the rectangular steel plate (512); An exhaust hole (5123) is provided at the upper right corner of the rectangular steel plate (512); The optical axis sleeve (515) is sealedly connected to the piston hole (5121) via an O-ring (5124); The connection positioning device (530) comprises an L-shaped base (531), a screw rod (532) and a hexagonal nut (533); The L-shaped base (531) is respectively connected to the left flexible loading system (510) and the right flexible loading system (520) via threads, and the left flexible loading system (510) and the right flexible loading system (520) are connected via the screw rod 1 (532) and the hexagonal nut (533); The bottom surface of the L-shaped base (531) is connected to a hole on the loading base (121) that matches the loading base via a bolt 1 (534); The side surface of the L-shaped base (531) is connected to the rectangular steel plate (512) via bolt 2 (535).

7. The multi-loading boundary true triaxial apparatus according to claim 1, characterized in that: The pressure chamber structure (6) comprises a pressure chamber body (610) and a plurality of load frames (620); the pressure chamber body (610) comprises a cubic pressure chamber (611), a left pressure chamber door (612) and a right pressure chamber door (613); the cubic pressure chamber (611) is connected to the left pressure chamber door (612) via a damping hinge (614), and the cubic pressure chamber (611) and the left pressure chamber door (612) are sealed via a rubber ring (615); a window is opened at the center of the left pressure chamber door (612), and an acrylic plate (616) is embedded therein; the right pressure chamber door (613) and the left pressure chamber door (612) have the same structure; the load frame (620) comprises a column (621) and a loading pier (622), and the loading pier (622) is threadedly connected to the pressure chamber body (610) via the column (621).

8. The multi-loading boundary true triaxial apparatus according to claim 2, characterized in that: The sample preparation device (8) comprises a sample rubber membrane (810), a membrane holding cylinder (820), a sample cap (830), a first sample base (840) and a sample preparation angle adjustment device (850); The bottom end of the sample rubber membrane (810) is sleeved on the first sample base (840); The film-holding cylinder (820) is sleeved on the outer side of the middle part of the sample rubber film (810); The film bearing cylinder (820) comprises a left split mold (821) and a right split mold (822) connected by bolt three (823); The top of the sample rubber membrane (810) is turned outward and sleeved on the upper edge of the membrane-supporting cylinder (820), and the sample is added into the sample rubber membrane (810) and compacted; The sample cap (830) is then placed on the top of the sample, and the top of the sample rubber membrane (810) is turned back and placed on the outside of the sample cap (830), and the upper O-ring (834) fixes the sample rubber membrane (810) and the sample cap (830) through the upper lateral groove (833); The lower O-ring (844) fixes the sample rubber membrane (810) and the first sample base (840) via the lower lateral groove (843); A hemispherical groove (831) is provided on the top of the sample cap (830), a second steel ball (835) is placed in the hemispherical groove (831), and the first rigid plate (114) of the upper loading system (110) transfers the load to the sample cap (830) through the second steel ball (835); The top surface of the sample cap (830) is provided with a sample preparation exhaust pipe (832); The bottom surface of the first sample base (840) is provided with a first disc groove (841) adapted to match the outer convex disc (122); The first sample base (840) is connected to a first saturation hole (842); The sample preparation angle adjustment device (850) comprises two adjustable angle gauges (851) and an angle steel (852). The model specification of the adjustable angle gauge (851) is NYN-906. The angle steel (852) is an unequal-leg angle steel. The length of the long side of the angle steel (852) is equal to the height of the sample.

9. The multi-loading boundary true triaxial apparatus according to claim 8, characterized in that: The first sample base (840) is replaced by a sample curing system (9); The sample curing system (9) comprises a second sample base (910) and a curing device (920); The second sample base (910) comprises a second disc groove (911) adapted to match the outer convex disc (122); A curing hole (913) is arranged inside the second sample base (910) and is arranged obliquely from bottom to top and passes through the second sample base (910); The second sample base (910) is also provided with an L-shaped second saturation hole (912) penetrating the top surface and the side surface of the second sample base (910); the second saturation hole (912) is movably provided with a plug (914) at the opening of the top surface of the second sample base (910); The curing device (920) comprises a rubber hose (923) for being inserted into the curing hole (913); The rubber hose (923) is connected to the separatory funnel (921) via a valve (922).

10. A test method of a true triaxial apparatus with multiple loading boundaries according to any one of claims 1 to 9, characterized in that: The following steps are involved: for σ 1 Rigidity+ σ 2 Rigidity + σ 3 Confining pressure loading boundary combination: First, select σ 1-direction rigid loading system (1), σ 2-direction rigid loading system (3), pressure chamber structure (6) and displacement measurement system (7); prepare the sample using the sample preparation device (8), and then take the sealed sample out of the film support tube (820); place the prepared and sealed sample on the loading base (121); close the left pressure chamber door (612) and ensure good sealing; control the upper servo motor (111), the front servo motor (311) and the rear servo motor to rotate through computer control, so that the first rigid plate (114) and the second steel ball (835) are in contact, and the second rigid plate (315) and the sample surface are in contact; the above is completed σ 1 Rigidity+ σ 2 Rigidity + σ 3 Sample preparation and installation of confining pressure loading boundary combination; the following will σ 1 Rigidity+ σ 2 Rigidity + σ 3 Confining pressure is referred to as the basic combination; for σ 1 Rigidity+ σ 2 Rigidity + σ 3. Water bag loading boundary combination. On the basis of the basic combination operation, a flexible loading system (5) is installed to control the pressure of the rubber membrane water bag through the motor to control the water pressure; for σ 1 Rigidity+ σ 2 semi-rigid + σ 3. Confining pressure loading boundary combination: on the basis of the basic combination operation, a force transmission block base (420) is installed on the loading base (121), a compressible force transmission block (410) is arranged on the front and rear sides of the specimen, and the front loading system (310) and the rear loading system (320) are controlled to make the second rigid plate (315) contact the compressible force transmission block (410); for σ 1 Rigidity+ σ 2 semi-rigid + σ 3 Water bag loading boundary combination, in σ 1 Rigidity+ σ 2 Rigidity + σ 3. Based on the combined operation of water bags, arrange them on the front and rear sides of the specimen. σ 2-way semi-rigid force transmission device (4); for σ 1 semi-rigid + σ 2 Rigidity + σ 3. Confining pressure loading boundary combination, based on the basic combination operation, is arranged at the top and bottom of the specimen σ 1-direction semi-rigid force transmission device (2); for σ 1 semi-rigid + σ 2 Rigidity + σ 3 Water bag loading boundary combination, in" σ 1 Rigidity+ σ 2 Rigidity + σ 3 water bags” combined operation, arranged at the top and bottom of the specimen σ 1-direction semi-rigid force transmission device (2); for σ 1 semi-rigid + σ 2 semi-rigid + σ 3 confining pressure loading boundary combination, in σ 1 Rigidity+ σ 2 semi-rigid + σ 3. Based on the combined operation of confining pressure, the top and bottom of the specimen are arranged σ 1-direction semi-rigid force transmission device (2); for σ 1 semi-rigid + σ 2 semi-rigid + σ 3 Water bag loading boundary combination, in σ 1 Rigidity+ σ 2 semi-rigid + σ 3. Based on the water bag operation, arrange it on the top and bottom of the sample σ 1-way semi-rigid force transmission device (2).

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