Clamp for fracture test of dangerous rock bridge

Abstract

The invention discloses a clamp for a dangerous rock bridge fracture test, and relates to the field of rock mechanical property testing, the clamp comprises a clamp I mainly composed of a clamping base I, a sliding clamping assembly, a front side plate and a plurality of connecting rods, or a clamp II mainly composed of a clamping base II, a left side plate, a right side plate, a front side plate and a plurality of connecting rods; the clamping base I, the sliding clamping assembly, the front side plate and the connecting rod are connected to form a frame, or the clamping base II, the left side plate, the right side plate, the front side plate and the connecting rod are connected to form a frame. The clamp disclosed by the invention is uniform in lateral constraint, the wedge-shaped nuts and the bolts are adopted at the joints of all the parts, the cushion block and the experimental rock sample can be fixed through the bolts and the wedge-shaped nuts, and the rock sample can be stably clamped under the dynamic and static combined loading condition; a clamp reserved threaded hole is used for installing and protecting auxiliary testing equipment, and the capturing precision of the fracture characteristics of the dangerous rock body rock bridge is ensured; the modular design is adopted, the clamp is assembled according to different test requirements, and the adaptability is high.

Description

Technical Field

[0001] The invention relates to the technical field of rock mechanics testing, in particular to a clamp used for a dangerous rock mass rock bridge fracture test. Background Art

[0002] Karst geological landforms are widespread in southwestern my country, and frequent karst rockfall disasters pose a serious threat to infrastructure safety, livelihood security, and the ecological environment. Regarding infrastructure, rockfalls have caused over 200 railway disruptions in the past five years, resulting in economic losses and impacting transportation efficiency. Regarding livelihoods, rockfalls in Yunnan, Guizhou, and Sichuan provinces caused over 1,300 deaths between 2018 and 2024. Furthermore, rockfalls can block river channels, forming barrier lakes and triggering secondary disasters such as floods and dam failures. According to the 2024 annual report of the China Geological Survey, dynamic disturbances are the primary cause of rockfalls, accounting for a significant proportion. These disturbances can be categorized as natural disturbances such as earthquakes and heavy rain infiltration, and engineering disturbances such as blasting vibrations and traffic loads. The primary cause of rockfalls is the gradual damage and fracture of rock bridges under dynamic disturbances. Therefore, when studying the fracture mechanisms of rock bridges in these dynamic disturbance-dominated collapses, an experimental approach combining dynamic disturbances with static loading is necessary. However, the existing test fixture is unable to achieve stable clamping of rock samples under combined dynamic and static loading conditions, and no space is reserved for the installation of auxiliary testing equipment such as acoustic emission monitoring and high-speed photography, resulting in difficulty in accurately capturing the rock bridge fracture process; at the same time, the bolt connection structure of the fixture has weak resistance to vibration loosening, and it is difficult to adapt to mainstream equipment such as high-voltage servo dynamic triaxial testing machines and electro-hydraulic servo rock multi-functional testing machines at the same time, which restricts the research on the fracture mechanism of dangerous rock bridges under complex stress paths. Summary of the Invention

[0003] The main purpose of the present invention is to provide a fixture for dangerous rock mass rock bridge fracture tests, which is used to solve the problems of uneven lateral constraints of existing traditional fixtures, inability to ensure the stability of rock samples under dynamic disturbance conditions, inability to carry out dangerous rock mass rock bridge fracture tests under dynamic and static combined loading, no installation space reserved for auxiliary testing equipment, inability to collect acoustic emission signals and high-speed cameras under dynamic disturbance, inability to assemble traditional fixtures on demand, weak anti-vibration loosening ability of various connecting components, and low adaptability.

[0004] The technical solution to the above technical problem is: a fixture for a fracture test of a dangerous rock mass rock bridge, comprising a fixture I mainly consisting of a clamping base I, a sliding clamping assembly, a front side plate and a plurality of connecting rods, or a fixture II mainly consisting of a clamping base II, a left side plate, a right side plate, a front side plate and a plurality of connecting rods; The cam is fixedly mounted on the top of the U-shaped support frame, and the cam is fixedly mounted on the top of the U-shaped support frame. The clamping base II is composed of a rear side plate II, a top plate II and a bottom plate II arranged on the same side of the rear side plate II. The top plate II and the bottom plate II are both U-shaped plates and are arranged opposite to each other. A plurality of threaded holes are provided on both sides of the top plate II and the bottom plate II, and some of the threaded holes are used to install auxiliary test equipment. The two sides of the top plate II and the two sides of the bottom plate II are respectively connected to the two sides of the upper part of the front side plate and the two sides of the lower part of the front side plate through connecting rods to form a frame. The upper part and the lower part of the left plate or the right plate are both provided with a plurality of threaded holes. The left plate and the right plate are symmetrically installed on both sides of the clamping base II to form a semi-enclosed structure with the clamping base II. The pad is placed on the bottom plate II, and the rock sample is placed on the pad; The clamping base I or clamping base II and the connecting rod, the left side plate or the right side plate and the connecting rod, the front side plate and the connecting rod, and the U-shaped slider and the clamping plate are all connected by wedge nuts and bolts.

[0005] A further technical solution of the present invention is: two rows of threaded holes are opened on both sides of the top plate I and both sides of the bottom plate I, one row of threaded holes is used for connecting with the connecting rod, and the other row of threaded holes is used for installing auxiliary testing equipment or fixing rock samples or pads by bolts and wedge nuts.

[0006] A further technical solution of the present invention is: two rows of threaded holes are opened on both sides of the top plate II and the bottom plate II, one row of threaded holes is used for connecting with the connecting rod, and the other row of threaded holes is used for installing auxiliary testing equipment or fixing rock samples or pads through bolts and wedge nuts.

[0007] A further technical solution of the present invention is: the mounting groove is at a certain distance from the bottom of the top plate I and the top of the bottom plate I, the depth of the mounting groove is greater than 1 / 4 of the width of the rear side plate I and less than 1 / 3 of the width of the rear side plate I, and the width of the mounting groove is greater than the thickness of the bent part of the clamping plate and less than 1 / 3 of the thickness of the rear side plate I.

[0008] A further technical solution of the present invention is that the number of threaded holes opened on one side of the U-shaped slider is greater than or equal to two.

[0009] A further technical solution of the present invention is: the clamping plate includes a symmetrical left clamping plate and a right clamping plate, the main panel of the left clamping plate or the right clamping plate extends downward and forms a step, the upper surface of the step is used to support the U-shaped slider, the U-shaped slider is fixedly connected to the main panel of the left clamping plate or the right clamping plate, and the side of the step is used to limit the pad.

[0010] A further technical solution of the present invention is: a row of threaded holes is opened on the side surface of the step, and bolts pass through the threaded holes and cooperate with wedge nuts to fix the spacer.

[0011] A further technical solution of the present invention is that the lateral distance between the left splint or the right splint and the pad is greater than the thickness of the side wall of the bottom plate I.

[0012] The beneficial effects of the present invention are: 1. Uniform lateral restraint and stable clamping The clamping base I, the clamping plate and the front side plate of the clamp I of the present invention, or the clamping base II, the left side plate, the right side plate and the front side plate of the clamp II are all combined to form a structure capable of bearing force on six sides. For example, the front side plate is in contact and fixed with the Y-axis push head of the high-pressure servo dynamic true triaxial testing machine; the clamping plate or the left side plate and the right side plate are in contact and fixed with the X-axis push head of the high-pressure servo dynamic true triaxial testing machine; this ensures uniform lateral constraint of the clamp, thereby achieving stable clamping of the rock sample under dynamic and static combined loading conditions; When using fixture I, the rock sample is placed on the U-shaped slider, and the top plate I, rear side plate I and U-shaped slider limit the top, bottom, left, right and rear sides of the rock sample, and can also be fixed by bolts and wedge nuts. The pad is placed on the bottom plate I, and the bottom plate I, rear side plate I and U-shaped slider limit the top, bottom, left, right and rear sides of the pad, and can also be fixed by bolts and wedge nuts, making the clamp more stable in holding the rock sample. When using the clamp II, the pad is placed on the bottom plate II, and the rock sample is placed directly on the pad. The clamping base II, the left plate and the right plate limit the top, bottom, left, right and back sides of the rock sample and pad assembly. In addition, the rock sample and the pad can be fixed by bolts and wedge nuts, making the clamp more stable in holding the rock sample. In addition, the innovative wedge-shaped nut and bolt connection structure utilizes its dynamic self-locking characteristics to significantly enhance the anti-vibration loosening ability of each connecting component; Therefore, the present invention can carry out dangerous rock mass rock bridge fracture tests on a high-pressure servo dynamic true triaxial testing machine and can ensure the stability of rock samples under dynamic disturbance conditions.

[0013] 2. High adaptability The present invention adopts a modular design and adopts different installation methods according to the characteristics of different testing machines. For example, when using the present invention to conduct experiments on an electro-hydraulic servo rock multifunctional testing machine, a fixture I without left and right plates can be used. Alternatively, corresponding accessories can be selectively installed according to different experimental purposes to achieve rapid adaptation to testing machines of different specifications (such as a high-voltage servo dynamic triaxial testing machine, an electro-hydraulic servo rock multifunctional testing machine, etc.); By adjusting the U-shaped slider, the spacer, the wedge-shaped nut, and the bolt, dynamic disturbance experiments on rock samples of different sizes and shapes, as well as dynamic disturbance experiments on rock samples at different rock bridge positions, can be performed, thereby improving the adaptability of the present invention. In addition, the connection structure of wedge nuts and bolts uses its dynamic self-locking characteristics to significantly enhance the anti-vibration loosening ability of each connecting component, and can be well adapted to mainstream equipment such as high-voltage servo dynamic triaxial testing machines and electro-hydraulic servo rock multi-functional testing machines.

[0014] 3. Ensure signal capture accuracy The top plate or bottom plate of the present invention has some threaded holes reserved for installing auxiliary test equipment, for example, installing acoustic emission sensors. The threaded holes better fix and protect the acoustic emission sensors, ensuring the accuracy, efficiency and safety of acoustic signal collection during the rock mass and rock bridge fracture test; and the design of the clamp I reserves space for high-speed photography, which is convenient for accurately capturing the dynamic fracture process of the rock bridge, thereby constructing a multi-source monitoring data synchronous acquisition system, and improving the capture accuracy of the fracture characteristics of dangerous rock masses and rock bridges under dynamic disturbances. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings that constitute part of the specification of this application are used to provide further explanation of the present invention. The exemplary embodiments of the present invention and their descriptions are used to understand the present invention and do not constitute improper limitations on the present invention.

[0016] Figure 1 This is a three-dimensional schematic diagram of a fixture for a dangerous rock mass rock bridge fracture test according to Example 1; Figure 2 This is a three-dimensional schematic diagram of a fixture for a dangerous rock mass rock bridge fracture test according to Example 1 after a rock sample and a spacer are placed; Figure 3 This is a three-dimensional schematic diagram of a fixture for a dangerous rock mass rock bridge fracture test as described in Example 2; Figure 4 This is a three-dimensional schematic diagram of a fixture for a dangerous rock mass rock bridge fracture test described in Example 2 after a rock sample and a spacer are placed; Figure 5 This is a three-dimensional schematic diagram of a fixture for a dangerous rock mass rock bridge fracture test as described in Example 3; Figure 6-1This is a three-dimensional schematic diagram of a fixture for a dangerous rock mass rock bridge fracture test described in Example 3 after a rock sample and a spacer are placed; Figure 6-2 for Figure 6-1 Schematic diagram of the enlarged structure at A in the middle; Figure 7-1 Schematic diagram of a three-dimensional view of a clamping base I of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 7-2 for Figure 7-1 Schematic diagram of the enlarged structure at B in the middle; Figure 8 This is a three-dimensional schematic diagram of a U-shaped slider of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 9 This is a three-dimensional schematic diagram of a clamping plate of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 10 Schematic diagram of a three-dimensional view of a clamping base II of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 11 This is a three-dimensional schematic diagram of the left side plate or the right side plate of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 12 This is a three-dimensional schematic diagram of a connecting rod of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 13 This is a three-dimensional schematic diagram of the front side plate of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 14 This is a three-dimensional schematic diagram of a wedge-shaped nut and a bolt of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment; Figure 15 This is a schematic structural diagram of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment, wherein a static loading test is performed on a high-pressure servo dynamic true triaxial testing machine; Figure 16 is the loading path diagram of the static loading test; Figure 17 This is a schematic structural diagram of a fixture for a dangerous rock mass rock bridge fracture test according to an embodiment, wherein a dynamic and static combined loading test is performed on a high-pressure servo dynamic true triaxial testing machine; Figure 18 Loading path diagram for dynamic and static combined loading test.

[0017] In the attached figure: 11-Clamping base I; 111-Rear side plate I; 112-Top plate I; 113-Bottom plate I; 114-Mounting slot; 12-U-shaped slider; 13-Clamping plate; 131-Step; 21-Clamping base II; 211-Rear side plate II; 212-Top plate II; 213-Bottom plate II; 22-Left side plate; 23-Right side plate; 31-Connecting rod; 41-Front side plate; 51-Threaded hole; 52-Wedge nut and bolt; 61-Spacer; 71-Loading spacer; 81-Rock sample; 9-High-pressure servo dynamic true triaxial testing machine; 91-X-axis loading pusher; 92-Y-axis loading pusher; 93-Z-axis loading pusher; 94-Movable trolley bottom plate; 95-Z-axis disturbance rod; L1-installation groove depth; L2-installation groove width; W-rear side plate I width; D-rear side plate I thickness; d-clamping plate bending part thickness; H-lateral distance between the left or right clamping plate and the pad; h-side wall thickness of the bottom plate I. DETAILED DESCRIPTION

[0018] In order to make the purpose of the invention, technical features and implementation effects of the technical solution of the present invention clearer, typical embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] It should be noted that the specific embodiments listed are merely representative implementations for facilitating understanding of the present invention and are not intended to be exhaustive of the implementation forms of the technical solutions. For those skilled in the art, all technical implementations obtained through conventional technical means or equivalent substitutions based on the technical concepts disclosed in the present invention, without departing from the scope of protection defined in the claims, should be deemed to fall within the legal protection scope of the present invention.

[0020] It is particularly pointed out that the detailed description of the embodiments shown in the drawings of the specification is intended to assist in understanding the core innovations of the present invention, rather than to constitute any limitation on the scope of protection of the patent rights.

[0021] In addition, it should be noted that the expressions "comprising" and "including" and similar expressions used in this application are open-ended restrictive terms. Their meaning is to indicate that in addition to the constituent elements explicitly listed, the technical solution may also be compatible with additional elements that are not directly stated in the text but conform to technical logic, or components that are necessarily present during the implementation of the technical solution. The scope of application of such terms should not be interpreted narrowly in the claims. Their legal connotations should be based on the inclusive definition understood by those skilled in the art in combination with technical common sense. Example 1

[0022] like Figures 1-2 、 Figures 7-1 to 9 、 Figures 12-14As shown, a fixture for a dangerous rock mass rock bridge fracture test includes a fixture I mainly composed of a clamping base I 11, a sliding clamping assembly, a front side plate 41 and a plurality of connecting rods 31; The clamping base I11 is composed of a rear side plate I111, a top plate I112 and a bottom plate I113 arranged on the same side of the rear side plate I111. The rear side plate I111 is symmetrically provided with mounting grooves 114 on both sides. The mounting grooves 114 are located in the middle of the rear side plate I111 and are a certain distance away from the bottom of the top plate I and the top of the bottom plate I. The depth L1 of the mounting groove is greater than 1 / 4 of the width W of the rear side plate I and less than 1 / 3 of the width W of the rear side plate I. The width L2 of the mounting groove is greater than the thickness d of the bent portion of the clamping plate and less than 1 / 3 of the thickness D of the rear side plate I, thereby ensuring the rigidity of the rear side plate I111. The top plate I 112 and the bottom plate I 113 are both U-shaped plates and are arranged opposite to each other. Two rows of threaded holes 51 are opened on both sides of the top plate I 112 and the bottom plate I 113. One row of threaded holes is used to connect with the connecting rod 31, and the other row of threaded holes is used to install auxiliary test equipment or fix the rock sample 81 or the spacer 61 by bolts and wedge nuts. The threaded holes better fix and protect the auxiliary test equipment, such as the acoustic emission sensor, to ensure the accuracy, efficiency and safety of the acoustic signal collection during the rock bridge fracture test. The sliding clamping assembly includes a U-shaped slider 12 and a clamping plate 13 symmetrically mounted on both sides of the U-shaped slider 12. A plurality of threaded holes 51 are opened on both sides of the U-shaped slider 12. The number of threaded holes opened on one side of the U-shaped slider 12 is greater than or equal to two. Preferably, the number of threaded holes opened on one side of the U-shaped slider 12 is six to ensure the stability of the connection between the U-shaped slider and the clamping plate 13. The clamping plate 13 includes a symmetrical left clamping plate and a right clamping plate. The left clamping plate or the right clamping plate is an L-shaped plate. A plurality of threaded holes are opened on the main panel of the left clamping plate or the right clamping plate, and the main panel extends downward to form a step 131. The upper surface of the step 131 is used to support the U-shaped slider 12. The U-shaped slider 12 is fixedly connected to the main panel of the left clamping plate or the right clamping plate. A row of threaded holes 51 are opened on the side of the step 131. Bolts pass through these threaded holes and cooperate with wedge-shaped nuts to fix the spacer 61. The bent portion of the left or right splint is slidably connected to the mounting groove 114 of the clamping base Ⅰ 11; the lateral distance H between the left or right splint and the pad is greater than the side wall thickness h of the bottom plate Ⅰ (reference Figure 6-2 ).

[0023] Several threaded holes are formed on the connecting rod 31 body and on both sides of the front side plate 41. The two sides of the top plate I 112 and the two sides of the bottom plate I 113 are respectively connected to the two sides of the upper part of the front side plate 41 and the two sides of the lower part of the front side plate 41 through the connecting rod 31 to form a frame. The pad 61 is placed on the bottom plate I 113, and the rock sample 81 is placed on the U-shaped slider 12. The six sides of the clamp I are evenly stressed, so that the rock sample can be stably clamped under dynamic and static combined loading conditions. The clamping base Ⅰ11 and the connecting rod 31, the front side plate 41 and the connecting rod 31, and the U-shaped slider 12 and the clamping plate 13 are all connected by wedge nuts and bolts to improve the anti-vibration loosening ability of the connection between the components; The bolts are M12 hexagonal head bolts with nominal lengths of 50 mm and 30 mm. The bolts can not only connect the various components but also adjust and fix the spacer 61 or the rock sample 81 to make the clamping of the fixture I more stable. Example 2

[0024] like Figures 3-4 、 Figures 10-14 As shown, a fixture for a fracture test of a dangerous rock mass rock bridge includes a fixture II mainly composed of a clamping base II 21, a left side plate 22, a right side plate 23, a front side plate 41 and a plurality of connecting rods 31; The clamping base II 21 is composed of a rear side plate II 211, a top plate II 212 and a bottom plate II 213 arranged on the same side of the rear side plate II 211. The top plate II 212 and the bottom plate II 213 are both U-shaped plates and are arranged opposite to each other. Two rows of threaded holes 51 are opened on both sides of the top plate II 212 and the bottom plate II 213. One row of threaded holes is used to connect with the connecting rod 31, and the other row of threaded holes is used to install auxiliary test equipment or fix the rock sample 81 or the spacer 61 by bolts and wedge nuts. The threaded holes better fix and protect the auxiliary test equipment, such as the acoustic emission sensor, to ensure the accuracy, efficiency and safety of the acoustic signal collection during the rock bridge fracture test. The two sides of the top plate II 212 and the two sides of the bottom plate II 213 are respectively connected to the two sides of the upper part of the front side plate 41 and the two sides of the lower part of the front side plate 41 through the connecting rods 31 to form a frame. The upper and lower parts of the left side plate 22 or the right side plate 23 are each provided with a plurality of threaded holes 51. Preferably, the left side plate 22 or the right side plate 23 has six threaded holes. The left side plate 22 and the right side plate 23 are symmetrically mounted on both sides of the clamping base II 21 to form a semi-enclosed structure with the clamping base II 21. The pad 61 is placed on the bottom plate II 213, and the rock sample 81 is placed on the pad 61. The six sides of the clamp II are evenly stressed, thereby achieving stable clamping of the rock sample under dynamic and static combined loading conditions. The clamping base II 21 and the connecting rod 31, the left side plate 22 or the right side plate 23 and the connecting rod 31, and the front side plate 41 and the connecting rod 31 are all connected by wedge nuts and bolts to improve the anti-vibration loosening ability of the connection between each component; The bolts are M12 hexagonal head bolts with nominal lengths of 50 mm and 30 mm. The bolts can not only connect the various components but also adjust and fix the spacer 61 or the rock sample 81 to make the clamping of the fixture II more stable. Example 3

[0025] As a variation of the first embodiment, this embodiment further includes a left side plate 22 and a right side plate 23 on the basis of the first embodiment, and the specific structure is as follows: like Figures 5 to 9 、 Figures 11-14 As shown, a fixture for a fracture test of a dangerous rock mass rock bridge includes a fixture III mainly composed of a clamping base I 11, a sliding clamping assembly, a left side plate 22, a right side plate 23, a front side plate 41 and a plurality of connecting rods 31; The clamping base I11 is composed of a rear side plate I111, a top plate I112 and a bottom plate I113 arranged on the same side of the rear side plate I111. The rear side plate I111 is symmetrically provided with mounting grooves 114 on both sides. The mounting grooves 114 are located in the middle of the rear side plate I111 and are a certain distance away from the bottom of the top plate I and the top of the bottom plate I. The depth L1 of the mounting groove is greater than 1 / 4 of the width W of the rear side plate I and less than 1 / 3 of the width W of the rear side plate I. The width L2 of the mounting groove is greater than the thickness d of the bent portion of the clamping plate and less than 1 / 3 of the thickness D of the rear side plate I, thereby ensuring the rigidity of the rear side plate I111. The top plate I 112 and the bottom plate I 113 are both U-shaped plates and are arranged opposite to each other. Two rows of threaded holes 51 are formed on both sides of the top plate I 112 and the bottom plate I 113. One row of threaded holes is used for connection with the connecting rod 31, and the other row of threaded holes is used for installing auxiliary test equipment or fixing the rock sample 81 or the spacer 61 by bolts and wedge nuts. The threaded holes can better fix and protect the auxiliary test equipment, such as the acoustic emission sensor, to ensure the accuracy, efficiency and safety of the acoustic signal collection during the rock bridge fracture test. The sliding clamping assembly includes a U-shaped slider 12 and a clamping plate 13 symmetrically mounted on both sides of the U-shaped slider 12. A plurality of threaded holes 51 are opened on both sides of the U-shaped slider 12. The number of threaded holes opened on one side of the U-shaped slider 12 is greater than or equal to two. Preferably, the number of threaded holes opened on one side of the U-shaped slider 12 is six to ensure the stability of the connection between the U-shaped slider and the clamping plate 13. The clamping plate 13 includes a symmetrical left clamping plate and a right clamping plate. The left clamping plate or the right clamping plate is an L-shaped plate. A plurality of threaded holes 51 are opened on the main panel of the left clamping plate or the right clamping plate, and the main panel extends downward to form a step 131. The upper surface of the step 131 is used to support the U-shaped slider 12. The U-shaped slider 12 is fixedly connected to the main panel of the left clamping plate or the right clamping plate. A row of threaded holes is opened on the side of the step 131. Bolts pass through these threaded holes and cooperate with wedge-shaped nuts to fix the spacer 61. The bent portion of the left or right clamping plate is slidably connected to the mounting groove 114 of the clamping base Ⅰ 11; the lateral distance H between the left or right clamping plate and the pad is greater than the side wall thickness h of the bottom plate Ⅰ; The connecting rod 31 body and both sides of the front side plate 41 are provided with a plurality of threaded holes. The two sides of the top plate I 112 and the two sides of the bottom plate I 113 are respectively connected to the two sides of the upper part of the front side plate 41 and the two sides of the lower part of the front side plate 41 through the connecting rod 31 to form a frame. The upper and lower parts of the left side plate 22 or the right side plate 23 are each provided with a plurality of threaded holes 51. Preferably, the left side plate 22 or the right side plate 23 has six threaded holes. The left side plate 22 and the right side plate 23 are symmetrically mounted on both sides of the clamping base Ⅰ 11 to form a semi-enclosed structure with the clamping base Ⅰ 11. The pad 61 is placed on the bottom plate Ⅰ 113, and the rock sample 81 is placed on the U-shaped slider 12. The six sides of the clamp III are evenly stressed, thereby achieving stable clamping of the rock sample under dynamic and static combined loading conditions. The clamping base Ⅰ11 and the connecting rod 31, the left side plate 22 or the right side plate 23 and the connecting rod 31, the front side plate 41 and the connecting rod 31, and the U-shaped slider 12 and the clamping plate 13 are all connected by wedge nuts and bolts to improve the anti-vibration loosening ability of the connection between each component; The bolts are M12 hexagonal head bolts with nominal lengths of 50 mm and 30 mm. The bolts can not only connect the various components but also adjust and fix the spacer 61 or the rock sample 81 to make the clamping of the fixture III more stable.

[0026] The following describes the assembly process of the fixture III in detail, taking the fixture for the fracture test of a dangerous rock mass and a rock bridge in Example 3 as an example.

[0027] 1. Assembly process of fixture III and installation process of rock sample: Place the clamping base I11 on the predetermined movable cart bottom plate of the high-pressure servo dynamic true triaxial testing machine, and then place the pad 61 into the groove of the bottom plate I113; Furthermore, a U-shaped slider 12 is placed on the pad 61; Furthermore, the left and right clamping plates are respectively installed into the mounting grooves 114 of the rear side plate I 111 , while ensuring that the left and right clamping plates are completely fitted with the U-shaped slider 12 ; Furthermore, the left and right clamping plates are simply connected to the U-shaped slider 12 with bolts and wedge nuts. The bolts cannot be tightened at this time to facilitate the installation of the rock sample 81 in the next step. Further, the rock sample 81 is placed in the U-shaped slider 12, and the positions of the U-shaped slider 12, the spacer 61, the left clamping plate, and the right clamping plate are fine-tuned. When the optimal position is reached, the bolts are tightened to ensure that the bolts and the wedge nuts are fully fitted with the left clamping plate and the right clamping plate. Furthermore, an acoustic emission system probe is installed at the threaded hole of the top plate I 112, and then the microseismic monitoring instrument is connected to the strain gauge on the rock sample 81. At this time, the installation of the rock sample 81 is completed. Furthermore, the fixture III is mounted in contact with the high-voltage servo dynamic true triaxial testing machine to fix the left side plate 22, the right side plate 23, the connecting rod 31 and the front side plate 41; Install from bottom to top. First, align the lower connecting rod 31 with the threaded hole position of the bottom plate I 113, then align the threaded holes of the left side plate 22 and the right side plate 23 with the threaded holes of the connecting rod 31 and the bottom plate I 113, and then install the bolts and wedge nuts. At this time, they do not need to be fully tightened. Adjust the position of the left side plate 22 and the right side plate 23 to ensure that the threaded holes of the top plate I 112 are aligned with the threaded holes of the left side plate 22 and the right side plate 23; then install the connecting rod 31 at the top plate I 112. After the threaded holes of the left side plate 22 and the right side plate 23 are aligned with the threaded holes of the connecting rod 31 and the top plate I 112, install the bolts and wedge nuts. At this time, all bolts on the left side plate 22 and the right side plate 23 can be tightened; Next, install the front side panel 41. At this time, install the front side panel 41 from top to bottom to prevent it from falling over. Align the threaded holes on the upper portion of the front side panel 41 with the threaded holes of the corresponding connecting rods 31. Then install the bolts and wedge nuts. Do not tighten them completely at this time. Adjust the position of the front side panel 41 to ensure that the threaded holes on the lower portion of the front side panel 41 are aligned with the threaded holes of the corresponding connecting rods 31. Then install the bolts and wedge nuts. At this time, you can tighten all the bolts on the front side panel 41. At this point, the assembly of the entire fixture III and the installation of the rock sample have been completed.

[0028] The following takes the fixture for the fracture test of a dangerous rock bridge in Example 1 as an example to specifically describe the implementation process of the fracture test of a rock bridge using the fixture I.

[0029] This experiment uses a high-pressure servo dynamic triaxial testing machine to carry out static loading tests and static-dynamic combined loading tests on dangerous rock samples containing prefabricated structural surfaces, aiming to study the fracture mechanism of rock bridges under conditions of different structural surface penetration lengths, structural surface penetration positions, and structural surface inclinations. However, this experiment will not discuss in detail the fracture mechanism of rock bridges under three different working conditions. It will only list the entire process of installing this application and the test rock sample on the high-pressure servo dynamic triaxial testing machine and other loading processes. The pads in this experiment can be used to adjust the height of the U-shaped slider without being restricted by the above-mentioned pads, but they must meet the strength and stiffness requirements; Before the experiment, rock samples were prepared. Limestone was selected as the rock sample and cut into semi-finished test rock samples with an external size of 160mm×100mm×100mm (length×width×height) using a high-pressure water gun. The semi-finished test rock samples were then carefully cut into finished rock samples with different structural surface penetration lengths, structural surface penetration positions, and structural surface inclinations according to the experimental requirements. The strain gauges were then installed on the rock bridge section. Assemble fixture I by referring to the assembly process of fixture III (the difference between fixture I and fixture III is that fixture I does not have the left side plate 22 and the right side plate 23), and install the rock sample.

[0030] 1. Static loading test First, the entire fixture I with the rock sample installed is pushed into the high-pressure servo dynamic triaxial testing machine 9 through a predetermined movable trolley bottom plate, and the position is adjusted; like Figure 15 As shown, the loading pad 71 is placed on the rock sample, and the loading pad 71 is directly below the Z-axis loading push head 93 of the high-pressure servo dynamic triaxial testing machine; Furthermore, the X-axis loading pusher 91 of the high-pressure servo dynamic triaxial testing machine is brought into contact with the left and right clamping plates respectively, and the movable trolley bottom plate 94 is adjusted upward so that the Z-axis loading pusher 93 is in contact with the loading pad 71, and a pre-load of 2-5 kN is applied; Further, the Y-axis loading pusher head 92 is adjusted to contact the rear side plate I and the front side plate respectively, and a force of 2-5 kN is pre-applied to clamp the fixture I; Furthermore, other operations of the high-pressure servo dynamic triaxial testing machine were completed before the experiment, including increasing the oil pressure, installing the LVDT strain gauge, and turning on the preset high-speed camera; Furthermore, a static loading test was started, where a linearly increasing load was applied to the Z-axis loading pusher head, using displacement control, and the loading speed was v =0.02mm / min, the experimental loading path is as follows Figure 16 , load until the rock bridge is completely broken, and obtain the peak load of static loading F u The acoustic, optical and mechanical information of the test process are monitored through acoustic emission monitoring systems, high-speed cameras and LVDT strain gauges.

[0031] 2. Dynamic and static combined loading test Push the entire fixture I with the rock sample installed into the high-pressure servo dynamic triaxial testing machine 9 through the predetermined movable trolley bottom plate and adjust the position; like Figure 17 As shown, the loading pad 71 is placed on the rock sample, and the loading pad 71 is directly below the Z-axis loading push head 93 of the high-pressure servo dynamic triaxial testing machine; Furthermore, the X-axis loading pusher 91 of the high-pressure servo dynamic triaxial testing machine is brought into contact with the left and right clamping plates respectively, and the movable trolley bottom plate 94 is adjusted upward so that the Z-axis loading pusher 93 is in contact with the loading pad 71, and a pre-load of 2-5 kN is applied; Further, the Y-axis loading pusher head 92 is adjusted to contact the rear side plate I and the front side plate respectively, and a force of 2-5 kN is pre-applied to clamp the fixture I; Further, the Z-axis disturbance rod 95 is placed into a predetermined position in the Z-axis loading pusher head 93; Furthermore, other operations of the high-pressure servo dynamic triaxial testing machine were completed before the experiment, including increasing the oil pressure, installing the LVDT strain gauge, and turning on the preset high-speed camera; Furthermore, turn on the control switch for the Z-axis disturbance, click on the control cabinet disturbance to open the oil, and click on the pressure after an interval of 10-15 seconds to apply a static load to the Z-axis loading push head. Use displacement control and the loading speed is v =0.02mm / min, loaded to the set value of 0.7 F u , then remain unchanged; Then, the cyclic disturbance load was added, and the dynamic disturbance loading was realized by controlling the Z-axis disturbance rod through software. The disturbance frequency was 10 Hz and the disturbance amplitude was 0.05. F u. ; After the first disturbance, if the rock bridge does not break, continue to add static load to 0.75 F u. , and then continue to apply the disturbance load, and so on. The experimental loading path is as follows Figure 18 , until the specimen rock bridge breaks; Furthermore, if the rock sample is damaged, the pressurization process of the Z-axis disturbance rod 95 in the Z-axis loading pusher 93 must be stopped first, and then the force of other subsequent loading pushers can be unloaded.

[0032] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the invention.

Claims

1. A fixture for dangerous rock mass rock bridge fracture test, characterized by: It comprises a clamp I mainly composed of a clamping base I (11), a sliding clamping assembly, a front side plate (41) and a plurality of connecting rods (31), or a clamp II mainly composed of a clamping base II (21), a left side plate (22), a right side plate (23), a front side plate (41) and a plurality of connecting rods (31); The clamping base I (11) is a whole composed of a rear side plate I (111), a top plate I (112) and a bottom plate I (113) arranged on the same side of the rear side plate I (111), and the rear side plate I (111) has mounting grooves (114) symmetrically opened on both sides. The top plate I (112) and the bottom plate I (113) are both U-shaped plates and are arranged opposite to each other. Both sides of the top plate I (112) and the bottom plate I (113) have a plurality of threaded holes, and some of the threaded holes are used to install auxiliary test equipment. The sliding clamping assembly includes a U-shaped slider (12), a clamping plate (13) symmetrically installed on both sides of the U-shaped slider (12), and a plurality of threaded holes on both sides of the U-shaped slider (12). The clamping plate (13) is an L-shaped plate. A plurality of threaded holes are opened on the main panel of the clamping plate (13) and fixedly connected to the U-shaped slider (12). The bent portion of the clamping plate (13) is slidably connected to the mounting groove (114) of the clamping base I (11). A plurality of threaded holes are opened on the main body of the connecting rod (31) and on both sides of the front side plate (41). Both sides of the top plate I (112) and both sides of the bottom plate I (113) are connected to both sides of the upper part of the front side plate (41) and both sides of the lower part of the front side plate (41) through the connecting rod (31) to form a frame. The rock sample (81) is placed on the U-shaped slider (12), and the pad (61) is placed on the bottom plate I (113); The clamping base II (21) is composed of a rear side plate II (211), a top plate II (212) and a bottom plate II (213) arranged on the same side of the rear side plate II (211). The top plate II (212) and the bottom plate II (213) are both U-shaped plates and are arranged opposite to each other. A plurality of threaded holes are opened on both sides of the top plate II (212) and the bottom plate II (213), and some of the threaded holes are used to install auxiliary test equipment. The two sides of the top plate II (212) and the two sides of the bottom plate II (213) are divided into The left side plate (22) and the right side plate (23) are connected to the upper sides of the front side plate (41) and the lower sides of the front side plate (41) through connecting rods (31) to form a frame. The upper and lower parts of the left side plate (22) or the right side plate (23) are both provided with a plurality of threaded holes. The left side plate (22) and the right side plate (23) are symmetrically mounted on both sides of the clamping base II (21) to form a semi-enclosed structure with the clamping base II (21). The pad (61) is placed on the bottom plate II (213), and the rock sample (81) is placed on the pad (61); The clamping base I (11) or the clamping base II (21) and the connecting rod (31), the left side plate (22) or the right side plate (23) and the connecting rod (31), the front side plate (41) and the connecting rod (31), and the U-shaped slider (12) and the clamping plate (13) are all connected by wedge nuts and bolts.

2. The fixture for dangerous rock mass rock bridge fracture test according to claim 1, characterized in that: Two rows of threaded holes (51) are provided on both sides of the top plate I (112) and the bottom plate I (113), one row of threaded holes is used for connection with the connecting rod (31), and the other row of threaded holes is used for installing auxiliary test equipment or fixing the rock sample (81) or the spacer (61) by matching bolts and wedge nuts.

3. The fixture for dangerous rock mass rock bridge fracture test according to claim 1, characterized in that: Two rows of threaded holes (51) are provided on both sides of the top plate II (212) and the bottom plate II (213), one row of threaded holes is used for connection with the connecting rod (31), and the other row of threaded holes is used for installing auxiliary test equipment or fixing the rock sample (81) or the spacer (61) by matching bolts and wedge nuts.

4. The fixture for dangerous rock mass rock bridge fracture test according to claim 1, characterized in that: The mounting groove (114) is at a certain distance from the bottom of the top plate I and the top of the bottom plate I, the mounting groove depth (L1) is greater than 1 / 4 of the width (W) of the rear side plate I and less than 1 / 3 of the width (W) of the rear side plate I, and the mounting groove width (L2) is greater than the thickness (d) of the bent portion of the clamping plate and less than 1 / 3 of the thickness (D) of the rear side plate I.

5. The fixture for dangerous rock mass rock bridge fracture test according to claim 1, characterized in that: The number of threaded holes (51) opened on one side of the U-shaped slider (12) is greater than or equal to two.

6. The fixture for dangerous rock mass rock bridge fracture test according to claim 1, characterized in that: The clamping plate (13) includes a symmetrical left clamping plate and a right clamping plate. The main panel of the left clamping plate or the right clamping plate extends downward to form a step (131). The upper surface of the step (131) is used to support the U-shaped slider (12). The U-shaped slider (12) is fixedly connected to the main panel of the left clamping plate or the right clamping plate. The side of the step (131) is used to limit the pad (61).

7. The fixture for dangerous rock mass rock bridge fracture test according to claim 6, characterized in that: A row of threaded holes (51) is formed on the side of the step (131), and bolts pass through the threaded holes and cooperate with wedge-shaped nuts to fix the spacer (61).

8. The fixture for dangerous rock mass and rock bridge fracture test according to claim 6, characterized in that: The lateral distance (H) between the left or right splint and the pad is greater than the side wall thickness (h) of the bottom plate I.

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