Rock dynamic compression testing device and testing method

Abstract

The rock dynamic compression testing device and testing method are provided, which comprise a Hopkinson pressure bar testing system, an acoustic emission detection device is arranged between an incident rod and a transmission rod, the acoustic emission sensor protection device is made of a material with high axial stiffness, and comprises a protection device upper shell and a pair of protection device side shells, which form a ring-shaped shell, a sample is located in the ring-shaped shell, a side shell main track and a side shell auxiliary track are arranged on each of the pair of protection device side shells and are arranged in parallel, an acoustic emission sensor is installed on the side shell main track, an acoustic emission sensor back baffle outside the acoustic emission sensor is installed on the side shell auxiliary track through a back baffle diagonal screw nut 7, and the acoustic emission sensor is connected with a data processing system through a data acquisition line. The rock dynamic compression testing device and testing method can protect the acoustic emission probe during dynamic loading and will not affect the damage characteristics and strain distribution of the rock determined by the acoustic emission detection system.

Description

Technical Field

[0001] This invention relates to the field of testing rocks and rock-like materials under dynamic loading in rock engineering, specifically to a dynamic compression testing device and method for rocks. Background Technology

[0002] To further develop deep mineral resources, it is necessary to continue studying the dynamic mechanical properties of deep rocks. Acoustic emission testing, as a non-destructive, real-time passive detection technology, more closely reflects the actual changes in rock materials compared to other non-destructive testing techniques. It has high practical application value and has been widely used and recognized in many fields.

[0003] Current methods for determining the dynamic strength of rock-like materials primarily involve dynamically loading the specimen using a Hopkinson bar and employing appropriate testing devices. Acoustic emission (AE) testing systems, as a non-destructive testing technique, have been applied to dynamic loading tests of rock-like materials. During the test, the AE probe needs to be tightly fitted to the specimen; currently, this is often achieved through adhesive bonding. This method is complex, requiring regular cleaning of residual adhesive, which affects the test process, and the probe is easily dislodged under confined pressure. Furthermore, when using traditional Hopkinson bars for dynamic testing, the AE probe mounted on the specimen is highly susceptible to damage from the bar's impact. AE probes are precision instruments, expensive, and the testing operation is complex; therefore, extending their lifespan is crucial, necessitating protection. Because AE sensors are highly sensitive to signals, traditional fixing methods can easily interfere with the sensor's signal, affecting data results. Based on these findings, it is necessary to develop a testing device and method that allows for convenient use of the AE system, effectively protects the AE sensor, and does not affect test results, providing experimental basis for theoretical analysis and numerical calculations. Summary of the Invention

[0004] The present invention aims to develop a testing device and testing method that can provide a safe and reliable working environment for acoustic emission detection systems under dynamic loading conditions and accurately record the dynamic damage and other related characteristics of rocks and rock-like materials, thus providing a theoretical basis for the research on the dynamic mechanical properties of rocks and their engineering applications.

[0005] To address the current limitations of dynamic compression testing of rocks and rock-like materials using acoustic emission testing systems, this paper presents a dynamic compression testing device and method for rocks. The aim is to protect the acoustic emission probe during dynamic loading without affecting the damage characteristics and strain distribution of the rock measured by the acoustic emission testing system.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A rock dynamic compression testing device includes a Hopkinson bar testing system, wherein the Hopkinson bar testing system includes an incident bar and a transmission bar;

[0008] The incident rod and the transmission rod are two rods of the same material but different lengths. Both rods are fitted with strain gauges and connected to the data processing system to detect the strain of the incident rod and the transmission rod, and to further calculate the strain and stress of the rock sample.

[0009] A launching device is provided in front of the incident rod to apply stress waves to the incident rod and transmit them to the sample; a shaper is provided on the front end face of the incident rod for waveform shaping.

[0010] An acoustic emission detection device is installed between the incident rod and the transmission rod. The acoustic emission detection device includes: an acoustic emission sensor, an acoustic emission sensor protection device, and a data acquisition line.

[0011] The acoustic emission sensor protection device is made of a high axial stiffness material and includes an upper protective shell and a pair of side protective shells. The two ends of the upper protective shell are connected to the upper ends of the pair of side protective shells, and the lower ends of the pair of side protective shells are connected to form an annular shell. All connections are made by connecting nuts and screws. The sample is located inside the annular shell. Each of the pair of side protective shells is provided with a main side shell track and a secondary side shell track, which are arranged in parallel. The acoustic emission sensor is installed on the main side shell track, and the acoustic emission sensor rear baffle on the outside of the acoustic emission sensor is installed on the secondary side shell track by diagonal screws and nuts 7. The acoustic emission sensor is connected to the data processing system through a data acquisition line.

[0012] A method for dynamic compression testing of rock includes the following steps:

[0013] S1: Sample preparation: First, cut the original rock sample and drill the core. According to the method recommended by the International Society for Rock Mechanics, process the rock into a cylindrical sample with a diameter of 50 mm and a length of 50 mm.

[0014] S2: Clamp the sample between the incident rod and the transmission rod: Apply an appropriate amount of lubricant to both ends of the sample to reduce the frictional effect caused by the sample and the end faces of the incident and transmission rods. Align the central axis of the sample with the central axes of the incident and transmission rods, so that the incident rod, sample, and transmission rod are on the same axis.

[0015] S3: Assemble the acoustic emission sensor protection device: The rear baffle of the acoustic emission sensor is mounted on the side shell sub-rail. The side shell and upper shell of the protection device are connected to form a ring-shaped housing.

[0016] S4: Install the acoustic emission sensor protection device and fix the acoustic emission sensor: Place the acoustic emission protection device on the sample, adjust the radius, and ensure that the protection device is symmetrical. Connect the data acquisition cable to the acoustic emission sensor. Install the acoustic emission sensor on the main track of the side shell according to the test position required by the experiment and adjust the angle to keep the contact surface of the acoustic emission sensor at the required point, ensuring that the end face of the acoustic emission sensor is in close contact with the sample surface; adjust the position of the back baffle of the acoustic emission sensor so that the back baffle can completely cover the acoustic emission sensor; connect the other end of the data acquisition cable to the data processing system.

[0017] S5: Incident Wave Applied to the Incident Rod: After a safety warning, the experimenter starts the transmitting device. The experimenter records the first incident strain pulse received by the strain gauge on the incident rod and the reflected strain pulse after the stress wave is reflected. The transmitted strain pulse received by the strain gauge on the transmission rod is recorded. The acoustic emission signal received by the acoustic emission sensor is recorded. The experiment concludes here.

[0018] The specific technical effects of this invention are as follows:

[0019] 1. The acoustic emission sensor protection device can protect the acoustic emission sensor during dynamic loading, solving the problem that the instrument is easily damaged when using acoustic emission probes for measurement.

[0020] 2. The acoustic emission sensor protection device can achieve a better fixation effect for the acoustic emission sensor, solving the problems of the current ordinary pasting method, which is cumbersome to operate, easy to fall off when disturbed, and requires regular cleaning of residual adhesive.

[0021] 3. Due to the pre-designed protection device for the acoustic emission sensor, the test process will not affect the stress on the sample or the detection signal of the acoustic emission sensor. Therefore, the deformation and stress response of the rock under dynamic loading obtained are more consistent with the real situation, and can better study the deformation characteristics of rocks and rock-like materials in real natural environments. Attached Figure Description

[0022] Figure 1 A schematic diagram of the acoustic emission sensor protection device of the present invention is shown;

[0023] Figure 2 A schematic diagram (front view) of the acoustic emission sensor protection device and sample assembly in this invention is shown.

[0024] Figure 3 A schematic diagram (side view) of the acoustic emission sensor protection device and sample combination in this invention is shown;

[0025] Figure 4 A flowchart of the rock dynamic compression test method combined with an acoustic emission device in this invention is shown. Detailed implementation method:

[0026] The specific technical solution of the present invention will be described in conjunction with the accompanying drawings.

[0027] like Figure 1 , Figure 2 and Figure 3 As shown, a rock dynamic compression testing device includes a Hopkinson bar testing system, wherein the Hopkinson bar testing system includes an incident bar 11 and a transmission bar 12;

[0028] The incident rod 11 and the transmission rod 12 are two rods of the same material but different lengths. Both rods are fitted with strain gauges and connected to the data processing system to detect the strain of the incident rod 11 and the transmission rod 12, and to further calculate the strain and stress of the rock sample.

[0029] A launching device is provided in front of the incident rod 11 for the bullet to apply stress wave to the incident rod 11 and transmit it to the sample 10; a shaper is provided on the front end face of the incident rod 11 for waveform shaping.

[0030] An acoustic emission detection device is provided between the incident rod 11 and the transmission rod 12. The acoustic emission detection device includes: an acoustic emission sensor 8, an acoustic emission sensor protection device, and a data acquisition line 9.

[0031] The acoustic emission sensor protection device is made of a high axial stiffness material and includes an upper protective shell 1 and a pair of side protective shells 2. The two ends of the upper protective shell 1 are connected to the upper ends of the pair of side protective shells 2, and the lower ends of the pair of side protective shells 2 are connected to form an annular shell. All connections are made by connecting nuts and screws 3. The sample 10 is located inside the annular shell. Each of the pair of side protective shells 2 is provided with a main side shell track 6 and a secondary side shell track 5, which are arranged in parallel. The acoustic emission sensor 8 is installed on the main side shell track 6, and the acoustic emission sensor rear baffle 4 on the outside of the acoustic emission sensor 8 is installed on the secondary side shell track 5 by diagonal screws and nuts 7. The acoustic emission sensor 8 is connected to the data processing system through a data acquisition line 9.

[0032] The acoustic emission sensor 8 is placed within the pre-reserved side shell main tracks 6 on both sides. After adjusting its position according to the experimental requirements, it is fixed using the acoustic emission sensor rear baffle 4 on the protective device, ensuring that the contact surface of the acoustic emission sensor 8 is in close contact with the rock sample 10. When impacted by a rod, the protective device can prevent the acoustic emission sensor 8 from directly contacting the rod, thus protecting the sensor. The pre-set side shell main tracks 6 allow the acoustic emission sensor 8 to move freely up and down on the side of the rock sample 10, expanding the range of selectable detection positions. The pre-set opening at the bottom of the protective device has an adjustable radius. The width of the protective device is larger than that of the sample 10, so it will not affect the force on the sample 10 when impacted by a rod. Furthermore, the outer shell connection does not need to be overtightened, allowing the sample 10 to deform freely during the stress process, thus not affecting the signal received by the acoustic emission sensor 8. The protective device side shell 2 has a symmetrical structure with openings at both the top and bottom for connecting screws and nuts, allowing for arbitrary selection and easy processing. If the connection is damaged, the connection port on the other side can be replaced to continue the connection, improving the service life of the protective device.

[0033] To test the feasibility of this device for monitoring damage and deformation in rock-like materials, a granite sample was used as an example. Figure 4 As shown, the specific test steps are as follows:

[0034] S1: Preparation of Specimen 10: First, cut the original rock sample and drill the core. According to the method recommended by the International Society for Rock Mechanics, process the rock into a cylindrical specimen 10 with a diameter of 50 mm and a length of 50 mm.

[0035] S2: Clamp the sample 10 between the incident rod 11 and the transmission rod 12: Apply an appropriate amount of lubricant to both ends of the sample 10 to reduce the frictional effect caused by the sample 10 and the end faces of the incident rod 11 and the transmission rod 12. Align the central axis of the sample 10 with the central axis of the incident rod 11 and the transmission rod 12, so that the incident rod 11, the sample 10, and the transmission rod 12 are on the same axis.

[0036] S3: Assemble the acoustic emission sensor protection device: First, use four diagonal screws to pass through the pre-drilled screw holes in the side shell sub-rail 5 and the acoustic emission sensor rear baffle 4 from the inside. Then, screw in the nuts on the outside without tightening them completely, to facilitate subsequent position adjustments, thus installing the two acoustic emission sensor rear baffles 4 onto the protection device side shell 2. Next, use four screws to pass through the pre-drilled screw holes in the upper part of the protection device side shell 2, with each screw fitted with two nuts. Then, pass the screws through the four pre-drilled screw holes in the upper shell 1 of the protection device and fit the nuts on. Arrange the nuts according to... Figure 1 The nuts are screwed in in a spiral motion. To adjust the radius of the subsequent protection device, there is no need to tighten the nuts; it is sufficient to ensure that the three components do not come apart.

[0037] S4: Install the acoustic emission sensor protection device and fix the acoustic emission sensor. 8: Install the acoustic emission protection device according to... Figure 2 The protective device is fitted onto sample 10, and its radius is adjusted to ensure overall symmetry. Data acquisition line 9 is connected to acoustic emission sensor 8. According to the required test position, acoustic emission sensor 8 is first passed laterally through the main track 6 of the side shell, and then adjusted to... Figure 1 Adjust the angle shown to maintain the contact surface of the acoustic emission sensor 8 at the required position. Next, tighten the nuts between the upper protective shell 1 and the side protective shell 2 until the main track 6 of the side shell is flush against the acoustic emission sensor 8. Then, adjust the position of the rear baffle 4 of the acoustic emission sensor so that it completely covers the acoustic emission sensor 8, and tighten the corresponding nuts to ensure that the end face of the acoustic emission sensor 8 is flush against the surface of the sample 10. Connect the other end of the data acquisition line 9 to the data processing system.

[0038] S5: Incident wave is applied to incident rod 11: After the experimenter issues a safety warning, the transmitting device is activated. The experimenter records the first incident strain pulse received by the strain gauge on incident rod 11 and the reflected strain pulse after the stress wave is reflected. The transmitted strain pulse received by the strain gauge on transmission rod 12 is recorded. The acoustic emission signal received by acoustic emission sensor 8 is recorded. The experiment ends here.

Claims

1. A dynamic compression testing device for rocks, characterized in that, The system includes a Hopkinson bar test system, which includes an incident bar (11) and a transmission bar (12). The incident rod (11) and the transmission rod (12) are two rods of the same material but different lengths. Both rods are fitted with strain gauges and connected to the data processing system to detect the strain of the incident rod (11) and the transmission rod (12) and to further calculate the strain and stress of the rock sample. A launching device is provided in front of the incident rod (11) for the bullet to apply stress wave to the incident rod (11) and transmit it to the sample (10); a shaper is provided on the front end face of the incident rod (11) for waveform shaping; An acoustic emission detection device is provided between the incident rod (11) and the transmission rod (12). The acoustic emission detection device includes: an acoustic emission sensor (8), an acoustic emission sensor protection device, and a data acquisition line (9). The acoustic emission sensor protection device is made of a material with high axial stiffness and includes an upper shell (1) and a pair of side shells (2). The two ends of the upper shell (1) are connected to the upper ends of the pair of side shells (2) respectively, and the lower ends of the pair of side shells (2) are connected to form an annular shell. The connection is made by connecting nuts and bolts (3) of the shell. The sample (10) is located inside the annular shell. The pair of side shells (2) are provided with a main track (6) and a secondary track (5), which are arranged in parallel. The acoustic emission sensor (8) is installed on the main track (6), and the acoustic emission sensor back baffle (4) on the outside of the acoustic emission sensor (8) is installed on the secondary track (5) of the side shell by diagonal screws and nuts (7). The acoustic emission sensor (8) is connected to the data processing system through a data acquisition line (9).

2. A method for dynamic compression testing of rock, characterized in that, The method using the apparatus of claim 1 comprises the following steps: S1: Sample preparation (10): First, cut the original rock sample and drill the core. According to the method recommended by the International Society for Rock Mechanics, process the rock into a cylindrical sample (10) with a diameter of 50 mm and a length of 50 mm. S2: Clamp the sample (10) between the incident rod (11) and the transmission rod (12): Apply an appropriate amount of lubricant to both ends of the sample (10) to reduce the friction effect caused by the sample (10) and the ends of the incident rod (11) and the transmission rod (12); Align the central axis of the sample (10) with the central axis of the incident rod (11) and the transmission rod (12) so that the incident rod (11), the sample (10), and the transmission rod (12) are on the same axis; S3: Assemble the acoustic emission sensor protection device: The acoustic emission sensor rear baffle (4) is installed on the side shell sub-track (5); the protection device side shell (2) and the protection device upper shell (1) are connected to form a ring-shaped shell; S4: Install the acoustic emission sensor protection device and fix the acoustic emission sensor (8): Place the acoustic emission protection device on the sample (10), adjust the radius to ensure the overall symmetry of the protection device; connect the data acquisition line (9) to the acoustic emission sensor (8), install the acoustic emission sensor (8) on the main track (6) of the side shell according to the test position required by the test and adjust the angle to keep the contact surface of the acoustic emission sensor (8) at the required position, and ensure that the end face of the acoustic emission sensor (8) is in close contact with the surface of the sample (10); adjust the position of the acoustic emission sensor back baffle (4) so ​​that the acoustic emission sensor back baffle (4) can completely cover the acoustic emission sensor (8); connect the other end of the data acquisition line (9) to the data processing system; S5: The incident rod (11) applies the incident wave: After the experimenter gives a safety warning, the transmitting device is started. The experimenter records the first incident strain pulse received by the strain gauge of the incident rod (11) and the reflected strain pulse after the stress wave is reflected; records the transmitted strain pulse received by the strain gauge on the transmission rod (12); records the acoustic emission signal received by the acoustic emission sensor (8); the experiment ends here.

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