Cyclic test method and device for simulating principal stress of three-surface joint distribution rock

Abstract

The invention belongs to the field of rock mass engineering, and provides a cyclic test method for simulating the principal stress of a three-surface joint distribution rock, which comprises the following steps: step 1, sample processing; step 2, placing the concrete sample on a bearing bracket; 3, the loading device A loads the pressure # imgabs 0 #, the loading device B loads the pressure # imgabs 1 #, the loading device C loads the pressure # imgabs 2 #, and the loading device A loads the pressure # imgabs 0 #, the loading device B loads the pressure # imgabs 1 #, the loading device C loads the pressure # imgabs 2 #, and the loading device B loads the pressure # imgabs 3 #; the loading device A loads # imgabs4 # to # imgabs5 #, and # imgabs6 # is recovered after the loading device A is stable; the positions of the loading device A and the loading device B are exchanged, then the loading device A loads # imgabs7 # to # imgabs8 #, and # imgabs9 # is recovered after stabilization; the positions of the loading device A and the loading device C are changed, then the loading device A loads # imgabs 10 # to # imgabs 11 #, the sigma is reduced before the concrete sample reaches a yield point, and # imgabs 12 # is recovered after the concrete sample is stabilized; 4, progressively increasing # imgabs13 #, and repeating the step 3 until the concrete sample is damaged; according to the invention, the stress of the sample in different directions can be variably loaded, and the consistency and uniformity in the test loading process are ensured.

Description

Technical Field

[0001] The invention belongs to the field of rock mass engineering, and in particular relates to a method and a device for simulating a three-surface joint distribution rock principal stress cycle test. Background Art

[0002] Conjugate joints are common structural features in rock masses in nature, and they have a profound impact on the properties and stability of rocks. As a relatively common structure in rock masses, especially in hard rocks such as granite, gneiss, basalt, limestone, etc., they usually exist in the form of two intersecting faces or cracks, forming an intersection point, so that there are two specific angles at this point. The study of conjugate joints helps to assess the risk of geological hazards such as landslides, rock collapses and earthquake-induced rock faulting, and understand the formation and evolution of rocks.

[0003] Conjugate joints usually develop after the formation of rocks, through processes over long geological time scales. They may expand and deform over time. This development process can include the following stages: ① Crack formation: Some tiny cracks in rocks may initially be caused by tectonic stresses, temperature changes, or chemical reactions. ② Crack expansion: These cracks may expand and deepen over time to form larger joint planes. ③ Formation of conjugate joints: When multiple cracks intersect at a specific angle, they form conjugate joints, where one crack plane is the conjugate of another. The understanding of conjugate joints is crucial to rock mechanics and geological engineering, and it affects the strength of rocks and the stability of rock masses. The study of conjugate joints provides important information about the structure of underground and surface rocks, and has a wide range of application value in engineering, geology, and the environment.

[0004] The causes of conjugate joints and their influence on the mechanical characteristics of rock mass are relatively complex. Current research mainly focuses on the causes of joints and their influence on rock mass strength. 3DEC, PFC and other simulation software are usually used to simulate the expansion, intersection and development process of joint surfaces in terms of the formation mechanism, and then evaluate their influence on rock mass strength. There are few physical experiments and test methods related to conjugate joints. Therefore, it is urgent to develop a method for making conjugate joints in rock mass and a test device for the causes and failure process of conjugate joints. The test device and test method are simple, economical and repeatable. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method and device for simulating the principal stress cycle test of rock with three-sided joint distribution to solve the problems in the prior art. The technical solution adopted by the present invention is: A method for simulating a three-sided joint distribution rock principal stress cycle test comprises the following steps: Step 1, sample processing: cutting is performed on the concrete sample to cut out the groove, and the groove is filled with loess to simulate the joint; The cutting angle is calculated by the following formula: , is the cutting inclination angle, is the internal friction angle of rock; Step 2: placing the concrete 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 concrete sample, so that three sides of the concrete sample are exposed, and loading devices are respectively arranged on the three exposed sides, and the two opposite sides of the concrete sample are the loading device and the plate respectively; Step 3, applying pressure to the concrete sample through a loading device, wherein the three loading devices are loading device A, loading device B and loading device C; (a) Loading pressure of loading device A , Loading pressure of loading device B , Loading device C loading pressure , and make ; (b) Loading by loading device A to , before the concrete sample reaches the yield point, σ is reduced, and after it stabilizes, it is restored ; (c) Swap the positions of loading device A and loading device B, and then load device A to load to , before the concrete sample reaches the yield point, σ is reduced, and after it stabilizes, it is restored ; (d) Swap the positions of loading device A and loading device C, and then load device A to load to , before the concrete sample reaches the yield point, σ is reduced, and after it stabilizes, it is restored ; Step 4: Increment Repeat step 3 until the concrete specimen is destroyed.

[0006] A test device for simulating the principal stress cycle of rock with three-sided joint distribution, the test device comprising: a loading device, a bottom plate, a side plate, a top plate and a bearing bracket; The bearing bracket is arranged above the bottom plate, and the bearing bracket is used to place the concrete sample. The bearing bracket 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 top corner of the concrete sample, wraps the three surfaces of the concrete 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 concrete sample are the loading device and the plates respectively; Four side panels are fixedly connected to the bottom plate, and the four side panels are distributed around the concrete sample, wherein two adjacent side panels are detachably connected to two of the loading devices through a connecting assembly, and another two adjacent side panels are fixedly connected to the load-bearing bracket through a supporting column, and the bottom of the load-bearing bracket is fixedly connected to the bottom plate through a supporting column; wherein the tops of the two opposite side panels are detachably connected to the top panel, and the top panel is detachably connected to another loading device through a connecting assembly; The loading device is used to apply pressure to the wall surface of the concrete sample.

[0007] Furthermore, the three loading devices are loading device A, loading device B and loading device C respectively; wherein loading device A is an adjustable maximum pressure loading device, and loading device B and loading device C are fixed maximum pressure loading devices.

[0008] Furthermore, the connection assembly includes a plug-in box, a rotating shaft, a snap-on pin and a connecting rod; The side plate and the top plate are both provided with through holes adapted to the plug-in box, the plug-in box is plugged into the through holes, a T-shaped portion is provided at one end of the plug-in box away from the concrete sample, the T-shaped portion abuts against the outer end surface of the through hole, the end of the plug-in box close to the concrete sample is fixedly connected to the loading device, and the output end of the loading device faces the concrete sample; A cavity is provided in the plug-in box, the plug-in box is rotatably connected to the rotating shaft, one end of the rotating shaft is located in the cavity, the connecting rod is provided in the cavity, a pin hole connected to the cavity is provided on the wall of the plug-in box, the engaging pin is slidably provided in the pin hole, the side surface of the rotating shaft is rotatably connected to one end of the connecting rod, and the other end of the connecting rod is rotatably connected to the engaging pin; the rotating shaft is used to rotate to push the engaging pin to extend or retract into the pin hole; The locking pin and the T-shaped portion are located at two ends of the through hole.

[0009] Furthermore, the adjustable maximum pressure 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 concrete 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 travel of the stopper to separate from the second limit block is changed to adjust the movement of the threaded sleeve, thereby adjusting the maximum pressure value applied by the pressure plate to achieve adjustment. function.

[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 concrete 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 pressing plate away from the concrete 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 against the lower end of the first limit block and moves onto the second limit block.

[0012] Further, the lifting mechanism includes a crossbar, a rotating ring, a spring, a sliding sleeve, a fixed ring plate, a plug-in sheet, a wedge-shaped bottom surface, an arc-shaped groove and a vertical rod; The third waist-shaped through hole is provided on the vertical rod, and the cross bar passes through the third waist-shaped through hole, and the third waist-shaped through hole can slide up and down and is located in the third waist-shaped through hole, and the cross bar is located below the second limit block, and one end of the cross bar is fixedly connected to the telescopic rod, and the other end of the cross bar is fixedly connected to the outer ring of the rotating ring, and the inner ring of the rotating ring is rotatably sleeved on the sliding sleeve, and the sliding sleeve can be slidably sleeved on the screw rod, and the sliding sleeve and the screw rod are circumferentially constrained by splines; the spring in a compressed state is provided at the bottom of the sliding sleeve, and the spring is sleeved on the screw rod, and the top and bottom of the spring respectively abut against the bottom of the sliding sleeve and the top of the rotating seat, and the fixing ring plate is provided above the sliding sleeve, and the screw rod passes through the fixing ring plate, and the bottom of the fixing ring plate is fixedly connected to the top of the vertical rod, and the bottom of the vertical rod is fixedly connected to the top of the connecting plate, and the vertical rod is located between the vertical rod and the screw rod. A fourth waist-shaped hole is provided on the vertical rod, and the cross bar passes through the fourth waist-shaped hole; The top end surface of the sliding sleeve is provided with the arc groove, the bottom surface of the arc groove is the wedge-shaped bottom surface, the matching plug-in piece is provided in the arc groove, the top of the plug-in piece is fixedly connected to the fixed ring plate, and the bottom of the plug-in piece is matched with the wedge-shaped bottom surface; When the screw rod drives the sliding sleeve to rotate, the sliding sleeve is lifted and lowered by the cooperation between the plug-in piece and the wedge-shaped bottom surface, thereby causing the first limiting block to be lifted and lowered.

[0013] Furthermore, the connecting rod is fixedly connected to the transition plate, and the transition plate is rotatably connected to the pressure plate.

[0014] Furthermore, the side surface of the threaded sleeve is fixedly connected to the connecting rod via a support rod.

[0015] The present invention has the following beneficial effects: the present invention can realize variable loading of stresses in different directions of a specimen, and by exchanging the positions of three loading devices, it can be ensured that only the pressure of one specific loading device is adjusted during the test, while the other two loading devices are always pressurized to a fixed value, thereby ensuring consistency and uniformity during the test loading process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of step three in the test method of the present invention; Figure 2 is a schematic diagram of three joints of the specimen; Figure 3 It is a schematic diagram of the overall structure of the present invention; Figure 4 It is a schematic diagram after the loading device has exchanged positions; Figure 5 is a schematic diagram of an adjustable maximum pressure loading device; Figure 6 is a schematic diagram of the maximum pressure state of the adjustable maximum pressure loading device; Figure 7 is a schematic diagram when the first and second limit blocks are in contact; Figure 8 is a top view schematic diagram of the connection relationship of the second limit block; Fig. 9 1. It is a top view schematic diagram of the connection relationship of the sliding sleeve; Fig.10 It is a schematic diagram of the connection relationship of the plug-in piece; Fig.11 It is a top view schematic diagram; Fig.12 is a schematic diagram of connected components; Fig.13 This is a schematic diagram of the snap-in pin passing through the pin hole; Fig.14 It is a schematic diagram of the bayonet pin being retracted into the pin hole. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention Figure 1-Figure 14 , 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.

[0018] like Figure 1 , Figure 2 A method for simulating the principal stress cycle test of rock with three-sided joint distribution includes the following steps: Step 1, sample processing: cutting is performed on the concrete sample 41 to cut out a groove, and the groove is filled with loess to simulate joints; The cutting angle is calculated by the following formula: , is the cutting angle, is the internal friction angle of rock; Sample preparation, cutting and filling are carried out in the above manner to form J1 joint 42, J2 joint 43 and J3 joint 44.

[0019] The cutting is performed using a 2mm frosted glass plate to cut the concrete sample that is about to set, along the joint path planned in advance. After the cutting is completed, the three joints are filled with loess in a plastic state to simulate the bonding filling between the joints. Finally, the sample is waited for to be completely hardened. After the internal filling of the joint is completed, the test loading can be carried out, and the variable principal stress loading and unloading cycle of the conjugate joint distribution is studied.

[0020] Step 2: Place the concrete sample 41 on the load-bearing bracket 5. The load-bearing bracket 5 includes three plates, which are fixedly connected and wrap a top corner of the bottom of the concrete sample 41, so that three surfaces of the concrete sample 41 are exposed. Loading devices are respectively arranged on the three exposed surfaces, and two opposite surfaces of the concrete sample 41 are the loading device and the plate respectively. Step 3, applying pressure to the concrete sample 41 by means of loading devices, wherein the three loading devices are loading device A, loading device B and loading device C; (a) Loading pressure of loading device A , Loading pressure of loading device B , Loading device C loading pressure , and make ; (b) Loading by loading device A to , before concrete sample 41 reaches the yield point, σ1 is reduced, and after it stabilizes, it is restored ; (c) Swap the positions of loading device A and loading device B, and then load device A to load to , before concrete sample 41 reaches the yield point, σ1 is reduced, and after it stabilizes, it is restored ; (d) Swap the positions of loading device A and loading device C, and then load device A to load to , before concrete sample 41 reaches the yield point, σ1 is reduced, and after it stabilizes, it is restored ; In step 3, the directions of the sample and the pressure device are not changed, and only the positions of the loading device A, loading device B and loading device C corresponding to σ1, σ2 and σ3 are changed.

[0021] Step 4: Increment And repeat step 3 until the concrete sample 41 is destroyed.

[0022] 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.

[0023] The present invention can realize variable loading of stresses in different directions of a sample. By exchanging the positions of three loading devices, it can be ensured that only the pressure of one specific loading device is adjusted during the test, while the other two loading devices are always pressurized to a fixed value, thereby ensuring consistency and uniformity during the test loading process.

[0024] like Figure 3 , a test device for simulating the principal stress cycle of rock with three-sided joint distribution, the test device comprising: a loading device, a bottom plate 1, a side plate 3, a top plate 4 and a bearing bracket 5; The bearing bracket 5 is arranged above the bottom plate 1, and the bearing bracket 5 is used to place the concrete sample 41. 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 concrete sample 41, wraps the three surfaces of the concrete sample 41 and exposes the other three surfaces. The loading devices are respectively arranged on the three exposed surfaces, and the two opposite surfaces of the concrete sample 41 are the loading device and the plate respectively; Four side panels 3 are fixedly connected to the bottom plate 1, and the four side panels 3 are distributed around the concrete sample 41, wherein two adjacent side panels 3 are detachably connected to two of the loading devices through a connecting assembly 2, and another two adjacent side panels 3 are fixedly connected to the load-bearing bracket 5 through a supporting column 7, and the bottom of the load-bearing bracket 5 is fixedly connected to the bottom plate 1 through a supporting column 7; wherein the tops of the two opposite side panels 3 are detachably connected to the top panel 4, and the top panel 4 is detachably connected to another loading device through a connecting assembly 2; The loading device is used to apply pressure to the wall surface of the concrete sample 41 .

[0025] Furthermore, the three loading devices are loading device A, loading device B and loading device C respectively; wherein loading device A is an adjustable maximum pressure loading device 6, and loading device B and loading device C are fixed maximum pressure loading devices 8.

[0026] There are four side panels 3 in total, and the four side panels 3 are distributed around the concrete sample 41 , wherein the tops of two opposite side panels 3 are connected to the top panel 4 by bolts. Figure 3 This is the initial state of the invention.

[0027] like Figure 3 , Fig.11 The three plates of the support bracket 5 are attached to the three mutually perpendicular surfaces of the concrete sample 41, and the three plates are perpendicular to each other, so as to form a square opening groove to wrap the bottom corner of the concrete sample 41. When the loading device applies pressure to the exposed surface of the concrete sample 41, the wall surface opposite to the concrete sample 41 is supported by the plate, the support column 7 and the side plate 3.

[0028] There are three loading devices in total. Figure 5 The adjustable maximum pressure loading device 6 in the figure is used as an example to illustrate its structure, wherein the upper and lower positions of each component are all referred to this loading device, that is, Figure 5 The position in Figure 3 , Figure 4 The orientation of the loading device 6 in Figure 5 And convert.

[0029] The adjustable maximum pressure loading device 6 can adjust the maximum pressure it applies, and its output pressure is , thus progressively adjusting The fixed maximum pressure loading device 8 is a prior art device, such as a cylinder, a hydraulic cylinder, etc., which has a fixed stroke and realizes the function of increasing the fixed pressure. Its output pressure ,

[0030] like Figure 12-14 , the connection assembly 2 includes a plug-in box 901, a rotating shaft 902, a snap-in pin 904 and a connecting rod 903; The side plate 3 and the top plate 4 are both provided with through holes adapted to the plug-in box 901, the plug-in box 901 is plugged into the through holes, a T-shaped portion is provided at one end of the plug-in box 901 away from the concrete sample 41, the T-shaped portion abuts against the outer end surface of the through hole, the end of the plug-in box 901 close to the concrete sample 41 is fixedly connected to the loading device, and the output end of the loading device faces the concrete sample 41; A cavity is provided in the plug-in box 901, and the plug-in box 901 is rotatably connected to the rotating shaft 902, one end of the rotating shaft 902 is located in the cavity, the connecting rod 903 is provided in the cavity, a pin hole connected to the cavity is provided on the wall of the plug-in box 901, the engaging pin 904 is slidably provided in the pin hole, the side of the rotating shaft 902 is rotatably connected to one end of the connecting rod 903, and the other end of the connecting rod 903 is rotatably connected to the engaging pin 904; the rotating shaft 902 is used to rotate to push the engaging pin 904 to extend or retract into the pin hole; The locking pin 904 and the T-shaped portion are located at two ends of the through hole.

[0031] The T-shaped portion and the clamping pin 904 together form an I-shaped structure to realize the function of restraining the side plate 3 and the top plate 4. When pressurized, the clamping pin 904 bears the reverse thrust. A plurality of clamping pins 904 can be arranged around the rotating shaft 902, and the rotating shaft 902 can pass through the plug-in box 901 to facilitate the control of rotation.

[0032] like Fig.13 When the engaging pin 904 passes through the pin hole, the distance between the end of the engaging pin 904 and the rotating shaft 902 is the maximum, and the connecting rod 903 is coaxial with the engaging pin 904 or has a certain small angle. When the rotating shaft 902 is rotated, the engaging pin 904 retracts into the pin hole, and a large angle exists between the connecting rod 903 and the engaging pin 904.

[0033] like Figure 5-Figure 10 The adjustable maximum pressure loading device 6 includes a fixed 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 concrete sample 41.

[0034] 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.

[0035] 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 can slide up and down in the second waist-shaped through hole, and the cover plate 617 and the vertical pole 612 are provided with a tooth portion 600 to constrain the vertical height; the inner side surface of the cover plate 617 and the outer side surface of the vertical pole 612 are respectively provided with meshing teeth 600 to produce vertical constraints and facilitate precise adjustment of the upper and lower heights of the cover plate 617 and the second limit block 615.

[0036] 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.

[0037] 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.

[0038] 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 concrete sample 41, 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 pressing plate 611 away from the concrete sample 41, 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.

[0039] 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.

[0040] The pressurization process of the present invention is as follows: like Figure 5 When the pressure is applied, the driving device 603 rotates forward, so that the threaded sleeve 607 drives the pressing plate 611 to move toward the concrete sample 41, thereby generating an extrusion force until the pressure reaches σ c or During 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. σ c or When the stopper 614 is just separated from the top of the second stopper 615, it enters the gap between the second stopper 615 and the first stopper 618, forming a Figure 6 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.

[0041] The process of releasing pressure (resetting process) of the present invention is as follows: like Figure 6 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 7 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.

[0042] 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 .

[0043] 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.

[0044] 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.

[0045] 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.

[0046] like Figure 5 , Fig. 9 and Fig.10 The lifting mechanism includes a crossbar 621, a rotating ring 622, a spring 623, a sliding sleeve 624, a fixed ring plate 625, a plug-in piece 626, a wedge-shaped bottom surface 627, an arc groove 628 and a vertical rod 629; The vertical rod 612 is provided with a third waist-shaped through hole, and the cross bar 621 passes through the third waist-shaped through hole. The third waist-shaped through hole can slide up and down in the third waist-shaped through hole, and the cross bar 621 is located below the second limit block 615. One end of the cross bar 621 is fixedly connected to the telescopic rod 620, and the other end of the cross bar 621 is fixedly connected to the outer ring of the rotating ring 622. The inner ring of the rotating ring 622 is rotatably sleeved on the sliding sleeve 624, and the sliding sleeve 624 is slidably sleeved on the screw rod 606. The sliding sleeve 624 and the screw rod 606 are circumferentially constrained by splines; the bottom of the sliding sleeve 624 The spring 623 in a compressed state is provided, and the spring 623 is sleeved on the screw rod 606. The top and bottom of the spring 623 respectively abut against the bottom of the sliding sleeve 624 and the top of the rotating seat 605. The fixing ring plate 625 is provided above the sliding sleeve 624. The screw rod 606 passes through the fixing ring plate 625. The bottom of the fixing ring plate 625 is fixedly connected to the top of the vertical rod 629. The bottom of the vertical rod 629 is fixedly connected to the top of the connecting plate 604. The vertical rod 629 is located between the vertical rod 612 and the screw rod 606. A fourth waist-shaped hole is provided on the vertical rod 629, and the cross bar 621 passes through the fourth waist-shaped hole. The top end surface of the sliding sleeve 624 is provided with the arc groove 628, the bottom surface of the arc groove 628 is the wedge-shaped bottom surface 627, the arc groove 628 is provided with the matching plug-in piece 626, the top of the plug-in piece 626 is fixedly connected to the fixing ring plate 625, and the bottom of the plug-in piece 626 is matched with the wedge-shaped bottom surface 627; When the screw rod 606 drives the sliding sleeve 624 to rotate, the sliding sleeve 624 is lifted or lowered by the cooperation between the plug-in piece 626 and the wedge-shaped bottom surface 627 , thereby causing the first limiting block 618 to be lifted or lowered.

[0047] The rotating ring 622, the sliding sleeve 624, the fixed ring plate 625 and the screw 606 are coaxially arranged. The spline between the sliding sleeve 624 and the screw 606 can realize sliding and form a circumferential constraint at the same time. The spline can be set at the lower end of the screw 606, and the upper end of the screw 606 is provided with a thread to connect the threaded sleeve 607. The inner side of the sliding sleeve 624 is provided with a corresponding spline groove. The bottom of the plug-in piece 626 is preferably a wedge-shaped structure, which is adapted to the wedge-shaped bottom surface 627. The plug-in piece 626 is arc-shaped and adapted to the arc groove 628. The plug-in piece 626 and the arc groove 628 are arranged in multiple directions around the screw 606. The rotating ring 622 and the fixed ring plate 625 are components that never rotate, and the sliding sleeve 624 rotates with the screw 606 and changes in height. The rotating ring 622 can be connected to the sliding sleeve 624 through a bearing to achieve a rotating connection and enable the sliding sleeve 624 to drive the rotating ring 622 to rise and fall.

[0048] In the pressurizing stage, when the driving device 603 rotates forward slowly, the plug-in piece 626 moves toward the lower end of the wedge-shaped bottom surface 627, and then the sliding sleeve 624 rises in height under the action of the spring 623, and the first limit block 618 rises through the cross bar 621 and the telescopic rod 620, so that a gap is formed between the first limit block 618 and the second limit block 615. The plug-in piece 626 moves to abut against the wall surface of the arc groove 628, and the plug-in piece 626 rotates along with it in the circumferential direction of the sliding sleeve 624, so as to maintain the height of the sliding sleeve 624. When releasing the pressure, the driving device 603 slowly reverses, and the plug-in piece 626 moves toward the higher end of the wedge-shaped bottom surface 627, and the sliding sleeve 624 drops in height, and the first limit block 618 drops to contact the second limit block 615 through the cross bar 621 and the telescopic rod 620.

[0049] The lifting mechanism of the present invention can make full use of the power source of the driving device 603 itself and the characteristics of the screw rod 606 rotating in different directions to produce different movements, so as to lift the first limit block 618, thereby fully cooperating with the movement of the stop block 614 during the pressurization and pressure release stages.

[0050] 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 concrete sample 41 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 concrete sample 41).

[0051] Furthermore, the side surface of the threaded sleeve 607 is fixedly connected to the connecting rod 609 via a support rod 608 .

[0052] Furthermore, the limiting structures are arranged in plurality around the screw rod 606; specifically, the stoppers 614 of the plurality of limiting structures can disperse the circumferential torque, making the overall structure more stable and reliable. Among the plurality of limiting structures, the sliding sleeve 624, the rotating ring 622, the fixed ring plate 625 and the connected parts located in the middle are arranged in one, that is, the plurality of limiting structures are shared. The components located on the outside, such as the vertical rod 612, the protrusion 613, the stopper 614, the first limiting block 618, the second limiting block 615, etc., are arranged in plurality around the screw rod 606.

[0053] 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 method for simulating the principal stress cycle test of rock with three-sided joint distribution, characterized in that: The following steps are involved: Step 1, sample processing: cutting is performed on the concrete sample (41), cutting out a groove body, and filling the groove body with loess to simulate a joint; The cutting angle is calculated by the following formula: , is the cutting inclination angle, is the internal friction angle of rock; Step 2: placing the concrete sample (41) on a load-bearing bracket (5), wherein the load-bearing bracket (5) comprises three plates, which are fixedly connected and wrap a top corner of the bottom of the concrete sample (41), so that three surfaces of the concrete sample (41) are exposed, and loading devices are respectively arranged on the three exposed surfaces, and two opposite surfaces of the concrete sample (41) are the loading device and the plate respectively; Step 3, applying pressure to the concrete sample (41) by means of loading devices, wherein the three loading devices are loading device A, loading device B and loading device C; (a) Loading pressure of loading device A , Loading pressure of loading device B , Loading device C loading pressure , and make ; (b) Loading by loading device A to , the concrete sample (41) reduces σ1 before reaching the yield point, and recovers after it stabilizes. ; (c) Swap the positions of loading device A and loading device B, and then load device A to load to , the concrete sample (41) reduces σ1 before reaching the yield point, and recovers after it stabilizes. ; (d) Swap the positions of loading device A and loading device C, and then load device A to load to , the concrete sample (41) reduces σ1 before reaching the yield point, and recovers after it stabilizes. ; Step 4: Increment Repeat step 3 until the concrete specimen (41) is destroyed.

2. A test device for simulating the principal stress cycle of rock with three-sided joint distribution, using the test method described in claim 1, characterized in that: The test device comprises: a loading device, a bottom plate (1), a side plate (3), a top plate (4) and a load-bearing bracket (5); The bearing bracket (5) is arranged above the bottom plate (1), and the bearing bracket (5) is used to place a concrete sample (41). 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 concrete sample (41), wraps three surfaces of the concrete sample (41) and exposes the other three surfaces. The loading devices are respectively arranged on the three exposed surfaces, and the two opposite surfaces of the concrete sample (41) are the loading device and the plate bodies respectively. Four side panels (3) are fixedly connected to the bottom plate (1), and the four side panels (3) are distributed around the concrete sample (41), wherein two adjacent side panels (3) are detachably connected to two of the loading devices via a connecting assembly (2), and another two adjacent side panels (3) are fixedly connected to the bearing bracket (5) via a supporting column (7), and the bottom of the bearing bracket (5) is fixedly connected to the bottom plate (1) via a supporting column (7); wherein the tops of two opposite side panels (3) are detachably connected to the top plate (4), and the top plate (4) is detachably connected to another loading device via a connecting assembly (2); The loading device is used to apply pressure to the wall surface of the concrete sample (41).

3. A cyclic test device for simulating three-sided joint distribution of rock principal stress according to claim 2, characterized in that: The three loading devices are loading device A, loading device B and loading device C; loading device A is an adjustable maximum pressure loading device (6), and loading device B and loading device C are fixed maximum pressure loading devices (8).

4. The device for simulating the principal stress cycle test of rock with three-sided joint distribution according to claim 2, characterized in that: The connection assembly (2) comprises a plug-in box (901), a rotating shaft (902), a snap-on pin (904) and a connecting rod (903); The side plate (3) and the top plate (4) are both provided with through holes adapted to the plug-in box (901), the plug-in box (901) being plugged into the through holes, a T-shaped portion being provided at one end of the plug-in box (901) away from the concrete sample (41), the T-shaped portion abutting against an outer end surface of the through hole, and an end of the plug-in box (901) close to the concrete sample (41) being fixedly connected to the loading device, the output end of the loading device facing the concrete sample (41); A cavity is provided in the plug-in box (901), the plug-in box (901) is rotatably connected to the rotating shaft (902), one end of the rotating shaft (902) is located in the cavity, the connecting rod (903) is provided in the cavity, a pin hole connected to the cavity is provided on the wall of the plug-in box (901), the engaging pin (904) is slidably provided in the pin hole, the side of the rotating shaft (902) is rotatably connected to one end of the connecting rod (903), and the other end of the connecting rod (903) is rotatably connected to the engaging pin (904); the rotating shaft (902) is used to rotate to push the engaging pin (904) to extend out of or retract into the pin hole; The locking pin (904) and the T-shaped portion are located at two ends of the through hole.

5. The device for simulating the principal stress cycle test of rock with three-sided joint distribution according to claim 3 is characterized in that: The adjustable maximum pressure 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 pressing plate (611) faces the wall surface of the concrete sample (41).

6. The device for simulating the principal stress cycle test of rock with three-sided joint distribution 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 to adjust the movement amount of the threaded sleeve (607), thereby adjusting the maximum pressure value applied by the pressure plate (611), thereby achieving the adjustment of ∆ σ function.

7. The device for simulating the principal stress cycle test of rock with three-sided joint distribution 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 concrete sample (41), 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 pressing plate (611) away from the concrete sample (41), 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 device for simulating the principal stress cycle test of rock with three-sided joint distribution according to claim 7, characterized in that: The lifting mechanism comprises a crossbar (621), a rotating ring (622), a spring (623), a sliding sleeve (624), a fixed ring plate (625), a plug-in plate (626), a wedge-shaped bottom surface (627), an arc-shaped groove (628) and a vertical rod (629); The vertical rod (612) is provided with a third waist-shaped through hole, the cross rod (621) passes through the third waist-shaped through hole, the third waist-shaped through hole can slide up and down in the third waist-shaped through hole, the cross rod (621) is located below the second limit block (615), one end of the cross rod (621) is fixedly connected to the telescopic rod (620), and the other end of the cross rod (621) is fixedly connected to the outer ring of the rotating ring (622), the inner ring of the rotating ring (622) is rotatably sleeved on the sliding sleeve (624), the sliding sleeve (624) is slidably sleeved on the screw rod (606), and the sliding sleeve (624) and the screw rod (606) are circumferentially constrained by a spline; the bottom of the sliding sleeve (624) is provided with a compression The spring (623) is in a contracted state, the spring (623) is sleeved on the screw rod (606), the top and bottom of the spring (623) respectively abut against the bottom of the sliding sleeve (624) and the top of the rotating seat (605), the fixing ring plate (625) is arranged above the sliding sleeve (624), the screw rod (606) passes through the fixing ring plate (625), the bottom of the fixing ring plate (625) is fixedly connected to the top of the vertical rod (629), the bottom of the vertical rod (629) is fixedly connected to the top of the connecting plate (604), the vertical rod (629) is located between the vertical rod (612) and the screw rod (606), the vertical rod (629) is provided with a fourth waist-shaped hole, and the cross rod (621) passes through the fourth waist-shaped hole; The top end surface of the sliding sleeve (624) is provided with the arc-shaped groove (628), the bottom surface of the arc-shaped groove (628) is the wedge-shaped bottom surface (627), the matching plug-in piece (626) is provided in the arc-shaped groove (628), the top of the plug-in piece (626) is fixedly connected to the fixed ring plate (625), and the bottom of the plug-in piece (626) is matched with the wedge-shaped bottom surface (627); When the screw rod (606) drives the sliding sleeve (624) to rotate, the sliding sleeve (624) is lifted or lowered through the cooperation between the plug-in piece (626) and the wedge-shaped bottom surface (627), thereby causing the first limiting block (618) to lift or lower.

9. The device for simulating the principal stress cycle test of rock with three-sided joint distribution according to claim 5, characterized in that: 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).

10. The device for simulating the principal stress cycle test of rock with three-sided joint distribution according to claim 5, characterized in that: The side surface of the threaded sleeve (607) is fixedly connected to the connecting rod (609) via a supporting rod (608).

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