Three-way cyclic shear test device and test method thereof

Abstract

The invention relates to a three-way cyclic shear test device and a test method thereof. The three-direction cyclic shear test device comprises a frame, an upper cyclic shear box, a lower cyclic shear box, an x-direction oil cylinder, a y-direction oil cylinder, a z-direction oil cylinder, a sample conveying device, an x-direction counter-force assembly, a y-direction counter-force assembly, a y-direction antifriction roller pin, a servo control system, a hydraulic oil system, a data acquisition system and a computer control system. The x-direction oil cylinder and the y-direction oil cylinder are arranged on the side wall of the frame and horizontally act on the lower circulating shear box and the lower circulating shear box respectively; and the z-direction oil cylinder is vertically arranged at the top of the frame and acts on the y-direction antifriction roller pin through the normal pressure head. The device has the beneficial effects that the bidirectional cyclic shear test of a fractured rock mass sample under the conditions of constant normal load, dynamic normal load and constant normal rigidity can be realized, the influence of seismic oscillation multidirectivity on the dynamic characteristics of rock can be researched, and the revelation of a slope dynamic instability mechanism is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of rock and soil mechanics testing, and in particular to a three-way cyclic shear testing device and a testing method thereof. Background Art

[0002] As a natural structure, rock slopes usually have a large number of structural surfaces, and the stability of rock slopes is largely controlled by these structural surfaces. Therefore, studying the shear characteristics of rock structural surfaces under seismic loads is an important prerequisite for dynamic stability analysis of rock slopes. In actual engineering, rock strength is crucial to engineering safety, especially in the southwestern mountainous areas of my country where strong earthquakes frequently occur. The accumulated losses of rock mass under the action of external forces such as earthquakes have become one of the important causes of rock structure instability.

[0003] As a dynamic load, earthquake has a constantly changing magnitude and direction of acceleration. For structural surfaces, earthquake loads have both dynamic characteristics and obvious cyclic properties. The shear characteristics of rock structural surfaces are affected by the amplitude and loading rate of dynamic loads on the one hand, and by the cyclic shear or cyclic loading and unloading formed by dynamic loads on the other hand. Specifically, under the action of cyclic shear loads, the roughness and undulation of the rock structural surface will suffer periodic wear and passivation, resulting in the degradation of its shear strength parameters, which in turn causes the slope rock mass to displace and slide along the structural surface, and ultimately causes the instability of the slope rock mass. The shear test device is a key device for exploring the shear mechanical properties, failure mechanism and instability sliding mechanism of rock mass. However, due to the limitations of production technology level and the understanding of rock mechanical behavior, the early shear test device was mainly used for quasi-static shear tests on rock structural surfaces under constant normal load boundary conditions. However, deep underground, the force or stress perpendicular to the shear direction is not necessarily constant. Joints may slide on asperities, resulting in expansion, thereby counteracting the normal stiffness of the surrounding rock mass. At the same time, near-field strong earthquakes have significant three-dimensional dynamic characteristics, that is, near the epicenter area, in addition to being affected by horizontal seismic forces, they are also affected by significant vertical seismic forces. Since the rock mass of underground engineering and the rock mass under anchoring conditions are both under constant normal stiffness boundary conditions, most traditional cyclic shear testers can only achieve constant normal loads, cannot consider the influence of complex confining pressure conditions, and cannot simulate three-dimensional dynamic characteristics. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a three-way cyclic shear test device and a test method thereof, which can realize a two-way cyclic shear test of a fractured rock sample under the conditions of constant normal load, dynamic normal load and constant normal stiffness, and can study the influence of the multi-directionality of seismic motion on the dynamic characteristics of rock, which is conducive to revealing the dynamic instability mechanism of the slope.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A three-way cyclic shear test device comprises a frame, an upper cyclic shear box, a lower cyclic shear box, an x-direction oil cylinder, a y-direction oil cylinder, a z-direction oil cylinder, a sample conveying device, an x-direction reaction force assembly and a y-direction reaction force assembly, wherein the upper cyclic shear box, the lower cyclic shear box, the x-direction reaction force assembly and the y-direction reaction force assembly are all arranged in the frame, the y-direction reaction force assembly is arranged at the bottom of the frame, the lower cyclic shear box is arranged on the y-direction reaction force assembly, the upper cyclic shear box is arranged on the lower cyclic shear box, a plurality of y-direction anti-friction rollers are arranged on the top of the upper cyclic shear box rolling along the working direction of the y-direction oil cylinder, the x-direction oil cylinder and the y-direction oil cylinder are arranged on the side wall of the frame and act horizontally on the lower cyclic shear box and the upper cyclic shear box respectively, and the z-direction oil cylinder is arranged vertically The frame is provided with a servo control system, which is used to control the loading process of the x-axis oil cylinder, the y-axis oil cylinder and the z-axis oil cylinder; the hydraulic oil system is used to provide hydraulic oil to the x-axis oil cylinder, the y-axis oil cylinder and the z-axis oil cylinder; the data acquisition system is used to measure and collect the loading parameters of the x-axis oil cylinder, the y-axis oil cylinder and the z-axis oil cylinder; the computer control system is provided with the servo control system, the hydraulic oil system and the data acquisition system are electrically connected to the computer control system.

[0007] Furthermore, a shear box base is provided on the y-direction reaction force assembly, a lower circulation shear box is provided on the shear box base, and an upper circulation shear box is supported on the lower circulation shear box through spacer balls.

[0008] Furthermore, the y-axis reaction force assembly includes an x-axis anti-friction roller, a y-axis reaction force seat, an x-axis anti-friction ball and a stopper. A placement groove is provided at the top of the y-axis reaction force seat along the working direction of the x-axis cylinder. A plurality of x-axis anti-friction rollers are rollingly provided at the bottom of the placement groove and are arranged side by side along the length direction of the placement groove. The shear box base is arranged in the placement groove and supported on the x-axis anti-friction roller. Receiving grooves are provided on both side walls of the placement groove along the length direction of the placement groove. A plurality of x-axis anti-friction balls are rollingly provided in the receiving groove and are in contact with the shear box base. Stoppers are provided at both ends of the receiving groove on the y-axis reaction force seat, and a mounting hole is provided on the top surface of the y-axis reaction force seat.

[0009] Furthermore, the x-direction reaction force assembly includes a hydraulic buffer, a top plate, a z-direction limit seat, a reaction flange, a reaction column, a stop column and a z-direction anti-friction roller. The reaction flange is arranged on the inner wall of the frame. The z-direction limit seat is vertically arranged on the reaction flange through the reaction column. The upper and lower ends of the z-direction limit seat are respectively provided with a top plate and a stop column. A plurality of z-direction anti-friction rollers arranged side by side in the vertical direction are rollingly provided on the z-direction limit seat between the top plate and the stop column. The z-direction anti-friction rollers are in rolling contact with the normal pressure head. The hydraulic buffer is arranged on the top plate and acts on the z-direction anti-friction rollers.

[0010] Furthermore, the side walls of the upper circulation shear box and the side walls of the lower circulation shear box are respectively provided with a y-direction force-bearing pad and an x-direction force-bearing pad, and a plurality of fastening holes are opened on the y-direction force-bearing pad and the x-direction force-bearing pad, and the x-direction oil cylinder acts on the x-direction reaction cap, and the y-direction force-bearing pad is provided with a y-direction reaction cap, and the y-direction reaction cap is connected to the y-direction force-bearing pad through a connecting cap, and a connecting tightening block is provided between the connecting cap and the y-direction force-bearing pad, and the y-direction oil cylinder acts on the y-direction reaction cap.

[0011] Furthermore, the data acquisition system includes a controller, a data acquisition card, a test force sensor and a displacement sensor. The loading ends of the x-axis cylinder, the y-axis cylinder and the z-axis cylinder are all provided with test force sensors, and the end faces of the x-axis cylinder, the y-axis cylinder and the z-axis cylinder are all provided with displacement sensors. The data acquisition card, the controller, and the computer control system are electrically connected in sequence, and the test force sensor and the displacement sensor are electrically connected to the data acquisition card.

[0012] Furthermore, based on the above three-way cyclic shear test device, the present invention also provides a three-way cyclic shear test method, comprising the following steps:

[0013] S1. Turn on the machine and check whether all equipment and instruments are normal;

[0014] S2. Select a circulation shear box of corresponding size according to the size of the sample, place the base of the shear box on the y-direction reaction force assembly, put the lower part of the sample into the lower circulation shear box and place the lower circulation shear box on the base of the shear box, then place the upper circulation shear box on the lower circulation shear box, adjust the orientation of the upper circulation shear box so that the upper circulation shear box covers the upper part of the sample and is aligned with the sample, and complete the sample loading;

[0015] S3: After the sample is loaded, the circulating shear box is transported to the bottom of the z-axis cylinder by the sample conveying device, and the initial normal pressure is applied to the sample by the z-axis cylinder, and then the x-axis reaction force cap and the y-axis reaction force cap are fastened and connected to the lower circulating shear box and the upper circulating shear box respectively;

[0016] S4, start the servo control system and perform a three-way cyclic shear test on the sample until the sample reaches the designed number of cyclic shear times;

[0017] S5. When the shear displacement of the cylinder reaches the set stroke or number of times, it automatically stops and saves the test data. The computer control system processes and analyzes the data collected by the data acquisition system.

[0018] Furthermore, in step S4, a three-way cyclic shear test is performed on the sample under a constant normal load, and a cyclic shear force is applied to the sample through the x-axis cylinder and the y-axis cylinder according to a pre-input constant normal load value until the sample reaches the designed number of cyclic shear times.

[0019] Furthermore, in step S4, a three-way cyclic shear test is performed on the sample under a dynamic normal load, the frequency and amplitude of the z-axis cylinder are set according to the pre-input seismic wave transformation, and then a cyclic shear force is applied to the sample through the x-axis cylinder and the y-axis cylinder until the sample reaches the designed number of cyclic shear times.

[0020] Further, in step S4, a three-way cyclic shear test is performed on the sample under constant normal stiffness, the constant normal stiffness test function built into the software is started, and the initial normal stress σ0 and the constant normal stiffness coefficient K are input. n , and then apply cyclic shear force to the specimen through the x-axis cylinder and the y-axis cylinder until the specimen reaches the designed number of cyclic shear times.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention can realize bidirectional cyclic shear test of fractured rock samples under the conditions of constant normal load, dynamic normal load and constant normal stiffness, can realize multi-directional dynamic loading shear servo dynamic loading in two horizontal and vertical directions, and can also realize strain rate and multi-frequency band loading under the action of seismic load (including pulse load). The device of the present invention can be used to study the influence of the multi-directionality of seismic motion on the dynamic characteristics of rock, which is conducive to revealing the dynamic instability mechanism of slope and is of great significance to the theoretical research and engineering design of fractured rock. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 It is a schematic diagram of the overall structure of the circulating shear box in the present invention;

[0025] Figure 3 It is a side structural schematic diagram of the circulating shear box in the present invention;

[0026] Figure 4 It is a structural schematic diagram of the y-direction reaction force component in the present invention;

[0027] Figure 5 It is a structural schematic diagram of the x-direction reaction force component in the present invention;

[0028] Figure 6 It is a schematic diagram of the test results of the present invention.

[0029] In the figure: 1, z-axis oil cylinder; 2, x-axis oil cylinder; 3, y-axis oil cylinder; 4, column; 5, lifting ring; 6, frame; 7, displacement sensor; 8, sample conveying device; 9, normal pressure head; 10, y-axis reaction force cap; 11, y-axis force pad; 12, y-axis anti-friction roller; 13, reserved acoustic emission hole; 14, x-axis reaction force cap; 15, shear box base; 16, connection cap; 17, connection block; 18, upper circulation shear Cutting box; 19. X-axis force pad; 20. Fastening hole; 21. Lower circulation shear box; 22. Spacer ball; 23. X-axis force pad; 24. Hydraulic buffer; 25. Top plate; 26. Z-axis limit seat; 27. Reaction flange; 28. Reaction column; 29. ​​Stop column; 30. Z-axis anti-friction needle roller; 31. X-axis anti-friction needle roller; 32. Y-axis reaction seat; 33. Mounting hole; 34. X-axis anti-friction ball; 35. Stop block. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0031] like Figure 1-Figure 5 As shown, a three-axis cyclic shear test device includes a frame 6, a cyclic shear box, an x-axis cylinder 2, a y-axis cylinder 3, a z-axis cylinder 1, a sample conveying device 8, an x-axis reaction force component, a y-axis reaction force component, a servo control system, a hydraulic oil system, a data acquisition system and a computer control system.

[0032] The frame 6 is supported as a whole by the upright column 4. A lifting ring 5 is provided on the top of the frame 6 for easy lifting. The circulating shear box, the x-axis reaction force assembly and the y-axis reaction force assembly are all arranged in the frame 6. The circulating shear box is divided into an upper circulating shear box 18 and a lower circulating shear box 21. An opening is provided on one side of the frame 6. The sample conveying device is installed at the opening. The circulating shear box can be transported into the frame 6 through the sample conveying device; the lower circulating shear box 21 is arranged on the y-axis reaction force assembly, the upper circulating shear box 18 is arranged on the lower circulating shear box 21, and a plurality of y-axis anti-friction rollers 12 are provided on the top of the upper circulating shear box 18 to roll along the working direction of the y-axis cylinder 3. The x-axis cylinder 2 and the y-axis cylinder 3 are installed on the side walls of the frame 6 and act horizontally on the lower circulating shear box 21 and the upper circulating shear box 18 respectively, so that the x-axis cylinder 2 and the y-axis cylinder 3 apply a cyclic shear force to the sample through the circulating shear box; the z-axis cylinder 1 is installed vertically on the top of the frame 6, and the working direction of the z-axis cylinder 1 A normal pressure head 9 is connected to the end, and the z-axis cylinder 1 acts on the y-axis friction reducing needle 11 through the normal pressure head 9, and then applies normal pressure to the sample through the circulating shear box. The x-axis reaction force components are arranged on both sides of the normal pressure head and act on the normal pressure head; the servo control system is used to control the loading process of the x-axis cylinder 2, the y-axis cylinder 3, and the z-axis cylinder 1; the hydraulic oil system is used to provide hydraulic oil to the x-axis cylinder 2, the y-axis cylinder 3 and the z-axis cylinder 1; the data acquisition system is used to measure and collect the loading parameters of the x-axis cylinder 2, the y-axis cylinder 3, and the z-axis cylinder 1; the servo control system, the hydraulic oil system, and the data acquisition system are all electrically connected to the computer control system, and then uniformly deployed through the computer control system to enable the various systems to work in coordination.

[0033] like Figure 2 , Figure 3 As shown, a shear box base 15 is provided on the y-direction reaction force assembly, a lower circulation shear box 21 is placed on the shear box base 15, a spacer ball 22 is rotatably mounted on the top of the lower circulation shear box 21, and the upper circulation shear box 18 is supported on the lower circulation shear box 21 through the spacer ball 22. When the sample is loaded, the x-direction oil cylinder 2 applies a cyclic shear force to the sample through the lower circulation shear box 21 to perform x-direction cyclic shearing, and the y-direction oil cylinder 3 applies a cyclic shear force to the sample through the upper circulation shear box 18 to perform y-direction cyclic shearing; the spacer ball 22 can reduce the friction between the upper circulation shear box 18 and the lower circulation shear box 21 while supporting the upper circulation shear box 18. In addition, a plurality of reserved acoustic emission holes 13 are provided on the side walls of the upper circulation shear box 18 and the lower circulation shear box 21, which can be compatible with the acoustic emission test when performing the cyclic shear test.

[0034] like Figure 3As shown, the side walls of the upper circulation shear box 18 and the side walls of the lower circulation shear box 21 are respectively provided with a y-direction force pad 11 and an x-direction force pad 19. Specifically, a plurality of fastening holes 20 are provided on the x-direction force pad 19, and the x-direction force pad 19 is fixedly connected to the lower circulation shear box 21 through the fastening holes 20 in cooperation with fastening bolts and other connecting parts, and the x-direction reaction cap 14 is connected to the x-direction force pad 19 through fastening bolts, and the x-direction oil cylinder acts on the x-direction reaction cap. Similarly, the upper circulation shear box 18 is also connected to the y-direction force pad 11 through fastening holes in cooperation with fastening bolts and other connecting parts, and the y-direction reaction cap 10 is provided on the y-direction force pad 11, and the y-direction reaction cap 10 is connected to the y-direction force pad 11 through a connecting cap 16, and a connecting block 17 is provided between the connecting cap 16 and the y-direction force pad 11, and the y-direction oil cylinder 3 acts on the y-direction reaction cap 10.

[0035] The working end of the y-direction oil cylinder 3 is fixed to the frame 6 through a connecting flange, and a test force sensor is arranged between the connecting cap and the y-direction oil cylinder 3 to measure the size of the tangential load applied to the y-direction oil cylinder 3. The test force sensor is connected and contacted with the y-direction reaction cap 10, and the y-direction reaction cap 10 is threadedly connected to the y-direction force pad 11. By tightening the threads of the connecting cap 16 and the connecting block 17, the working end of the y-direction oil cylinder 3 can be fastened to the upper circulation shear box. The connecting block 17 is used to bear the fastening force between the connecting cap 16 and the y-direction force pad 11. Similarly, the connection principle between the working end of the x-direction oil cylinder 2 and the lower circulation shear box is similar to that in the y direction, except that the x-direction reaction cap 14 is directly connected to the x-direction force pad 19 through a fastening bolt.

[0036] like Figure 5 As shown, the y-direction reaction force assembly includes an x-direction anti-friction needle roller 31, a y-direction reaction force seat 31, an x-direction anti-friction ball 34 and a stopper 35. Among them, a placement groove is provided on the top of the y-direction reaction force seat 32 along the working direction of the x-direction oil cylinder 2, and a plurality of x-direction anti-friction needle rollers 31 are arranged side by side along the length direction of the placement groove for rolling at the bottom of the placement groove; a receiving groove is provided on both side walls of the placement groove along the length direction of the placement groove, and a plurality of x-direction anti-friction balls 34 are arranged in the receiving groove, and a stopper 34 for preventing the x-direction anti-friction balls 34 from escaping from the receiving groove is fixed at both ends of the receiving groove on the y-direction reaction force seat 32; the shear box base 15 is placed in the placement groove and supported on the x-direction anti-friction needle roller 31, and at the same time, the shear box base 15 is in rolling contact with the x-direction anti-friction ball 34; a mounting hole 33 is provided on the top surface of the y-direction reaction force seat 32 for fixing the shear box to prevent the shear box from tilting.

[0037] like Figure 4As shown, the x-direction reaction force assembly includes a hydraulic buffer 24, a top plate 25, a z-direction limit seat 26, a reaction flange 27, a reaction column 28, a stop column 29 and a z-direction anti-friction needle roller 30. Among them, the reaction flange is fixed on the inner wall of the frame 6, the reaction column 28 is fixed on the reaction flange 27, the z-direction limit seat 26 is vertically fixed on the reaction column 28, the top plate 25 and the stop column 29 are fixed at the upper and lower ends of the z-direction limit seat 26 respectively, and a plurality of z-direction anti-friction needle rollers 30 arranged side by side in the vertical direction are rollingly arranged on the z-direction limit seat 26 between the top plate 25 and the stop column 29, the z-direction anti-friction needle rollers 30 are in rolling contact with the normal pressure head 9, and the hydraulic buffer 24 is installed on the top plate 25 and acts on the z-direction anti-friction needle rollers 30.

[0038] When performing x-direction cyclic shearing, the horizontal reaction force assembly moves toward the x-direction by limiting the friction reaction force of the upper cyclic shearing box 18, and the x-direction anti-friction needle roller ensures that the normal pressure head 9 does not generate additional friction to affect its movement when it is affected by shear expansion; the hydraulic buffer 24 supports the z-direction anti-friction needle roller 30 to prevent the z-direction anti-friction needle roller 30 from falling due to gravity when it is not subject to reaction force and cannot move effectively; the x-direction anti-friction ball 34 and the x-direction anti-friction needle roller 31 can also limit the y-direction shearing function of the lower cyclic shearing box 21 when performing x-direction shearing. When performing y-direction cyclic shearing, the y-direction reaction force seat 32 limits the lower cyclic shearing box 21 from moving toward the y-direction due to the friction reaction force, and the y-direction anti-friction needle roller 12 ensures that the normal pressure head 9 does not generate additional friction to affect its movement when it is affected by shear expansion.

[0039] In this embodiment, the structure and working principle of the servo control system are prior art, which includes about 100 subVIs, and the main software consists of a top-level VI. The graphical interface consists of a pair of front panels and a block diagram. The front panel has a set of controls and indicators, such as buttons and pointers, as well as digital controls and indicators, and two display windows for multiple drawings. Data such as servo control speed, specified time intervals, and data acquisition rates can be entered from the keyboard. As the experiment proceeds, the shear stress-shear displacement and shear stress-normal stress curves will be updated on the graphic window of the shear main screen panel. At the end of the experiment, the selected storage parameters, such as normal stress, shear stress, and shear displacement, will be saved. Using Excel software, the shear characteristic curve can be easily obtained.

[0040] As the power source for loading, the structure and working principle of the hydraulic system are also existing technologies. The main structure consists of a box, an oil pump-motor group, a precision oil filter, a relief valve, a pressure gauge, an air filter, a transducer and pipelines. It can provide hydraulic oil of a certain pressure, and the remaining amount of hydraulic oil can be observed by observing the liquid level on the oil tank. When the motor drives the oil pump to rotate, the high-pressure oil enters the oil cylinder through the precision oil filter-relief valve-electro-hydraulic servo valve. The full digital controller controls the valve opening size and direction of the electro-hydraulic servo valve according to the instructions sent by the computer and the signal fed back by the sensor, so that the piston in the loading oil cylinder rises or falls according to the instructions of the computer, realizing the closed-loop control of axial displacement, test force or deformation, and smooth switching of the three control modes. The main function of the cooling system is to reduce the oil temperature during use to prevent the oil temperature from being too high and causing safety hazards. The cooling water cools the oil source through a plate heat exchanger, and then returns to the cooling water pool through a return pipe, which can avoid the waste of water resources.

[0041] The data acquisition system includes a controller, a data acquisition card, a test force sensor and a displacement sensor. The loading ends of the x-axis oil cylinder 2, the y-axis oil cylinder 3 and the z-axis oil cylinder 1 are all provided with a test force sensor, and the end faces of the x-axis oil cylinder 2, the y-axis oil cylinder 3 and the z-axis oil cylinder 1 are all provided with a displacement sensor. The data acquisition card, the controller, and the computer control system are electrically connected in sequence, and the test force sensor and the displacement sensor are electrically connected to the data acquisition card. In this embodiment, the maximum range of the test force sensor is ±1500kN; the displacement sensor is used to track and measure the piston displacement of the oil cylinder in real time, and the maximum range is 300mm. Data acquisition and normal stiffness setting are performed digitally using a 16-bit A / D and D / A board installed in the computer. The AD / DA / DIO board is used with Windows-NT and a faster PC processor to enable the system to scan 16 input channels and 32 output channels. The collected test data includes the normal pressure, shear force, corresponding displacement and stroke of the x-axis oil cylinder 2, the y-axis oil cylinder 3 and the z-axis oil cylinder 1. The digital control program is designed using LabVIEW programming language to build a data acquisition and instrumentation system. LabVIEW is used to quickly create interactive controls for the system, with the time interval set to 100Hz.

[0042] The structure and working principle of the computer control system are existing technologies, and it consists of three software sets: control software and standard data storage and processing system. Constant and variable normal stiffness control conditions are realized by digital closed-loop control with electrical and hydraulic servos. This is a nonlinear feedback and is measured on a PC through a multifunctional analog-to-digital conversion, digital-to-analog conversion and digital input / output (A / D, D / A and DIO) board, using the graphical programming language LabVIEW, a customized "virtual instrument" (VI) and a PID control toolkit. The normal load is changed by comparing the vertical displacement of the joint during shearing with the feedback signal, which is calculated based on the normal stiffness value kn as follows:

[0043] ΔP n =k n Δδ n

[0044] P n (t+Δt)=P n (t)+ΔP n

[0045] In the formula, ΔP n and Δδ n are the changes of normal load and vertical displacement, respectively.

[0046] When the three-way cyclic shear test device is used to perform the three-way cyclic shear test, the following steps are included:

[0047] S1. Turn on the machine and check whether all equipment and instruments are normal.

[0048] S2. Select a circulation shear box of corresponding size according to the size of the sample, place the base 15 on the y-direction reaction force assembly, place the lower part of the sample into the lower circulation shear box 21 and place the lower circulation shear box 21 on the base 15, then place the upper circulation shear box 18 on the lower circulation shear box 21, adjust the orientation of the upper circulation shear box 18 so that the upper circulation shear box 18 covers the upper part of the sample and is aligned with the sample to complete the loading.

[0049] S3: After the sample is loaded, the circulating shear box is transported to the bottom of the z-direction oil cylinder 1 by the sample conveying device, and the initial normal pressure is applied to the sample by the z-direction oil cylinder 1, and then the x-direction reaction force cap 14 and the y-direction reaction force cap 10 are respectively fastened to the lower circulating shear box 18 and the upper circulating shear box 21. In this embodiment, the normal pressure is applied to 5MPa at a rate of 1MPa / min.

[0050] S4. Turn on the servo control system and perform a three-way cyclic shear test on the sample until the sample reaches the designed number of cyclic shears. In this embodiment, when the cyclic shear force is applied to the sample, the x-axis cylinder and the y-axis cylinder simultaneously start shearing to the target distance of 4mm, then shear to -4mm in the negative direction of shearing, and finally shear to 0mm, which is a complete cycle until the set number of cyclic shears is reached.

[0051] S5. When the shear displacement of the cylinder reaches the set stroke or number of times, it automatically stops and saves the test data. The computer control system processes and analyzes the data collected by the data acquisition system.

[0052] In step S4, when the sample is subjected to a three-way cyclic shear test, three test methods are included: one is to perform a three-way cyclic shear test on the sample under a constant normal load, the second is to perform a three-way cyclic shear test on the sample under a dynamic normal load, and the third is to perform a three-way cyclic shear test on the sample under a constant normal stiffness.

[0053] When a three-way cyclic shear test is performed on a specimen under a constant normal load, a cyclic shear force is applied to the specimen through the x-axis cylinder 2 and the y-axis cylinder 3 according to the pre-input constant normal load value until the specimen reaches the designed number of cyclic shear times.

[0054] A three-way cyclic shear test was carried out on the specimen under dynamic normal load. The frequency and amplitude of the z-axis cylinder 1 were set according to the pre-input seismic wave transformation, and then cyclic shear force was applied to the specimen through the x-axis cylinder 2 and the y-axis cylinder 3 until the specimen reached the designed number of cyclic shears.

[0055] The sample was subjected to a three-way cyclic shear test under constant normal stiffness. The constant normal stiffness test function built into the software was started, and the initial normal stress σ0 and the constant normal stiffness coefficient K were input. n , and then apply cyclic shear force to the specimen through x-axis cylinder 2 and y-axis cylinder 3 until the specimen reaches the designed number of cyclic shear times.

[0056] The present invention has carried out actual tests using the above three-way cyclic shear test device and test method, and the test results are as follows: Figure 6 As shown, according to the shear displacement-shear stress variation curve, the present invention can realize the bidirectional cyclic shear test of fractured rock samples under the conditions of constant normal load, dynamic normal load and constant normal stiffness, and the three-way dynamic cyclic shear test can realize multi-directional dynamic loading shear servo dynamic loading in two horizontal and vertical directions, and can also realize strain rate and multi-frequency band loading under the action of seismic load (including pulse load). Therefore, the three-way cyclic shear test device of the present invention can be used to study the influence of the multi-directionality of earthquake motion on the dynamic characteristics of rock, which is conducive to revealing the dynamic instability mechanism of slope, and has important significance for the theoretical research and engineering design of fractured rock mass.

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

Claims

1. A three-way cyclic shear test device, comprising a frame (6), characterized in that: Also includes: An upper circulation shear box (18), a lower circulation shear box (21), an x-direction oil cylinder (2), a y-direction oil cylinder (3), a z-direction oil cylinder (1), a sample conveying device (8), an x-direction reaction force assembly and a y-direction reaction force assembly. The upper circulation shear box (18), the lower circulation shear box (21), the x-direction reaction force assembly and the y-direction reaction force assembly are all arranged in a frame (6). The y-direction reaction force assembly is arranged at the bottom of the frame (6). The lower circulation shear box (21) is arranged on the y-direction reaction force assembly. The upper circulation shear box (18) is arranged on the lower circulation shear box (21). The upper circulation shear box (18) ) is provided with a plurality of y-direction anti-friction needle rollers (12) at the top thereof so as to roll along the working direction of the y-direction oil cylinder (3); the x-direction oil cylinder (2) and the y-direction oil cylinder (3) are provided on the side wall of the frame (6) and respectively act horizontally on the lower circulation shear box (21) and the upper circulation shear box (18); the z-direction oil cylinder (1) is vertically provided on the top of the frame (6) and acts on the y-direction anti-friction needle rollers (12) through the normal pressure head (9); the x-direction reaction force components are provided on both sides of the normal pressure head (9) and act on the normal pressure head (9); an opening is provided on one side of the frame (6), and a sample conveying device (8) is provided at the opening; A servo control system, the servo control system is used to control the loading process of the x-axis oil cylinder (2), the y-axis oil cylinder (3), and the z-axis oil cylinder (1); A hydraulic oil system, the hydraulic oil system is used to supply hydraulic oil to the x-direction oil cylinder (2), the y-direction oil cylinder (3) and the z-direction oil cylinder (1); A data acquisition system, the data acquisition system is used to measure and acquire loading parameters of the x-axis oil cylinder (2), the y-axis oil cylinder (3), and the z-axis oil cylinder (1); The computer control system, servo control system, hydraulic oil system and data acquisition system are all electrically connected to the computer control system.

2. A three-way cyclic shear test device according to claim 1, characterized in that: A shear box base (15) is provided on the y-direction reaction force assembly, a lower circulation shear box (21) is provided on the shear box base (15), and an upper circulation shear box (18) is supported on the lower circulation shear box (21) via a spacing ball (22).

3. A three-way cyclic shear test device according to claim 2, characterized in that: The y-direction reaction force assembly comprises an x-direction friction-reducing needle roller (31), a y-direction reaction force seat (32), an x-direction friction-reducing ball roller (34) and a stopper (35); a placement groove is provided at the top of the y-direction reaction force seat (32) along the working direction of the x-direction oil cylinder (2); a plurality of x-direction friction-reducing needle rollers (31) are rollably provided at the bottom of the placement groove and arranged side by side along the length direction of the placement groove; a shear box base (15) is arranged in the placement groove and supported on the x-direction friction-reducing needle roller (31); accommodating grooves are provided on both side walls of the placement groove along the length direction of the placement groove; a plurality of x-direction friction-reducing balls (34) are rollably provided in the accommodating groove and are in contact with the shear box base (15); stoppers (35) are provided at both ends of the accommodating groove on the y-direction reaction force seat (32); and a mounting hole (33) is provided on the top surface of the y-direction reaction force seat (32).

4. A three-way cyclic shear test device according to claim 1, characterized in that: The x-direction reaction force assembly comprises an oil pressure buffer (24), a top plate (25), a z-direction limit seat (26), a reaction flange (27), a reaction column (28), a stop column (29) and a z-direction anti-friction needle roller (30). The reaction flange (27) is arranged on the inner wall of the frame (6). The z-direction limit seat (26) is vertically arranged on the reaction flange (27) through the reaction column (28). The upper and lower ends of the z-direction limit seat (26) are respectively provided with a top plate (25) and a stop column (29). A plurality of z-direction anti-friction needle rollers (30) arranged side by side in a vertical direction are rollingly arranged on the z-direction limit seat (26) between the top plate (25) and the stop column (29). The z-direction anti-friction needle rollers (30) are in rolling contact with the normal pressure head (9). The oil pressure buffer (24) is arranged on the top plate (25) and acts on the z-direction anti-friction needle rollers (30).

5. A three-way cyclic shear test device according to claim 2, characterized in that: The side walls of the upper circulation shear box (18) and the side walls of the lower circulation shear box (21) are respectively provided with a y-direction force pad (11) and an x-direction force pad (19), and a plurality of fastening holes (20) are provided on the y-direction force pad (11) and the x-direction force pad (19), and an x-direction reaction cap (14) is provided on the x-direction force pad (19), and an x-direction oil cylinder (2) acts on the x-direction reaction cap (14), and a y-direction reaction cap (10) is provided on the y-direction force pad (11), and the y-direction reaction cap (10) is connected to the y-direction force pad (11) through a connecting cap (16), and a connecting fastening block (17) is provided between the connecting cap (16) and the y-direction force pad (11), and the y-direction oil cylinder (3) acts on the y-direction reaction cap (10).

6. A three-way cyclic shear test device according to claim 1, characterized in that: The data acquisition system comprises a controller, a data acquisition card, a test force sensor and a displacement sensor (7); the loading ends of the x-axis oil cylinder (2), the y-axis oil cylinder (3) and the z-axis oil cylinder (1) are all provided with test force sensors; the end surfaces of the x-axis oil cylinder (2), the y-axis oil cylinder (3) and the z-axis oil cylinder (1) are all provided with displacement sensors (7); the data acquisition card, the controller and the computer control system are electrically connected in sequence; and the test force sensor and the displacement sensor (7) are both electrically connected to the data acquisition card.

7. A three-way cyclic shear test method, characterized in that: The following steps are involved: S1. Turn on the machine and check whether all equipment and instruments are normal; S2. Select a circulation shear box of corresponding size according to the size of the sample, place the shear box base (15) on the y-direction reaction force assembly, place the lower part of the sample into the lower circulation shear box (21) and place the lower circulation shear box (21) on the shear box base (15), then place the upper circulation shear box (18) on the lower circulation shear box (21), adjust the orientation of the upper circulation shear box (18) so that the upper circulation shear box (18) covers the upper part of the sample and is aligned with the sample, and complete the sample loading; S3: After the sample is loaded, the circulating shear box is transported to the bottom of the z-axis oil cylinder (1) by the sample conveying device (8), and the initial normal pressure is applied to the sample by the z-axis oil cylinder (1), and then the x-axis reaction force preparation cap (14) and the y-axis reaction force preparation cap (10) are respectively fastened and connected to the lower circulating shear box (21) and the upper circulating shear box (18); S4, start the servo control system and perform a three-way cyclic shear test on the sample until the sample reaches the designed number of cyclic shear times; S5. When the shear displacement of the cylinder reaches the set stroke or number of times, it automatically stops and saves the test data. The computer control system processes and analyzes the data collected by the data acquisition system.

8. The three-way cyclic shear test method according to claim 7, characterized in that: In step S4, a three-way cyclic shear test is performed on the sample under a constant normal load. According to the pre-input constant normal load value, a cyclic shear force is applied to the sample through the x-axis cylinder (2) and the y-axis cylinder (3) until the sample reaches the designed number of cyclic shear times.

9. The three-way cyclic shear test method according to claim 7, characterized in that: In step S4, a three-way cyclic shear test is performed on the sample under a dynamic normal load, the frequency and amplitude of the z-axis cylinder (1) are set according to the pre-input seismic wave transformation, and then a cyclic shear force is applied to the sample through the x-axis cylinder (2) and the y-axis cylinder (3) until the sample reaches the designed number of cyclic shear times.

10. The three-way cyclic shear test method according to claim 7, characterized in that: In step S4, a three-way cyclic shear test is performed on the specimen under constant normal stiffness. The constant normal stiffness test function built into the software is started, and the initial normal stress σ0 and the constant normal stiffness coefficient K are input. n Then, a cyclic shear force is applied to the specimen through the x-axis cylinder (2) and the y-axis cylinder (3) until the specimen reaches the designed number of cyclic shear times.

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