An internal cutting and external resistance barrel-shaped shear apparatus for joint surfaces combined with 3D printing technology

Abstract

The present invention relates to an internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology, comprising: a frame; a shear box, which has an inner barrel bottom plate arranged corresponding to the bottom surface of the barrel-shaped inner specimen, and an outer cover bottom plate and a shear box outer side wall respectively arranged corresponding to the bottom surface and the outer side surface of the ring-shaped outer specimen, and the shear box outer side wall and the outer cover bottom plate are integrally formed to form a shear box outer cover; the inner barrel bottom plate and the outer cover bottom plate are both rotatably mounted on the frame around their axes; an axial pressing mechanism I, located above the barrel-shaped inner specimen, for applying an axial pressure to the barrel-shaped inner specimen; an axial pressing mechanism II, located above the ring-shaped outer specimen, for applying an axial pressure to the ring-shaped outer specimen; a rotation driving mechanism, connected to the inner barrel bottom plate, for driving the barrel-shaped inner specimen to rotate around its axis through the inner barrel bottom plate; and a shear monitoring mechanism, for collecting shear parameters between the outer structural plane of the barrel-shaped inner specimen and the inner structural plane of the ring-shaped outer specimen.

Description

Technical Field

[0001] The present invention relates to an internal cutting and external resistance type barrel-shaped structural plane shear instrument combined with 3D printing technology, which is applicable to the mechanical behavior tester of rock mass structural plane. Background Art

[0002] The direct shear instrument is a commonly used test instrument for studying the shear characteristics of geotechnical materials. It is applicable to the shear of soil and is also often used for the shear of rock mass structural plane and the shear of soil-rock contact surface. The advantages of the direct shear instrument are: (1) the shear surface morphology condition is clear; (2) the loading condition is direct and straightforward; (3) the test steps are relatively simple. However, it also has the following disadvantages: (1) it can only achieve one-way short-distance shear to obtain the peak strength, but it is difficult to obtain the residual strength; (2) during the test process, the effective shear area continuously decreases, and the test data needs to be corrected.

[0003] In recent years, geological disasters have occurred frequently in mountainous areas, and many large-scale bedding rock slides have emerged. Such slides usually occur large-displacement shear failure along the existing rock bedding plane (or large rock mass structural plane), and finally develop into super-large rock mass high-speed long-distance slides or high-speed long-distance transported debris flows, seriously threatening the lives and property of people in mountainous areas. Obviously, this dynamic process is closely related to the strength characteristics of the structural plane (bedding plane), and the shear failure of the structural plane in this process will directly affect its mechanical strength, and the change of mechanical strength can in turn affect the dynamic characteristics of the rock mass slide. Therefore, the research on the strength change characteristics (especially the residual strength) of the structural plane (bedding plane) during the long-distance shear process has practical significance.

[0004] However, so far, no suitable test instrument has appeared to study the strength mechanical characteristics of rock mass structural plane during the long-distance one-way shear process. Although the ring shear instrument can achieve long-distance shear in one direction and has been widely used in soil mechanics. However, for hard rock mass structural planes, once they undergo one-way displacement, the shear direction (the morphological characteristics in this direction) is already determined, and it is impossible to perform circumferential shear. Obviously, the planar annular structure of the ordinary ring shear instrument restricts the accurate sample preparation of the rock mass structural plane in the established direction. Therefore, the ring shear instrument cannot be used to conduct long-distance and full-process shear mechanics research on the rock mass structural plane like soil. In addition, due to the structural characteristics of the conventional ring shear instrument, the shear stress distributed along the radial direction of the shear surface increases with the increase of the radial length. Therefore, the designer usually limits the size of the annular shear surface to obtain an approximately equal shear stress on the shear surface. However, the result is that it is difficult for this type of ring shear instrument to carry out large-scale shear tests.

[0005] The development of technology has led to the continuous emergence of high - tech. For example, in the acquisition of geometric form data and form reproduction, technologies such as three - dimensional laser scanning technology and 3D printing technology have become increasingly mature and have been applied in many fields. In the field of rock mechanics research, some scholars have applied three - dimensional laser scanning technology to obtain the point - cloud data of the rock mass structural plane morphology and imported it into computer software for precise modeling. However, it is not common to use the combined method of three - dimensional laser scanning technology and 3D printing technology to conduct solid shaping of the rock mass structural plane and apply it to solid experimental research. And currently, there is no concept of conducting equal - proportion barrel - shaped structural plane 3D shaping based on the point - cloud data of the planar state structural plane.

[0006] Therefore, based on the current research requirements and combined with existing high - tech, it is meaningful to jointly develop corresponding test instruments to study the long - distance shear mechanical properties of the rock mass structural plane. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: in view of the above - mentioned problems, to provide an internal - cutting and external - resisting barrel - shaped structural plane shear instrument combined with 3D printing technology.

[0008] The technical solution adopted by the present invention is: an internal - cutting and external - resisting barrel - shaped structural plane shear instrument combined with 3D printing technology, which is characterized in that it is used for shear mechanical testing of the outer structural plane of the barrel - shaped internal specimen and the inner structural plane of the matching annular outer specimen, and includes:

[0009] A frame;

[0010] A shear box, which has an inner barrel bottom plate corresponding to the bottom surface of the barrel - shaped internal specimen, and an outer cover bottom plate and a shear box outer side wall corresponding to the bottom surface and the outer side surface of the annular outer specimen respectively. The shear box outer side wall and the outer cover bottom plate are integrally formed to form a shear box outer cover; both the inner barrel bottom plate and the outer cover bottom plate are rotatably mounted on the frame around their axes;

[0011] An axial pressing mechanism I, located above the barrel - shaped internal specimen, for applying axial pressure to the barrel - shaped internal specimen;

[0012] An axial pressing mechanism II, located above the annular outer specimen, for applying axial pressure to the annular outer specimen;

[0013] A rotation driving mechanism, connected to the inner barrel bottom plate, for driving the barrel - shaped internal specimen to rotate around its axis through the inner barrel bottom plate;

[0014] A shear monitoring mechanism, for collecting shear parameters between the outer structural plane of the barrel - shaped internal specimen and the inner structural plane of the annular outer specimen.

[0015] The axial pressing mechanism I has an inner barrel pressing plate placed on the top surface of the barrel - shaped internal specimen, and a pressing mechanism is arranged above the inner barrel pressing plate;

[0016] The pressurizing mechanism has a hydraulic lift installed on the frame, and an inner barrel pressurizing shaft vertically arranged and corresponding to the position of the lower inner barrel pressing plate is installed on the lifting platform of the hydraulic lift.

[0017] The lower end of the inner barrel pressurizing shaft is made with a conical tip, and a pressing plate stress groove capable of cooperating with the conical tip to achieve point contact is made on the upper surface of the inner barrel pressing plate.

[0018] The axial pressurizing mechanism II has a hollow vertical shaft sleeved on the inner barrel pressurizing shaft and capable of rotating around the axis of the inner barrel pressurizing shaft. The hollow vertical shaft is connected to an outer barrel pressing plate placed on the top surface of the annular outer specimen through an outer barrel pressure application arm.

[0019] A pressing plate located above the hollow vertical shaft and a lifting plate located below the hollow vertical shaft are made on the inner barrel pressurizing shaft.

[0020] The shear box outer cover is formed by splicing a plurality of arc-shaped outer covers.

[0021] One end of the arc-shaped outer cover is made with a male ear plate, and the other end is made with a female ear plate capable of cooperating with the male ear plate on another arc-shaped outer cover to achieve connection.

[0022] The male ear plate has positive magnetism, and the female ear plate has negative magnetism.

[0023] The rotary drive mechanism includes an inner barrel chassis coaxially made on the end face of the inner barrel bottom plate. A circle of chassis gears is made on the outer side wall of the inner barrel chassis. A number of motors are arranged around the chassis gears, and motor gears meshing with the chassis gears are arranged on the rotating shafts of the motors.

[0024] The shear monitoring mechanism includes a load cell and a displacement sensor. Among them, the load cell abuts against a resistance rod fixed on the shear box outer cover through a load cell rod; the displacement sensor is used to collect the shear displacement between the outer structural surface of the barrel-shaped inner specimen and the inner structural surface of the annular outer specimen.

[0025] A drainage groove is formed between the inner barrel bottom plate and the outer cover bottom plate, and a drain pipe is provided corresponding to the drainage groove.

[0026] Axial pressure sensors are provided on the axial pressurizing mechanisms I and II.

[0027] The barrel-shaped inner specimen and the annular outer specimen are printed by 3D printing technology. Among them, the outer structural surface of the barrel-shaped inner specimen is configured proportionally based on the point cloud data of the upper survey points on the natural rock mass structure surface, and the inner structural surface of the annular outer specimen is configured proportionally based on the point cloud data of the lower survey points on the natural rock mass structure surface.

[0028] The annular outer specimen is formed by splicing a plurality of arc-shaped specimen modules corresponding to the arc-shaped outer covers one by one.

[0029] The beneficial effects of the present invention are as follows: By using three-dimensional laser scanning to obtain the point cloud data of the upper and lower plates of the natural rock mass structural plane, and constructing the three-dimensional geological models of the outer structural plane of the barrel-shaped inner specimen and the inner structural plane of the annular outer specimen based on the point cloud data of the upper and lower plates of the natural rock mass structural plane, the problem of accurately preparing samples for the barrel-shaped structural plane in the prior art is solved, so that the shear mechanical properties of the structural plane can be studied over a long distance and throughout the process using a ring shear apparatus like that for soil.

[0030] The present invention provides a cylindrical shear surface mode, in which the normal direction of the shear surface is perpendicular to the direction of the shear angular velocity vector. The adopted barrel-shaped cylindrical shear form can not only achieve large-displacement shear, but also keep the shear area unchanged, ensuring that the shear displacement and shear stress are equal everywhere on the shear surface. Different from the conventional ring shear apparatus, the barrel-shaped shear apparatus provided by the present invention is not limited by the width of the shear surface. Therefore, the size of the structural plane can be infinitely large in theory, thus avoiding the size effect.

[0031] In the present invention, the computer can issue commands to the motor in a timely manner by receiving the monitoring data fed back by the load cell ring to achieve torque control. The computer can issue commands to the motor by receiving the monitoring data fed back by the displacement sensor to achieve displacement control. The computer can perform real-time calculation of the normal pressure on the structural plane by receiving the monitoring data fed back by the axial pressure sensor and combining the structural plane pressure formula, and can perform servo control on the lifting platform based on the calculation result to adjust the loading and unloading of the specimen, ensuring that the normal pressure on the structural plane remains unchanged during the shear process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of an embodiment.

[0033] Figure 2 It is a schematic diagram for preparing the barrel-shaped specimen in the embodiment.

[0034] Figure 3 It is a schematic structural diagram of the shear box in the embodiment.

[0035] Figure 4 It is Figure 1 the AA-sectional view of

[0036] Figure 5 It is Figure 1 the BB-sectional view of

[0037] Figure 6 It is Figure 1 the CC-sectional view of

[0038] Figure 7 It is Figure 1 the DD-sectional view of

[0039] Figure 8For Figure 1 EE-direction sectional view of

[0040] Figure 9 For Figure 1 FF-direction sectional view of

[0041] Figure 10 Is a three-dimensional view of the inner barrel pressure shaft in the embodiment.

[0042] Among them, 1. Hydraulic lift; 2. Frequency converter; 3. Vertical bearing balls; 4. Hollow vertical shaft; 5. Displacement sensor; 6. Outer barrel pressure application arm; 7. Pressing plate balls; 8. Load cell; 8b. Load rod; 9. Barrel-shaped inner specimen; 10. Ring-shaped outer specimen; 11. Rock mass structural plane; 11a. Structural plane on the outside of the barrel-shaped inner specimen; 11b. Structural plane on the inside of the ring-shaped outer specimen; 12. Drainage groove; 13. Outer barrel chassis balls; 14. Drain pipe; 15. Lifting platform; 15b. Axial pressure sensor; 16. Inner barrel pressure shaft; 16b. Conical tip; 17. Lifting plate; 18. Pressing plate force receiving groove; 19. Inner barrel pressing plate; 20. Outer barrel pressing plate; 21. Seepage hole; 22. Computer; 23. Resistance rod; 24. Shear box outer cover; 24b. Outer cover bottom plate; 25. Inner barrel bottom plate; 26. Frame; 26b. Frame column; 27. Inner barrel chassis balls; 28. Chassis gear; 29. Motor; 29b. Motor gear; 30. Male ear plate; 30b. Female ear plate; 31. Load rod fulcrum; 32. Inner pressing plate convex point; 33. Outer bottom plate convex strip; 34. Inner barrel bottom plate convex point. Specific implementation mode

[0043] This embodiment is an internal cutting and external resistance type barrel-shaped structural plane shear instrument, mainly including a frame 26, a shear box, an axial pressing mechanism I, an axial pressing mechanism II, a rotation driving mechanism, a shear monitoring mechanism, a computer 22, etc., and is used for performing shear mechanical tests on the structural plane 11a on the outside of the barrel-shaped inner specimen and the structural plane 11b on the inside of the ring-shaped outer specimen.

[0044] For the purpose of facilitating the precise alignment and assembly of the rock mass structural plane 11 between the barrel-shaped inner specimen 9 and the ring-shaped outer specimen 10 during the test, avoiding rough operation methods such as directly sleeving the ring-shaped outer specimen 10 on the barrel-shaped inner specimen 9, and reducing the damage to the original form of the structural plane caused during the alignment and fitting process of the inner and outer specimen structural planes, in this example, the ring-shaped outer specimen 10 is evenly divided into 4 arc-shaped outer specimen modules, and the 4 arc-shaped outer specimen modules are assembled to form the ring-shaped outer specimen 10.

[0045] In this example, the shear box has an inner barrel bottom plate 25 arranged corresponding to the bottom surface of the barrel-shaped inner sample 9, and an inner barrel bottom plate 25 and a shear box outer side wall 24 respectively arranged corresponding to the bottom surface and outer side surface of the annular outer sample 10. The shear box outer side wall 24 is connected to the inner barrel bottom plate 25 to form a shear box outer cover 24. In this embodiment, the lower part of the inner barrel bottom plate is rotatably mounted on the base of the frame 26 through the inner barrel bottom plate and the inner barrel bottom plate ball 27 around its own axis; the lower part of the shear box outer cover 24 is rotatably mounted on the base of the frame 26 through the outer barrel bottom plate ball 13 around its own axis.

[0046] In order to facilitate the loading of the arc-shaped external sample module, in this example, the shear box outer cover 24 is divided into four arc-shaped outer covers corresponding to the four arc-shaped external sample modules of the annular external sample 10. The arc-shaped outer cover has an inner barrel bottom plate 25 and an outer side wall 24 of the shear box corresponding to the arc-shaped external sample module. The two ends of the arc-shaped outer cover are respectively provided with a male ear plate 30 and a female ear plate 30b. The male ear plate 30 and the female ear plate 30b have positive and negative magnetic properties respectively. The arc-shaped outer cover realizes the splicing of two arc-shaped outer covers through the magnetic adsorption of the male ear plate 30 and the female ear plate 30b of another arc-shaped outer cover. The male ear plate and the female ear plate 30b can make each module fit tightly after the arc-shaped external sample module in the arc-shaped outer cover is accurately aligned.

[0047] In this embodiment, the axial pressure mechanism I is used to apply axial pressure to the barrel-shaped inner sample 9, and has an inner barrel pressure plate 19 placed on the top surface of the barrel-shaped inner sample 9, and a pressure mechanism arranged above the inner barrel pressure plate 19. In this example, the pressure mechanism has a hydraulic lift installed and fixed on the frame column 26b of the frame 26, and a vertically arranged inner barrel pressure shaft 16 for applying axial pressure to the inner barrel pressure plate 19 is installed on the lifting platform 15 of the hydraulic lift through the axial pressure sensor 15b. The inner barrel pressure shaft 16 is coaxially arranged with the inner barrel pressure plate 19, the barrel-shaped inner sample 9 and the inner barrel bottom plate.

[0048] In this embodiment, the lower end of the inner barrel pressure shaft 16 is a conical tip 16b, and a conical pressure plate force groove 18 is provided at the center position of the upper surface of the inner barrel pressure plate 19. The conical tip 16b of the inner barrel pressure shaft 16 can be inserted into the pressure plate force groove 18 and make point contact with the pressure plate force groove 18 through the tip to avoid as much as possible the mechanical friction between the inner barrel pressure shaft 16 and the inner barrel pressure plate 19 when they rotate relative to each other around the axial direction, thereby eliminating the measurement error caused by the mechanical friction.

[0049] In this example, the axial pressure mechanism II is used to apply axial pressure to the annular external sample 10, and has a hollow vertical shaft 4, an outer barrel pressure arm 6 and an outer barrel pressure plate 20, wherein the hollow vertical shaft 4 is rotatably mounted on the inner barrel pressure shaft 16 in the axial pressure mechanism I through the vertical bearing ball 3, and the hollow vertical shaft 4 is connected to the outer barrel pressure plate 20 arranged on the top surface of the annular external sample 10 through the outer barrel pressure arm 6.

[0050] In this embodiment, a pressure application plate and a lifting plate 17 are made on the inner barrel pressure shaft 16, which are respectively located above and below the hollow vertical shaft 4. The pressure application plate is used to transmit the pressure generated by the hydraulic lift to the hollow vertical shaft 4, and through the hollow vertical shaft 4, act on the top surface of the annular outer specimen 10 via the outer barrel pressure application arm 6 and the outer barrel pressure plate 20. The upper end of the hollow vertical shaft 4 contacts the pressure application plate via the upper disc ball, avoiding mechanical frictional force between the two during relative rotation. The function of the lifting plate 17 is that when the test is over and the lifting table 15 drives the pressure shaft to rise, the hollow vertical shaft 4, the outer barrel pressure application arm 6 and the outer barrel pressure plate 20 can be lifted by the lifting plate 17, realizing the unloading of the upper part of the specimen and the removal of the instrument components.

[0051] In this example, the inner barrel pressure plate 19 and the outer barrel pressure plate 20 are in contact with each other via the pressure plate ball 7, avoiding mechanical frictional resistance between the two.

[0052] To avoid relative sliding between the barrel-shaped inner specimen 9 and the inner barrel pressure plate 19 and the inner barrel bottom plate during the test, in this example, inner pressure plate bumps 32 and a hydraulic lift 1 are respectively made on the contact surfaces of the inner barrel pressure plate 19 and the inner barrel bottom plate with the barrel-shaped inner specimen 9. To avoid relative sliding between the annular outer inner specimen and the shear box outer cover 24 during the test and enhance the integrity, in this embodiment, an outer bottom plate rib 33 is provided on the inner barrel bottom plate 25.

[0053] In this embodiment, the rotary drive mechanism is used to drive the inner barrel bottom plate to rotate around its axis. It has a circle of chassis gears made on the outer wall of the inner barrel chassis. Four motors 29 fixed on the frame base are evenly arranged around the chassis gears. The rotating shaft of the motor 29 is provided with a motor gear 29b on the motor 29 that meshes with the outer cover gear.

[0054] In this embodiment, the shear monitoring mechanism includes a displacement sensor 5 and a load cell 8. Among them, the displacement sensor 5 is installed on the outer barrel pressure application arm 6 of the axial pressure application mechanism II, and can monitor the angular displacement passed by the inner barrel pressure plate 19 during the rotary shear process, and feed back the data to the computer 22 through the signal transmission cable. The computer 22 system calculates the shear displacement of the inner test structural plane. There are two load cells 8, which are arranged symmetrically about the axis center of the shear box. The load cells 8 are fixed on the frame columns 26b of the frame 26. The load cells 8 are abutted against the corresponding resistance rods on the side wall of the shear box via the load cell rods 8b. The resistance rods 23 are symmetrically connected to the shear box outer cover 24, and a square load cell rod fulcrum 31 is provided at the rod head. The load cell rods 8b can be abutted against the load cell rod fulcrum 31 to prevent the outer barrel from rotating and measure the shear strength of the structural plane.

[0055] To enable the internal cutting and external resistance barrel shear apparatus to conduct shear tests under water-containing conditions, in this embodiment, a number of seepage holes 21 are evenly formed in the outer barrel pressing plate 20, a drain groove 12 in the shape of a ring is provided between the inner barrel bottom plate and the inner barrel bottom plate 25, a drain pipe 14 is provided corresponding to the drain groove 12, the upper end of the drain pipe 14 is connected to the drain groove 12, and the lower end is led out from inside the base of the frame 26. By measuring the water discharge amount and pore water pressure of the drain pipe 14, the most direct test data can be provided for calculating the volume strain of the specimen and the effective stress of the shear plane.

[0056] The test method of this embodiment includes the following steps:

[0057] I. Specimen preparation and installation

[0058] The production of the barrel-shaped structural surface specimen includes the following steps:

[0059] (1) Obtain the point cloud data of the upper and lower plates of the natural rock mass structural plane 11 by using three-dimensional laser scanning technology;

[0060] (2) Based on the original point cloud data, use computer 22 technology for coordinate transformation, proportionally transform the point cloud data of the planar natural structural plane into the point cloud data of the barrel-shaped structural plane, achieve proportional configuration, and generate three-dimensional geological models of the outer structural surface 11a of the barrel-shaped inner specimen and the inner structural surface 11b of the annular outer specimen. In this step, the upper plate of the structural plane can correspond to the outer structural surface 11a of the barrel-shaped inner specimen, and the lower plate of the structural plane corresponds to the inner structural surface 11b of the annular outer specimen, and ensure that the various indexes (such as JRC) of the configured structural plane are the same as those of the natural structural plane; in addition, for the 3D printing material used, it is necessary to ensure that the elastoplastic mechanical indexes of the printed specimen are the same as those of the original rock.

[0061] (3) Combine 3D printing technology to print the three-dimensional models of the barrel-shaped inner specimen 9 and the annular outer specimen 10 established by the computer 22. In this step, the barrel-shaped inner specimen 9 is printed as a whole, and spherical concave points corresponding to the inner barrel pressing plate 19 and the bottom plate are printed on its top and bottom surfaces, and the position marks of (A, B, C, D) are made. The annular outer specimen 10 is printed in four equal division modules with the corresponding A, B, C, D marked points as the boundaries, and its edge should be printed based on the shape of the upper ear plate of the shear box outer cover 24, and a concave strip corresponding to the convex strip 33 of the outer bottom plate is printed on the bottom surface.

[0062] After sample preparation is completed, sample loading begins. First, start the hydraulic lift to raise the inner barrel pressure shaft 16, and the hollow vertical shaft 4, the outer barrel pressure application arm 6, and the outer barrel pressing plate 20 are lifted by the lifting plate 17 to create enough space for sample loading. Second, install the barrel-shaped inner sample 9 marked with points (A, B, C, D) on the inner barrel bottom plate, and make the spherical concave point on the bottom surface of the sample fit with the convex point 34 on the upper surface of the inner barrel bottom plate of the inner barrel bottom plate. Then cover the inner barrel pressing plate 19, and make the convex point on the bottom surface of the pressing plate fit into the spherical concave point on the top surface of the sample. Install the annular outer sample 10 into the corresponding arc-shaped outer covers of each sub-module in modules, and make the concave strip on the bottom surface of the sample fit into the convex strip on the bottom plate of the shear box outer cover. Then, step by step and precisely align it with the barrel-shaped inner sample 9 according to the marked points (A, B, C, D) in modules, so that the structural surfaces of the inner and outer samples coincide. At this time, the positive and negative ear plates on the shear box outer cover 24 attract each other to form a relatively firm complete sample. As Figure 2 shows several ideal planar structural surface models, and the inner and outer barrel-shaped structural surfaces obtained by 3D printing can well simulate the basic morphological characteristics of the planar structural surface.

[0063] II. Specimen Loading

[0064] After sample loading is completed, the specimen can be loaded. First, design the specimen plan and set the target pressure value to be applied in the positive direction of the structural surface. Then, adjust the frequency converter 2 of the hydraulic lift through the computer 22 to lower the hydraulic lift, so that the lifting platform 15 drives the inner barrel pressure shaft 16 and the hollow vertical shaft 4 to slowly descend until the outer barrel pressing plate 20 touches the top surface of the annular outer sample 10, and the dot-shaped bottom end of the inner barrel pressure shaft 16 touches the force-receiving groove on the inner barrel pressing plate 19. When in contact, the axial pressure sensor 15b will measure the initial contact pressure value and feedback it to the computer 22 system in real time. The computer 22 system can convert the positive pressure value of the structural surface in real time according to the sensor pressure value and the mechanical calculation formula (1). When the positive pressure value does not reach the preset target value, the computer 22 continues to control the frequency converter 2 to make the hydraulic lift continue to descend to load the specimen until the positive pressure value of the structural surface reaches the target value.

[0065] During the actual test process, the positive pressure of the structural surface will be affected by shear disturbance and fluctuate around the target value. At this time, the computer 22 can perform servo control on the hydraulic lift according to the real-time monitored pressure data, and adjust the real-time lifting of the lifting system to ensure that the positive pressure of the structural surface remains at the target value during the test.

[0066] The positive pressure of the structural surface here can be directly converted from the pressure value F measured by the axial pressure sensor 15b through the generalized Hooke's law of elasticity mechanics:

[0067]

[0068]

[0069] Among them, ε r is the radial strain of the specimen, and ε t is the strain in the direction perpendicular to the radial direction. Due to the limitation of the shear box outer cover 24, so ε r = 0, and ε t = 0; is the axial compressive stress; A is the area of the top surface of the specimen (or the pressure plate); E is the elastic modulus of the specimen; μ is the Poisson's ratio of the specimen. σ r is the normal compressive stress of the structural plane obtained by solution, and σ t is the normal compressive stress in the direction perpendicular to σ r (F, A, E, and μ are all known parameters).

[0070] III. Shear Test

[0071] After the loading is implemented, the shear test of the barrel-shaped structural plane can be carried out. The rotation speed of the motor 29 can be adjusted by the computer 22. After the speed is set, the motor 29 can be started to drive the inner barrel chassis, the inner barrel bottom plate 25, the barrel-shaped inner specimen 9, and the inner barrel pressure plate 19 to rotate, so that the outer structural plane of the barrel-shaped inner specimen shears the inner structural plane 11b of the annular outer specimen. During this process, the outer specimen remains stationary because the load cell lever 8b abuts against the resistance lever 23 on the shear box outer cover 24. Therefore, a shear mode is achieved in which the barrel-shaped inner specimen 9 rotates while the annular outer specimen 10 is prevented from rotating. The shear force (or shear strength) of the outer structural plane 11a of the barrel-shaped inner specimen shearing the inner structural plane 11b of the annular outer specimen can be measured by the load cell lever 8b and the load cell ring 8, and is transmitted to the computer 22 in real time for data storage until the residual state after the structural plane is completely broken by shearing. The measurement principle of the shear stress τ on the barrel-shaped structural plane is as follows: the resistances measured by the two load cell rings are respectively denoted as P1 and P2, the distance from the load cell lever to the central rotation axis of the barrel-shaped specimen is denoted as R1, the height of the barrel-shaped specimen is denoted as H, and the radius of the barrel-shaped structural plane is denoted as R1. Then, from the moment balance analysis formula of the annular outer specimen (P1 + P2)·R1 = 2πR2 2 Hτ, we obtain , where P1 and P2 are the measured values of the load cell rings, and R1 and R2 are fixed values.

[0072] When the equipment is sheared under water-containing conditions, the water pressures in the drainage groove 12 and the drainage pipe 14 can be monitored simultaneously to correct the effective stress in the normal direction of the structural plane in real time to ensure the accuracy of the analysis of the test stress conditions.

[0073] If it is necessary to study the shear fracture of the structural plane at different stages during the shearing process, the test can be stopped at any shearing stage, and then the specimen can be taken out, the broken particles near the structural plane can be collected, and the particle size grading analysis can be carried out. In this way, the particle breakage law during the whole shearing process of the structural plane can be revealed, and the internal relationship between the particle breakage law and the shear strength evolution can be established.

Claims

1. An internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology, characterized in that: It is used for shear mechanical testing of the outer structural surface of the barrel-shaped inner specimen and the inner structural surface of the annular outer specimen adapted thereto, including: Frame; Shear box, which has an inner barrel bottom plate corresponding to the bottom surface of the barrel-shaped inner specimen, and an outer cover bottom plate and a shear box outer side wall corresponding to the bottom surface and the outer side surface of the annular outer specimen respectively. The shear box outer side wall and the outer cover bottom plate are integrally formed to form a shear box outer cover; the inner barrel bottom plate and the outer cover bottom plate are both rotatably mounted on the frame around their axes; Axial pressing mechanism I, located above the barrel-shaped inner specimen, for applying axial pressure to the barrel-shaped inner specimen; Axial pressing mechanism II, located above the annular outer specimen, for applying axial pressure to the annular outer specimen; Rotation driving mechanism, connected to the inner barrel bottom plate, for driving the barrel-shaped inner specimen to rotate around its axis through the inner barrel bottom plate; Shear monitoring mechanism, for collecting shear parameters between the outer structural surface of the barrel-shaped inner specimen and the inner structural surface of the annular outer specimen; The shear box outer cover is formed by splicing a plurality of arc-shaped outer covers; The barrel-shaped inner specimen and the annular outer specimen are printed by 3D printing technology. Among them, the outer structural surface of the barrel-shaped inner specimen is formed by coordinate transformation and equal-proportion configuration based on the point cloud data of the upper measuring points on the natural rock mass structure surface, and the inner structural surface of the annular outer specimen is formed by coordinate transformation and equal-proportion configuration based on the point cloud data of the lower measuring points on the natural rock mass structure surface; The annular outer specimen is formed by splicing a plurality of arc-shaped specimen modules corresponding to the arc-shaped outer covers one by one.

2. The internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology according to claim 1, characterized in that: The axial pressing mechanism I has an inner barrel pressing plate placed on the top surface of the barrel-shaped inner specimen, and a pressing mechanism is arranged above the inner barrel pressing plate; The pressing mechanism has a hydraulic lift installed on the frame, and an inner barrel pressing shaft vertically arranged and corresponding to the position of the lower inner barrel pressing plate is installed on the lifting platform of the hydraulic lift.

3. The internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology according to claim 2, characterized in that: The lower end of the inner barrel pressing shaft is made with a conical tip, and a pressing plate force-receiving groove capable of cooperating with the conical tip to achieve point contact is made on the upper surface of the inner barrel pressing plate.

4. A shear apparatus for an inner-cut and outer-block barrel-shaped structural plane combined with 3D printing technology according to claim 2 or 3, characterized in that: The axial pressing mechanism II has a hollow vertical shaft sleeved on the inner barrel pressing shaft and capable of rotating around the axis of the inner barrel pressing shaft. The hollow vertical shaft is connected to an outer barrel pressing plate placed on the top surface of the annular outer specimen through an outer barrel pressure application arm.

5. A shear apparatus for an inner-cut and outer-resistance barrel-shaped structural plane according to claim 4, characterized in that: A pressure application plate is made on the inner barrel pressing shaft above the hollow vertical shaft, and a lifting plate is made below the hollow vertical shaft.

6. The shear apparatus for the inner-cut and outer-block barrel-shaped structural plane according to claim 1, which is combined with 3D printing technology, is characterized in that: One end of the arc-shaped outer cover is made with a male ear plate, and the other end is made with a female ear plate capable of cooperating with the male ear plate on another arc-shaped outer cover to achieve connection.

7. An internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology according to claim 6, characterized in that: The male ear plate has positive magnetism, and the female ear plate has negative magnetism.

8. The internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology according to claim 1, characterized in that: The rotation driving mechanism includes an inner barrel chassis coaxially made on the end surface of the inner barrel bottom plate. A circle of chassis gears is made on the outer side wall of the inner barrel chassis, and several motors are arranged around the chassis gears. Motor gears meshing with the chassis gears are arranged on the rotation shafts of the motors.

9. The internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology according to claim 1, characterized in that: The shear monitoring mechanism includes a load cell and a displacement sensor. Among them, the load cell abuts against a resistance rod fixed on the shear box outer cover through a load cell rod; the displacement sensor is used for collecting the shear displacement between the outer structural surface of the barrel-shaped inner specimen and the inner structural surface of the annular outer specimen.

10. The internal cutting and external resistance barrel-shaped structural plane shear apparatus combined with 3D printing technology according to claim 1, characterized in that: A drainage groove is formed between the inner barrel bottom plate and the outer cover bottom plate, and a drain pipe is arranged corresponding to the drainage groove.

11. A shear apparatus for an internal cutting and external resistance barrel-shaped structural surface combined with 3D printing technology according to claim 1, characterized in that: Axial pressure sensors are provided on the axial compression mechanisms Ⅰ and Ⅱ.

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