A method and device for simulating the principal stress cycle test of rock with three-sided joint distribution

Abstract

The invention belongs to the field of rock mass engineering and provides a method for simulating a three-sided joint distributed rock principal stress cycle test. The method comprises the following steps: step one, sample processing; step two, placing a concrete sample on a bearing bracket; step three, applying pressure to a loading device A, applying pressure to a loading device B, and applying pressure to a loading device C, and making: loading device A load to σ, and recovering after stabilization; exchanging the positions of loading device A and loading device B, and then loading device A load to σ, and recovering after stabilization; exchanging the positions of loading device A and loading device C, and then loading device A load to σ, reducing σ before the concrete sample reaches a yield point, and recovering after stabilization; and step four, increasing and repeating step three until the concrete sample is destroyed. The invention can realize variable loading of stresses in different directions of the sample, thereby ensuring consistency and uniformity in the test loading process.

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 principal stress cycle test of a rock with three-surface joint distribution. Background Art

[0002] Conjugate joints are common structural features found in natural rock masses, profoundly affecting their properties and stability. As a relatively common structure in rock masses, particularly in hard rocks such as granite, gneiss, basalt, and limestone, they typically occur as two intersecting planes or cracks, forming an intersection point at which two specific angles exist. The study of conjugate joints helps assess the risk of geological hazards such as landslides, rockfalls, and earthquake-induced rock faulting, and helps understand rock formation and evolution.

[0003] Conjugate joints typically develop after rock formation, over long geological timescales. They may expand and deform over time. This development process can include the following stages: ① Crack formation: Some tiny cracks in the rock may initially be caused by tectonic stress, temperature changes, or chemical reactions. ② Crack propagation: These cracks may expand and deepen over time, forming larger joint planes. ③ Conjugate joint formation: When multiple cracks intersect at a specific angle, they form conjugate joints, where one crack plane is conjugate of the other. Understanding conjugate joints is crucial to rock mechanics and geological engineering, as it affects rock strength and rock mass stability. The study of conjugate joints provides important information about underground and surface rock structure, and has broad applications in engineering, geology, and the environment.

[0004] The causes of conjugate joint formation and their impact on the mechanical properties of rock masses are complex. Current research focuses primarily on the causes of joints and their impact on rock mass strength. Simulation software such as 3DEC and PFC are typically used to simulate the expansion, intersection, and development of joint planes in terms of their genetic mechanisms, and then evaluate their impact on rock mass strength. However, physical experiments and testing methods related to conjugate joints are rarely explored. Therefore, there is an urgent need to develop a method for fabricating conjugate joints in rock masses and a test device for their formation and failure processes that is simple, economical, and repeatable. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method and device for simulating a three-sided joint distribution rock principal stress cycle test to solve the problems in the prior art. The technical solution adopted by the present invention is:

[0006] A method for simulating a cyclic test of principal stresses in rocks with three-sided joint distribution, comprising the following steps:

[0007] Step 1, sample processing: cutting on the concrete sample, cutting out the groove, and filling the groove with loess to simulate the joint;

[0008] The cutting angle is calculated by the following formula: , is the cutting angle, is the internal friction angle of rock;

[0009] Step 2: Place the concrete sample on a load-bearing bracket. The load-bearing bracket includes three plates. The three plates are fixedly connected and wrap around a top corner of the bottom of the concrete sample, exposing three sides of the concrete sample. Loading devices are respectively provided on the three exposed sides. The two opposite sides of the concrete sample are the loading device and the plates respectively.

[0010] Step 3: applying pressure to the concrete sample through the loading devices, wherein the three loading devices are loading device A, loading device B and loading device C;

[0011] (a) Loading pressure of loading device A , Loading pressure of loading device B , Loading pressure of loading device C , and make ;

[0012] (b) Loading by loading device A to , before the concrete sample reaches the yield point, reduce σ, and after it stabilizes, restore ;

[0013] (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, reduce σ, and after it stabilizes, restore ;

[0014] (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, reduce σ, and after it stabilizes, restore ;

[0015] Step 4: Increment Repeat step 3 until the concrete specimen is destroyed.

[0016] 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;

[0017] The load-bearing bracket is arranged above the bottom plate, and the load-bearing bracket is used to place the concrete sample. The load-bearing bracket includes three plates, which are fixedly connected and located on three mutually perpendicular spatial surfaces. The three plates together form a square opening groove, and the square opening groove wraps the bottom corner of the concrete sample, wraps 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 respectively the loading device and the plates;

[0018] Four side panels are fixedly connected to the bottom plate, and the four side panels are distributed around the concrete specimen, wherein two adjacent side panels are detachably connected to two of the loading devices via a connecting assembly, and another two adjacent side panels are fixedly connected to the load-bearing bracket via a supporting column, and the bottom of the load-bearing bracket is fixedly connected to the bottom plate via a supporting column; wherein the tops of two opposing side panels are detachably connected to the top panel, and the top panel is detachably connected to another loading device via a connecting assembly;

[0019] The loading device is used to apply pressure to the wall surface of the concrete sample.

[0020] Furthermore, the three loading devices are loading device A, loading device B and loading device C; 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.

[0021] Furthermore, the connection assembly includes a plug-in box, a rotating shaft, a snap-on pin and a connecting rod;

[0022] The side panels and the top panel are both provided with through holes adapted to the plug-in box, the plug-in box is inserted 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;

[0023] 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 communicating with 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;

[0024] The locking pin and the T-shaped portion are located at two ends of the through hole.

[0025] Furthermore, the adjustable maximum pressure loading device includes a fixed plate, a driving device, a connecting plate, a rotating seat, a screw rod, a threaded sleeve, a connecting rod, a pressure plate and a limiting structure;

[0026] The fixed plate and the connecting plate are arranged side by side, the driving device is installed between the fixed 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, the 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;

[0027] The driving device is used to drive the rotating seat to rotate, causing the screw to rotate; the side of the connecting rod is connected to the limiting structure, which is used to limit the connecting rod from rotating around the screw, so that the threaded sleeve moves along the screw and the pressure plate faces the wall of the concrete sample.

[0028] Furthermore, the limiting structure includes a vertical rod, a protrusion, a stopper, a second limiting block, an intermediate plate and a cover plate;

[0029] The vertical rod is parallel to the connecting rod and is spaced apart. 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. The end of the middle plate away from the connecting rod is detachably connected to the cover plate.

[0030] The side surface 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;

[0031] The middle plate is slidable up and down in the second waist-shaped through hole, and teeth are provided between the cover plate and the vertical pole to constrain the vertical height;

[0032] By adjusting the height of the second limit block, the travel of the stop block 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.

[0033] Furthermore, the limiting structure further includes a first limiting block, a transmission block, a telescopic rod and a lifting mechanism;

[0034] A first waist-shaped through hole is provided on the vertical pole, the transmission block is provided 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 pole, and the telescopic rod is connected to the lifting mechanism at one end away from the transmission block for lifting the first limit block;

[0035] When the screw rotates to move the pressing plate 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;

[0036] 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 the lower end of the first limit block and moves onto the second limit block.

[0037] Furthermore, the lifting mechanism includes a crossbar, a rotating ring, a spring, a sliding sleeve, a fixed ring plate, a plug-in piece, a wedge-shaped bottom surface, an arc-shaped groove and a vertical rod;

[0038] The top end of the sliding sleeve is fixedly provided with a spring, and the sliding sleeve has a third end which is fixedly provided with a screw rod and a third end which is fixedly provided with a screw rod.

[0039] The top end surface of the sliding sleeve is provided with the arc-shaped groove, the bottom surface of the arc-shaped groove is the wedge-shaped bottom surface, the plug-in piece adapted thereto is provided in the arc-shaped 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 adapted to the wedge-shaped bottom surface;

[0040] 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 lift and lower.

[0041] Furthermore, the connecting rod is fixedly connected to the transition plate, and the transition plate is rotatably connected to the pressure plate.

[0042] Furthermore, the side surface of the threaded sleeve is fixedly connected to the connecting rod via a support rod.

[0043] The present invention has the following beneficial effects: the present invention can realize variable loading of stress in different directions of the sample. By exchanging the positions of the 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 in the test loading process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of step 3 in the test method of the present invention;

[0045] Figure 2 is a schematic diagram of three joints of the specimen;

[0046] Figure 3 It is a schematic diagram of the overall structure of the present invention;

[0047] Figure 4 It is a schematic diagram after the loading device exchanges positions;

[0048] Figure 5 is a schematic diagram of an adjustable maximum pressure loading device;

[0049] Figure 6 This is a schematic diagram of the maximum pressure state of the adjustable maximum pressure loading device;

[0050] Figure 7 It is a schematic diagram when the first and second limit blocks are in contact;

[0051] Figure 8 1 is a top view schematic diagram of the connection relationship of the second limit block;

[0052] Figure 9 1. It is a top view schematic diagram of the sliding sleeve connection relationship;

[0053] Figure 10 It is a schematic diagram of the connection relationship of the plug-in piece;

[0054] Figure 11 It is a top view schematic diagram;

[0055] Figure 12 is a schematic diagram of connected components;

[0056] Figure 13 This is a schematic diagram of the snap-in pin passing through the pin hole;

[0057] Figure 14 This is a schematic diagram of the bayonet pin retracted into the pin hole. DETAILED DESCRIPTION

[0058] The following is a combination of the embodiments of the present invention Figures 1-14 , 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.

[0059] 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:

[0060] 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;

[0061] The cutting angle is calculated by the following formula: , is the cutting angle, is the internal friction angle of rock;

[0062] Sample preparation, cutting and filling are performed in the above manner to form J1 joint 42, J2 joint 43 and J3 joint 44.

[0063] 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, three joints are filled with loess in a fluid plastic state to simulate the cementation filling between the joints. Finally, after the sample is completely hardened and the internal filling of the joints 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.

[0064] Step 2: Place the concrete sample 41 on the support frame 5. The support frame 5 includes three plates. The three plates are fixedly connected and wrap around a top corner of the bottom of the concrete sample 41, exposing three sides of the concrete sample 41. Loading devices are respectively provided on the three exposed sides. The two opposite sides of the concrete sample 41 are the loading device and the plates respectively.

[0065] 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;

[0066] (a) Loading pressure of loading device A , Loading pressure of loading device B , Loading pressure of loading device C , and make ;

[0067] (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 ;

[0068] (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 ;

[0069] (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 ;

[0070] In step 3, the directions of the sample and the pressurizing 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.

[0071] Step 4: Increment Repeat step 3 until the concrete specimen 41 is destroyed.

[0072] In the method of the present invention, the loading device 6 can be the loading device 6 proposed in the present invention, or a jack or other equipment can be used.

[0073] The present invention can realize variable loading of stress in different directions of the sample. By exchanging the positions of the 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 in the test loading process.

[0074] 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;

[0075] The load-bearing bracket 5 is provided above the bottom plate 1. The load-bearing bracket 5 is used to place the concrete sample 41. The load-bearing bracket 5 includes three plates, which are fixedly connected and located on three mutually perpendicular spatial surfaces. The three plates together form a square opening groove, which 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 provided on the three exposed surfaces. The two opposite surfaces of the concrete sample 41 are respectively the loading device and the plates;

[0076] Four side panels 3 are fixedly connected to the bottom plate 1, and the four side panels 3 are distributed around the concrete specimen 41. Two adjacent side panels 3 are detachably connected to two of the loading devices via a connecting assembly 2, and two other adjacent side panels 3 are fixedly connected to the load-bearing bracket 5 via a support column 7. The bottom of the load-bearing bracket 5 is fixedly connected to the bottom plate 1 via a support column 7; the tops of two opposing side panels 3 are detachably connected to the top panel 4, and the top panel 4 is detachably connected to another loading device via a connecting assembly 2;

[0077] The loading device is used to apply pressure to the wall surface of the concrete sample 41 .

[0078] Furthermore, the three loading devices are loading device A, loading device B and loading device C; 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.

[0079] There are four side panels 3 in total, which are distributed around the concrete sample 41 , and 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.

[0080] like Figure 3 、 Figure 11 The three plates of the support bracket 5 are attached to three mutually perpendicular surfaces of the concrete specimen 41. Each of the three plates is perpendicular to the other, forming a square opening that wraps around the bottom corners of the concrete specimen 41. When the loading device applies pressure to the exposed surface of the concrete specimen 41, the opposite wall of the concrete specimen 41 is supported by the plates, support columns 7, and side panels 3.

[0081] 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 referenced 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.

[0082] 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 conventional 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 ,

[0083] like Figure 12-14 , the connecting assembly 2 includes a plug-in box 901, a rotating shaft 902, a snap-in pin 904 and a connecting rod 903;

[0084] The side panels 3 and the top panel 4 are both provided with through holes adapted to the plug-in box 901. The plug-in box 901 is inserted into the through holes. A T-shaped portion is provided at one end of the plug-in box 901 away from the concrete specimen 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 specimen 41 is fixedly connected to the loading device, and the output end of the loading device faces the concrete specimen 41.

[0085] 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, and the connecting rod 903 is provided in the cavity. A pin hole communicating with the cavity is provided on the wall of the plug-in box 901, and 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.

[0086] The locking pin 904 and the T-shaped portion are located at two ends of the through hole.

[0087] The T-shaped portion and the engaging pin 904 together form an I-shaped structure, constraining the side panels 3 and top panel 4. During pressure application, the engaging pin 904 bears the reverse thrust. Multiple engaging pins 904 can be positioned around the rotating shaft 902, which can extend through the connector box 901 to facilitate controlled rotation.

[0088] like Figure 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 at its maximum. At this time, the connecting rod 903 and the engaging pin 904 are coaxial or have a small angle therebetween. When the rotating shaft 902 is rotated, the engaging pin 904 retracts into the pin hole. At this time, a large angle is formed between the connecting rod 903 and the engaging pin 904.

[0089] like Figure 5-10 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;

[0090] The fixed plate 601 and the connecting plate 604 are arranged side by side, and 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. The 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. The end of the connecting rod 609 away from the connecting plate 604 is connected to the pressing plate 611.

[0091] 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.

[0092] Drive device 603 is conventionally used and can be an electric motor, hydraulic motor, or other device. Connecting plate 604 is parallel to fixed plate 601, and screw rod 606 is perpendicular to connecting plate 604. Screw rod 606 and threaded sleeve 607 form a transmission structure that converts the rotation of screw rod 606 into axial movement of threaded sleeve 607 along screw rod 606.

[0093] 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;

[0094] The vertical rod 612 is parallel to the connecting rod 609 and is spaced apart. The vertical rod 612 is located on the 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. The vertical rod 612 is provided with a second waist-shaped through hole. The middle plate 616 is located in the second waist-shaped through hole. The end of the middle plate 616 facing the connecting rod 609 is fixedly connected to the second limit block 615. The end of the middle plate 616 away from the connecting rod 609 is detachably connected to the cover plate 617.

[0095] 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.

[0096] The middle plate 616 can slide up and down in the second waist-shaped through hole, and the tooth portion 600 is used between the cover plate 617 and the vertical pole 612 to constrain the vertical height; the meshing tooth portions 600 are respectively arranged between the inner side surface of the cover plate 617 and the outer side surface of the vertical pole 612 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.

[0097] By adjusting the height of the second limit block 615, the travel of the stop block 614 away 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.

[0098] The middle plate 616 can move up and down within 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 via bolts. The protrusion 613 and the stopper 614 are located on the radial side of the connecting rod 609. The stopper 614 is connected to the protrusion 613 via threads or screws. The depth of the stopper 614 can be adjusted, thereby adjusting the amount of interference when the stopper 614 collides with the second stopper 615. Damaged stoppers 614 can also be replaced.

[0099] Furthermore, the limiting structure further includes a first limiting block 618, a transmission block 619, a telescopic rod 620 and a lifting mechanism;

[0100] The vertical rod 612 is provided with a first waist-shaped through hole, in which the transmission block 619 is provided. The 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. The 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. The 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.

[0101] When the screw rod 606 rotates to move the pressing plate 611 toward the concrete sample 41, the first limit block 618 moves to its 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;

[0102] 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 is in contact with the top of the second limit block 615; the stop block 614 abuts the lower end of the first limit block 618 and moves onto the second limit block 615.

[0103] Specifically, a sliding groove is provided on the 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 sliding groove.

[0104] The pressurization process of the present invention is as follows:

[0105] like Figure 5 , which is the initial state. When the pressure starts to increase, the driving device 603 rotates forward, causing the threaded sleeve 607 to drive 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 limit block 615, it enters the gap between the second limit block 615 and the first limit block 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.

[0106] The process of releasing pressure (resetting process) of the present invention is as follows:

[0107] like Figure 6 When the pressure plate 611 moves to the farthest stroke, the driving device 603 slowly reverses. At this time, 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. Then the stop block 614 reverses to abut 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 stop block 614, forming Figure 7In 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.

[0108] When the pressure is re-applied, the driving device 603 slowly rotates forward, and the lifting mechanism pushes the first limiting block 618 to rise, so as to form a gap between the first limiting block 618 and the second limiting block 615 .

[0109] When adjusting ， Specifically, when adjusting the maximum pressure, the height of the second stopper 615 is adjusted to adjust the movement of the threaded sleeve 607, thereby adjusting the maximum travel of the threaded sleeve 607 and adjusting the maximum pressure. Furthermore, the length of the telescopic rod 620 is adjusted to maintain a fixed distance between the first stopper 618 and the second stopper 615. The telescopic rod 620 is conventional.

[0110] In addition, scale lines can be set on the outside of the vertical rod 612 to reflect the movement of the cover 617, thereby progressively adjusting the height of the second limit block 615 to form a function of progressively adjusting the maximum pressure.

[0111] 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, and the maximum pressure can be accurately adjusted and controlled.

[0112] like Figure 5 、 Figure 9 and Figure 10 The lifting mechanism includes a horizontal rod 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-shaped groove 628 and a vertical rod 629;

[0113] 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 mounted on the sliding sleeve 624. The sliding sleeve 624 is slidably mounted on the screw rod 606. The sliding sleeve 624 and the screw rod 606 are circumferentially constrained by a spline; 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.

[0114] 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, and the adaptable 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 adapted to the wedge-shaped bottom surface 627;

[0115] 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 lift or lower.

[0116] The rotating ring 622, sliding sleeve 624, fixed ring plate 625, and screw 606 are coaxially arranged. A splined connection between the sliding sleeve 624 and screw 606 allows for both sliding movement and circumferential constraint. Splines can be provided at the lower end of screw 606, with threads provided at the upper end for connection to the threaded sleeve 607. A corresponding splined groove is provided on the inner side of the sliding sleeve 624. The bottom of the connector 626 is preferably wedge-shaped, matching the wedge-shaped bottom surface 627. The connector 626 is curved and matches the arcuate groove 628. Multiple connectors 626 and arcuate grooves 628 are provided circumferentially around the screw 606. The rotating ring 622 and fixed ring plate 625 are stationary components. The sliding sleeve 624 rotates with the screw 606 and undergoes height changes. The rotating ring 622 can be connected to the sliding sleeve 624 via a bearing, achieving a rotational connection and enabling the sliding sleeve 624 to drive the rotating ring 622 up and down.

[0117] During the pressurization phase, as the drive unit 603 slowly rotates forward, the connector 626 moves toward the lower end of the wedge-shaped bottom surface 627. Consequently, under the action of the spring 623, the sliding sleeve 624 rises, and the crossbar 621 and telescopic rod 620 cause the first stopper 618 to rise, creating a gap between the first stopper 618 and the second stopper 615. The connector 626 then moves until it contacts the wall of the arcuate slot 628, rotating along the circumference of the sliding sleeve 624 to maintain the height of the sliding sleeve 624. To release pressure, the drive unit 603 slowly rotates backward, causing the connector 626 to move toward the higher end of the wedge-shaped bottom surface 627. The sliding sleeve 624 then descends, and the crossbar 621 and telescopic rod 620 cause the first stopper 618 to descend until it contacts the second stopper 615.

[0118] 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 that the first limit block 618 can be raised and lowered, thereby fully cooperating with the movement of the block 614 during the pressurization and pressure release stages.

[0119] Furthermore, the connecting rod 609 is fixedly connected to the transition plate 610, and the transition plate 610 is rotatably connected to the pressure plate 611. When the stopper 614 is within the gap, the friction between the pressure plate 611 and the concrete specimen 41 causes the pressure plate 611 to remain relatively stationary, while the transition plate 610 and the threaded sleeve 607 rotate relative to each other, thereby preventing the threaded sleeve 607 from continuing axial movement due to the friction (friction between the pressure plate 611 and the concrete specimen 41).

[0120] Furthermore, the side surface of the threaded sleeve 607 is fixedly connected to the connecting rod 609 via a support rod 608 .

[0121] Furthermore, multiple limiting structures are provided around the screw rod 606. Specifically, the multiple stoppers 614 of the limiting structures can disperse circumferential torque, making the overall structure more stable and reliable. Within the multiple limiting structures, the central sliding sleeve 624, rotating ring 622, fixed ring plate 625, and connected components are provided in a single configuration, i.e., shared by multiple limiting structures. The outer components, such as the vertical rod 612, protrusion 613, stopper 614, first limit block 618, and second limit block 615, are provided in multiple configurations around the screw rod 606.

[0122] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the 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 fall within the scope of protection determined by the claims of the present invention.

Claims

1. A test device for simulating the principal stress cycle of rock with three-sided joint distribution, characterized in that: The test device comprises: a loading device, a bottom plate (1), side plates (3), a top plate (4) and a load-bearing bracket (5); The bearing bracket (5) is provided 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 surfaces. The three plates 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 provided 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 specimen (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 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 via a connecting assembly (2); The loading device is used to apply pressure to the wall surface of the concrete specimen (41); The three loading devices are loading device A, loading device B and loading device C; 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); The adjustable maximum pressure loading device (6) comprises 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 pressure 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 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, 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), thereby causing the threaded sleeve (607) to move along the screw rod (606), and the pressing plate (611) to face the wall surface of the concrete sample (41); 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 spaced apart. 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 limiting 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 intermediate plate (616) is slidable up and down 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 of the threaded sleeve (607), thereby adjusting the maximum pressure value applied by the pressure plate (611) to achieve adjustment. Function; The limiting structure further includes a first limiting block (618), a transmission block (619), a telescopic rod (620) and a lifting mechanism; A first waist-shaped through hole is provided on the vertical rod (612), and the transmission block (619) is provided in the first waist-shaped through hole. The transmission block (619) is fixedly connected to the first limit block (618) at one end facing the connecting rod (609), and the first limit block (618) is located above the second limit block (615). The transmission block (619) is fixedly connected to the telescopic rod (620) at one end away from the connecting rod (609). The telescopic rod (620) is parallel to the vertical rod (612), and the telescopic rod (620) is connected to the lifting mechanism at one end away from the transmission block (619) for lifting and lowering the first limit block (618). When the screw rod (606) rotates to move the pressing plate (611) 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 the lower end of the first limit block (618) and moves onto the second limit block (615).

2. A cyclic testing device for simulating three-surface joint distribution rock principal stress according to claim 1, characterized in that: The connecting assembly (2) comprises a plug-in box (901), a rotating shaft (902), a snap-on pin (904) and a connecting rod (903); The side panels (3) and the top panel (4) are both provided with through holes adapted to the plug box (901), the plug box (901) being plugged into the through holes, a T-shaped portion being provided at one end of the plug box (901) away from the concrete specimen (41), the T-shaped portion being in contact with the outer end surface of the through hole, and an end of the plug box (901) close to the concrete specimen (41) being fixedly connected to the loading device, with the output end of the loading device facing the concrete specimen (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 communicating with 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 both ends of the through hole.

3. The device for simulating the principal stress cycle of rock with three-sided joint distribution according to claim 1, characterized in that: 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 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 cross rod (621) is slidable 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 mounted on the sliding sleeve (624), the sliding sleeve (624) is slidably mounted 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 The spring (623) is in a compressed state, 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 fixed ring plate (625) is provided above the sliding sleeve (624). The screw rod (606) passes through the fixed ring plate (625). The bottom of the fixed 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 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 and lowered by the cooperation between the plug-in piece (626) and the wedge-shaped bottom surface (627), thereby causing the first limit block (618) to lift and lower.

4. The device for simulating the principal stress cycle of rock with three-sided joint distribution according to claim 1, 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 pressure plate (611).

5. The device for simulating the principal stress cycle of rock with three-sided joint distribution according to claim 1, characterized in that: The side surface of the threaded sleeve (607) is fixedly connected to the connecting rod (609) via a support rod (608).

6. A method for simulating a three-sided joint distribution rock principal stress cycle test, applied to the device for simulating a three-sided joint distribution rock principal stress cycle test according to claim 1, characterized in that: The following steps are involved: Step 1, sample processing: cutting on the concrete sample (41), cutting out the groove, and filling the groove with loess to simulate the joint; The cutting inclination angle is calculated by the following formula: , is the cutting angle, is the internal friction angle of the 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 sides of the concrete sample (41) are exposed, and loading devices are respectively provided on the three exposed sides, and the two opposite sides of the concrete sample (41) are the loading device and the plate respectively; Step 3, applying pressure to the concrete sample (41) through the 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 pressure of loading device C , 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.

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