Multi-group conjugate jointed rock variable principal stress experiment method and equipment

Abstract

The invention belongs to the field of rock mass engineering, and provides a multi-group conjugate jointed rock variable principal stress experiment method and equipment, and the method comprises the following steps: 1, sample processing; step 2, placing the rock sample on a bearing bracket; 3, the three loading devices load the pressure # imgabs0 #, the pressure # imgabs1 # and the pressure # imgabs2 # at the same time, and the pressure # imgabs3 # is made; the method comprises the following steps that 1, the number 4 is kept constant, the number 5 to the number 6 are loaded, the number 7 to the number 8 are unloaded, and resetting is carried out after the number 7 to the number 8 are stabilized; the method comprises the following steps that 1, the number-# imgabs9 is kept constant, the number-# imgabs10 is loaded to the number-# imgabs11 is loaded, the number-# imgabs12 is unloaded to the number-# imgabs13 is unloaded, and resetting is conducted after the number-# imgabs9 is stabilized; (2) after the loading is finished, the # 14 imgabs is kept constant, the # 15 imgabs to the # 16 imgabs continue to be loaded, the # 17 imgabs to the # 18 imgabs are unloaded, and resetting is conducted after the # 14 imgabs is stabilized; 4, progressively increasing # imgabs19 #, and repeating the step 3 until the rock sample is damaged; through a variable principal stress direction loading and unloading cyclic experiment method, the stress condition and the damage process of the rock mass having multiple groups of X-shaped conjugate joints in a complex stress environment under a real condition in the nature are simulated, so that the rock mass internally containing large conjugate joints is subjected to effective experimental analysis.

Description

Technical Field

[0001] The invention belongs to the field of rock mass engineering, and in particular relates to a variable principal stress experimental method and equipment for multiple groups of conjugate jointed rocks. Background Art

[0002] Natural rocks inevitably have natural defects such as microcracks, faults and holes due to long-term and complex geological movements. The initiation, expansion and penetration of cracks inside the fractured rock mass are the causes of engineering accidents.

[0003] The structural planes of rock mass space often exist in the form of joints with different lengths, angles and orientations. The joints, fissures, cleavage planes and weak interlayers in the jointed rock mass will destroy the integrity of the rock mass. The cracking and expansion of the wing-shaped cracks generated at the joint tips under the compression and shearing action of external loads often lead to the instability and destruction of the rock mass. The geometric characteristics of the joints mainly include the length of the joints, the inclination of the joints, and the degree of penetration, which are the main factors affecting the mechanical properties of the jointed rock mass. In engineering, the conjugate "X" type joint fissures play a controlling role in the stability of the rock mass. At the same time, the secondary joints also have a certain influence on the strength of the rock mass. When the inclination of the primary and secondary joints is the same, the peak strength of the single jointed rock mass is significantly higher than that of the X-type jointed rock mass.

[0004] At present, the main view of research is that there is a group of conjugate "X" type joints and fissures in the rock mass. In addition, the cracks in the material are usually simplified into several types such as opening type, sliding type, tearing type, etc. In engineering, joints are rarely simplified into three groups of conjugate "X" type joints and fissures. However, in actual engineering, due to factors such as earthquakes and blasting, three groups of conjugate "X" type joints and fissures appear in the rock mass in three-dimensional space. Based on the above problems, there is currently a lack of a device for conducting experiments on the three groups of conjugate "X" type joint and fissure models. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a variable principal stress experimental method and equipment for multiple sets of conjugate jointed rocks to solve the problems in the prior art. The technical solution adopted by the present invention is: A variable principal stress experimental method for multiple sets of conjugate jointed rocks: including: Step 1, sample processing: processing rock samples; Step 2: placing the rock sample on a load-bearing bracket, the load-bearing bracket comprising three plates, the three plates are fixedly connected and wrap a top corner of the bottom of the rock sample, so that three surfaces of the rock sample are exposed, and loading devices are respectively arranged on the three exposed surfaces, and the two opposite surfaces of the rock sample are the loading device and the plate respectively; Step 3: Apply pressure to the rock sample through the loading device: (a) Three loading devices apply pressure simultaneously , and , and make ; (b) Maintain Constant, loaded to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; (c) Maintain Constant, loaded to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; (d) Maintain Constant, continue loading to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; Step 4: Increment Repeat step 3 until the rock sample is destroyed.

[0006] A variable principal stress experimental device for multiple groups of conjugate jointed rocks, the experimental device comprising: a loading device, a bottom plate, a side plate, a top plate and a bearing bracket; The bottom plate is connected to the bearing bracket, which is used to place the rock sample. The bearing bracket includes three plates, which are fixedly connected and located on three mutually perpendicular spatial planes. The three plates together form a square opening groove, which wraps the bottom corner of the rock sample, wraps three surfaces of the rock sample and exposes the other three surfaces. The loading devices are respectively arranged on the three exposed surfaces, and the two opposite surfaces of the rock sample are the loading device and the plates respectively. The top of the loading device located above the rock sample is fixedly connected to the top plate, the outer ends of the loading devices located on both sides of the rock sample are respectively fixedly connected to the side plates, and the bottoms of the side plates are connected to the bottom plate; The loading device is used to apply pressure to the wall surface of the rock sample.

[0007] Furthermore, four side panels are provided, wherein two adjacent side panels are connected to the loading device, and the other two adjacent side panels are fixedly connected to the plate body via support columns.

[0008] Furthermore, the bottoms of the four side panels are fixedly connected to a lifting plate, the lifting plate is located above the bottom plate, both ends of the lifting plate are respectively provided with inclined connecting rods, the top of the connecting rod is rotatably connected to the end of the lifting plate, the bottom of the connecting rod is rotatably connected to a slide plate, and the slide plate is slidably connected to the bottom plate; The bottom of the plate body at the bottom is fixedly connected to a limiting sleeve, the lifting plate can slidably pass through the top rod, the top of the top rod can slidably pass through the limiting sleeve, the plate body at the bottom is provided with a through hole adapted to the top rod, the through hole is coaxially arranged with the limiting sleeve, and the bottom of the top rod is connected to the bottom plate; The two ends of the top plate are rotatably connected to the top of the slide rod, wherein the two opposite side plates are provided with through holes adapted to the slide rod, the slide rod can slide through the through holes, the bottom plate is provided with positioning holes adapted to the slide rod, the bottom of the slide rod passes through the lifting plate and the slide plate in sequence and is located in the positioning holes; A protrusion is fixedly connected in the positioning hole, and an annular groove adapted to the protrusion is provided at the bottom of the slide rod, and a notch is provided on the annular groove. The protrusion is used to pass through the notch and be clamped in the annular groove after rotation, so as to form an axial constraint on the slide rod; The slide bar is used to slide upward to separate from the slide plate, so that the lifting plate descends under the action of its own weight, and the push rod lifts up the rock sample.

[0009] Furthermore, the loading device includes a fixing plate, a driving device, a connecting plate, a rotating seat, a screw rod, a threaded sleeve, a connecting rod, a pressing plate and a limiting structure; The fixing plate and the connecting plate are arranged side by side, the driving device is installed between the fixing plate and the connecting plate, the output end of the driving device passes through the connecting plate and is fixedly connected to the rotating seat, the rotating seat is rotatably arranged on the connecting plate, one end of the rotating seat away from the driving device is fixedly connected to one end of the screw rod, the other end of the screw rod is threadedly connected to the threaded sleeve, the side surface of the threaded sleeve is connected to the connecting rod, the connecting rod is parallel to the axis of the screw rod, and the end of the connecting rod away from the connecting plate is connected to the pressing plate; The driving device is used to drive the rotating seat to rotate, so that the screw rod rotates; the side of the connecting rod is connected to the limiting structure, which is used to limit the connecting rod to rotate around the screw rod, so that the threaded sleeve moves along the screw rod and the pressure plate faces the wall of the rock sample.

[0010] Furthermore, the limiting structure includes a vertical rod, a protrusion, a stopper, a second limiting block, an intermediate plate and a cover plate; The vertical rod is parallel to the connecting rod and is arranged at an interval. The vertical rod is located on a side of the connecting rod away from the screw rod. One end of the vertical rod is fixedly connected to the connecting plate. A second waist-shaped through hole is provided on the vertical rod. The middle plate is located in the second waist-shaped through hole. One end of the middle plate facing the connecting rod is fixedly connected to the second limit block. One end of the middle plate away from the connecting rod is detachably connected to the cover plate. The side of the connecting rod is fixedly connected to the protrusion, the end of the protrusion can remove the stopper, the second limit block is located on the rotation path of the stopper, and the second limit block is used to abut against the stopper to form a circumferential constraint; The middle plate is slidable up and down in the second waist-shaped through hole, and the cover plate and the vertical pole are provided with teeth to restrict the vertical height; By adjusting the height of the second limit block, the stroke of the stopper to disengage from the second limit block is changed to adjust the movement amount of the threaded sleeve, thereby adjusting the maximum pressure value applied by the pressure plate.

[0011] Furthermore, the limiting structure also includes a first limiting block, a transmission block, a telescopic rod and a lifting mechanism; The vertical rod is provided with a first waist-shaped through hole, the transmission block is arranged in the first waist-shaped through hole, the transmission block is fixedly connected to the first limit block at one end facing the connecting rod, the first limit block is located above the second limit block, the transmission block is fixedly connected to the telescopic rod at one end away from the connecting rod, the telescopic rod is parallel to the vertical rod, and the telescopic rod is connected to the lifting mechanism at one end away from the transmission block for lifting the first limit block; When the screw is rotated to make the pressing plate move toward the rock sample, the first limit block moves to the highest height, and a gap is formed between the bottom of the first limit block and the top of the second limit block; when the stop block is separated from the second limit block, the stop block enters the gap above the second limit block; When the screw rotates to move the pressure plate away from the rock sample, the first limit block moves to the lowest height, and the bottom of the first limit block fits with the top of the second limit block; the stop block abuts the lower end of the first limit block and moves onto the second limit block.

[0012] Further, the lifting mechanism includes a linear propulsion device; The linear driving device is installed on the connecting plate, and the output end of the linear driving device is fixedly connected to the bottom of the telescopic rod. The linear driving device is used to drive the telescopic rod to move up and down.

[0013] Furthermore, the three fixing plates of the loading devices are respectively fixedly connected to the top plate and the two side plates.

[0014] The present invention has the following beneficial effects: the present invention simulates the stress conditions and failure process of a rock mass with multiple groups of "X"-type conjugate joints in a complex stress environment under real natural conditions through a loading and unloading cycle experimental method with a variable principal stress direction, thereby performing effective experimental analysis on a rock mass containing large conjugate joints inside. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the experimental method of the present invention; Figure 2 It is a schematic diagram of the overall structure of the experimental device of the present invention; Figure 3 is a schematic diagram of the slide bar being separated from the slide plate; Figure 4 is a schematic diagram of the initial state of the loading device; Figure 5 is a schematic diagram of the loading device being loaded to the maximum pressure state; Figure 6 is a schematic diagram when the first and second limit blocks are in contact; Figure 7 is a top view schematic diagram of the connection relationship of the second limit block; Figure 8 is a schematic diagram of a top view of a load-bearing bracket; Fig. 9 It is a schematic diagram when the protrusion is located in the annular groove and staggered from the notch; Fig.10 This is a schematic diagram when the protrusion is aligned with the notch. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention Figure 1-Figure 10 , the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0017] like Figure 1 , a variable principal stress experimental method for multiple sets of conjugate jointed rocks, including: Step 1, sample processing: Process rock sample 2; prepare a rock sample with three-sided discontinuous "X"-shaped conjugate joints by 3D printing, that is, the rock sample 2 includes three-sided conjugate joints. The size of rock sample 2 is 150 mm~300 mm; Step 2: Place the rock sample 2 on the support bracket 5. The support bracket 5 includes three plates. The three plates are fixedly connected and wrap a top corner of the bottom of the rock sample 2, so that three surfaces of the rock sample 2 are exposed. The loading devices 6 are respectively arranged on the three exposed surfaces. The two opposite surfaces of the rock sample 2 are the loading device 6 and the plate respectively. Step 3: Apply pressure to the rock sample 2 through the loading device 6: (a) Three loading devices 6 load pressure simultaneously , and , and make ; (b) Maintain Constant, loaded to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; (c) Maintain Constant, loaded to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; (d) Maintain Constant, continue loading to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; Steps (b), (c), and (d) in step 3 can be interchanged in any order; Step 4: Incremental And repeat step 3 until rock sample 2 is destroyed.

[0018] The shear failure process of rock sample 2 follows the Mohr-Coulomb criterion: , Where: For cohesion, is the internal friction angle, For shear strength.

[0019] In the method of the present invention, the loading device 6 may be the loading device 6 proposed in the present invention, or may be a jack or other equipment.

[0020] The present invention uses a loading and unloading cycle experimental method with a variable principal stress direction to simulate the stress conditions and failure process of a rock mass with multiple groups of "X"-type conjugate joints in a complex stress environment under real natural conditions, thereby performing effective experimental analysis on a rock mass containing large conjugate joints inside.

[0021] like Figure 2 , a variable principal stress experimental device for multiple sets of conjugate jointed rocks, the experimental device comprises: a loading device 6, a bottom plate 1, a side plate 3, a top plate 4 and a bearing bracket 5; The bottom plate 1 is connected to the bearing bracket 5, and the bearing bracket 5 is used to place the rock sample 2. The bearing bracket 5 includes three plates, and the three plates are fixedly connected and located on three mutually perpendicular spatial planes. The three plates together form a square opening groove, and the square opening groove wraps the bottom corner of the rock sample 2, wraps the three surfaces of the rock sample 2 and exposes the other three surfaces. The loading devices 6 are respectively arranged on the three exposed surfaces, and the two opposite surfaces of the rock sample 2 are the loading device 6 and the plates respectively; The top of the loading device 6 located above the rock sample 2 is fixedly connected to the top plate 4, the outer ends of the loading devices 6 located on both sides of the rock sample 2 are respectively fixedly connected to the side plates 3, and the bottoms of the side plates 3 are connected to the bottom plate 1; The loading device 6 is used to apply pressure to the wall surface of the rock sample 2 .

[0022] Furthermore, four side panels 3 are provided, wherein two adjacent side panels 3 are connected to the loading device 6 , and the other two adjacent side panels 3 are fixedly connected to the panel body via support columns 301 .

[0023] There are three loading devices 6 in total. Figure 4 The structure of the loading device 6 is illustrated by way of example, wherein the upper and lower positions of each component refer to the loading device 6, that is, Figure 4 The position in Figure 2 , Figure 3 The orientation of the loading device 6 in Figure 4 And convert.

[0024] There are four side plates 3 in total, and the four side plates 3 are distributed around the rock sample 2 , wherein the tops of two opposite side plates 3 are connected to the top plate 4 . Figure 3 In the initial state of the invention, there is an equal distance between the rock sample 2 and each pressing plate 611 .

[0025] like Figure 2 , Figure 8 The three plates of the support bracket 5 are attached to the three mutually perpendicular surfaces of the rock sample 2, and the three plates are perpendicular to each other, so as to form a square opening groove to wrap the bottom corner of the rock sample 2. When the loading device 6 applies pressure to the exposed surface of the rock sample 2, the wall surface opposite to the rock sample 2 is supported by the plate, the support column 301 and the side plate 3.

[0026] Further, the bottoms of the four side panels 3 are fixedly connected to the lifting plate 7, the lifting plate 7 is located above the bottom plate 1, and the two ends of the lifting plate 7 are respectively provided with inclined connecting rods 701, the top of the connecting rod 701 is rotatably connected to the end of the lifting plate 7, the bottom of the connecting rod 701 is rotatably connected to the slide plate 702, and the slide plate 702 is slidably connected to the bottom plate 1; The bottom of the plate body at the bottom is fixedly connected to the limiting sleeve 704, the lifting plate 7 can slidably pass through the top rod 704, the top of the top rod 704 can slidably pass through the limiting sleeve 704, the plate body at the bottom is provided with a through hole adapted to the top rod 704, the through hole is coaxially arranged with the limiting sleeve 704, and the bottom of the top rod 704 is connected to the bottom plate 1; The two ends of the top plate 4 are rotatably connected to the top of the slide rod 401, wherein the two opposite side plates 3 are provided with through holes adapted to the slide rod 401, and the slide rod 401 can slide through the through holes, and the bottom plate 1 is provided with positioning holes adapted to the slide rod 401, and the bottom of the slide rod 401 passes through the lifting plate 7 and the slide plate 702 in sequence and is located in the positioning holes; The positioning hole is fixed with a protrusion 402, and the bottom of the slide bar 401 is provided with an annular groove adapted to the protrusion 402. A notch is provided on the annular groove, and the protrusion 402 is used to pass through the notch and rotate to be clamped in the annular groove, so as to form an axial constraint on the slide bar 401; The slide bar 401 is used to slide upward to disengage from the slide plate 702 , so that the lifting plate 7 descends under its own weight, and the push rod 704 lifts up the rock sample 2 .

[0027] The lifting plate 7 is parallel to the bottom plate 1, the bottom of the connecting rod 701 is tilted outward, and the two connecting rods 701 are symmetrical. The slide plate 702 can be connected to the bottom plate 1 through a slide rail. The bottom of the top rod 704 is fixedly connected to the base 705, and the base 705 is connected to the bottom plate 1 with an adjustable height. The height of the base 705 can be adjusted by means of threads and lifting bolts, thereby adjusting the height of the top rod 704 lifting the rock sample 2.

[0028] The specific implementation refers to the following process: like Figure 3Before the experiment, the two slide bars 401 are moved upward to raise the top plate 4 to a certain height so as to facilitate the placement of the rock sample 2. The lifting plate 7 is lowered under its own weight, and the connecting rod 701 is rotated to slide the slide plate 702. Then the rock sample 2 is placed. Figure 3 The rock sample 2 is supported by the top rod 704 to a certain height. Then the two slide plates 702 are pushed inward, the lifting plate 7 moves upward, and after the slide plates 702 are in place, the two slide bars 401 are moved downward, so that the slide bars 401 pass through the lifting plate 7 and the slide plates 702 and are located in the positioning holes. During this process, the protrusion 402 passes through the notch, and finally the slide bar 401 is rotated so that the protrusion 402 is engaged in the annular groove to form an axial constraint on the slide bar 401, and finally a Figure 2 status in .

[0029] When the rock sample 2 needs to be removed after the experiment is completed, the slide bar 401 is rotated to align the protrusion 402 with the notch, and then the slide bar 401 is raised. When the slide bar 401 is separated from the slide plate 702, the lifting plate 7 is lowered under the action of its own weight to reduce the height of the supporting bracket 5, so that the push rod 704 lifts up the rock sample 2. The present invention uses the dead weight of the lifting plate 7 to push out the rock sample 2, which can facilitate the placement and removal of the rock sample 2. The weight of the lifting plate 7 is much greater than that of the rock sample 2.

[0030] Additional references Fig. 9 , Fig.10 The protrusions 402 and the notch portions may be provided in plurality and arranged circumferentially around the slide bar 401 .

[0031] Further, such as Figure 4-Figure 6 The loading device 6 includes a fixing plate 601, a driving device 603, a connecting plate 604, a rotating seat 605, a screw rod 606, a threaded sleeve 607, a connecting rod 609, a pressing plate 611 and a limiting structure; The fixing plate 601 and the connecting plate 604 are arranged side by side, the driving device 603 is installed between the fixing plate 601 and the connecting plate 604, the output end of the driving device 603 passes through the connecting plate 604 and is fixedly connected to the rotating seat 605, the rotating seat 605 is rotatably arranged on the connecting plate 604, one end of the rotating seat 605 away from the driving device 603 is fixedly connected to one end of the screw rod 606, the other end of the screw rod 606 is threadedly connected to the threaded sleeve 607, the side of the threaded sleeve 607 is connected to the connecting rod 609, the connecting rod 609 is parallel to the axis of the screw rod 606, and the end of the connecting rod 609 away from the connecting plate 604 is connected to the pressing plate 611; The driving device 603 is used to drive the rotating seat 605 to rotate, so that the screw rod 606 rotates; the side of the connecting rod 609 is connected to the limiting structure, which is used to limit the connecting rod 609 to rotate around the screw rod 606, so that the threaded sleeve 607 moves along the screw rod 606, and the pressure plate 611 faces the wall of the rock sample 2.

[0032] The driving device 603 is a prior art device, which can be a motor, a hydraulic motor, etc. The connecting plate 604 is parallel to the fixing plate 601, and the screw rod 606 is perpendicular to the connecting plate 604. The screw rod 606 and the threaded sleeve 607 form a transmission structure, which converts the rotation of the screw rod 606 into the movement of the threaded sleeve 607 along the axial direction of the screw rod 606.

[0033] Furthermore, the limiting structure includes a vertical rod 612, a protrusion 613, a stopper 614, a second limiting block 615, an intermediate plate 616 and a cover plate 617; The vertical rod 612 is parallel to the connecting rod 609 and is arranged at intervals. The vertical rod 612 is located on a side of the connecting rod 609 away from the screw rod 606. One end of the vertical rod 612 is fixedly connected to the connecting plate 604. A second waist-shaped through hole is provided on the vertical rod 612. The middle plate 616 is located in the second waist-shaped through hole. One end of the middle plate 616 facing the connecting rod 609 is fixedly connected to the second limit block 615. One end of the middle plate 616 away from the connecting rod 609 is detachably connected to the cover plate 617. The side of the connecting rod 609 is fixedly connected to the protrusion 613, and the end of the protrusion 613 can remove the stopper 614. The second limit block 615 is located on the rotation path of the stopper 614, and the second limit block 615 is used to resist the stopper 614 to form a circumferential constraint; The middle plate 616 is slidable up and down in the second waist-shaped through hole, and the cover plate 617 and the vertical rod 612 are connected by a tooth portion 600 to restrict the vertical height; By adjusting the height of the second limit block 615, the travel of the stop block 614 to disengage from the second limit block 615 is changed to adjust the movement of the threaded sleeve 607, thereby adjusting the maximum pressure value applied by the pressure plate 611 to achieve adjustment. function.

[0034] The middle plate 616 can move up and down in the second waist-shaped through hole to adjust the height of the second stopper 615. The cover plate 617 is connected to the middle plate 616 by bolts. The protrusion 613 and the stopper 614 are located on the radial side of the connecting rod 609. The stopper 614 can be connected to the protrusion 613 by means of threads or screws. The depth of the stopper 614 can be adjusted, thereby adjusting the interference amount when the stopper 614 collides with the second stopper 615, and the damaged stopper 614 can be replaced.

[0035] Furthermore, the limiting structure also includes a first limiting block 618, a transmission block 619, a telescopic rod 620 and a lifting mechanism; The vertical rod 612 is provided with a first waist-shaped through hole, in which the transmission block 619 is provided, and one end of the transmission block 619 facing the connecting rod 609 is fixedly connected to the first limit block 618, and the first limit block 618 is located above the second limit block 615, and one end of the transmission block 619 away from the connecting rod 609 is fixedly connected to the telescopic rod 620, and the telescopic rod 620 is parallel to the vertical rod 612, and one end of the telescopic rod 620 away from the transmission block 619 is connected to the lifting mechanism for lifting the first limit block 618; When the screw rod 606 rotates to make the pressing plate 611 move toward the rock sample 2, the first limit block 618 moves to the highest height, and a gap is formed between the bottom of the first limit block 618 and the top of the second limit block 615; when the stop block 614 is separated from the second limit block 615, the stop block 614 enters the gap above the second limit block 615; When the screw rod 606 rotates to move the pressure plate 611 away from the rock sample 2, the first limit block 618 moves to the lowest height, and the bottom of the first limit block 618 fits with the top of the second limit block 615; the stop block 614 abuts against the lower end of the first limit block 618 and moves onto the second limit block 615.

[0036] Specifically, a slide groove is provided on one side of the vertical rod 612 facing the connecting rod 609 , and the first limiting block 618 and the second limiting block 615 are both located in the slide groove.

[0037] The pressurization process of the present invention is as follows: like Figure 4, which is the initial state. When the pressure starts to be applied, the driving device 603 rotates forward, so that the threaded sleeve 607 drives the pressure plate 611 to move toward the rock sample 2, thereby generating an extrusion force; in this process, the second limit block 615 abuts against the stop block 614 to form a circumferential constraint to prevent the stop block 614 from rotating. When the pressure value reaches the maximum value, the stop block 614 just breaks away from the top of the second limit block 615 and enters the gap between the second limit block 615 and the first limit block 618, forming a Figure 5 In the middle state, the stopper 614 is not constrained, and the friction between the threaded sleeve 607 and the screw rod 606 causes the threaded sleeve 607 to rotate along with the screw rod 606.

[0038] The process of releasing pressure (resetting process) of the present invention is as follows: like Figure 5 When the pressure plate 611 moves to the farthest stroke, the driving device 603 slowly reverses, and the lifting mechanism causes the telescopic rod 620 and the first limit block 618 to descend, so that the top of the second limit block 615 fits with the bottom of the first limit block 618, and then the stopper 614 reverses to abut against the junction of the top of the second limit block 615 and the bottom of the first limit block 618, thereby forming a circumferential constraint on the stopper 614, forming Figure 6 In the state, under the rotation of the screw rod 606, the threaded sleeve 607 moves downward, so that the stopper 614 returns to the coverage range of the second limit block 615.

[0039] When the pressure is re-applied, the driving device 603 slowly rotates forward, and the lifting mechanism pushes the first limit block 618 to rise, so as to form a gap between the first limit block 618 and the second limit block 615 .

[0040] When adjusting ， That is, when adjusting the maximum pressure, the movement of the threaded sleeve 607 is adjusted by adjusting the height of the second limit block 615, so as to adjust the maximum movement stroke of the threaded sleeve 607. In addition, the length of the telescopic rod 620 is adjusted so that the spacing distance between the first limit block 618 and the second limit block 615 is a fixed value. The telescopic rod 620 is a prior art.

[0041] In addition, scale lines may be provided on the outer side of the vertical rod 612 to reflect the movement of the cover plate 617 , thereby progressively adjusting the height of the second limit block 615 to form a function of progressively adjusting the maximum pressure.

[0042] The present invention utilizes the adjustable stroke of the second limit block 615 to adjust the movement stroke of the threaded sleeve 607, thereby adjusting the maximum pressure, and can realize the function of progressively adjusting the maximum pressure. The stroke change can be intuitively reflected through the scale line. There is a definite conversion relationship between the stroke and pressure, which can be directly obtained by setting a pressure sensor on the pressure plate 611 and calculating the linear relationship between the stroke, so that the maximum pressure can be accurately adjusted and controlled.

[0043] Furthermore, the lifting mechanism includes a linear push device 621; the linear push device 621 is installed on the connecting plate 604, the output end of the linear push device 621 is fixedly connected to the bottom of the telescopic rod 620, and the linear push device 621 is used to push the telescopic rod 620 up and down.

[0044] The linear push device 621 is a prior art device, such as a cylinder, a hydraulic cylinder, a linear guide rail, etc. In the pressure application stage, the linear push device 621 pushes the first limit block 618 to the maximum stroke, and in the pressure release stage, the linear push device 621 pushes the first limit block 618 to the minimum stroke.

[0045] Furthermore, the fixing plates 601 of the three loading devices 6 are respectively fixedly connected to the top plate 4 and the two side plates 3 .

[0046] Furthermore, the connecting rod 609 is fixedly connected to the transition plate 610, and the transition plate 610 is rotatably connected to the pressing plate 611. When the stopper 614 is in the interval, the friction between the pressing plate 611 and the rock sample 2 makes the pressing plate 611 relatively stationary, while the transition plate 610 and the threaded sleeve 607 rotate relatively, which can prevent the threaded sleeve 607 from continuing to move axially under the action of the friction (friction between the pressing plate 611 and the rock sample 2).

[0047] Furthermore, the side surface of the threaded sleeve 607 is fixedly connected to the connecting rod 609 via a support rod 608 .

[0048] Furthermore, a plurality of the limiting structures are arranged around the screw rod 606 .

[0049] The embodiments described above are only descriptions of the preferred modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, and substitutions made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A variable principal stress experimental method for multiple sets of conjugate jointed rocks, characterized in that: The following steps are involved: Step 1, sample processing: processing rock samples (2); Step 2: placing the rock sample (2) on a load-bearing support (5), wherein the load-bearing support (5) comprises three plates, which are fixedly connected and wrap around a top corner of the bottom of the rock sample (2), so that three surfaces of the rock sample (2) are exposed, and loading devices (6) are respectively arranged on the three exposed surfaces, and two opposite surfaces of the rock sample (2) are the loading device (6) and the plate respectively; Step 3: Apply pressure to the rock sample (2) through the loading device (6): (a) Three loading devices (6) apply pressure simultaneously , and , and make ; (b) Maintain Constant, loaded to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; (c) Maintain Constant, loaded to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; (d) Maintain Constant, continue loading to ,uninstall to ,make becomes the maximum principal stress, is the minimum principal stress. After it stabilizes, restore ; Step 4: Increment Repeat step 3 until the rock sample (2) is destroyed.

2. A variable principal stress experimental device for multiple sets of conjugate jointed rocks, using the experimental method described in claim 1, characterized in that: The experimental device comprises: a loading device (6), a bottom plate (1), a side plate (3), a top plate (4) and a load-bearing bracket (5); The bottom plate (1) is connected to the bearing bracket (5), and the bearing bracket (5) is used to place the rock sample (2). The bearing bracket (5) comprises three plate bodies, and the three plate bodies are fixedly connected and located on three mutually perpendicular spatial planes. The three plate bodies together form a square opening groove, and the square opening groove wraps the bottom corner of the rock sample (2), wraps three surfaces of the rock sample (2) and exposes the other three surfaces. The loading devices (6) are respectively arranged on the three exposed surfaces, and the two opposite surfaces of the rock sample (2) are respectively provided with the loading device (6) and the plate bodies; The top of the loading device (6) located above the rock sample (2) is fixedly connected to the top plate (4), the outer ends of the loading devices (6) located on both sides of the rock sample (2) are respectively fixedly connected to the side plates (3), and the bottoms of the side plates (3) are connected to the bottom plate (1); The loading device (6) is used to apply pressure to the wall surface of the rock sample (2).

3. The variable principal stress experimental equipment for multiple sets of conjugate jointed rocks according to claim 2 is characterized in that: Four side panels (3) are provided, of which two adjacent side panels (3) are connected to the loading device (6), and the other two adjacent side panels (3) are fixedly connected to the panel body via support columns (301).

4. The variable principal stress experimental device for multiple sets of conjugate jointed rocks according to claim 3 is characterized in that: The bottoms of the four side panels (3) are fixedly connected to a lifting plate (7), the lifting plate (7) is located above the bottom plate (1), and both ends of the lifting plate (7) are respectively provided with inclined connecting rods (701), the top of the connecting rod (701) is rotatably connected to the end of the lifting plate (7), the bottom of the connecting rod (701) is rotatably connected to a slide plate (702), and the slide plate (702) is slidably connected to the bottom plate (1); The bottom of the plate body at the bottom is fixedly connected to a limiting sleeve (704), a top rod (704) can be slidably passed through the lifting plate (7), the top of the top rod (704) can be slidably passed through the limiting sleeve (704), a through hole adapted to the top rod (704) is provided on the plate body at the bottom, the through hole is coaxially arranged with the limiting sleeve (704), and the bottom of the top rod (704) is connected to the bottom plate (1); The two ends of the top plate (4) are rotatably connected to the top of the slide rod (401), wherein the two opposite side plates (3) are provided with through holes adapted to the slide rod (401), and the slide rod (401) can slide through the through holes, and the bottom plate (1) is provided with a positioning hole adapted to the slide rod (401), and the bottom of the slide rod (401) passes through the lifting plate (7) and the slide plate (702) in sequence and is located in the positioning hole; A protrusion (402) is fixedly connected in the positioning hole, and an annular groove adapted to the protrusion (402) is provided at the bottom of the slide rod (401), and a notch portion is provided on the annular groove, and the protrusion (402) is used to pass through the notch portion and rotate to be clamped in the annular groove, so as to form an axial constraint on the slide rod (401); The sliding rod (401) is used to slide upward to disengage from the sliding plate (702), thereby causing the lifting plate (7) to descend under the action of its own weight, and causing the push rod (704) to lift up the rock sample (2).

5. The variable principal stress experimental equipment for multiple sets of conjugate jointed rocks according to claim 2 is characterized in that: The loading device (6) comprises a fixing plate (601), a driving device (603), a connecting plate (604), a rotating seat (605), a screw rod (606), a threaded sleeve (607), a connecting rod (609), a pressing plate (611) and a limiting structure; The fixed plate (601) and the connecting plate (604) are arranged side by side, the driving device (603) is installed between the fixed plate (601) and the connecting plate (604), the output end of the driving device (603) passes through the connecting plate (604) and is fixedly connected to the rotating seat (605), the rotating seat (605) is rotatably arranged on the connecting plate (604), one end of the rotating seat (605) away from the driving device (603) is fixedly connected to one end of the screw rod (606), the other end of the screw rod (606) is threadedly connected to the threaded sleeve (607), the side surface of the threaded sleeve (607) is connected to the connecting rod (609), the connecting rod (609) is parallel to the axis of the screw rod (606), and one end of the connecting rod (609) away from the connecting plate (604) is connected to the pressing plate (611); The driving device (603) is used to drive the rotating seat (605) to rotate, thereby rotating the screw rod (606); the side surface of the connecting rod (609) is connected to the limiting structure, which is used to limit the connecting rod (609) to rotate around the screw rod (606), so that the threaded sleeve (607) moves along the screw rod (606) and the pressure plate (611) faces the wall surface of the rock sample (2).

6. The variable principal stress experimental equipment for multiple sets of conjugate jointed rocks according to claim 5, characterized in that: The limiting structure comprises a vertical rod (612), a protrusion (613), a stopper (614), a second limiting block (615), an intermediate plate (616) and a cover plate (617); The vertical rod (612) is parallel to the connecting rod (609) and is arranged at an interval. The vertical rod (612) is located on a side of the connecting rod (609) away from the screw rod (606). One end of the vertical rod (612) is fixedly connected to the connecting plate (604). A second waist-shaped through hole is provided on the vertical rod (612). The middle plate (616) is located in the second waist-shaped through hole. One end of the middle plate (616) facing the connecting rod (609) is fixedly connected to the second limit block (615). One end of the middle plate (616) away from the connecting rod (609) is detachably connected to the cover plate (617). The side of the connecting rod (609) is fixedly connected to the protrusion (613); the end of the protrusion (613) can remove the stopper (614); the second limit block (615) is located on the rotation path of the stopper (614); the second limit block (615) is used to abut against the stopper (614) to form a circumferential constraint; The middle plate (616) is slidable up and down and is located in the second waist-shaped through hole, and a tooth portion (600) is provided between the cover plate (617) and the vertical rod (612) to constrain the vertical height; By adjusting the height of the second limit block (615), the stroke of the stop block (614) disengaging from the second limit block (615) is changed, so as to adjust the movement amount of the threaded sleeve (607), thereby adjusting the maximum pressure value applied by the pressure plate (611).

7. The variable principal stress experimental equipment for multiple sets of conjugate jointed rocks according to claim 6, characterized in that: The limiting structure further comprises a first limiting block (618), a transmission block (619), a telescopic rod (620) and a lifting mechanism; The vertical rod (612) is provided with a first waist-shaped through hole, the transmission block (619) is arranged in the first waist-shaped through hole, one end of the transmission block (619) facing the connecting rod (609) is fixedly connected to the first limit block (618), the first limit block (618) is located above the second limit block (615), one end of the transmission block (619) away from the connecting rod (609) is fixedly connected to the telescopic rod (620), the telescopic rod (620) is parallel to the vertical rod (612), and one end of the telescopic rod (620) away from the transmission block (619) is connected to the lifting mechanism for lifting the first limit block (618); When the screw rod (606) rotates to cause the pressing plate (611) to move toward the rock sample (2), the first limit block (618) moves to the highest height, and a gap is formed between the bottom of the first limit block (618) and the top of the second limit block (615); when the stop block (614) is separated from the second limit block (615), the stop block (614) enters the gap above the second limit block (615); When the screw rod (606) rotates to move the pressure plate (611) away from the rock sample (2), the first limit block (618) moves to the lowest height, and the bottom of the first limit block (618) fits with the top of the second limit block (615); the stop block (614) abuts against the lower end of the first limit block (618) and moves onto the second limit block (615).

8. The variable principal stress experimental equipment for multiple sets of conjugate jointed rocks according to claim 7 is characterized in that: The lifting mechanism comprises a linear propulsion device (621); The linear pushing device (621) is mounted on the connecting plate (604); an output end of the linear pushing device (621) is fixedly connected to the bottom of the telescopic rod (620); and the linear pushing device (621) is used to push the telescopic rod (620) up and down.

9. The variable principal stress experimental equipment for multiple sets of conjugate jointed rocks according to claim 5, characterized in that: The fixing plates (601) of the three loading devices (6) are respectively fixedly connected to the top plate (4) and the two side plates (3).

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