Endogenous jointed rock sample preparation device and method based on electric pulse directional fracturing

Abstract

The invention discloses an endogenous jointed rock sample preparation device and method based on electric pulse directional fracturing, and relates to the technical field of jointed rock sample preparation, the preparation device comprises a jointed rock sample pouring mold, and the jointed rock sample pouring mold can be placed in a directional fracturing container; the top surface of the directional fracturing container is fixedly connected with a directional fracturing rotary clamp; in the preparation method, a passive joint preparation thought of external implantation is abandoned, directional fracture is induced in a rock sample through high-voltage electric pulses, the formation process of natural joint stress driving-internal initiation-dynamic expansion is simulated, homologous symbiosis of the joint and a rock sample body is achieved, the natural simulation degree of the joint is improved from the aspect of mechanism, and the simulation degree of the joint is improved from the aspect of mechanism. Quantitative control over the joint thickness and the joint inclination angle can be achieved by designing a linear pulse source and adjusting energy parameters and electrode positions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of jointed rock sample preparation, and particularly relates to an endogenous jointed rock sample preparation device and method based on electric pulse directional fracturing. BACKGROUND

[0002] Under the action of long-term geological tectonic movement, rock mass will be stressed and fractured, thus forming a large number of randomly distributed joint fissures. The existence of joint fissures makes the mechanical behavior of rock mass exhibit significant size effect and anisotropy. The anisotropy is mainly caused by the response difference of joint surfaces in different stress directions. In the joint intersection area, energy accumulation and release often occur, which may induce rock mass deformation and even instability and failure. For example, landslides along the fissure surface of rock slope, collapse along the fissure of dam foundation under the action of stress and water seepage, and collapse along the joint surface of traffic tunnel, etc. Therefore, the study on the influence of joints on the mechanical properties of rock is of great significance for revealing the failure mechanism of rock mass, predicting the stability of engineering and optimizing the design of rock engineering.

[0003] It is difficult to drill complete rock samples containing joints in actual engineering sites, and the physical properties of natural rock samples containing joints may change under the disturbance during drilling. At present, the methods for preparing jointed rock samples in the laboratory mainly include the following three kinds: (1) mold casting method, that is, filling similar materials in the mold to prepare rock samples, and simulating joint surfaces by pre-embedding resin sheets, steel sheets, mica sheets, etc. during casting, such as patents CCN116202831A and CN113092210A; (2) mechanical processing method, that is, drilling the original rock at the engineering site, and then cutting and preparing joints by means of high-pressure water jet, diamond wire saw, etc., such as patent CN114354305A; (3) 3D printing technology, that is, first obtaining digital information of the fissure surface by three-dimensional scanning, then using 3D printing to prepare the joint surface, and finally preparing the jointed rock mass by using similar materials, such as patent CN115993272B.

[0004] Natural rock samples may have other initial defects in addition to joints, which may cause large errors when exploring the influence of joints on the mechanical properties of rock samples. When rock samples are prepared by using similar materials, this problem can be avoided. The existing methods for preparing jointed rock samples, such as the mold casting method, use pre-embedded resin sheets, steel sheets, etc. to prepare joints, which are completely different from the mechanical properties of rock. The joint surface formed by the mechanical processing method is too smooth and flat, which is quite different from the real joint. Although the 3D printing technology can reconstruct the real joint surface, the joint surface prepared by using the printing materials cannot reflect the mechanical properties of rock. Therefore, the technical scheme of the endogenous jointed rock sample preparation device and method based on electric pulse directional fracturing is provided by the person skilled in the art to solve the above-mentioned defects and problems. SUMMARY

[0005] In order to solve the technical problems existing in the present joint rock sample preparation method, realize more accurate simulation of the joint characteristics in the real rock mass, help to reveal the rock mass failure mechanism, predict the engineering stability and optimize the rock mass engineering design technical effect, the present application provides an endogenous joint rock sample preparation device and method based on electric pulse directional cracking.

[0006] The technical solution adopted by the present application to solve its technical problems is: An endogenous joint rock sample preparation device based on electric pulse directional cracking, comprising a joint rock sample pouring mold, the joint rock sample pouring mold can be placed in a directional cracking container, and the top surface of the directional cracking container is fixedly connected with a directional cracking rotary clamp; the endogenous joint rock sample is obtained by pouring through the joint rock sample pouring mold, placed in the directional cracking container, and the electrode is uniformly moved upward and downward in the joint thickness range in sequence through the directional cracking rotary clamp, and the discharging and cracking are repeatedly performed.

[0007] Preferably, the joint rock sample pouring mold comprises a bottom pouring groove, a middle section cylinder screwed and fixed at the top of the bottom pouring groove, and a top section cylinder screwed and fixed at the top of the middle section cylinder, the bottom pouring groove and the middle section cylinder are both provided with an equal number of side steel wires and a middle section steel wire located in the middle, the upper surface of the middle section steel wire is fixed with a pulling wire for pulling the middle section steel wire upward; the inner cavities of the middle section cylinder and the top section cylinder are placed with an equal number of side steel wires.

[0008] Further, the top ports of the bottom pouring groove, the middle section cylinder and the top section cylinder are all provided with threads, and the bottom sections of the middle section cylinder and the top section cylinder are both provided with external threads.

[0009] Preferably, the directional cracking container comprises an operation box filled with an oil phase medium, a test piece immersed in the oil phase medium in the inner cavity of the operation box, a high-voltage power supply and a rectifier fixed on the front side of the operation box, an oscilloscope fixed on the rear side of the operation box, and an energy storage capacitor fixedly connected to the right side of the operation box.

[0010] Further, the directional cracking rotary clamp comprises two vertical columns, a support plate fixed at the top end of the vertical column, and a servo motor fixed at the top of the support plate, the bottom output shaft of the servo motor penetrates through the support plate and is connected with a fixed block, the inside of the fixed block is fixedly embedded with an electric telescopic rod, the bottom end of the electric telescopic rod is fixed with a movable block, the left and right sides of the movable block are hingedly connected with connecting rods, the bottom left and right sides of the fixed block are both hingedly connected with two pulling arms, the bottom ends of the pulling arms are respectively fixed with electric cylinders, the sides of the connecting rods away from the movable block are respectively hingedly connected with the pulling arms, and the bottom ends of the electric cylinders are fixedly connected with rubber insulation clamping jaws, wherein the bottom ends of the rubber insulation clamping jaws are respectively fixed with linear low-voltage electrodes and linear high-voltage electrodes.

[0011] Further, the rectifier is connected with the positive pole of the high-voltage power supply, and the rectifier is used for rectifying the alternating current of the high-voltage power supply into direct current and delivering the direct current to the linear high-voltage electrode; and the oscilloscope is connected with the negative pole of the high-voltage power supply and electrically connected between the linear low-voltage electrode and the oscilloscope.

[0012] Further, the linear high-voltage electrode is connected with the rectifier through a cable, and a switch is arranged on the cable; and the linear low-voltage electrode is connected with the oscilloscope through a cable, and the energy storage capacitor is connected in parallel with the circuit.

[0013] Further, the bottom ends of the columns are fixedly connected with the left and right side walls of the operation box on the side close to each other.

[0014] Further, the linear low-voltage electrode and the linear high-voltage electrode are in contact with the outer surface of the test piece on the side close to each other.

[0015] In addition, the application also discloses a preparation method of an endogenous joint rock sample based on electric pulse directional cracking, and the preparation method is suitable for the preparation device of any one of the above. S1: according to the rock type, a similar material with a corresponding mixing ratio is prepared, and after being fully stirred and uniformly mixed, the test piece is poured in the mold; the inner cavity part of the bottom pouring groove of the test piece is poured, and the pouring height is determined according to the angle α of the joint; the bottom pouring groove is placed on the inclined surface with an angle α between the inclined surface and the horizontal surface; the geometric center height of the joint surface is ensured to be flush with the 1 / 2 height of the mold, that is, h / 2, the joint thickness is b, the diameter is d, and the height of the left side of the model is , and the corresponding height of the right side of the model is .

[0016] S2: after the partial pouring of the bottom pouring groove is completed, the first part is compacted, and after the first part is solidified, the upper side steel wire and the middle steel wire are laid on the upper surface of the first part; and the second part joint layer is continuously poured above the inner cavity of the bottom pouring groove; S3: before the second part joint layer is completely solidified, the side steel wire located at the geometric center of the lower surface of the second part joint layer is pulled out along the joint angle direction, and the middle steel wire is pulled out vertically from bottom to top, so that the joint layer is cut; and after the cutting is completed, the side steel wire is continuously laid on the upper surface of the joint layer; S4: the third part is continuously poured on the upper surface of the second part joint layer, and before the second part joint layer and the third part are completely solidified, the side steel wire in the test piece is pulled out along the joint angle direction, so that the initial defect at the joint layer is formed; and when different numbers of joints are made, the above method can be repeated. S5: After the curing of the test piece is completed, the joint rock sample directional cracking test system is assembled, the joint test piece is placed in the operation box filled with oil phase medium, the high-voltage power supply converts alternating current into high-voltage direct current through a rectifier, and each energy is only enough to make the crack expand along the direction with the minimum resistance to a preset distance.

[0017] The beneficial effects of the present application are: 1) The present application realizes the precise preparation of endogenous joint rock samples by the combined use of the joint rock sample pouring mold and the directional cracking container, solves the problem of other initial defects that may exist in the existing natural rock samples, and greatly reduces the error when studying the influence of joints on the mechanical properties of rock samples; 2) The present application adopts high-voltage electric pulse directional cracking technology, avoids the defects of traditional mold pouring method of pre-embedding resin sheet, steel sheet and other heterogeneous materials as joints, and the formed joints have the same material and mechanical properties as the rock; 3) The joint surface formed by electric pulse discharge in the rock sample has natural roughness and irregularity, which overcomes the shortcomings of the joint surface formed by mechanical processing being too smooth and smooth, and is closer to the morphological characteristics of the real joint; 4) The present application combines pouring forming and electric pulse cracking technology, which not only ensures the homogeneity of the rock sample material, but also realizes the true simulation of the joint surface, compared with the 3D printing technology, it is not limited by the printing material, and can more accurately reflect the mechanical properties of the rock.

[0018] 5) The joint angle, joint number and joint thickness and other parameters in the present application can also be adjusted during the preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce and describe the drawings needed to be used in the description of the embodiments of the present application or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0020] Figure 1 It is a schematic view of the joint rock sample pouring mold; Figure 2 It is a schematic view of the high-voltage electric pulse directional cracking mechanism; Figure 3 It is a schematic view of the sample structure; Figure 4 It is a top view of laying side steel wires and middle steel wires between the first part and the second part joint layer; Figure 5 It is a schematic view of the directional cracking container; Figure 6A schematic diagram of the directional fracturing rotary clamp; Figure 7 A flow chart of the method of the present application; 1, jointed rock sample pouring mold; 1-1, bottom pouring groove; 1-2, middle section cylinder; 1-3, top section cylinder; 1-4, side steel wire; 1-5, pulling wire; 1-10, middle section steel wire; 2, directional fracturing container; 2-1, operation box; 2-2, high-voltage power supply; 2-3, rectifier; 2-4, test sample; 2-5, energy storage capacitor; 2-6, oscilloscope; 3, directional fracturing rotary clamp; 3-1, vertical column; 3-2, movable block; 3-3, fixed block; 3-4, electric cylinder; 3-5, support plate; 3-6, servo motor; 3-7, electric telescopic rod; 3-8, connecting rod; 3-9, pulling arm; 3-10, linear low-voltage electrode; 3-11, linear high-voltage electrode; 3-12, rubber insulated clamping jaw. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the following described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application. In order to more clearly explain and illustrate the technical solutions and implementation modes of the present application, the following introduces the specific embodiments for implementing the technical solutions of the present application.

[0022] Embodiment one: The endogenous jointed rock sample preparation device based on electric pulse directional fracturing, as shown in Figures 1-6 includes a jointed rock sample pouring mold 1, a directional fracturing container 2, and a directional fracturing rotary clamp 3. The jointed rock sample pouring mold 1 is located inside the directional fracturing container 2, and the directional fracturing rotary clamp 3 is fixedly connected to the top surface of the directional fracturing container 2. The device pours a rock sample through the jointed rock sample pouring mold 1, places it into the directional fracturing container 2, and then moves the electrodes uniformly upward and downward in the joint thickness range in sequence through the directional fracturing rotary clamp 3, and repeatedly discharges to crack to obtain an endogenous jointed rock sample.

[0023] The jointed rock sample pouring mold 1, as shown in Figure 1As shown, it includes a bottom pouring groove 1-1, a middle cylinder 1-2 and a top cylinder 1-3. The top ports of the bottom pouring groove 1-1, the middle cylinder 1-2 and the top cylinder 1-3 are all threaded, and the bottom sections of the middle cylinder 1-2 and the top cylinder 1-3 are both externally threaded. The middle cylinder 1-2 is screwed onto the top of the bottom pouring groove 1-1, and the top cylinder 1-3 is screwed onto the top of the middle cylinder 1-2. The bottom pouring groove 1-1 and the middle cylinder 1-2 are both evenly distributed with several side steel wires 1-4 and a middle steel wire 1-10 in the middle. The upper surface of the middle steel wire 1-10 is fixed with a pulling wire 1-5, which is used to pull the middle steel wire 1-10 upwards. The inner cavities of the middle cylinder 1-2 and the top cylinder 1-3 are both evenly distributed with several side steel wires 1-4. This structure design enables the pouring mold to form a rock sample with an initial defect preset joint morphology, providing a basis for subsequent directional cracking.

[0024] The directional cracking container 2, as shown in Figure 5 includes an operation box 2-1, a high-voltage power supply 2-2, a rectifier 2-3, a test piece 2-4, an energy storage capacitor 2-5 and an oscilloscope 2-6. The operation box 2-1 contains an oil phase medium, and the test piece 2-4 is placed in the inner cavity of the operation box 2-1 and soaked in the oil phase medium. The high-voltage power supply 2-2 and the rectifier 2-3 are fixed on the front side of the operation box 2-1, the oscilloscope 2-6 is fixed on the rear side of the operation box 2-1, and the energy storage capacitor 2-5 is fixedly connected to the right side of the operation box 2-1. The rectifier 2-3 is connected to the positive electrode of the high-voltage power supply 2-2, and is used to rectify the alternating current of the high-voltage power supply 2-2 into direct current and deliver it to the linear high-voltage electrode 3-11. The oscilloscope 2-6 is connected to the negative electrode of the high-voltage power supply 2-2, and is electrically connected between the oscilloscope 2-6 and the linear low-voltage electrode 3-10. The oil phase medium acts as an insulating medium, which can effectively prevent high-voltage electrical breakdown of air and ensure that the electrical pulse energy is concentrated on the test piece 2-4, thereby improving the cracking efficiency.

[0025] The directional cracking rotary clamp 3, as shown in Figure 6As shown, including two columns 3-1, support plate 3-5, servo motor 3-6, fixed block 3-3, movable block 3-2, connecting rod 3-8, electric telescopic rod 3-7, pull arm 3-9, electric cylinder 3-4, linear low-voltage electrode 3-10, linear high-voltage electrode 3-11 and rubber insulation clamp jaw 3-12. The bottom end of the column 3-1 is fixedly connected to the left and right side walls of the operation box 2-1. The support plate 3-5 is fixed at the top end of the column 3-1, and the servo motor 3-6 is fixed at the top of the support plate 3-5. The bottom output shaft of the servo motor 3-6 penetrates the support plate 3-5 and is connected to the fixed block 3-3, and the fixed block 3-3 is fixedly embedded with the electric telescopic rod 3-7. The bottom end of the electric telescopic rod 3-7 is fixed to the movable block 3-2, and the left and right sides of the movable block 3-2 are hingedly connected to the connecting rod 3-8. The bottom left and right sides of the fixed block 3-3 are hingedly connected to two pull arms 3-9, and the bottom ends of the pull arms 3-9 are fixedly connected to the electric cylinders 3-4. The end of the connecting rod 3-8 away from the movable block 3-2 is hingedly connected to the side wall of the pull arm 3-9, and the bottom end of the electric cylinder 3-4 is fixedly connected to the rubber insulation clamp jaw 3-12. The bottom of the rubber insulation clamp jaw 3-12 is fixedly connected to the linear low-voltage electrode 3-10 and the linear high-voltage electrode 3-11. The linear high-voltage electrode 3-11 is connected to the rectifier 2-3 through a cable, and a switch is provided on the cable. The linear low-voltage electrode 3-10 is connected to the oscilloscope 2-6 through a cable, and the energy storage capacitor 2-5 is connected in parallel with the circuit. The side of the linear low-voltage electrode 3-10 and the linear high-voltage electrode 3-11 close to each other is in contact with the outside surface of the joint layer of the test piece 2-4. This structure design enables the directional cracking rotary clamp 3 to accurately control the electrode position and realize uniform movement within the joint thickness range, thereby ensuring the consistency and controllability of the electric pulse cracking effect.

[0026] The working principle of the device is: first, the rock sample with initial defects is obtained by pouring through the joint rock sample pouring mold 1, and then the rock sample is placed in the oil phase medium in the directional cracking container 2. Start the directional cracking rotary clamp 3, rotate the fixed block 3-3 by the servo motor 3-6, control the movable block 3-2 to move up and down by the electric telescopic rod 3-7, and adjust the electrode position by the pull arm 3-9 and the electric cylinder 3-4. The rubber insulation clamp jaw 3-12 at the bottom of the electric cylinder 3-4 fixes the linear low-voltage electrode 3-10 and the linear high-voltage electrode 3-11, so that they are in contact with the surface (joint section) of the test piece 2-4. The switch is initially in the off state, the high-voltage power supply 2-2 generates high-voltage electricity, which is converted to direct current by the rectifier 2-3 and stored in the energy storage capacitor 2-5, and when the switch is closed, the energy is injected into the linear high and low voltage electrodes through the transmission cable in a very short time. The oscilloscope 2-6 is connected to the linear low-voltage electrode 3-10 to monitor the electric pulse parameters. By moving the electrodes uniformly upwards and downwards within the joint thickness range and repeatedly discharging to crack, the rock sample with ideal endogenous joint morphology is finally obtained.

[0027] The device has reasonable structure design and simple operation, can accurately control the electric pulse parameters and electrode position, realizes efficient preparation of endogenous jointed rock sample, provides standardized test piece 2-4 for rock mechanics test, and has high practical value.

[0028] Embodiment two This embodiment relates to a jointed rock sample pouring mold structure, which comprises a bottom pouring groove 1-1, a middle section cylinder 1-2, a top section cylinder 1-3, side steel wires 1-4, middle section steel wires 1-10 and a pulling wire 1-5. Figure 1 , 3 , 4, the mold comprises a bottom pouring groove 1-1, a middle section cylinder 1-2, a top section cylinder 1-3, side steel wires 1-4, middle section steel wires 1-10 and a pulling wire 1-5. As shown in Figure 3 , the first part is the bottom pouring groove 1-1 poured; the second part is the part poured by the middle section cylinder 1-2, which is also the jointed layer part obtained by subsequent high-voltage electric pulse cracking; the third part is the part poured by the top section cylinder 1-3.

[0029] The bottom pouring groove 1-1 is located at the bottom of the mold and is used for accommodating pouring materials. The bottom pouring groove 1-1 is made of metal material and has sufficient strength and rigidity to withstand pressure changes in the pouring process. The inner surface of the bottom pouring groove 1-1 is smooth, which facilitates the removal of the formed rock sample and avoids surface adhesion.

[0030] The middle section cylinder 1-2 is screwed and fixed at the top of the bottom pouring groove 1-1. The middle section cylinder 1-2 and the bottom pouring groove 1-1 are fixed by thread connection, which ensures that the two parts are tightly combined and prevents leakage during pouring.

[0031] The top section cylinder 1-3 is screwed and fixed at the top of the middle section cylinder 1-2. The top section cylinder 1-3 and the middle section cylinder 1-2 are also fixed by thread connection, which ensures the stability of the overall structure. The diameter of the top section cylinder 1-3 is the same as that of the middle section cylinder 1-2, forming a continuous pouring space for the pouring and forming of the pouring material.

[0032] A plurality of side steel wires 1-4 are evenly distributed at equal distances in the bottom pouring groove 1-1 and the middle section cylinder 1-2. These side steel wires 1-4 are evenly distributed along the circumferential direction and are fixed on the inner walls of the bottom pouring groove 1-1 and the middle section cylinder 1-2. The side steel wires 1-4 are made of high-strength stainless steel material and have good corrosion resistance and high-temperature resistance. The role of these side steel wires 1-4 is to form initial defects during pouring, so that the energy can be released along these initial cracks during the later high-voltage pulse cracking, and the propagation path of the induced current is realized to achieve directional cracking and obtain an ideal "jointed layer".

[0033] A middle segment steel wire 1-10 is arranged between the bottom pouring groove 1-1 and the middle segment cylinder 1-2. The upper surface of the middle segment steel wire 1-10 is fixed with a pulling wire 1-5. The pulling wire 1-5 is vertically connected with the middle segment steel wire 1-10 and extends upward to the outside of the top segment cylinder 1-3. The upper end of the pulling wire 1-5 is provided with a handle for the operator to grasp. The main function of the pulling wire is to form a specific initial defect in the rock sample by pulling the middle segment steel wire 1-10 upward when the pouring material is initially solidified but not completely hardened.

[0034] In use, first, the bottom pouring groove 1-1, the middle segment cylinder 1-2 and the top segment cylinder 1-3 are screwed and fixed in sequence to form a complete pouring space. Then, the side steel wire 1-4 and the middle segment steel wire 1-10 are installed in place according to the design requirements. The pouring material is poured into the inner cavity of the mold through the grouting port at the upper part of the top segment cylinder 1-3. After the pouring material reaches a proper solidification degree, the middle segment steel wire 1-10 is pulled upward through the pulling wire, and the side steel wire 1-4 is pulled out along the inclined direction of the joint. Then, the side steel wire 1-4 is laid on the second part of the joint layer II, and the third part III is poured. When the third part III is not completely solidified, the side steel wire 1-4 between the second part of the joint layer II and the third part III is pulled out along the inclined direction of the joint to form the required initial defect structure. Finally, after the pouring material is completely solidified, the molded joint rock sample with the initial defect is obtained.

[0035] The joint rock sample pouring mold 1 has a reasonable structure design and is easy to operate, and provides a reliable test sample preparation tool for rock mechanics research.

[0036] Example Three The directional fracturing rotary clamp structure, as shown in Figure 6 includes two upright columns 3-1, a support plate 3-5, a servo motor 3-6, a fixed block 3-3, an electric telescopic rod 3-7, a movable block 3-2, a connecting rod 3-8, a pulling arm 3-9, an electric cylinder 3-4, a rubber insulated clamping jaw 3-12, a linear low-voltage electrode 3-10 and a linear high-voltage electrode 3-11.

[0037] The two upright columns 3-1 are vertically fixed on the workbench surface, and the upright columns 3-1 have sufficient height and strength to support the entire clamp structure. The top end of the upright column 3-1 is fixedly connected with a support plate 3-5, and the support plate 3-5 is made of metal material and has sufficient rigidity to bear the weight of the upper assembly and the force generated during work.

[0038] A servo motor 3-6 is fixedly mounted at the top center of the support plate 3-5. The servo motor 3-6 employs a high-precision control system, enabling precise angle control and speed adjustment, providing stable rotational power. The bottom output shaft of the servo motor 3-6 passes through the support plate 3-5 and connects to the fixing block 3-3. The fixing block 3-3 is located below the support plate 3-5 and is fixed to the output shaft of the servo motor 3-6 using a key connection, ensuring that no relative slippage occurs during rotation.

[0039] An electric telescopic rod 3-7 is fixedly embedded in the center of the fixed block 3-3. The electric telescopic rod 3-7 can achieve linear movement in the vertical direction, adjust the height, and apply pressure. A movable block 3-2 is fixedly connected to the bottom end of the electric telescopic rod 3-7. The movable block 3-2 moves vertically with the telescopic movement of the electric telescopic rod 3-7, providing a power source for the lower mechanism.

[0040] Connecting rods 3-8 are hinged to both the left and right sides of the movable block 3-2. The connecting rods 3-8 are made of high-strength alloy material, with one end hinged to the movable block 3-2, allowing them to rotate freely around the hinge point. The design of the connecting rods 3-8 allows them to transmit motion and change the direction of motion when the movable block 3-2 moves up and down.

[0041] Two tension arms 3-9 are hinged to the bottom left and right sides of the fixed block 3-3, and the tension arms 3-9 are arranged at an angle. The upper end of the tension arm 3-9 is hinged to the fixed block 3-3 and can rotate freely around the hinge point. The design of the tension arm 3-9 allows it to rotate with the rotation of the fixed block 3-3, and it can also achieve opening and closing action under the action of the connecting rod 3-8.

[0042] Electric cylinders 3-4 are fixed to the bottom ends of the traction arms 3-9. Electric cylinders 3-4 provide precise linear movement for adjusting the opening and closing extension positions of the grippers. The use of electric cylinders 3-4 allows the electrodes to contact the fracturing points at different heights.

[0043] The end of the connecting rod 3-8 furthest from the movable block 3-2 is hinged to the side wall of the traction arm 3-9. This connection method constitutes a compound motion mechanism. When the electric telescopic rod 3-7 drives the movable block 3-2 to move up and down, the opening and closing motion of the gripper can be realized through the cooperation of the connecting rod 3-8 and the traction arm 3-9.

[0044] The bottom end of the electric cylinder 3-4 is fixedly connected to a rubber insulating gripper 3-12. The rubber insulating gripper 3-12 is made of a specially formulated insulating rubber material, possessing excellent insulation properties and appropriate elasticity, enabling it to safely clamp workpieces and prevent current leakage. The surface of the rubber insulating gripper 3-12 is designed with anti-slip textures to enhance clamping stability.

[0045] A linear low-voltage electrode 3-10 and a linear high-voltage electrode 3-11 are fixed to the bottom of the rubber insulating gripper 3-12. The linear low-voltage electrode 3-10 and the linear high-voltage electrode 3-11 are arranged linearly along the bottom of the gripper, which can apply voltage to the clamped workpiece and form an electric field. The low-voltage electrode 3-10 is connected to a low-voltage power supply, and the high-voltage electrode 3-11 is connected to a high-voltage power supply 2-2. The potential difference between the two can generate a directional electric field distribution inside the workpiece.

[0046] During operation, the rotation angle of the fixed block 3-3 is first adjusted by the servo motor 3-6 to position the gripper appropriately. Then, the height of the movable block 3-2 is adjusted by the electric telescopic rod 3-7, driving the connecting rod 3-8 to move, thereby controlling the angle of the pulling arm 3-9. The electric cylinder 3-4 precisely controls the opening, closing, and extension positions of the rubber-insulated gripper 3-12, ensuring the electrode contacts the workpiece at the appropriate location. Finally, the linear low-voltage electrode 3-10 and the linear high-voltage electrode 3-11 are energized, creating a directional electric field inside the workpiece to achieve a directional fracturing effect.

[0047] When the fracturing direction needs to be adjusted, the servo motor 3-6 drives the fixed block 3-3 to rotate. Since the fixed block 3-3 is connected to the lower component, the entire clamping mechanism will rotate together, thereby changing the direction of the electrode and realizing the multi-angle directional fracturing function. The telescopic movement of the electric telescopic rod 3-7, in conjunction with the movement of the connecting rod 3-8 and the pulling arm 3-9, can adjust the clamping force and clamping position to adapt to workpieces of different shapes and sizes.

[0048] This directional cracking rotary fixture structure achieves precise directional cracking of workpieces through a combination of mechanical motion and electric field action, improving processing accuracy and efficiency. At the same time, the design of the rubber insulated grippers 3-12 ensures operational safety.

[0049] Example 4 like Figure 7 As shown, the method for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses includes the following steps: S1: Prepare similar materials with appropriate mix proportions according to the rock type, mix them thoroughly, and then start casting specimen 2-4 in the mold. The casting height of the inner cavity of the bottom casting groove 1-1 of specimen 2-4 is determined according to the joint angle α. The bottom casting groove 1-1 is placed on the inclined surface with an angle of α between the inclined surface and the horizontal surface. The height of specimen (2-4) is h, and the height of the geometric center of the joint surface is flush with 1 / 2 of the height of the casting mold (1) (i.e., h / 2). Assuming the joint thickness is b, the casting height on the left side is... The corresponding pouring height on the right side is ; S2: After the partial pouring of the bottom pouring groove 1-1 is completed, the first part is compacted, and after it is solidified, the upper side steel wire 1-4 and the middle segment steel wire 1-10 are laid on the upper surface thereof, and the second part joint layer is continuously poured above the inner cavity of the bottom pouring groove 1-1.

[0050] S3: Before the second part joint layer is completely solidified, the side steel wire 1-4 located at the geometric center of the lower surface thereof is pulled out along the joint angle direction, and the middle segment steel wire 1-10 is pulled out vertically from bottom to top, the joint layer is cut, and after the cutting is completed, the side steel wire 1-4 is continuously laid on the upper surface of the joint layer.

[0051] S4: The third part is continuously poured on the upper surface of the second part joint layer, and before the second part joint layer and the third part are completely solidified, the side steel wire 1-4 in the test piece 2-4 is pulled out along the joint angle direction, so as to form the initial defect at the joint layer. When different numbers of joints are made, the above method can be repeated.

[0052] S5: After the test piece 2-4 is cured, the joint rock sample directional cracking test system is assembled, and the joint test piece 2-4 is placed in the operation box 2-1 filled with oil phase medium. The high-voltage power supply 2-2 converts alternating current into high-voltage direct current through the rectifier 2-3. In order to avoid excessive fragmentation of the joint rock sample, multiple low-energy pulses are used instead of a single high-energy pulse. A single high-energy pulse can release a large amount of energy instantaneously, which is easy to produce multiple random cracks. Multiple low-intensity pulses are used for fatigue loading, and each energy is only enough to make the crack expand a preset distance along the direction with the smallest resistance.

[0053] The linear high-voltage electrode 3-10 and the linear low-voltage electrode 3-10 are symmetrically arranged close to the joint test piece 2-4, the length of the linear electrode is not more than the diameter of the test piece 2-4, and the relative position between the two is maintained during the discharge cracking process, and a low-energy electric pulse with a voltage rise time greater than 500 ns is preferably provided. When the switch is opened, the energy storage capacitor 2-5 stores the power energy; when the switch is closed, the energy is injected into the linear high-voltage electrode 3-11 and the linear low-voltage electrode 3-10 through the transmission cable in a very short time, and the rock is broken by a single pulse discharge. Because the breakdown voltage rise time is greater than 500 ns, the breakdown field strength of the oil phase medium liquid medium is greater than that of the rock, and the plasma channel between the discharge electrodes is preferentially formed in the medium with relatively low breakdown field strength, so the rock is first broken under the action of the low-energy electric pulse; The placement position of the linear electrode follows the following principles. Specifically, in order to avoid damage to other areas outside the joint layer caused by a single pulse, the linear electrode is first placed at half the thickness of the joint, such as Figure 4As shown, after multiple low-intensity pulse fatigue loading and achieving the predetermined crack effect, the electrodes are uniformly moved upwards and downwards in the joint thickness range, and the discharge crack is repeated. Since the joint surface is pretreated (i.e. the setting of the side steel wire and the middle steel wire) when the joint rock sample is made, the initial damage is formed. When the plasma channel breaks through the solid medium, it will always prefer to pass through the path with the smallest impedance. Therefore, when the electric pulse acts near the joint surface, it will break along the initial damage path. Combined with multiple, low-intensity pulse fatigue loading, the damage and interference to the area outside the joint layer are minimized. In addition, to strengthen the crack effect, the energy parameters can be adjusted and optimized in combination with the oscilloscope 2-6 and the actual crack effect (using CT to scan the joint rock sample).

[0054] In actual operation, any angle between 10° and 80° can be selected according to the required joint angle α, preferably 30°, 45° or 60°. The joint thickness b can be selected between 0.5mm and 5mm according to actual needs, preferably 1mm to 3mm. The height of the model can be set according to the test requirements, usually between 25mm and 100mm, preferably 30mm to 60mm.

[0055] When preparing similar materials, a mixture of cement, gypsum, sand and water can be used, and the preferred ratio is cement: gypsum: sand: water = 1:0.25:9:0.3. The endogenous joint rock sample prepared by the above method has a controllable angle, and the joint surface produced is the natural result of the original rupture of the rock itself, retains the true physical and mechanical properties of the rock material itself, and can truly simulate the joint characteristics inside the rock mass, providing a reliable experimental basis for studying the influence of joints on the mechanical properties of rock mass.

[0056] Finally, it should be noted that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the scope of the present application shall be included in the protection scope of the present application.

Claims

1. A device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses, comprising a jointed rock sample casting mold (1), characterized in that: The jointed rock sample casting mold (1) can be placed inside the directional fracturing container (2). The top surface of the directional fracturing container (2) is fixedly connected to a directional fracturing rotating clamp (3). An endogenous jointed rock sample is obtained by casting through the jointed rock sample casting mold (1) and placed inside the directional fracturing container (2). The electrode is moved uniformly upward and downward within the joint thickness range by the directional fracturing rotating clamp (3), and the discharge fracturing is repeated.

2. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 1, characterized in that, The jointed rock sample casting mold (1) includes a bottom casting groove (1-1), a middle section cylinder (1-2) screwed and fixed to the top of the bottom casting groove (1-1), and a top section cylinder (1-3) screwed and fixed to the top of the middle section cylinder (1-2). Several side steel wires (1-4) and a middle section steel wire (1-10) are evenly arranged in the bottom casting groove (1-1) and the middle section cylinder (1-2). A pulling wire (1-5) for pulling the middle section steel wire (1-10) upward is fixed on the upper surface of the middle section steel wire (1-10). Several side steel wires (1-4) are evenly spaced in the inner cavity of the middle section cylinder (1-2) and the top section cylinder (1-3).

3. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 2, characterized in that: The top port of the bottom casting trough (1-1), the top port of the middle section cylinder (1-2), and the top port of the top section cylinder (1-3) are all threaded, and the bottom sections of the middle section cylinder (1-2) and the top section cylinder (1-3) are all provided with external threads.

4. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 1, characterized in that, The directional fracturing container (2) includes an operating box (2-1) containing an oil phase medium, a specimen (2-4) placed in the inner cavity of the operating box (2-1) and immersed in the oil phase medium, a high voltage power supply (2-2) and a rectifier (2-3) fixed on the front side of the operating box (2-1), an oscilloscope (2-6) fixed on the rear side of the operating box (2-1), and an energy storage capacitor (2-5) fixedly connected to the right side of the operating box (2-1).

5. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 4, characterized in that, The directional fracturing rotary fixture (3) includes two columns (3-1), a support plate (3-5) fixed to the top of the columns (3-1), and a servo motor (3-6) fixed to the top of the support plate (3-5). The bottom output shaft of the servo motor (3-6) passes through the support plate (3-5) and is connected to a fixing block (3-3). An electric telescopic rod (3-7) is fixedly embedded inside the fixing block (3-3). A movable block (3-2) is fixed to the bottom end of the electric telescopic rod (3-7). The left and right sides of the movable block (3-2) are hinged to... The connecting rod (3-8) has two traction arms (3-9) hinged to the bottom left and right sides of the fixed block (3-3). The bottom ends of the traction arms (3-9) are respectively fixed with electric cylinders (3-4). The end of the connecting rod (3-8) away from the movable block (3-2) is respectively hinged to the side wall of the traction arm (3-9). The bottom end of the electric cylinder (3-4) is fixedly connected with a rubber insulating gripper (3-12). The bottom of the rubber insulating gripper (3-12) is respectively fixed with a linear low-voltage electrode (3-10) and a linear high-voltage electrode (3-11).

6. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 5, characterized in that: The rectifier (2-3) is connected to the positive terminal of the high-voltage power supply (2-2). The rectifier (2-3) is used to rectify the AC power of the high-voltage power supply (2-2) into DC power and deliver it to the linear high-voltage electrode (3-11). The oscilloscope (2-6) is connected to the negative terminal of the high-voltage power supply (2-2). The oscilloscope (2-6) is electrically connected to the linear low-voltage electrode (3-10).

7. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 5, characterized in that: The linear high-voltage electrode (3-11) is connected to the rectifier (2-3) by a cable, and a switch is provided on the cable. The linear low-voltage electrode (3-10) is connected to the oscilloscope (2-6) by a cable, and the energy storage capacitor (2-5) is connected in parallel with the line.

8. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 5, characterized in that: The bottom ends of the columns (3-1) are fixedly connected to the left and right side walls of the control box (2-1) on opposite sides.

9. The device for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses according to claim 5, characterized in that: The linear low-voltage electrode (3-10) and the linear high-voltage electrode (3-11) are in contact with the outer surface of the joint layer of the specimen (2-4) on the side closest to each other.

10. A method for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses, characterized in that: The apparatus for preparing endogenous jointed rock samples based on directional fracturing by electrical pulses, applicable to any one of claims 1-9, comprises the following steps: S1: Prepare similar materials with appropriate mix proportions according to the rock type, mix them thoroughly, and then start casting the specimen in the mold; the inner cavity of the bottom casting groove (1-1) of the specimen is cast, and its casting height is determined according to the joint angle α. The bottom casting groove (1-1) is placed on the inclined surface with an angle of α between the inclined surface and the horizontal surface; the height of the specimen (2-4) is h, the height of the geometric center of the joint surface is flush with 1 / 2 of the height of the casting mold (1), i.e., h / 2, the joint thickness is b, the diameter is d, and the casting height on the left side is... The corresponding pouring height on the right side is ; S2: After the bottom pouring trough (1-1) is partially poured, it is compacted to form the first part. After it has solidified, the upper side steel wire (1-4) and the middle section steel wire (1-10) are laid on its upper surface. The second part of the joint layer is poured above the inner cavity of the bottom pouring trough (1-1). S3: Before the second joint layer is fully cured, the side steel wire (1-4) located at the geometric center of its lower surface is pulled out along the joint angle direction and the middle steel wire (1-10) is pulled out vertically from bottom to top to cut the joint layer. After the cutting is completed, the side steel wire (1-4) continues to be laid on the upper surface of the joint layer. S4: Continue casting on the upper surface of the second joint layer to form the third part, and before the second joint layer and the third part are completely cured, pull out the side steel wires (1-4) in the specimen along the joint angle direction to form the initial defect at the joint layer; the above method can be repeated when making joints with different numbers of joints; S5: After the specimens have been cured, a jointed rock sample directional cracking test system is set up. The jointed specimen (2-4) is placed in an operating box (2-1) filled with oil phase medium. The high-voltage power supply (2-2) is converted from AC to high-voltage DC after passing through a rectifier (2-3). Each time, the energy is only enough to allow the crack to extend a preset distance along the direction of least resistance.

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