A device and method for impact fracture experiment of plate-shaped rock under two-dimensional static load

Abstract

The application discloses a kind of two-dimensional static load under plate rock impact fracture experimental device and method, belong to rock mechanics experimental field.The plate rock dynamic and static loading fracture experimental device is carried out by design, including the steps of preparing test instrument, installing sample, setting experimental parameters, starting experiment and data image processing;Plate rock dynamic and static loading fracture experimental device includes Hopkinson pressure bar experimental system, axial static load loading system, lateral static load loading system, plate rock sample and crack real-time monitoring system, etc.The device can adapt to any placed inclination of plate rock sample during experiment without affecting the independent application of axial static load and impact dynamic load on its left and right ends and lateral static load on its upper and lower ends, as well as the arrangement of monitoring system.It is simple in structure, easy to disassemble and assemble, highly adaptable, easy to use, and can meet the requirements of two-dimensional static load and impact dynamic load coupling under plate rock sample dynamic and static mechanical property experiment and non-contact real-time monitoring of fracture process.

Description

Technical Field

[0001] This invention belongs to the field of rock mechanics experiments, and specifically relates to a two-dimensional static load test apparatus and method for impact fracture of plate-shaped rocks. Background Technology

[0002] Stress is the driving force behind rock mass disasters. Rock mass instability is the process by which cracks initiate, propagate, and penetrate under the drive of stress, forming macroscopic rupture.

[0003] Currently, hard rock mines commonly employ the drill-and-blast method. In addition to the static load of in-situ stress, the rock mass is also subjected to the dynamic load of surrounding explosives. Under drill-and-blast conditions, the stress pattern of deep rock masses is "high-stress static load + strong dynamic disturbance." Therefore, studying the fracture evolution process of rocks under coupled dynamic and static loading is crucial. To observe the crack propagation process, samples are typically fabricated into thin plates for experiments, as surface cracks in thick samples cannot accurately reflect the internal fracture development. Therefore, research usually involves preparing thin-plate samples with fractures or pores for dynamic and static rock mechanics experiments to explore the fracture evolution mechanism of fractured rock masses and surrounding rock in hard rock tunnels. Patent CN112284922A discloses a high-temperature triaxial dynamic-static combined loading device for coal and rock masses, which uses a servo control system to achieve dynamic-static coupling loading under axial low strain rate dynamic load and water medium confining pressure for cylindrical specimens; Patents (CN1731133A, CN100397063C) disclose a Hopkinson bar test system that can perform one-dimensional dynamic impact tests under one-dimensional static load and one-dimensional dynamic impact tests under three-dimensional static load (pseudo-triaxial) on cylindrical specimens; Patent CN1102860 Patent 28A discloses a multi-dimensional dynamic-static combined loading rock mechanics experimental device, capable of performing one-dimensional dynamic impact tests on cuboid specimens under one, two, and three-dimensional static loads; Patent CN114778344A discloses a three-dimensional static and one-dimensional dynamic combined loading experimental device for anchored solids using a drop hammer system and a true triaxial system; Patent CN109406311A also discloses a true triaxial dynamic-static combined loading Hopkinson bar system, capable of simultaneously applying dynamic and static loads in three directions to cubic specimens in three dimensions. As can be seen, the above patents achieve one-dimensional to three-dimensional dynamic-static combined loading for cylindrical and cubic specimens, but are not suitable for one-dimensional dynamic impact fracture tests under two-dimensional static loads on thin plate specimens. This is because the plate surface of the thin plate specimen is fixed and difficult to adjust after being clamped in the above devices, resulting in limited space and making it unsuitable for real-time crack monitoring systems such as high-speed cameras and digital imaging systems at different distances. Therefore, there is an urgent need to invent a two-dimensional static load-bearing experimental device and method for impact fracturing of plate-shaped rocks, so as to provide sufficient guarantee for experimental research on the fracturing evolution behavior of roadway surrounding rock. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this paper provides a two-dimensional static load impact fracture test apparatus and method for plate-shaped rocks. This apparatus can adjust the inclination angle of the rock sample plate under two-dimensional static and dynamic loads, allowing the plate surface to face in any direction. This provides spatial conditions for real-time monitoring of dynamic crack development in the sample, solving the technical challenges of simultaneous loading and unloading of two-dimensional static and dynamic impact loads on plate-shaped rocks and real-time monitoring of rock damage and fracture during the experiment. It also enables impact fracture tests of plate-shaped rocks under different dynamic loads under varying two-dimensional static loads. The apparatus is simple in structure, easy to use, and highly practical.

[0005] To achieve the above objectives, the present invention provides a two-dimensional static load impact fracture test device for plate rock, comprising a Hopkinson bar test system, an axial static load loading system, a lateral static load loading system, and a crack real-time monitoring system that work together. The lateral static load loading system is a gantry structure arranged longitudinally. The plate rock sample to be monitored is placed in the gantry structure of the lateral static load loading system. The plate rock sample is arranged vertically, with its square front and back sides arranged. The left, right, top, and bottom sides are the four identical sides of the plate rock sample. The axial static load loading system and the lateral static load loading system are respectively arranged on the left, right, top, and bottom sides of the plate rock sample.

[0006] The crack real-time monitoring system is a high-speed industrial camera installed on the side of the slab rock sample to capture the development of cracks and defects on the slab rock sample in real time. The high-speed industrial camera is connected to an image acquisition terminal.

[0007] The Hopkinson pressure bar test system includes an incident bar that is laterally positioned and in contact with the left side of the plate rock sample, and a transmission bar that is laterally positioned and in contact with the right side of the plate rock sample. The other end of the incident bar is connected to a high-pressure gas excitation device via a base platform, and the other end of the transmission bar is connected to a buffer bar.

[0008] The axial static load loading system is used in conjunction with the Hopkinson bar test system. It includes a hydraulic cylinder with a T-shaped plunger connected to a buffer rod at its end. The T-shaped plunger is connected to the buffer rod via a piston rod. The rodless chamber of the hydraulic cylinder is connected to a manual hydraulic pump.

[0009] The lateral static load loading system includes a movable gantry frame with its bottom set on two gantry rails. The gantry frame includes two vertically arranged columns, with an I-beam beam between the tops of the two columns. The I-beam beam is equipped with a suspension roller assembly that can move left and right. Below the suspension roller assembly is a multi-angle clamping assembly that can clamp the upper and lower sides of the plate-shaped rock sample. The multi-angle clamping assembly is connected to a lateral static load hydraulic control terminal via wiring to control its operation. The bottoms of the two vertical columns are respectively matched and connected to the gantry rails via rail-clamping roller assemblies.

[0010] Furthermore, the multi-angle clamping assembly includes two parts, an upper part and an lower part, which respectively contact the upper and lower sides of the plate-shaped rock sample. The upper part is connected to a suspension roller assembly via an upper hydraulic support, and the suspension roller assembly is movably mounted on an I-beam. The lower part is connected to a base platform via a lower hydraulic support. Both the upper and lower hydraulic supports are connected to a lateral static load hydraulic control terminal via wires. The rail-holding roller assembly is equipped with locking screws for fixing the position.

[0011] Furthermore, the upper part of the multi-angle clamping assembly includes a steering base connected to the upper hydraulic support. The steering base is connected to an upper turntable via an arc-shaped slide rail. The upper turntable is provided with a loading end for contacting the top surface of the plate-shaped rock sample. The lower part of the multi-angle clamping assembly includes a steering base connected to the end of the lower hydraulic support via an arc-shaped slide rail. The steering base is provided with a loading end for contacting the bottom surface of the plate-shaped rock sample. There are fastening screws between the arc-shaped slide rail and the steering base to fix their respective positions. An angle scale line of the steering base angle is marked on the arc-shaped slide rail.

[0012] Furthermore, the high-pressure gas excitation device includes a launch tube connected to an incident rod via a base platform. The launch tube contains a punch that can move along the launch tube and eventually impact the incident rod. An excitation chamber for exciting the punch is embedded at the end of the launch tube, and the excitation chamber is connected to a nitrogen tank as a power source.

[0013] Furthermore, strain gauges are installed on the incident rod and the transmission rod respectively, and all strain gauges are connected to an oscilloscope via a dynamic strain gauge.

[0014] Furthermore, a velocimeter is connected to the base platform to detect the impact velocity after the punch is fired.

[0015] A method for a two-dimensional static load test apparatus for impact fracturing of plate-shaped rocks, characterized by the following steps:

[0016] S1. Prepare the test equipment: Prepare, assemble, and fix the Hopkinson bar test system, axial static load system, lateral static load system, and crack real-time monitoring system. Without placing the plate-shaped rock sample initially, apply a small axial horizontal load to the Hopkinson bar system using the axial static load system to ensure close contact between the incident bar, transmission bar, and buffer bar. Then, conduct three consecutive air-impact tests at the same air pressure to check for abnormalities in the incident, reflected, and transmitted wave waveforms displayed on the oscilloscope, and to verify the consistency of the impact velocity measured by the velocimeter. Improve the stress wave waveform by verifying the alignment accuracy of the bar system, the position of the strain gauges, and the initial position of the impactor until the stress uniformity assumption is met.

[0017] S2. Sample Installation: Apply Vaseline to the four loading end faces of a complete or through-defect plate-shaped rock sample with speckled patterns on the surface to be observed. Then, place the plate-shaped rock sample between the incident rod and the transmission rod, adjust it so that the plate surface faces the high-speed industrial camera in the crack real-time monitoring system at a certain distance in front of the sample, and apply a certain axial static load to press the left and right sides of the plate-shaped rock sample to initially fix it. Move and fix the rail-holding roller assembly and suspension roller assembly of the lateral pressure loading system, place the multi-angle clamping assembly directly above the plate-shaped rock sample, and adjust the upper hydraulic support, lower hydraulic support and rotate the upper turntable and lower turntable with the help of the lateral load hydraulic control terminal to align the loading end with the upper and lower end faces of the plate-shaped rock sample and tighten the fastening screws.

[0018] S3. Set experimental parameters: Reset the dynamic strain gauge, oscilloscope, and velocimeter. Set the parameters for two-dimensional dynamic and static load and image acquisition according to the preset experimental scheme, including impact air pressure, axial static load, lateral static load, dynamic strain gauge bridge pressure and bridging method, oscilloscope bandwidth and sampling rate, and high-speed industrial camera image acquisition frequency.

[0019] S4. Start-up test: Simultaneously turn on the dynamic strain gauge, oscilloscope, tachometer, and lateral static load hydraulic control terminal. According to the experimental plan, first use a manual hydraulic pump to slowly apply the axial static load to the predetermined load. Then use the lateral static load hydraulic control terminal to apply the lateral static load to the predetermined load at the same rate. After that, turn on the switch of the excitation and emission chamber filled with nitrogen at a certain pressure to carry out the impact fracture test of the plate rock under two-dimensional static load.

[0020] S5. Data and Image Processing: Based on the stress wave voltage signal collected by the dynamic strain gauge, the stress wave time history curve and stress-strain curve are calculated and plotted based on the stress wave theory to analyze the dynamic mechanical properties of the plate rock sample; based on the real-time acquired images, the dynamic initiation, propagation and penetration characteristics of cracks are analyzed, thereby revealing the fracture evolution mechanism of the plate rock sample.

[0021] Restore all experimental setups and prepare for the next set of experiments. Beneficial effects

[0022] This device enables the study of dynamic and static fracturing behavior of slab rock samples, providing equipment support and experimental methods for researching rock tunnel failure behavior. Its main advantages are:

[0023] 1) The axial static load system uses a manually operated hydraulic pump to inject / unload oil, driving the piston to compress the rod. Combined with the Hopkinson bar test system, this achieves the application and unloading of a constant axial horizontal static load on the plate-shaped specimen. The lateral static load system relies on a sliding roller assembly to easily move forward, backward, left, and right, enabling the direct and independent application of lateral static loads on the plate-shaped rock specimen. The various systems in this device are well-matched, and dynamic and static loads can be applied independently. The device has high reliability and a wide load range.

[0024] 2) In addition to laterally clamping the plate-shaped sample between the incident rod and the transmission rod to transfer the lateral static load exerted by the lateral static load loading system at its upper and lower ends, the multi-angle clamping assembly's main function is to adapt to plate-shaped rock samples with different placement angles through its own adjustment. This can meet the monitoring requirements of the high-speed industrial camera lens in the crack real-time monitoring system placed in front of the sample being perpendicular to the sample's plate surface to be observed, ensuring accurate and continuous monitoring of the plate-shaped sample's fracture state during dynamic and static loading. Attached Figure Description

[0025] Figure 1 This is a front view of the experimental apparatus for dynamic and static loading fracture of plate-shaped rock according to an embodiment of the present invention;

[0026] Figure 2 This is a left view of the experimental apparatus for dynamic and static loading fracture of plate-shaped rock according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the stress on a plate-shaped rock sample under two-dimensional static impact loading according to an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the Hopkinson bar test system according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the axial static load loading system according to an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the lateral static load loading system structure according to an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the crack real-time monitoring system according to an embodiment of the present invention;

[0032] Figure 8 This is a schematic diagram of the multi-angle clamping component structure according to an embodiment of the present invention;

[0033] Figure 9(a) is a waveform voltage diagram of stress wave in the air-impact test of a plate-shaped rock sample according to an embodiment of the present invention.

[0034] Figure 9(b) is a stress wave equilibrium test diagram of a plate-shaped rock sample in an air-impact test according to an embodiment of the present invention.

[0035] Figure 10(a) is a voltage diagram of stress wave in a fractured plate rock specimen under two-dimensional static load impact fracture test according to an embodiment of the present invention.

[0036] Figure 10(b) is a stress wave equilibrium test diagram of a fractured plate rock specimen under two-dimensional static load impact fracture test according to an embodiment of the present invention.

[0037] Figure 10(c) is a stress-strain diagram of the impact fracture test of a fractured plate-shaped rock sample under two-dimensional static load according to the present invention.

[0038] In the diagram: 1-Hopkinson bar test system, 2-Axial static load system, 3-Lateral static load system, 4-Plate rock sample, 5-Crack real-time monitoring system; 101-Nitrogen tank, 102-Excitation emission chamber, 103-Emission tube, 104-Punch, 105-Velocity meter, 106-Base platform; 107-Incident rod, 108-Transmission rod, 109-Buffer rod, 110-Strain gauge, 111-Dynamic strain gauge, 112-Oscilloscope; 201-Hydraulic cylinder, 202-T-piston, 203-Manual hydraulic pump; 301-Gantry frame, 3011-Vertical column, 3012 - I-beam crossbeam, 302- rail-holding roller assembly, 303- gantry rail, 304- locking screw, 305- suspension roller assembly, 306- upper hydraulic support, 307- multi-angle clamping assembly, 308- lower hydraulic support, 309- lateral static load hydraulic control terminal; 3071- steering base, 3072- upper turntable, 3073- lower turntable, 3074- fastening screw, 3075- loading end, 30711- arc-shaped slide rail, 30721- angle scale line, 30722- arc-shaped groove; 401- crack defect; 501- high-speed industrial camera; 502- image acquisition end. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0040] See Figure 1-8This invention discloses a two-dimensional static load impact fracture test apparatus for plate-shaped rocks, specifically comprising a Hopkinson bar test system 1, an axial static load loading system 2, a lateral static load loading system 3, a plate-shaped rock specimen 4, and a real-time crack monitoring system 5. The Hopkinson bar test system 1 applies horizontal impact dynamic loads to the left and right ends of the plate-shaped rock specimen 4. The axial static load loading system 2 works in conjunction with the Hopkinson bar test system 1 and is fixedly installed at its tail, applying horizontal static loads to the left and right ends of the plate-shaped rock specimen 4. The lateral static load loading system 3 is located above and passes through the middle of the Hopkinson bar test system 1, applying lateral static loads to the upper and lower ends of the plate-shaped rock specimen 4. The left and right ends of the plate-shaped rock specimen 4 are clamped by the Hopkinson bar test system 1, and the upper and lower ends are clamped by the lateral static load loading system 3. The real-time crack monitoring system 5 is located directly in front of the plate-shaped specimen 4, used for non-contact monitoring of crack propagation during impact.

[0041] See Figure 4 The Hopkinson pressure bar experimental system 1 includes a nitrogen tank 101, an excitation and emission chamber 102, an emission tube 103, a punch 104, a velocimeter 105, a base platform 106, an incident rod 107, a transmission rod 108, a buffer rod 109, strain gauges 110, a dynamic strain gauge 111, and an oscilloscope 112. One end of the excitation and emission chamber 102 is connected to the nitrogen tank 101 via a gas hose, and the other end is fitted with an emission tube 103 containing the punch 104. The base platform 106 is placed at a certain distance from the outlet of the emission tube, and the velocimeter 105 is placed between the two. The incident rod 107, the transmission rod 108, and the buffer rod 109 are placed sequentially on the base platform 106, and the three rods are coaxial and of equal diameter. Two strain gauges 110 are symmetrically attached to the center of the incident rod 107 and the transmission rod 108 in the axial direction. The strain gauges 110 are connected to the dynamic strain gauge 111 and the oscilloscope 112 via wired connections. During the experiment, nitrogen gas at a certain pressure is filled into the excitation and emission chamber 102 from the nitrogen cylinder 101 and stored therein. When the switch is turned on, the nitrogen gas is suddenly released, which drives the punch 104 in the emission tube 103 to strike the head of the incident rod 107 on the base platform 106, generating a stress wave. The impact velocity of the punch 104 can be measured by the velocimeter 105. The stress wave propagates along the incident rod 107, passes through the plate-shaped rock sample 4, and undergoes transmission and reflection through the transmission rod 108. The voltage signals of the incident wave, reflected wave, and transmitted wave, which are recorded in real time by the strain gauge 110, are acquired by the dynamic strain gauge 111 via a wired connection and displayed on the oscilloscope 112. The buffer rod 109 is used to absorb the impact energy to reduce the impact velocity of the transmission rod 108 on the T-shaped plunger 202.

[0042] See Figure 5The axial static load loading system 2 includes a hydraulic cylinder 201, a T-type plunger 202, and a manual hydraulic pump 203. The hydraulic cylinder 201 and the manual hydraulic pump 203 are connected by a rubber hose. The manual hydraulic pump 203 manually injects or releases oil into the hydraulic cylinder 201, causing the T-type plunger to move left and right. The T-type plunger piston rod extends out of the hydraulic cylinder 201 and is aligned coaxially and equally with the buffer rod 109. Through the piston movement, the horizontal static load can be transferred to the plate-shaped rock sample 4 between the incident rod 107 and the transmission rod 108 to achieve the loading and unloading of the axial static load. The axial horizontal static load on the plate-shaped sample is calculated according to the following formula:

[0043] (1),

[0044] In the formula, σ s This indicates the axial horizontal static load on the plate-shaped specimen. p This refers to the oil pressure when the manual hydraulic pump is under load. S p and S as These represent the axial cross-sectional areas of the T-shaped plunger and the plate-shaped specimen, respectively.

[0045] See Figure 6, the lateral static load loading system 3 includes a gantry 301, a rail clamping roller assembly 302, a gantry rail 303, a locking screw 304, a suspension roller assembly 305, an upper hydraulic strut 306, a multi-angle clamping assembly 307, a lower hydraulic strut 308, and a lateral static load hydraulic control terminal 309. The gantry 301 has a "冂"-shaped structure, which is composed of two vertical struts 3011 arranged vertically side by side and an I-beam crossbeam 3012 between the tops, connected by threading and penetrated by the base platform 106; the rail clamping roller assembly 302 is connected to the bottom end of the gantry vertical strut 3011 by threading and rides on the gantry rail 303, enabling the gantry 301 to move freely left and right along the gantry rail 303; the gantry rail 303 is anchored to the concrete foundation to guide the left and right movement of the gantry 301; the locking screw 304 is placed between the rail clamping roller assembly 302 and the gantry rail 303, and by its own rotation, the extrusion force between the two is increased, and then the rail clamping roller assembly 302 is fastened to the gantry rail 303. The suspension roller assembly 305 is suspended on the I-beam crossbeam 3012 of the gantry and can move freely along its extension direction; the upper hydraulic strut 306 is located below the suspension roller assembly 305 and is connected to it by threading, and is the actuating element of the lateral static load; the top and bottom of the multi-angle clamping assembly 307 are respectively connected to the upper hydraulic strut 306 and the lower hydraulic strut 308 placed on the Hopkinson bar system base platform 106 by threading, and can clamp the plate-shaped rock specimen 4 with any plate surface angle vertically; the lateral static load hydraulic control terminal 309 is wire-connected to the upper and lower hydraulic struts 306 and 308, and realizes the application and unloading of the lateral static load on the plate-shaped rock specimen 4 through signal control.

[0046] See Figure 7 , the crack real-time monitoring system 5 is composed of a high-speed industrial camera 501 and a picture acquisition terminal 502 connected by wire. The high-speed industrial camera 501 is placed at a certain distance directly in front of the plate-shaped rock specimen 4 and is vertically aligned with the monitored plate surface of the specimen, aiming to capture the fracture state of the specimen during the experiment accurately at high frequency; the picture acquisition terminal 502 is used to set picture acquisition parameters and store pictures.

[0047] See Figure 3 , the plate-shaped rock specimen 4 has a length of 30 - 100 mm, the width does not exceed the diameter of the rod in the Hopkinson bar experiment system 1, and the thickness is between 10 - 25 mm. Before the experiment, a thin layer of randomly distributed speckles is made on its observable surface using white and black paint to facilitate the identification of fracture cracks in pictures.

[0048] See Figure 4The Hopkinson pressure bar experimental system's launch tube 103 is a thick-walled cylinder 1.5~2.5m long. The punch 104 in the launch tube is spindle-shaped. Before each experiment, it needs to be driven into the same initial position with the help of an iron bar to ensure that the impact velocity of the punch is equal under the same gas pressure. The nitrogen tank 101 in the Hopkinson pressure bar experimental system 1 is equipped with a pressure gauge to control the release nitrogen pressure. By adjusting the valve of the pressure gauge, the nitrogen pressure injected into the excitation chamber 102 can be set.

[0049] See Figure 8 The multi-angle clamping assembly 307 consists of a steering base 3071, an upper turntable 3072, a lower turntable 3073, fastening screws 3074, and a loading end 3075. The upper turntable 3072 and lower turntable 3073 have symmetrically arranged arc-shaped grooves 30722 on both sides. The steering base 3071 has an arc-shaped slide rail 30711 that matches the arc-shaped grooves. The upper and lower turntables pass through the steering base 3071 and rotate freely and synchronously along the arc-shaped slide rail 30711 to accommodate plate-shaped rock samples 4 at different placement angles. Angle scale lines 30721 are used to read the rotation angle of the upper and lower turntables. The fastening screws 3074 are used to lock the upper and lower turntables. The plate-shaped rock sample 4 is placed between the upper turntable 3072 and the loading end 3075 of the lower turntable 3073 and is directly aligned with the high-speed industrial camera 501 of the real-time crack monitoring system 5.

[0050] A method for using a dynamic and static loading fracture test apparatus for plate-shaped rocks includes the following steps:

[0051] (S1) Prepare the test equipment: Prepare the Hopkinson bar test system 1, axial static load system 2, lateral static load system 3, and crack real-time monitoring system 5, and assemble, install, and fix them. Without placing the plate-shaped specimen 4, apply a small axial horizontal load to the Hopkinson bar system 1 using the axial static load system 2 to ensure close contact between the incident bar 107, the transmission bar 108, and the buffer bar 109. Then, turn on the Hopkinson bar test system 1 and perform three consecutive air-impact tests at the same air pressure to check for abnormalities in the incident wave, reflected wave, and transmitted wave waveforms displayed on the oscilloscope 112, and to check for consistency in the impact velocity of the punch 104 measured by the velocimeter 105. Improve the stress wave waveform until the stress uniformity assumption is met by verifying the alignment accuracy of the bar system, the position of the strain gauge 110, and the initial position of the punch 104.

[0052] (S2) Sample Installation: Apply Vaseline to the four loading end faces of the prepared slab rock sample 4, which has a speckled surface or contains penetrating defects. Then, place the sample 4 between the incident rod 107 and the transmission rod 108, adjust it so that the plate surface faces the high-speed industrial camera 501 in the crack real-time monitoring system 5, which is positioned a certain distance in front of the sample, and apply a certain axial static load to press the left and right ends of the sample to initially fix it. Move and fix the rail-holding roller assembly 302 and the suspension roller assembly 305 of the lateral pressure loading system 2. Place the multi-angle clamping assembly 307 directly above the sample 4. Adjust the upper and lower hydraulic supports 306 / 308 and rotate the upper and lower turntables 3072 and 3073 with the help of the lateral load hydraulic control terminal 309 so that the loading end 3075 is aligned with the upper and lower end faces of the sample 4 and tighten the fastening screws 3074.

[0053] (S3) Set experimental parameters: Reset the dynamic strain gauge 111, oscilloscope 112, and tachometer 105. Set the two-dimensional dynamic and static load and image acquisition parameters according to the experimental scheme, including impact air pressure, axial static load, lateral static load, dynamic strain gauge bridge pressure and bridging method, oscilloscope bandwidth and sampling rate, high-speed industrial camera image acquisition frequency, etc.

[0054] (S4) Start-up test: Simultaneously turn on the dynamic strain gauge 111, oscilloscope 112, tachometer 105, and lateral static load hydraulic control terminal 308. According to the experimental plan, first use the manual hydraulic pump 203 to slowly apply the axial static load to the predetermined load, and then use the lateral static load hydraulic control terminal 309 to apply the lateral static load to the predetermined load at the same rate. Then turn on the switch of the excitation and emission chamber 102 filled with nitrogen at a certain pressure to carry out the impact fracture test of the plate rock under two-dimensional static load.

[0055] (S5) Data and image processing: Based on the stress wave voltage signal collected by the dynamic strain gauge, the stress wave time history curve and stress-strain curve are calculated and plotted based on the stress wave theory to analyze the dynamic mechanical properties of the sample; based on the real-time acquired images, the dynamic initiation, propagation and penetration characteristics of cracks are analyzed, thereby revealing the fracture evolution mechanism of the plate rock sample.

[0056] Restore all experimental setups and prepare for the next set of experiments.

[0057] The following example illustrates the specific application of this preferred solution.

[0058] In this design, the nitrogen tank 101 of the Hopkinson pressure bar experimental system 1 is 1.5m high, 25cm in diameter, has a maximum pressure of 20MPa, and a valve control accuracy of 0.1MPa. The excitation chamber 102 is 40cm long and 30cm in diameter, and is manually controlled by a switch. The emission tube 103 is 2.0m long, 10cm in outer diameter, and 1.0cm thick. The punch 104 is spindle-shaped with a variable cross-section design, with a total length of 360.1mm; the central cylinder has a diameter of 50mm and a length of 66.7mm; the lengths and diameters of the tail and front cones are 106.7mm / 17.4mm and 186.7mm / 6.66mm, respectively. The velocimeter 105, model ZDS-1, can measure the instantaneous velocity of the punch 104 impacting the rod system. The base platform 106 is made of Q235 stainless steel. The incident rod 107 is 2.0m long, the transmission rod 108 is 1.5m long, and the buffer rod 109 is 0.5m long. All rods have a diameter of 50mm and are made of 40Cr alloy, which has an elastic modulus of 233GPa and a density of 7821kg / m³. 3 The average wave velocity is 5461 m / s. The strain gauge 110 used to monitor the strain signal is model B120-2AA. The dynamic strain gauge 111 is a CS-1D dynamic strain gauge manufactured by Beidaihe Electronic Instrument Factory, with a frequency range of 0~1MHz, a bridge resistance range of 60~1000Ω, and automatic balancing and calibration functions. The strain gauges use a ¼-bridge connection method. The oscilloscope 112 is a DL-850E oscilloscope recorder manufactured by Yokogawa Corporation of Japan, with a data update rate of 1MHz (1μs), a minimum measurement resolution of 625ps, and a measurement range (frequency) of 0.01Hz~500kHz.

[0059] In the axial static load loading system 2, the hydraulic cylinder has an inner diameter of 25cm, a wall thickness of 2cm, and a length of 30cm. The internal T-shaped plunger head is 15cm long, the tail plunger disc is 3cm thick, and the piston stroke is 0~10cm. The manual hydraulic pump 203 is a SZB-3 model produced by Taizhou Nanfang Hydraulic Components Factory. The pressure gauge is a YTN60 shockproof and vibration-resistant pressure gauge (dial diameter 60mm, installation diameter M14*1.5) with a range of 4MPa produced by Hongqi Instrument Factory.

[0060] In the lateral static load loading system 3, the gantry 101 consists of two vertical columns 3011 with dimensions of 20×20×200cm and a 3.0m long 16# I-beam crossbeam 3012 connected by M12×70 bolts. The upper end of the rail-holding roller assembly 302 is screwed to the vertical column 3011 with M12×40 screws. Each rail-holding roller assembly 302 includes four rollers. The roller assembly 302 is movably connected to the gantry rail 103 by a rail-holding method. There are two 16cm diameter rollers distributed on both sides of the gantry rail 303, which allows the vertical column 3011 to move left and right. The gantry rail 303 is a 3.0m long, 20A type I-beam anchored to the concrete foundation. The locking screws 304 between the rail-holding roller assembly 302 and the gantry rail 303 are M8×100 hexagonal bolts. The rail-holding roller assembly can be fixed by turning the locking screws 304 with a wrench. The suspension roller assembly 305 also consists of 4 rollers, with 2 rollers of 12cm diameter distributed on each side of the 16# I-beam crossbeam 3012, enabling the hydraulic support 306 to move back and forth. The upper hydraulic support 306 has an outer diameter of 108mm, a minimum length of 0.5m, and a maximum extension of 1.0m; the lower hydraulic support 306 has an outer diameter of 108mm, a minimum length of 0.1m, and a maximum extension of 0.30m. The upper and lower turntables 3072 and 3073 in the multi-angle clamping assembly 307 can rotate freely circumferentially along the slide groove 30722 in the steering base 3071. The upper and lower end faces of the plate-shaped rock sample 4 are aligned with the loading end 3075. After aligning the surface of the plate-shaped rock sample 4 to be monitored with the high-speed industrial camera 501, the upper and lower turntables can be fixed with fastening screws 3074. Then, the lateral load hydraulic control terminal 309 controls the extension and retraction of the hydraulic strut 306 via a signal to transfer the lateral static load to the rock sample 4 through the multi-angle clamping assembly 307, thus achieving the application of the lateral static load.

[0061] The crack real-time monitoring system 5 employs a digital image correlation system, positioned 1.0–1.5 m in front of the sample. The system is equipped with a CCD high-speed industrial camera 501 and an image acquisition terminal 502. The CCD high-speed industrial camera 501 is a German-made Basler / piA2400-17 with a maximum resolution of 2456×2058 (H×V pixels) and a maximum acquisition frequency of 17 FPS. In this case, the shooting speed was set to 75000 fps, meaning one image was captured every 13.33 μs. The PylonViewer software installed on the image control terminal 502 allows for setting the CCD high-speed industrial camera acquisition parameters 501 and storing images.

[0062] The slab-shaped rock sample 4 measures 45×45×20mm, with a 3cm long, 45° inclined through-crack at its center. The sample monitoring surface is painted with black and white paint to create random speckles, ensuring accurate crack identification. Vaseline is applied to all four ends of the sample, with the plate facing the CCD high-speed industrial camera 501. The left and right ends are clamped between the incident rod 107 and the transmission rod 108, while the top and bottom ends are clamped between the two loading ends.

[0063] A method for conducting two-dimensional static and impact-dynamic load coupled rock fracture experiments and monitoring using a plate-shaped rock dynamic-static loading fracture test device includes the following steps:

[0064] (S1) Prepare test instruments: Prepare and combine the Hopkinson bar test system, axial static load system, lateral static load system and crack real-time monitoring system. The crack real-time monitoring system is located 1.0m in front of the Hopkinson bar test system. Do not place the plate-shaped rock sample first. Apply an axial load of 1.0MPa (pump pressure about 0.04MPa) according to the formula (1) using the axial static load system. Tightly fit the incident rod, transmission rod, buffer rod and T-shaped plunger head. Then, perform three consecutive air-burst tests at 0.5MPa air pressure to check whether the waveform is abnormal. Improve the stress wave waveform by verifying the alignment accuracy of the rod system, the position of the strain gauge and the initial position of the punch until the stress uniformity assumption is met. See Figure 9(a) and Figure 9(b).

[0065] (S2) Sample Installation: Prepare a complete plate-shaped sample (45×45×20mm). Apply Vaseline to the four loading surfaces of the sample. Place the plate-shaped rock sample between the incident rod and the transmission rod, with the speckle surface facing the CCD high-speed industrial camera. Apply an axial static load of 1.0MPa to the left and right ends of the sample to initially fix it. Move the rail-holding roller assembly and suspension roller assembly of the lateral static load system so that the multi-angle clamping assembly is directly above the rock sample. Adjust the upper and lower hydraulic supports and synchronously rotate the upper and lower turntables to align the loading end with the upper and lower end faces of the sample. Tighten the fastening screws to lock it in place.

[0066] (S3) Set experimental parameters: Reset the dynamic strain gauge, oscilloscope, and tachometer; set the bridge voltage of the dynamic strain gauge to 4V and use the ¼-bridge method; set the bandwidth of the oscilloscope to 1MHz and the sampling rate to 1μs; set the impact air pressure to 0.5MPa, the manual hydraulic pump pressure to 0.83MPa (axial static load 20MPa), the lateral static load to 20MPa, and the image acquisition speed to 13.33μs / frame;

[0067] (S4) Start-up test: Simultaneously turn on the dynamic strain gauge, oscilloscope, tachometer, and lateral static load hydraulic control terminal. According to the experimental plan, first use a manual hydraulic pump to slowly apply the axial static load to the set pump pressure, and then use the lateral static load hydraulic control terminal to apply the lateral static load to 20MPa. Then quickly turn on the excitation chamber switch to carry out the impact test.

[0068] (S5) Data and Image Processing: Based on the acquired stress wave waveform voltage diagram (Fig. 10(a)), the stress wave balance is verified (Fig. 10(b)), and stress wave time history curves and stress-strain curves are generated. The dynamic mechanical properties of the plate rock specimen under the above static load conditions are analyzed (see Fig. 10(c)). Based on the real-time acquired images, the dynamic initiation, propagation, and penetration characteristics of cracks are analyzed to reveal the fracture evolution mechanism of the fractured plate specimen. All experimental setups are restored to prepare for the next set of experiments.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the technical solutions of the present invention.

Claims

1. A two-dimensional static load-bearing experimental apparatus for impact fracturing of plate-shaped rocks, characterized in that: The system includes a Hopkinson bar test system (1), an axial static load system (2), a lateral static load system (3), and a crack real-time monitoring system (5) that work together. The lateral static load system (3) is a gantry structure and is set longitudinally. The plate rock sample (4) being monitored is set in the gantry structure of the lateral static load system (3). The plate rock sample (4) is set vertically, with the square front of the plate rock sample (4) set in front and back. The left and right sides and the top and bottom sides of the plate rock sample (4) are the same. The axial static load system (2) and the lateral static load system (3) are set on the left and right sides and the top and bottom sides of the plate rock sample (4), respectively. The crack real-time monitoring system (5) is a high-speed industrial camera (501) installed on the side of the plate rock sample (4) to capture the development of crack defects (401) on the plate rock sample (4) in real time. The high-speed industrial camera (501) is connected to an image acquisition terminal (502). The Hopkinson pressure bar test system (1) includes an incident bar (107) that is laterally positioned and in contact with the left side of the plate rock sample (4), and a transmission bar (108) that is laterally positioned and in contact with the right side of the plate rock sample (4). The other end of the incident bar (107) is connected to a high-pressure gas excitation device through a base platform (106), and the other end of the transmission bar (108) is connected to a buffer bar (109). The axial static load loading system (2) is used in conjunction with the Hopkinson bar test system (1), including a hydraulic cylinder (201). The hydraulic cylinder (201) is equipped with a T-shaped plunger (202) whose end is connected to the buffer rod (109). The T-shaped plunger (202) is connected to the buffer rod (109) through a piston rod. The rodless chamber of the hydraulic cylinder is connected to a manual hydraulic pump (203). The lateral static load loading system (3) includes a gantry (301) that can move on two gantry rails (303) with its bottom set. The gantry (301) includes two vertical columns (3011) arranged vertically side by side. An I-beam (3012) is provided between the tops of the two vertical columns (3011). A suspension roller assembly (305) that can move left and right is provided on the I-beam (3012). A multi-angle clamping assembly (307) that can clamp the upper and lower sides of the plate-shaped rock sample (4) is provided below the suspension roller assembly (305). The multi-angle clamping assembly (307) is connected to a lateral static load hydraulic control terminal (309) that controls its operation via a line. The bottoms of the two vertical columns (3011) are respectively matched and connected to the gantry rails (303) through the rail-holding roller assembly (302). The multi-angle clamping assembly (307) includes two parts, an upper part and an lower part, which respectively contact the upper and lower sides of the plate-shaped rock sample (4). The upper part is connected to the suspension roller assembly (305) via the upper hydraulic support (306). The suspension roller assembly (305) is movably mounted on the I-beam crossbeam (3012). The lower part is connected to the base platform (106) via the lower hydraulic support (308). Both the upper hydraulic support (306) and the lower hydraulic support (308) are connected to the lateral static load hydraulic control terminal (309) via wires. The rail-holding roller assembly (302) is provided with locking screws (304) for fixing the position. The upper part of the multi-angle clamping assembly (307) includes a steering base (3071) connected to the upper hydraulic strut (306). The steering base (3071) is connected to an upper turntable (3072) via an arc-shaped slide rail (30711). The upper turntable (3072) is provided with a loading end (3075) for contacting the top surface of the slab rock sample (4). The lower part of the multi-angle clamping assembly (307) includes a section connected to the end of the lower hydraulic strut (308). A steering base (3071) is connected via an arc-shaped slide rail (30711). The steering base (3071) is provided with a loading end (3075) for contacting the bottom surface of the plate-shaped rock sample (4). A fastening screw (3074) is provided between the arc-shaped slide rail (30711) and the steering base (3071) to fix their respective positions. An angle scale line (30721) of the angle of the steering base (3071) is marked on the arc-shaped slide groove (30722).

2. The two-dimensional static load plate rock impact fracture experimental device according to claim 1, characterized in that: The high-pressure gas excitation device includes a launch tube (103) connected to an incident rod (107) via a base platform (106). The launch tube (103) contains a punch (104) that moves along the launch tube (103) and eventually impacts the incident rod (107). An excitation chamber (102) for exciting the punch (104) is embedded at the end of the launch tube (103). The excitation chamber (102) is connected to a nitrogen tank (101) that serves as a power source.

3. The experimental apparatus for two-dimensional static load-induced impact fracture of plate-like rock according to claim 1, characterized in that: Strain gauges (110) are provided on the incident rod (107) and the transmission rod (108), and all strain gauges (110) are connected to an oscilloscope (112) through a dynamic strain gauge (111).

4. The two-dimensional static load plate rock impact fracture experimental device according to claim 1, characterized in that: A velocimeter (105) is connected to the base platform (106) to detect the impact speed after the punch (104) is activated.

5. A method for using the two-dimensional static load impact fracture test apparatus for plate-like rocks as described in any one of claims 1-4, characterized in that... The steps are as follows: S1. Prepare the test instruments: Prepare the Hopkinson bar test system (1), axial static load system (2), lateral static load system (3) and crack real-time monitoring system (5) and assemble, install and fix them; do not place the plate-shaped rock sample (4) first, apply a small axial horizontal load to the Hopkinson bar test system (1) through the axial static load system (2) to make the incident bar (107), transmission bar (108) and buffer bar (109) in close contact, and then turn on the Hopkinson bar test system (1) to conduct three consecutive air-impact tests under the same air pressure to detect whether the waveforms of the incident wave, reflected wave and transmitted wave displayed in the oscilloscope (112) are abnormal and whether the impact speed of the punch (104) measured by the velocimeter (105) is consistent; improve the stress wave waveform until the stress uniformity assumption is met by verifying the alignment accuracy of the bar system, the position of the strain gauge (110) and the initial position of the punch (104); S2. Sample Installation: Apply Vaseline to the four loading ends of a prepared slab rock sample (4) with speckled surfaces or containing through defects (401) on the surface to be observed. Then place the slab rock sample (4) between the incident rod (107) and the transmission rod (108), adjust it so that the plate surface faces the high-speed industrial camera (501) in the crack real-time monitoring system (5) which is positioned a certain distance in front of the sample, and apply a certain axial static load to press the left and right sides of the slab rock sample (4) to initially fix it; move The rail-holding roller assembly (302) and the suspension roller assembly (305) of the dynamic lateral static load loading system (3) are fixed. The multi-angle clamping assembly (307) is placed directly above the plate rock sample (4). The upper hydraulic support (306) and the lower hydraulic support (308) are adjusted by means of the lateral load hydraulic control terminal (309). The upper turntable (3072) and the lower turntable (3073) are rotated so that the loading end (3075) is aligned with the upper and lower end faces of the plate rock sample (4) and the fastening screws (3074) are tightened. S3. Set experimental parameters: Reset the dynamic strain gauge (111), oscilloscope (112), and velocimeter (105). Set the two-dimensional dynamic and static load and image acquisition parameters according to the preset experimental scheme, including impact air pressure, axial static load, lateral static load, dynamic strain gauge bridge pressure and bridging method, oscilloscope bandwidth and sampling rate, and high-speed industrial camera image acquisition frequency. S4. Start-up test: Simultaneously turn on the dynamic strain gauge (111), oscilloscope (112), tachometer (105), and lateral static load hydraulic control terminal (309). According to the experimental plan, first use a manual hydraulic pump (203) to slowly apply the axial static load to the predetermined load, and then use the lateral static load hydraulic control terminal (309) to apply the lateral static load to the predetermined load at the same rate. Then turn on the switch of the excitation emission chamber (102) filled with nitrogen at a certain pressure to carry out the impact fracture test of the plate rock under two-dimensional static load. S5. Data and image processing: Based on the stress wave voltage signal collected by the dynamic strain gauge (111), the stress wave time history curve and stress-strain curve are calculated and plotted based on the stress wave theory to analyze the dynamic mechanical properties of the plate rock sample (4); based on the real-time collected images, the dynamic initiation, propagation and penetration characteristics of cracks are analyzed, and then the fracture evolution mechanism of the plate rock sample (4) is revealed. Restore all experimental setups and prepare for the next set of experiments.

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