A True Three-Dimensional Single-Face Unloading Rockburst Simulation Test Device and Method

Abstract

This invention discloses a true three-dimensional single-sided unloading rockburst simulation test device and method, belonging to the technical field of test equipment. It includes: an upper pressure head, a lower pressure head, a front pressure head, a rear pressure head, a left pressure head, and a right pressure head, as well as an acoustic emission monitoring mechanism, a deformation monitoring mechanism, and a rock sample. A sample follower is embedded on the right side of the rock sample. In this invention, the acoustic emission sensor has reasonable contact with the rock sample, resulting in high measurement accuracy. During the test, when the pressure is removed... s After pressing the right head in direction 3, you can continue in... s 1. s Pressure is applied in two directions until rock bursts occur in the rock sample. Stress-strain test data of the rock burst process are obtained using displacement sensors, and the spatiotemporal evolution characteristics of micro-fractures inside the rock sample are monitored in real time using acoustic emission sensors. The assembly method of each indenter creates a locking structure between them, eliminating the stress blank angle of true triaxial stress loading.

Description

Technical Field

[0001] This invention relates to a true three-dimensional single-sided unloading rockburst simulation test device and method, belonging to the technical field of test equipment. Background Technology

[0002] Deep engineering surrounding rock is subjected to true triaxial high geostress under the influence of gravity and horizontal tectonic stress of the overlying strata. s 1> s 2> s 3) Environmental Factors. Excavation in deep underground engineering projects leads to stress field redistribution. On the one hand, surface stress in the cavern is rapidly unloaded to zero radially; on the other hand, strong stress concentration occurs circumferentially, forming a true triaxial loading and unloading stress path. Extensive engineering practice shows that loading and unloading can easily induce surrounding rock fracturing, leading to rock mass instability. Especially with the lack of constraint on the free face, the strain energy accumulated in the surrounding rock can be rapidly released due to deformation and fracturing, resulting in severe rockburst disasters that seriously threaten the lives and property of engineering personnel. Therefore, conducting true triaxial single-face unloading tests on rock to simulate the loading and unloading stress path of surrounding rock in deep underground engineering projects is of great significance for revealing the mechanism of rockburst disasters in deep underground engineering and ensuring the safe and smooth construction of projects.

[0003] True triaxial single-plane unloading tests require a rigid-loading true triaxial testing apparatus. Principal stress is applied via hydraulic cylinders. The rock sample is a cuboid and assembled into a fixture consisting of six rigid loading plates. During simulated rapid unloading... s When one cylinder in one of the three directions rapidly retracts, the loading plate swings out with the swing rod, creating a single-sided unloaded state, causing dynamic damage to the rock similar to a rockburst. The test process primarily relies on deformation measurement and acoustic emission monitoring to assist in determining the rock fracture condition. Deformation monitoring is achieved by installing an LVDT between the two loading plates in the same direction to measure the relative displacement of the loading plates. However, in the single-sided unloading test, due to… s The three-directional loading plate was out of position, making it impossible to install the LVDT (Low-Level Dynamic Testing Device), resulting in missing deformation data during the rockburst incubation process and hindering the accurate understanding of the rockburst incubation and disaster-causing mechanism. Furthermore, because the rock sample was tightly encased by the loading plate, the acoustic emission sensor could only be fixed to the rigid loading plate and could not directly contact the sample surface. This prevented the location of micro-fractures within the rock through acoustic emission signals, thus making it impossible to perceive the fracture state of the rock sample. To clarify the dynamic instability evolution process induced by rock fracture under single-sided unloading conditions and to reveal the disaster-causing mechanism of rockburst hazards in deep underground engineering, it is urgently necessary to design a true three-dimensional single-sided unloading test device capable of monitoring deformation on the free face and accurately locating rockbursts using acoustic emission. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a true three-dimensional single-sided unloading rockburst simulation test device and method. The acoustic emission monitoring mechanism is set inside the pressure head and directly attached to the sample surface, eliminating the interference of the rock-loading plate interface on the acoustic emission signal and achieving high acoustic emission positioning accuracy. s The 3-directional LVDT deformation measurement is not affected by the indenter swing and can continuously monitor the deformation of the free surface before rockburst; in addition, the assembly method of the indenter can eliminate the stress blank angle of true triaxial stress loading.

[0005] The present invention achieves the above objectives by adopting the following technical solutions:

[0006] On the one hand, the present invention provides a true three-dimensional single-sided air-load unloading rockburst simulation test device, including: an upper pressure head, a lower pressure head, a front pressure head, a rear pressure head, a left pressure head, a right pressure head, as well as an acoustic emission monitoring mechanism, a deformation monitoring mechanism, and a rock sample, with each pressure head surrounding to form a sample placement cavity for placing the rock sample;

[0007] The front, rear, left, and right sides of the upper pressure head are detachably connected to the upper sides of the front pressure head, rear pressure head, left pressure head, and right pressure head via connectors, respectively. The front, rear, left, and right sides of the lower pressure head are detachably connected to the lower sides of the front pressure head, rear pressure head, left pressure head, and right pressure head via connectors, respectively.

[0008] A sample follower is embedded on the right side of the rock sample, and a notch is opened on the side wall of the front pressure head. The sample follower extends out of the sample placement cavity through the notch.

[0009] The front pressure head, rear pressure head, and left pressure head each have mounting holes for installing an acoustic emission monitoring mechanism on the side facing the sample placement cavity, and a first wire outlet communicating with the mounting holes is provided on the other side of the front pressure head, rear pressure head, and left pressure head.

[0010] The acoustic emission monitoring organization includes:

[0011] A cylindrical insulating shell, wherein a limiting step is provided on the inner wall of the first end of the insulating shell to reduce the inner diameter of the first end of the insulating shell, and a second wire outlet is provided on the side wall of the second end of the insulating shell;

[0012] An acoustic emission sensor is disposed inside the first end of an insulating shell. The outer diameter of the acoustic emission sensor is larger than the inner diameter of the first end of the insulating shell. The first end of the acoustic emission sensor is provided with a reduced diameter section. The reduced diameter section extends out from the first end of the insulating shell and contacts the corresponding side of the rock sample. The second end of the acoustic emission sensor is connected to a wire.

[0013] Tail end pad, the tail end pad is fixedly installed inside the second end of the insulating shell, and the first end of the tail end pad has a wire lead-out channel;

[0014] A spring is compressed between the second end of the acoustic emission sensor and the first end of the tail end pad. The wire passes through the inner hole of the spring, the wire lead-out channel, the second wire lead-out outlet, and the first wire lead-out outlet in sequence before being led out to the outside of the pressure head.

[0015] The deformation monitoring mechanism includes s 1. Deformation monitoring agency in one direction s 2-direction deformation monitoring mechanism and s A three-directional deformation monitoring mechanism is installed between the upper and lower pressure heads. s A deformation monitoring mechanism in one direction is provided, with a [device / equipment] installed between the front pressure head and the rear pressure head respectively. s A two-directional deformation monitoring mechanism is provided between the left indenter and the sample follower. s 3-directional deformation monitoring mechanism.

[0016] Specifically, the upper and lower indenters are offset by a certain distance along the right-front to left-rear direction, so that the front and right edges of the rock sample are aligned with the front and right edges of the lower indenter, and the rear and left edges of the rock sample are aligned with the rear and left edges of the upper indenter. The front and rear indenters are offset by a certain interval along the left-right direction, and the left and right indenters are offset by a certain distance along the front-back direction, so that the rear side of the front indenter abuts against the front side of the left indenter, the right side of the left indenter abuts against the left side of the rear indenter, the front side of the rear indenter abuts against the rear side of the right indenter, and the left side of the right indenter abuts against the right side of the front indenter. At the same time, the front and right sides of the upper indenter press against the rear side of the front indenter and the left side of the right indenter, respectively, and the left and rear sides of the lower indenter are supported by the right side of the left indenter and the front side of the rear indenter, respectively. The rear and left edges of the upper indenter are aligned with the rear and left edges of the rock sample, and the right and front edges of the lower indenter are aligned with the right and front edges of the rock sample.

[0017] In one specific embodiment, two acoustic emission monitoring mechanisms are respectively provided on the upper and lower parts of the front pressure head, the rear pressure head, and the left pressure head.

[0018] Furthermore, a screw is threaded onto the tail end pad, and the end of the screw passes through the tail end pad and presses against the insulating shell, causing the insulating shell to deform and be pressed tightly into the mounting hole.

[0019] Specifically, the s 1. Deformation monitoring agency in one direction s The deformation monitoring institutions in both directions include:

[0020] LVDT displacement sensor, wherein the LVDT displacement sensor is mounted on one of the pressure heads via a sensor holder;

[0021] An extension rod is provided, with its first end mounted on another pressure head via an extension rod mounting base, and its second end aligning with the contact of an LVDT displacement sensor.

[0022] The s The three-directional deformation monitoring mechanism includes:

[0023] LVDT displacement sensor, wherein the LVDT displacement sensor is mounted on the left pressure head via a sensor holder;

[0024] An extension rod is provided, with its first end fixed to the contact of an LVDT displacement sensor and its second end in contact with a sample follower.

[0025] In one specific embodiment, the front, rear, left, and right sides of the upper pressure head, as well as the upper sides of the front pressure head, rear pressure head, left pressure head, and right pressure head, are all provided with insertion holes; the connecting parts include a hinge bolt and a hexagon socket head cap screw, the head of the hinge bolt is provided with a retaining ring, the axis of the retaining ring is perpendicular to the axis of the hinge bolt, the tail of the hinge bolt is connected to the insertion hole on one of the pressure heads, and the hexagon socket head cap screw passes through the retaining ring and is connected to the insertion hole on the other pressure head.

[0026] Furthermore, the sensor holder is provided with a clamping opening, and the LVDT displacement sensor is clamped in the clamping opening, which is tightened by bolts;

[0027] The first end of the extension rod is fixed with a knurled high nut, and the end of the first end of the extension rod passes through the extension rod fixing seat.

[0028] On the other hand, the present invention also provides a true three-dimensional single-sided open-air unloading rockburst simulation test method, which uses the aforementioned test device and includes the following steps:

[0029] S1. Fix the sample follower on the right side of the rock sample;

[0030] A groove is excavated on the right side of the rock sample. One end of the follower of the sample is placed in the groove, and the groove is filled with cement mortar. After the cement mortar has cured, it is ground until it is flush with the surface of the rock sample.

[0031] S2. Install the acoustic emission monitoring mechanism into the pressure head;

[0032] Coupling agent is applied to the inner wall of the insulating shell. The spring is placed on the wire of the acoustic emission sensor and placed inside the insulating shell. The tail end pad is installed into the insulating shell. The wire is led out of the insulating shell through the wire lead-out channel and the second wire lead-out outlet. Then the insulating shell is inserted into the mounting hole of the pressure head. The wire is led out from the first wire lead-out outlet to the outside of the pressure head. The screw is tightened on the tail end pad to press the insulating shell into the mounting hole.

[0033] After the acoustic emission monitoring mechanism is installed, the reduced diameter section of the acoustic emission sensor is slightly higher than the surface of the indenter. When assembling the indenter and the rock sample, the rock sample will squeeze the reduced diameter section to shrink back to be flush with the surface of the indenter. The spring will then apply elastic force to the acoustic emission sensor, so that the reduced diameter section fits tightly with the rock sample.

[0034] S3. Assemble the various indenters and rock samples;

[0035] S3.1 Place the lower indenter, rock sample, and upper indenter sequentially from bottom to top;

[0036] S3.2 Apply coupling agent to the rock sample corresponding to the position of the acoustic emission sensor. Install the front, rear, left, and right indenters around the front, rear, left, and right sides of the rock sample. Install hinge bolts on the front, rear, left, and right sides of the upper indenter. Install hexagon socket head caps on the four hinge bolts. Connect the four hexagon socket head caps to the front, rear, left, and right indenters respectively.

[0037] Install hinge bolts on the lower sides of the front pressure head, rear pressure head, left pressure head, and right pressure head respectively. Install hex socket head cap screws on the four hinge bolts respectively. Connect the four hex socket head cap screws to the front, rear, left, and right sides of the lower pressure head respectively.

[0038] S4. Install deformation monitoring equipment;

[0039] Will s 1. Deformation monitoring agency in one direction s 2-direction deformation monitoring mechanism and s The three-directional deformation monitoring mechanisms are installed on the corresponding pressure heads;

[0040] S5. Place the assembled rock sample, acoustic emission monitoring mechanism, and deformation monitoring mechanism indenter assembly into the true triaxial testing instrument, adjust the range of the LVDT displacement sensor, connect the acoustic emission sensor of the acoustic emission monitoring mechanism and the LVDT displacement sensor of the deformation monitoring mechanism to the data acquisition unit, and connect the data acquisition unit to the main computer to display the measurement data in real time.

[0041] S6. Remove the connector and begin the experiment.

[0042] Step S6 is as follows:

[0043] S6.1 Remove the connecting parts between the indenters and control the true triaxial testing instrument. s 1. s 2 and s True triaxial pressure loading tests were conducted in three directions, and the pressure, acoustic emission, and deformation test data of the rock samples were recorded.

[0044] S6.2 Once the pressure reaches the required value, remove the right pressure head. Since the acoustic emission monitoring mechanism is installed on the front, rear, and left pressure heads, it is unaffected by the right pressure head and can continue monitoring. s 1. s Pressure is applied in two directions using a pressure head, and acoustic emission test data is acquired.

[0045] Simultaneously, the left pressure head continues to apply pressure to the rock sample, and the sample follower is fixed on the rock sample, causing the rock sample to... s Expansion deformation in three directions can still be achieved s The deformation monitoring mechanism in three directions reacted;

[0046] After a rock burst occurs in the rock sample, the follower detaches from the rock sample. s Expansion deformation in three directions cannot continue. s The deformation monitoring mechanism responded, and the experiment ended.

[0047] The beneficial effects of the present invention include, but are not limited to:

[0048] The true triaxial single-sided unloading rockburst simulation test device and method provided by the present invention has acoustic emission monitoring mechanisms set inside the front pressure head, rear pressure head and left pressure head, and deformation monitoring mechanisms set outside the pressure head, so that the acoustic emission sensor is in reasonable contact with the rock sample, realizing real-time monitoring and recording of stress, acoustic emission and deformation signals of the rock sample during the true triaxial test process, with high measurement accuracy.

[0049] Furthermore, when removed s After pressing the right head in direction 3, you can continue... s 1. s Pressure is applied in two directions until rock bursts occur in the rock sample. Stress-strain test data of the rock burst process are obtained by combining displacement sensors and acoustic emission sensors to monitor the spatiotemporal evolution characteristics of micro-fractures inside the rock sample in real time. This enables continuous monitoring of the deformation process of the free surface before rock bursts.

[0050] Furthermore, the assembly method of each indenter creates a locking structure between them, eliminating the stress gap angle during true triaxial stress loading. This also facilitates the assembly of the indenter with rock samples, acoustic emission monitoring mechanisms, and deformation monitoring mechanisms. It further simplifies the process of installing the indenter assembly into the true triaxial testing instrument. s 1. s 2. s Pressure is applied to each pressure head in three directions, and the right pressure head can be easily removed to continue the test. Attached Figure Description

[0051] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0052] Figure 1 A schematic diagram of the structure of the true three-dimensional single-face unloading rockburst simulation test device provided by the present invention;

[0053] Figure 2 This is a schematic diagram showing the relative positions of the lower indenter, the rock sample, and the upper indenter at one angle.

[0054] Figure 3 This is a schematic diagram showing the relative positions of the lower indenter, the rock sample, and the upper indenter at another angle.

[0055] Figure 4 This is a schematic diagram showing the relative positions of the front pressure head, rear pressure head, left pressure head, and right pressure head.

[0056] Figure 5 A schematic diagram of the structure for assembling an acoustic emission monitoring mechanism on the front pressure head;

[0057] Figure 6 This is a structural schematic diagram of the connector;

[0058] Figure 7 This is a schematic diagram of the acoustic emission monitoring mechanism;

[0059] Figure 8 for s Deformation monitoring mechanism in one direction and s Schematic diagram of the structure of the two-direction deformation monitoring mechanism;

[0060] Figure 9 for s Schematic diagram of the three-directional deformation monitoring mechanism and rock sample;

[0061] In the diagram, 110 is the upper pressure head; 120 is the lower pressure head; 130 is the front pressure head; 131 is the notch; 140 is the rear pressure head; 150 is the left pressure head; and 160 is the right pressure head.

[0062] 210. Insulating shell; 211. Limiting step; 212. Second wire outlet; 220. Acoustic emission sensor; 221. Reduced diameter section; 222. Wire; 230. Tail end pad; 231. Wire outlet channel; 232. Screw; 240. Spring;

[0063] 301. LVDT displacement sensor; 302. Extension rod; 303. Sensor clamp; 304. Extension rod fixing base; 305. Knurled high-strength nut; 310. s 1. Deformation monitoring agency; 320, s2. Deformation monitoring agencies; 330, s 3. Deformation monitoring institutions;

[0064] 400. Rock specimen; 410. Specimen follower;

[0065] 500. Connecting parts; 510. Hinged bolts; 520. Socket head cap bolts;

[0066] 610. Socket; 620. Mounting hole; 621. First wire outlet. Detailed Implementation

[0067] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0068] It should be noted that many specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0069] like Figure 1-Figure 9 As shown, the true three-dimensional single-sided air-load unloading rockburst simulation test device provided by the present invention includes an upper pressure head 110, a lower pressure head 120, a front pressure head 130, a rear pressure head 140, a left pressure head 150, a right pressure head 160, an acoustic emission monitoring mechanism, a deformation monitoring mechanism, and a rock sample 400. Each pressure head surrounds a sample placement cavity for placing the rock sample 400.

[0070] like Figure 2 As shown, a sample follower 410 is embedded on the right side of the rock sample 400, and a notch 131 is opened on the side wall of the front pressure head 130. The sample follower 410 extends out of the sample placement cavity through the notch 131.

[0071] Among them, the acoustic emission monitoring mechanism is used to monitor the acoustic emission signal of the rock sample 400 during the stress process, and the deformation monitoring mechanism is used to monitor the deformation of the rock sample 400.

[0072] The front, rear, left, and right sides of the upper pressure head 110 are detachably connected to the upper sides of the front pressure head 130, rear pressure head 140, left pressure head 150, and right pressure head 160 via connectors 500, respectively. The front, rear, left, and right sides of the lower pressure head 120 are detachably connected to the lower sides of the front pressure head 130, rear pressure head 140, left pressure head 150, and right pressure head 160 via connectors 500, respectively.

[0073] The assembly method of each pressure head is as follows:

[0074] like Figure 2 and Figure 3As shown, the upper pressure head 110 and the lower pressure head 120 are offset by a certain distance along the right front-left rear direction, so that the front and right edges of the rock sample 400 are aligned with the front and right edges of the lower pressure head 120, and the rear and left edges of the rock sample 400 are aligned with the rear and left edges of the upper pressure head 110.

[0075] like Figure 4 As shown, the front indenter 130 and the rear indenter 140 are offset by a certain interval in the left-right direction, and the left, right, and right indenters 160 are offset by a certain distance in the front-back direction. This arrangement ensures that the rear side of the front indenter 130 abuts against the front side of the left indenter 150, the right side of the left indenter 150 abuts against the left side of the rear indenter 140, the front side of the rear indenter 140 abuts against the rear side of the right indenter 160, and the left side of the right indenter 160 abuts against the right side of the front indenter 130. The four sides of the rock sample (front, rear, left, and right) are respectively attached to the corresponding sides of the front, rear, left, and right indenters.

[0076] At the same time, such as Figure 2 and Figure 3 As shown, the front and right sides of the upper pressure head 110 are pressed against the rear side of the front pressure head 130 and the left side of the right pressure head 160, respectively, while the left and rear sides of the lower pressure head 120 are supported on the right side of the left pressure head 150 and the front side of the rear pressure head 140, respectively. The rear and left edges of the upper pressure head 110 are aligned with the rear and left edges of the rock sample 400, and the right and front edges of the lower pressure head 120 are aligned with the right and front edges of the rock sample 400.

[0077] In this way, each pressure head forms a locking structure through the above assembly method, eliminating the stress blank angle of true triaxial stress loading.

[0078] like Figure 2-Figure 6 As shown, in one specific embodiment, the connector 500 has the following structure: insertion holes 610 are provided on the front, rear, left, and right sides of the upper pressure head 110, and on the upper sides of the front pressure head 130, rear pressure head 140, left pressure head 150, and right pressure head 160. The connector 500 includes a hinge bolt 510 and a hex socket head cap screw 520. A retaining ring is provided at the head of the hinge bolt 510, the axis of which is perpendicular to the axis of the hinge bolt 510. The tail of the hinge bolt 510 connects to the insertion hole on one of the pressure heads, and the hex socket head cap screw 520, after passing through the retaining ring, connects to the insertion hole on the other pressure head. Further, a flat washer can be placed between the hex socket head cap screw 520 and the retaining ring as needed.

[0079] like Figure 5As shown, the front pressure head 130, the rear pressure head 140, and the left pressure head 150 are respectively provided with mounting holes 620 for mounting acoustic emission monitoring mechanisms on the side facing the sample placement cavity, and a first wire outlet 621 communicating with the mounting holes 620 is provided on the other side of the front pressure head 130, the rear pressure head 140, and the left pressure head 150.

[0080] Typically, two acoustic emission monitoring mechanisms are installed on the upper and lower parts of the front pressure head 130, the rear pressure head 140, and the left pressure head 150, for a total of 12 acoustic emission monitoring mechanisms installed on the three pressure heads.

[0081] like Figure 7 As shown, specifically, the acoustic emission monitoring mechanism includes a cylindrical insulating shell 210, an acoustic emission sensor 220, a tail end pad 230, and a spring 240.

[0082] The insulating shell 210 has a limiting step 211 on the inner wall of the first end opening to reduce the inner diameter of the first end opening, and a second wire outlet 212 is provided on the side wall of the second end opening.

[0083] The acoustic emission sensor 220 is disposed inside the first end of the insulating shell 210. The outer diameter of the acoustic emission sensor 220 is larger than the inner diameter of the first end of the insulating shell 210. The first end of the acoustic emission sensor 220 is provided with a reduced diameter section 221. After the reduced diameter section 221 extends out from the first end of the insulating shell 210, it contacts the corresponding side of the rock sample 400. The second end of the acoustic emission sensor 220 is connected to a wire 222, which is flexible.

[0084] The tail end pad 230 is fixedly installed inside the second end of the insulating shell 210, and the first end of the tail end pad 230 has a wire lead-out channel 231.

[0085] The spring 240 is compressed between the second end of the acoustic emission sensor 220 and the first end of the tail pad 230. The wire 222 passes through the inner hole of the spring 240, the wire lead-out channel 231, the second wire lead-out outlet 212, and the first wire lead-out outlet 621 in sequence before being led out to the outside of the pressure head.

[0086] When no external force is applied, the spring 240 applies a spring force to the acoustic emission sensor 220, causing the narrowed section 221 at the first end of the acoustic emission sensor 220 to extend outward from the insulating shell 210.

[0087] Furthermore, a screw 232 is threaded onto the tail end pad 230. The end of the screw 232 passes through the tail end pad 230 and presses against the insulating shell 210, causing the insulating shell 210 to deform and be pressed tightly into the mounting hole 620.

[0088] In this invention, s1. Direction 1 refers to the up and down direction. s 2 refers to the forward and backward directions. s The third direction refers to the left and right directions.

[0089] To measure rock sample 400 at s 1. s 2. s Deformation in three directions, deformation monitoring mechanism includes s 1. Deformation monitoring mechanism 310 s 2-direction deformation monitoring mechanism 320 and s 330, a three-directional deformation monitoring mechanism. Specifically, such as... Figure 1 As shown, a [missing information] is provided between the upper pressure head 110 and the lower pressure head 120. s A deformation monitoring mechanism 310 is provided between the front pressure head 130 and the rear pressure head 140. s A two-way deformation monitoring mechanism 320 is provided between the left pressure head 150 and the sample follower 410. s 330-directional deformation monitoring mechanism.

[0090] Specifically, such as Figure 8 As shown, s 1. Deformation monitoring mechanism 310 s The two-directional deformation monitoring mechanism 320 includes an LVDT displacement sensor 301 and an extension rod 302.

[0091] The LVDT displacement sensor 301 is mounted on one of the pressure heads via a sensor clamp 303; the first end of the extension rod 302 is mounted on the other pressure head via an extension rod fixing seat 304, and the second end of the extension rod 302 is in contact with the contact of the LVDT displacement sensor 301. Further, in s 1. Deformation monitoring mechanism 310 s In the 2-direction deformation monitoring mechanism 320, the first end of the extension rod 302 is fixed with a knurled high nut 305. The first end of the extension rod 302 passes through the extension rod fixing seat 304. Rotating the knurled high nut 305 can move the position of the extension rod 302, thereby adjusting the effective range of the LVDT displacement sensor 301.

[0092] like Figure 9 As shown, s The three-direction deformation monitoring mechanism 330 also includes an LVDT displacement sensor 301 and an extension rod 302. Since it needs to cooperate with the sample follower 410, the LVDT displacement sensor 301 is mounted on the left pressure head 150 through a sensor holder. The first end of the extension rod is fixed to the contact of the LVDT displacement sensor 301, and the second end of the extension rod 302 is in contact with the sample follower 410. sIn the 3-direction deformation monitoring mechanism 330, when adjusting the range of the LVDT displacement sensor 301, the sensor clamp 303 can be loosened to allow the sensor clamp 303 to move.

[0093] Typically, the sensor holder 303 and the extension rod holder 304 are mounted on the corresponding pressure heads using hexagon socket head cap screws.

[0094] Specifically, the sensor holder 303 is provided with a clamping opening, and the LVDT displacement sensor 301 is clamped in the clamping opening, which is tightened by bolts.

[0095] On the other hand, the present invention also provides a true three-dimensional single-sided open-air unloading rockburst simulation test method, which adopts the above-mentioned test device and includes the following steps:

[0096] S1. Fix the sample follower 410 on the right side of the rock sample 400:

[0097] A groove is excavated on the right side of the rock sample 400. One end of the sample follower 410 is placed in the groove, and the groove is filled with cement mortar. After the cement mortar has cured, it is polished until it is flush with the surface of the rock sample 400.

[0098] Specifically, the sample follower 410 can be made of steel sheet. The steel sheet is cut into the corresponding shape according to the installation position, so that the first end of the sample follower 410 is fixed on the rock sample 400, and the other end extends out of the rock sample 400 and contacts and engages with the corresponding LVDT displacement sensor 301. In addition, it is preferable to first glue the sample follower 410 into the groove with strong adhesive to fix its position before filling it with cement mortar.

[0099] S2. Install the acoustic emission monitoring mechanism into the pressure head:

[0100] Coupling agent is applied to the inner wall of the insulating housing 210. The spring 240 is fitted onto the wire 222 of the acoustic emission sensor 220 and placed inside the insulating housing 210. The tail end pad 230 is inserted into the insulating housing 210. The wire 222 is led out of the insulating housing 210 through the wire lead-out channel 231 and the second wire lead-out outlet 212. Then, the insulating housing 210 is inserted into the mounting hole 620 of the pressure head. The wire 222 is led out from the first wire lead-out outlet 621 to the outside of the pressure head. The screw 232 is tightened on the tail end pad 230, thus securing the insulating housing 210 firmly within the mounting hole 620. The insulating housing 210 is typically made of plastic and is relatively thin, so it deforms when the screw is tightened, becoming stuck within the mounting hole 620.

[0101] After the acoustic emission monitoring mechanism is installed, the reduced diameter section 221 of the acoustic emission sensor 220 is slightly higher than the surface of the indenter. When assembling the indenter and the rock sample 400, the rock sample 400 will squeeze the reduced diameter section 221 to retract it to be flush with the surface of the indenter. The spring 240 will then apply elastic force to the acoustic emission sensor 220, so that the reduced diameter section 221 fits tightly with the rock sample 400, ensuring that a complete acoustic emission signal is received.

[0102] S3. Assemble all indenters and rock samples 400:

[0103] S3.1 Place the lower indenter 120, rock sample 400, and upper indenter 110 from bottom to top;

[0104] S3.2 Apply coupling agent to the rock sample 400 at the position corresponding to the acoustic emission sensor 220. Then, surround and install the front indenter 130, rear indenter 140, left indenter 150, and right indenter 160 on the front, rear, left, and right sides of the rock sample 400. Install hinge bolts 510 on the front, rear, left, and right sides of the upper indenter 110, and install hexagon socket head cap screws 520 on each of the four hinge bolts 510. Connect the four hexagon socket head cap screws 520 to the front indenter 130, rear indenter 140, left indenter 150, and right indenter 160 respectively.

[0105] Hinged bolts 510 are installed on the lower sides of the front pressure head 130, rear pressure head 140, left pressure head 150, and right pressure head 160, respectively. Hex socket head cap screws 520 are installed on the four hinged bolts 510, and the four hex socket head cap screws 520 are connected to the front, rear, left, and right sides of the lower pressure head 120, respectively, to ensure that the rock sample 400 is firmly installed in the pressure head without loosening or shifting.

[0106] S4. Install deformation monitoring equipment:

[0107] Will s 1. Deformation monitoring mechanism 310 s 2-direction deformation monitoring mechanism 320 and s The three-directional deformation monitoring mechanisms 330 are respectively installed on the corresponding pressure heads.

[0108] It should be noted that before installing the deformation monitoring mechanism, it is necessary to ensure that the acoustic emission sensor 220 is working properly. Specifically, the pressure head can be tapped to test whether the acoustic emission sensor 220 has a signal. If there is no signal, it needs to be reassembled and debugged.

[0109] S5. Place the assembled rock sample 400, acoustic emission monitoring mechanism, and deformation monitoring mechanism indenter assembly into the true triaxial testing instrument, adjust the range of LVDT displacement sensor 301, connect the acoustic emission sensor 220 of the acoustic emission monitoring mechanism and the LVDT displacement sensor 301 of the deformation monitoring mechanism to the data acquisition device, and connect the data acquisition device to the main computer to display the measurement data in real time.

[0110] S6. Remove the connector 500 between the pressure heads and begin the experiment.

[0111] Furthermore, step S6 specifically includes:

[0112] S6.1 Remove the connecting piece 500 between the indenters, and control the true triaxial testing instrument. s 1. s 2 and s A true triaxial pressure loading test was conducted in three directions, and the pressure, acoustic emission, and deformation test data of the rock sample 400 were recorded.

[0113] S6.2 Once the pressure reaches the required value, remove the right pressure head 160. Since the acoustic emission monitoring mechanism is installed on the front pressure head 130, rear pressure head 140, and left pressure head 150, it is unaffected by the right pressure head 160 and can continue to operate. s 1. s Pressure is applied in two directions using a pressure head, and acoustic emission test data is acquired.

[0114] Simultaneously, the left pressure head 150 continues to apply pressure to the rock sample 400, and the sample follower 410 is fixed on the rock sample 400. s Expansion deformation in three directions can still be achieved s The 3-directional deformation monitoring mechanism 330 reacted;

[0115] After a rockburst occurs in rock sample 400, the sample follower 410 detaches from rock sample 400. s Expansion deformation in three directions cannot continue. s The 3-direction deformation monitoring mechanism 330 reacted, and the experiment ended.

[0116] It should be noted that the data acquisition device and the loading system of the true triaxial tester involved in this invention can adopt conventional structures in the field and are not improvements of this invention.

[0117] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", "axial", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0118] In this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "link," and "fix" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0119] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A true triaxial single-sided free-face unloading rockburst simulation test device, characterized in that, The application relates to a rock sample testing device. The upper pressing head, the lower pressing head, the front pressing head, the rear pressing head, the left pressing head and the right pressing head are arranged around a sample placing cavity for placing a rock sample; The front, rear, left and right sides of the upper pressing head are detachably connected with the upper sides of the front pressing head, the rear pressing head, the left pressing head and the right pressing head through connecting members respectively, and the front, rear, left and right sides of the lower pressing head are detachably connected with the lower sides of the front pressing head, the rear pressing head, the left pressing head and the right pressing head through connecting members respectively; A sample follower is embedded in the right side of the rock sample, and a notch is formed in the side wall of the front pressing head, the sample follower extending out of the sample placing cavity through the notch; Mounting holes for mounting acoustic emission monitoring mechanisms are formed in the sides of the front pressing head, the rear pressing head and the left pressing head facing the sample placing cavity, and first wire exit holes are formed in the other sides of the front pressing head, the rear pressing head and the left pressing head and communicated with the mounting holes; The acoustic emission monitoring mechanism comprises: A cylindrical insulating shell, a limiting step is arranged on the inner wall of the first end barrel mouth of the insulating shell so that the inner diameter of the first end barrel mouth of the insulating shell is reduced, and a second wire exit hole is formed in the side wall of the second end barrel mouth of the insulating shell; An acoustic emission sensor is arranged in the first end of the insulating shell, the outer diameter of the acoustic emission sensor is larger than the inner diameter of the first end barrel mouth of the insulating shell, the first end of the acoustic emission sensor is provided with a reduced diameter section, the reduced diameter section is in contact with the corresponding side of the rock sample after extending out of the first end barrel mouth of the insulating shell, and a wire is connected to the second end of the acoustic emission sensor; A tail end pad is fixedly arranged in the second end of the insulating shell, and a wire exit channel is formed in the first end of the tail end pad; A spring is arranged in compression between the second end of the acoustic emission sensor and the first end of the tail end pad, and the wire is led out to the outside of the pressing head in sequence through the inner hole of the spring, the wire exit channel, the second wire exit hole, the first wire exit hole and then outwards; The deformation monitoring mechanism comprises a sigma 1 direction deformation monitoring mechanism, a sigma 2 direction deformation monitoring mechanism and a sigma 3 direction deformation monitoring mechanism, the sigma 1 direction deformation monitoring mechanism is arranged between the upper pressing head and the lower pressing head, the sigma 2 direction deformation monitoring mechanism is arranged between the front pressing head and the rear pressing head respectively, and the sigma 3 direction deformation monitoring mechanism is arranged between the left pressing head and the sample follower; The sigma 3 direction deformation monitoring mechanism comprises: An LVDT displacement sensor is installed on the left pressing head through a sensor clamping seat; A lengthened rod is fixed at the first end of the LVDT displacement sensor, and the second end of the lengthened rod is in contact with the sample follower.

2. The true tri-axial single-sided free-face unloading rockburst simulation test device according to claim 1, characterized in that, The upper and lower pressing heads are staggered in a right front-left rear direction, so that the front and right edges of the rock sample are aligned with the front and right edges of the lower pressing head, and the rear and left edges of the rock sample are aligned with the rear and left edges of the upper pressing head; the front and rear pressing heads are staggered in a left-right direction, and the left and right pressing heads are staggered in a front-rear direction, so that the rear surface of the front pressing head abuts against the front surface of the left pressing head, the right surface of the left pressing head abuts against the left surface of the rear pressing head, the front surface of the rear pressing head abuts against the rear surface of the right pressing head, and the left surface of the right pressing head abuts against the right surface of the front pressing head; meanwhile, the front and right surfaces of the upper pressing head are respectively pressed against the rear and left surfaces of the front and right pressing heads, and the left and rear surfaces of the lower pressing head are respectively supported on the right and front surfaces of the left and rear pressing heads; the rear and left edges of the upper pressing head are aligned with the rear and left edges of the rock sample, and the right and front edges of the lower pressing head are aligned with the right and front edges of the rock sample.

3. The true tri-axial single-sided free-face unloading rockburst simulation test device according to claim 1, characterized in that, Two acoustic emission monitoring mechanisms are respectively arranged on the upper and lower portions of the front, rear and left pressing heads.

4. The true tri-axial single-sided free-face unloading rockburst simulation test device according to claim 1, characterized in that, A screw is threadedly connected to the tail end pad, and the end of the screw penetrates through the tail end pad to press against the insulating shell, so that the insulating shell is deformed and tightly pressed in the mounting hole.

5. The true tri-axial single-sided free-face unloading rockburst simulation test device according to claim 1, characterized in that, The σ1 direction deformation monitoring mechanism and the σ2 direction deformation monitoring mechanism each include: An LVDT displacement sensor is installed on one of the pressing heads through a sensor clamping seat; An extension rod is installed on the other pressing head through an extension rod fixing seat at a first end thereof, and a contact of the LVDT displacement sensor is in contact with a second end of the extension rod.

6. The true tri-axial single-sided free-face unloading rockburst simulation test device according to claim 1, characterized in that, The front, rear, left and right surfaces of the upper pressing head and the upper surfaces of the front, rear, left and right pressing heads are each provided with a jack; the connecting member includes a universal bolt and an internal hexagonal bolt, the head of the universal bolt is provided with a fixing ring, the axis of the fixing ring is perpendicular to the axis of the universal bolt, the tail of the universal bolt is connected to the jack on one of the pressing heads, and the internal hexagonal bolt is connected to the jack on the other pressing head after penetrating through the fixing ring.

7. The true tri-axial single-sided free-face unloading rockburst simulation test device according to claim 5, characterized in that, The sensor clamping seat is provided with a clamping opening, the LVDT displacement sensor is clamped in the clamping opening, and the clamping opening is tightened through a bolt; The first end of the extension rod is fixed with a knurled high nut, and the first end of the extension rod penetrates through the extension rod fixing seat.

8. A true triaxial single-sided free-face unloading rockburst simulation test method, characterized in that, The test device of any one of claims 1-7 is adopted, and the following steps are included: S1. A sample follower is fixed on the right surface of the rock sample; A groove is excavated on the right surface of the rock sample, one end of the sample follower is placed in the groove, the groove is filled with cement mortar, and the cement mortar is polished to be flush with the surface of the rock sample after solidification; S2. The acoustic emission monitoring mechanism is installed in the pressing head; The coupling agent is coated on the inner wall of the insulating shell, the spring is sleeved on the lead wire of the acoustic emission sensor, and the acoustic emission sensor is placed in the insulating shell, the tail end pad is installed in the insulating shell, the lead wire is led out of the insulating shell through the lead wire outlet channel and the second lead wire outlet, then the insulating shell is inserted into the mounting hole of the pressure head, the lead wire is led out of the pressure head to the outside of the pressure head through the first lead wire outlet, and the screw is tightened on the tail end pad, and the insulating shell is tightly pressed in the mounting hole through the screw; After the acoustic emission monitoring mechanism is installed, the reduced diameter section of the acoustic emission sensor is slightly higher than the surface of the pressure head, and when the pressure head and the rock sample are assembled, the rock sample will extrude the reduced diameter section to make it retract to the same level as the surface of the pressure head, and the spring will exert a spring force on the acoustic emission sensor to make the reduced diameter section tightly fit the rock sample; S3. Assemble each pressure head and rock sample; S3.1 Place the lower pressure head, rock sample and upper pressure head in order from bottom to top; S3.2 Apply coupling agent to the position of the acoustic emission sensor on the rock sample, and install the front pressure head, rear pressure head, left pressure head and right pressure head around the front, rear, left and right four sides of the rock sample, install the knuckle bolts on the front, rear, left and right four sides of the upper pressure head, install the inner hexagonal bolts on the four knuckle bolts, and connect the four inner hexagonal bolts with the front pressure head, rear pressure head, left pressure head and right pressure head respectively; Install knuckle bolts on the lower sides of the front pressure head, rear pressure head, left pressure head and right pressure head, install inner hexagonal bolts on the four knuckle bolts, and connect the four inner hexagonal bolts with the front, rear, left and right four sides of the lower pressure head respectively; S4. Install the deformation monitoring mechanism; Install the σ1 direction deformation monitoring mechanism, σ2 direction deformation monitoring mechanism and σ3 direction deformation monitoring mechanism on the corresponding pressure head respectively; S5. Put the pressure head assembly with assembled rock sample, acoustic emission monitoring mechanism and deformation monitoring mechanism into the true triaxial testing instrument, adjust the range of the LVDT displacement sensor, connect the acoustic emission sensor of the acoustic emission monitoring mechanism and the LVDT displacement sensor of the deformation monitoring mechanism with the data acquisition device, and connect the data acquisition device with the host computer to display the measurement data in real time; S6. Remove the connecting parts and start the experiment.

9. The test method of claim 8, wherein, Step S6 is specifically: S6.1 Remove the connecting parts between the pressure heads, control the true triaxial testing instrument, and perform true triaxial pressure loading test in the σ1, σ2 and σ3 directions, and record the pressure and acoustic emission and deformation test data of the rock sample; S6.2 When the pressure increases to the required value, remove the right pressure head. Since the acoustic emission monitoring mechanism is installed on the front pressure head, rear pressure head and left pressure head, the acoustic emission monitoring mechanism is not affected by the right pressure head, and the acoustic emission monitoring mechanism can continue to be pressurized in the pressure heads in the σ1 and σ2 directions and obtain acoustic emission test data; At the same time, the left pressure head continues to give pressure to the rock sample, the sample follower is fixed on the rock sample, and the expansion deformation of the rock sample in the σ3 direction can still be reflected through the σ3 deformation monitoring mechanism; After the rock sample occurs rock burst, the sample follower falls off from the rock sample, the expansion deformation in the σ3 direction cannot continue to be reflected through the σ3 deformation monitoring mechanism, and the experiment is completed.

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