Controllable wave-absorbing anti-interference device in super-large triaxial testing instrument and use method thereof

Abstract

A controllable wave-absorbing anti-interference device in a super-large triaxial testing instrument and a use method thereof belong to the technical field of mechanical and electrical hydraulic control. The device is characterized in that, in a test loading stage, a controller adjusts an electronic air pressure regulator to control a pressure increasing valve according to pressure difference signals and pressure signals collected by a pressure difference sensor and a pressure sensor, so as to keep the air volume above an air-water reservoir unchanged and ensure that the wave-absorbing capacity is the same under different radial load test conditions. In a test test stage, an air inlet hole of the air-water reservoir is closed, and the device automatically absorbs pressure fluctuations caused by radial load changes in the axial excitation process. In a test end stage, the controller adjusts the electronic air pressure regulator to control the pressure increasing valve to slowly unload. The device has the effects and benefits that: the device has a simple structure and is convenient to control, is a pure mechanical decoupling device, can absorb pressure fluctuations caused by radial load changes in the axial excitation process, and has good popularization value.

Description

Technical Field

[0001] This invention belongs to the field of electromechanical-hydraulic control technology, and relates to soil mechanics electro-hydraulic triaxial loading test. In particular, it relates to a controllable wave-absorbing anti-interference device and its usage method in an ultra-large triaxial testing instrument, which can absorb pressure fluctuations caused by loading and achieve decoupling of radial load and axial load. Background Technology

[0002] Electro-hydraulic triaxial testing equipment is commonly used to test the strength and deformation characteristics of soil. This widely applied instrument can be used to study soil instability, stress, strain, and other mechanical properties. It mainly consists of an axial loading system and a radial loading system, both employing electro-hydraulic servo systems, offering good dynamic performance and high loading accuracy. The axial loading system applies an axial excitation force, while the radial loading system applies a constant radial force. However, in electro-hydraulic triaxial testing, the presence of gaps and air bubbles causes soil sample deformation, leading to a decrease in axial loading accuracy. Furthermore, as the rod moves up and down, the volume of the rod inserted into the container changes, causing a change in the radial constant force, ultimately resulting in a decrease in axial loading accuracy. The axial and radial loads are coupled and influence each other, significantly reducing the control accuracy of both axial and radial loads.

[0003] Currently, many scholars have proposed numerous decoupling methods for the coupling problem in electro-hydraulic loading systems, such as classical decoupling, adaptive decoupling control, neural network decoupling control, and fuzzy decoupling control. However, due to the presence of gaps and air bubbles, it is difficult to establish an accurate mathematical model of the soil sample specimen, making model-dependent classical and adaptive decoupling control methods unsuitable. Therefore, intelligent decoupling methods such as neural network decoupling control and fuzzy decoupling control can be selected. Neural networks are unsuitable for online real-time control due to their complex decoupling control algorithms and long solution times. Fuzzy decoupling control, on the other hand, does not require an accurate mathematical model and has a simple control algorithm, requiring only fuzzy decoupling control rules. These rules are derived from expert experience and judgment. During fuzzy decoupling control, current measurement data and facts need to be stored in a database. Experts obtain fuzzy control rules through decoupling experience and reasoning, and finally, the fuzzy decoupling control algorithm achieves decoupling. However, fuzzy decoupling rules can only be obtained through extensive experimentation, and different soil samples have different fuzzy rules, leading to a waste of numerous soil samples and a significant expenditure of experimental time. Summary of the Invention

[0004] The purpose of this invention is to provide a controllable wave-absorbing anti-interference device to solve the problem of mutual coupling between axial load and radial load in an electro-hydraulic triaxial tester. At the same time, it has the characteristics of simple structure, low cost and convenient control.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A controllable wave-absorbing anti-interference device for an ultra-large triaxial testing machine is a controllable wave-absorbing anti-interference device that can absorb pressure fluctuations. The controllable wave-absorbing anti-interference device includes an air-water reservoir 4, a shock-absorbing mesh 5, a differential pressure sensor 6, first and second A / D converters 7 and 9, a pressure sensor 8, a reversing valve 10, a digital output interface DO 11, a controller 12, a pressure boosting valve 13, an electronic air pressure regulator 14, a D / A converter 15, a dryer 16, a pressure reducing valve 17, an amplifier 18, a filter 19, an air tank 20, a pump 21, and a motor 22.

[0007] The air-water reservoir 4 is connected to the internal space of the pressure vessel 2 of the loading system via a pipe. The loading system includes the pressure vessel 2, a soil sample 3 inside the reservoir, and a hydraulic rod 1 on top of the soil sample 3. An air inlet is provided on the top of the air-water reservoir 4 to provide radial load to the loading system. The differential pressure sensor 6 is fixed to the upper end of the air-water reservoir 4. The differential pressure sensor 6 includes two fixed measuring ports: one port is exposed above the air portion inside the air-water reservoir 4, and the other port is inserted into the liquid portion inside the air-water reservoir 4. The differential pressure signals measured by the two measuring ports are acquired by a high-precision first A / D converter 7 and transmitted to the external controller 12. The pressure sensor 8 is fixed to the upper end of the air-water reservoir 4, and the measured pressure signal is acquired by a high-precision second A / D converter 9 and transmitted to the controller 12. The controller 12 is connected to the digital output interface DO11, and also sequentially connected to the first and second A / D converters 7 and 9, and the D / A converter 15. It controls the booster valve 13 via the amplifier 18 and the electronic pressure regulator 14. The reversing valve 10 is located between the air-water reservoir 4 and the booster valve 13, communicating with the internal space of the air-water reservoir 4. Changing the position of the valve core of the reversing valve 10 controls the flow of gas into or out of the air-water reservoir 4; it is controlled by the controller 12. The booster valve 13 is located between the electronic pressure regulator 14 and the reversing valve 10, directly connected to the air-water reservoir 4 via the reversing valve 10. It is used to change the air pressure above the air-water reservoir 4 and is controlled by the electronic pressure regulator 14. The electronic pressure regulator 14 is located between the controller 12 and the booster valve 13, controlling the booster valve to regulate the air pressure above the air-water reservoir 4; it is controlled by the controller 12. The gas tank 20 is located outside the air-water reservoir 4, and is sequentially connected to a filter 19, a dryer 16, a pressure reducing valve 17, and a pressure boosting valve 13. It is powered by a pump 21 connected to a motor 22, which provides gas pressure to the air-water reservoir 4. The signal processing procedure is as follows:

[0008] The controller 12 processes the differential pressure signal and pressure signal obtained from the first and second A / D converters 7 and 9, respectively, and then outputs an analog signal after sequential processing by the D / A converter 15 and amplifier 18. This signal is transmitted to the electronic pressure regulator 14, which in turn controls the booster valve 13, thereby changing the internal pressure of the air-water reservoir 4 while maintaining a constant air volume above the reservoir 4. This ensures that the controllable wave-absorbing and anti-interference device has the same wave-absorbing capability under different radial load test conditions. The booster valve 13 is located between the electronic pressure regulator 14 and the air-water reservoir 4, and is controlled by the electronic pressure regulator 14. It is connected to the air-water reservoir 4 via the reversing valve 10 to change the air pressure above the reservoir 4. The controller 12 controls the reversing valve 10 through the digital output interface 11, thereby changing the gas flow direction.

[0009] Furthermore, a shock-absorbing mesh 5 is provided at the liquid level inside the air-water reservoir 4 to reduce minor pressure fluctuations caused by the flow of liquid inside the air-water reservoir 4 and prevent liquid splashing.

[0010] Furthermore, amplifier 18 is used to amplify the analog signal output by D / A converter 15, thereby driving electronic barometric pressure regulator 14.

[0011] Furthermore, the gas tank 20 is connected to the filter 19 to filter out impurities in the gas and improve gas quality, and the dryer 16 is connected to the filter 19 to absorb moisture in the gas.

[0012] When the hydraulic rod 1 in the loading system moves downward, axial loading occurs, increasing the volume of the rod entering the pressure vessel 2, thus changing the radial pressure of the soil sample specimen 3. Simultaneously, due to the presence of gaps and air bubbles, the soil sample specimen 3 deforms, also causing changes in radial pressure and severely affecting the accuracy of axial loading. The controllable wave-absorbing and anti-interference device can automatically absorb pressure fluctuations caused during the test. The differential pressure sensor 6 measures the pressure difference between the air portion and a certain point in the water within the air-water reservoir 4. The pressure is controlled by the pressure boosting valve 13 and the electronic pressure regulator 14 to maintain a constant air volume, ensuring the controllable wave-absorbing and anti-interference device has the same absorption capacity under different radial load test conditions. When the pressure around the soil sample specimen 3 increases, some water from the pressure vessel 2 enters the air-water reservoir 4 through a pipe. Due to the compressibility of air, the air volume above the air-water reservoir 4 decreases, thus absorbing the pressure fluctuations caused during the test. Similarly, when the pressure around the soil sample 3 decreases, some water in the air-water reservoir 4 flows into the pressure vessel 2, and the volume of air above it increases, ultimately absorbing the pressure fluctuations caused during the test.

[0013] A method for using a controllable wave-absorbing anti-interference device in an ultra-large triaxial testing apparatus includes three stages: the initial test stage, the test phase stage, and the test completion stage. The specific steps are as follows:

[0014] In the initial stage of the test, the axial and radial loads increased slowly, and the pressure in the pressure vessel 2 continuously increased. Simultaneously, the first A / D converter 7 continuously acquired the differential pressure signal from the differential pressure sensor 6 and transmitted it to the controller 12; the second A / D converter 9 continuously acquired the pressure signal from the pressure sensor 8 and transmitted it to the controller 12. Based on the acquired differential and pressure signals, the controller 12 first caused the valve core of the reversing valve 10 to move to the left through the digital output interface 11, allowing gas to flow into the air-water reservoir 4. Then, the controller 12 controlled the D / A converter 15 to output an analog signal, which was amplified by the amplifier 18 to drive the electronic pressure regulator 14. The electronic pressure regulator 14 controlled the piston of the pressure boosting valve 13 to move to the left, allowing gas to flow into the air-water reservoir 4 through the reversing valve 10, slowly increasing the pressure above the air-water reservoir 4 and maintaining a constant air volume above the air-water reservoir 4, ensuring that the device has the same wave absorption capability under different radial load test conditions.

[0015] During the testing phase, before the axial excitation signal is applied, the hydraulic rod 1, pressure vessel 2, soil sample specimen 3, and air-water reservoir 4 are kept in equilibrium, and the air inlet at the top of the air-water reservoir 4 is sealed. When the axial excitation signal is applied, the radial pressure around the soil sample specimen 3 changes. Specifically, when the radial pressure in pressure vessel 2 increases, some water in pressure vessel 2 flows into the air-water reservoir 4 through the conduit, compressing the air above the air-water reservoir 4. The air-water reservoir 4 automatically absorbs the pressure fluctuations caused by the increase in radial pressure, and the damping net 5 prevents liquid splashing caused by the sudden increase in liquid in the air-water reservoir 4. When the radial pressure in pressure vessel 2 decreases, some water in the air-water reservoir 4 flows into pressure vessel 2 through the conduit, increasing the air volume above the air-water reservoir 4. The air-water reservoir 4 automatically absorbs the pressure fluctuations caused by the decrease in radial pressure.

[0016] At the end of the test, the axial and radial loads gradually decreased, and the pressure in the pressure vessel 2 continuously decreased. Based on the obtained differential pressure and pressure signals, the controller 12 first caused the valve core of the reversing valve 10 to move to the right through the digital output interface 11, allowing gas to flow out from the air-water reservoir 4. Then, the controller 12 outputs an analog signal through the D / A converter 15 and amplifier 18, driving the electronic pressure regulator 14. The electronic pressure regulator 14 controls the piston of the pressure booster valve to move to the right, gradually reducing the pressure above the air-water reservoir 4.

[0017] In summary, a controllable wave-absorbing and anti-interference device composed of a controller 12, a pressure boosting valve 13, an electronic air pressure regulator 14, a D / A converter 15, a reversing valve 10, a digital output interface 11, and an air-water reservoir 4 is designed. By utilizing the compressibility of the gas above the air-water reservoir 4, the pressure fluctuation problem caused by radial load changes during axial loading is solved.

[0018] The effects and benefits of this invention are:

[0019] 1) The controllable wave absorption and anti-interference device provided by the present invention solves the problem of mutual coupling between axial load and radial load during the test, and can absorb the pressure fluctuation caused by the change of radial load during axial excitation.

[0020] 2) The controllable wave absorption and anti-interference device provided by the present invention uses the differential pressure signal obtained by the differential pressure sensor and the pressure signal obtained by the pressure sensor. The controller controls the pressure boosting valve through the electronic air pressure regulator to change the air pressure above the air-water reservoir. This makes the wave absorption capacity of the controllable wave absorption and anti-interference device the same under different radial load test conditions.

[0021] 3) The controllable wave absorption and anti-interference device provided by the present invention is a purely mechanical decoupling device. It does not require the establishment of an accurate mathematical model or a complex algorithm. It has a simple structure, is easy to control, and has a low cost. It can significantly absorb pressure fluctuations caused during the test. Attached Figure Description

[0022] Figure 1 This is a controllable wave-absorbing anti-interference device control principle diagram.

[0023] Figure 2 This is a structural diagram of a controllable wave-absorbing anti-interference device.

[0024] In the diagram: 1 Hydraulic rod, 2 Pressure vessel, 3 Soil sample specimen, 4 Air-water reservoir, 5 Shock absorber net, 6 Differential pressure sensor, 7 First A / D converter, 8 Pressure sensor, 9 Second A / D converter, 10 Reversing valve, 11 Digital output interface (DO), 12 Controller, 13 Pressure booster valve, 14 Electronic air pressure regulator, 15 D / A converter, 16 Dryer, 17 Pressure reducing valve, 18 Amplifier, 19 Filter, 20 Air tank, 21 Pump, 22 Motor. Detailed Implementation

[0025] The specific embodiments of the present invention are described in detail below with reference to the technical solutions and accompanying drawings.

[0026] A controllable wave-absorbing and anti-interference device for an ultra-large triaxial testing machine includes an air-water reservoir 4, a shock-absorbing mesh 5, a differential pressure sensor 6, first and second A / D converters 7 and 9, a pressure sensor 8, a reversing valve 10, a digital output interface DO 11, a controller 12, a pressure boosting valve 13, an electronic air pressure regulator 14, a D / A converter 15, a dryer 16, a pressure reducing valve 17, an amplifier 18, a filter 19, an air tank 20, a pump 21, and a motor 22.

[0027] The air-water reservoir 4 is connected to the internal space of the pressure vessel 2 of the loading system via a pipe. The loading system includes the pressure vessel 2, the soil sample specimen 3 inside it, and the hydraulic rod 1 on top of the soil sample specimen 3. An air inlet is provided on the top of the air-water reservoir 4. The differential pressure sensor 6 is fixed to the upper end of the air-water reservoir 4. The differential pressure sensor 6 includes two measuring ports, and the positions of the measuring ports are fixed: one port is exposed above the air portion inside the air-water reservoir 4, and the other port is inserted into the liquid portion inside the air-water reservoir 4. The differential pressure signals measured by the two measuring ports are collected by a high-precision first A / D converter 7 and transmitted to the external controller 12. The pressure sensor 8 is fixed to the upper end of the air-water reservoir 4, and the measured pressure signal is collected by a high-precision second A / D converter 9 and transmitted to the controller 12. The controller 12 is connected to the digital output interface DO11, and also sequentially connected to the first and second A / D converters 7 and 9, and the D / A converter 15. It controls the pressure boosting valve 13 through an amplifier 18 and an electronic air pressure regulator 14. The reversing valve 10 is located between the air-water reservoir 4 and the booster valve 13, communicating with the internal space of the air-water reservoir 4. It controls the flow of gas into or out of the air-water reservoir 4 by changing the position of the valve core, and is controlled by the controller 12. The booster valve 13 is located between the electronic pressure regulator 14 and the reversing valve 10, directly connected to the air-water reservoir 4 via the reversing valve 10. It is used to change the air pressure above the air-water reservoir 4 and is controlled by the electronic pressure regulator 14. The electronic pressure regulator 14 is located between the controller 12 and the booster valve 13, controlling the booster valve to regulate the air pressure above the air-water reservoir 4, and is controlled by the controller 12. The gas tank 20 is located outside the air-water reservoir 4, sequentially connected to the filter 19, dryer 16, pressure reducing valve 17, and booster valve 13. It is connected to the motor 22 via the pump 21 to provide power, supplying gas pressure to the air-water reservoir 4.

[0028] In this embodiment, a shock-absorbing mesh 5 is provided at the liquid level inside the air-water reservoir 4 to reduce minor pressure fluctuations caused by the flow of liquid inside the air-water reservoir 4 and prevent liquid splashing. The gas tank 20 is connected to the filter 19 to filter out impurities in the gas and improve gas quality. The dryer 16 is connected to the filter 19 to absorb moisture from the gas.

[0029] As attached Figures 1-2 As shown, the two measuring ends of the differential pressure sensor 6 are always fixed, ensuring that the initial volume of air above the air-water reservoir 4 remains constant during each loading process, thus achieving the same wave absorption capacity under different radial load test conditions. The pressure sensor 8 measures the air pressure above the air-water reservoir 4, realizing closed-loop control.

[0030] A method for using a controllable wave-absorbing anti-interference device in an ultra-large triaxial testing apparatus includes three stages: the initial test stage, the test phase stage, and the test completion stage. The specific steps are as follows:

[0031] In the initial stage of the experiment, as shown in the attached document Figure 2 As shown, the axial and radial loads increase slowly, and the pressure in pressure vessel 2 continuously increases. Meanwhile, as shown in the attached diagram... Figure 1 As shown, the 16-bit A / D converter 7 continuously acquires the differential pressure signal obtained by the differential pressure sensor 6 and transmits it to the controller 12; the 16-bit A / D converter 9 continuously acquires the pressure signal obtained by the pressure sensor 8 and transmits it to the controller 12. Based on the acquired differential pressure and pressure signals, the controller 12 first uses the digital output interface 11 to move the valve core of the reversing valve 10 to the left, allowing gas to flow into the air-water reservoir 4. Then, the controller 12 controls the 16-bit D / A converter 15 to output an analog signal, which is amplified by the amplifier 18 to drive the electronic pressure regulator 14. The electronic pressure regulator 14 controls the piston of the pressure boosting valve 13 to move to the left, allowing gas to flow into the air-water reservoir 4 through the reversing valve 10, slowly increasing the pressure above the air-water reservoir 4 and maintaining a constant air volume above the air-water reservoir 4, ensuring that the device has the same wave absorption capability under different radial load test conditions.

[0032] During the testing phase, before the axial excitation signal is applied, the hydraulic rod 1, pressure vessel 2, soil sample 3, and air-water reservoir 4 are kept in balance, with the air inlet at the top of the air-water reservoir 4 sealed. When the axial excitation signal is applied, the hydraulic rod 1 moves up and down, causing a change in the volume of the rod entering the pressure vessel 2. This changes the radial pressure around the soil sample 3. Simultaneously, due to the presence of air bubbles and gaps around the soil sample 3, the volume of the soil sample 3 itself changes, further altering the radial pressure around it. As the radial pressure in the pressure vessel 2 increases, some water in the pressure vessel 2 flows into the air-water reservoir 4 through a conduit. The air above the air-water reservoir 4 is compressed, and the air-water reservoir 4 automatically absorbs the pressure fluctuations caused by the increased radial pressure. The damping mesh 5 prevents liquid splashing caused by a sudden increase in liquid in the air-water reservoir 4. When the radial pressure in the pressure vessel 2 decreases, some water from the air-water reservoir 4 flows into the pressure vessel 2 through the conduit, and the air volume above the air-water reservoir 4 increases. The air-water reservoir 4 automatically absorbs the pressure fluctuations caused by the decrease in radial pressure.

[0033] At the end of the test, the axial and radial loads gradually decreased, and the pressure in the pressure vessel 2 continuously decreased. Based on the obtained differential pressure and pressure signals, the controller 12 first caused the valve core of the reversing valve 10 to move to the right through the digital output interface 11, allowing gas to flow out from the air-water reservoir 4. Then, the controller 12 outputs an analog signal through the 16-bit D / A converter 15 and amplifier 18, driving the electronic pressure regulator 14. The electronic pressure regulator 14 controls the piston of the pressure boosting valve to move to the right, gradually reducing the pressure above the air-water reservoir 4.

[0034] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A controllable wave-absorbing anti-interference device for an ultra-large triaxial testing apparatus, characterized in that, The controllable wave-absorbing anti-interference device includes an air-water reservoir (4), a differential pressure sensor (6), a pressure sensor (8), a reversing valve (10), a controller (12), a booster valve (13), an electronic air pressure regulator (14), a dryer (16), a pressure reducing valve (17), an amplifier (18), a filter (19), an air tank (20), a pump (21), and a motor (22). The bottom of the air-water reservoir (4) is connected to the internal space of the pressure vessel (2) of the loading system through a pipe. The loading system includes the pressure vessel (2), the soil sample specimen (3) inside it, and the hydraulic rod (1) on the top of the soil sample specimen (3). An air inlet is provided on the top of the air-water reservoir (4) to provide radial load to the loading system. The differential pressure sensor (6) is fixed on the upper end of the air-water reservoir (4), and the differential pressure signal measured by its two measuring ports is transmitted to the controller (12). The pressure sensor (8) is fixed on the upper end of the air-water reservoir (4), and the measured pressure signal is transmitted to the controller (12). The reversing valve (10) is located between the air-water reservoir (4) and the booster valve (13), and is connected to the internal space of the air-water reservoir (4). It is controlled by the controller (12) to change the direction of gas flow. The booster valve (13) is located between the electronic pressure regulator (14) and the reversing valve (10), and is controlled by the electronic pressure regulator (14). It is connected to the air-water reservoir (4) through the reversing valve (10) to change the air pressure above the air-water reservoir (4). The electronic pressure regulator (14) is located between the controller (12) and the booster valve (13) to control the booster valve to achieve air pressure regulation above the air-water reservoir (4). It is controlled by the controller (12). The gas tank (20) is located outside the air-water reservoir (4) and is connected in sequence to the filter (19), dryer (16), pressure reducing valve (17), and pressure boosting valve (13). It is connected to the motor (22) via the pump (21) to provide power for supplying gas pressure to the air-water reservoir (4). After the controller (12) processes the obtained differential pressure signal and pressure signal, it outputs an analog signal after being processed by the D / A converter (15) and amplifier (18) in sequence, and transmits it to the electronic air pressure regulator (14), which then controls the booster valve (13) to change the internal pressure of the air-water reservoir (4) while keeping the air volume above the air-water reservoir (4) unchanged, so that the controllable wave absorption and anti-interference device has the same wave absorption capacity under different radial load test conditions.

2. The controllable wave absorption and interference suppression device in an ultra-large triaxial testing apparatus according to claim 1, characterized in that, The differential pressure sensor (6) has two fixed measuring ports: one port is exposed above the air portion inside the air-water reservoir (4), and the other port is inserted into the liquid portion inside the air-water reservoir (4).

3. The controllable wave absorption and interference suppression device in an ultra-large triaxial testing apparatus according to claim 1, characterized in that, The differential pressure signal measured by the two measuring ports of the differential pressure sensor (6) is acquired by a high-precision first A / D converter (7) and transmitted to the external controller (12); the pressure signal measured by the pressure sensor (8) is acquired by a high-precision second A / D converter (9) and transmitted to the controller (12).

4. The controllable wave absorption and interference suppression device in an ultra-large triaxial testing apparatus according to claim 1, characterized in that, The air-water reservoir (4) is provided with a shock-absorbing mesh (5) at the liquid level to reduce the slight pressure fluctuations caused by the flow of liquid in the air-water reservoir (4) and prevent liquid splashing.

5. A method of using the controllable wave-absorbing anti-interference device in the ultra-large triaxial testing apparatus according to any one of claims 1-4, characterized in that, The experiment consists of three phases: the initial phase, the testing phase, and the final phase. The specific steps are as follows: In the initial stage of the test, the axial load and radial load increased slowly, and the pressure in the pressure vessel (2) continued to increase. At the same time, the first A / D converter (7) continuously collected the differential pressure signal obtained by the differential pressure sensor (6) and transmitted it to the controller (12); the second A / D converter (9) continuously collected the pressure signal obtained by the pressure sensor (8) and transmitted it to the controller (12); the controller (12) based on the obtained differential pressure signal and pressure signal first caused the valve core of the reversing valve (10) to move to the left through the digital output interface (11), and the gas flowed into the air-water system. Above the reservoir (4); then the controller (12) controls the D / A converter (15) to output an analog signal, which is amplified by the amplifier (18) to drive the electronic air pressure regulator (14). The electronic air pressure regulator (14) controls the piston of the pressure boosting valve (13) to move to the left, and the gas flows into the air-water reservoir (4) above the air-water reservoir (4) through the reversing valve (10), slowly increasing the pressure above the air-water reservoir (4) and keeping the air volume above the air-water reservoir (4) constant, so that the device has the same wave absorption capacity under different radial load test conditions; During the test phase, before the axial excitation signal is applied, the hydraulic rod (1), pressure vessel (2), soil sample (3), and air-water reservoir (4) are kept in balance, and the air inlet of the air-water reservoir (4) is closed. When the axial excitation signal is applied, the radial pressure around the soil sample (3) changes. That is, when the radial pressure in the pressure vessel (2) increases, some water in the pressure vessel (2) flows into the air-water reservoir (4) through the conduit. The air above the air-water reservoir (4) is compressed. The air-water reservoir (4) automatically absorbs the pressure fluctuation caused by the increase in radial pressure. The damping net (5) prevents liquid splashing caused by the sudden increase in liquid in the air-water reservoir (4). When the radial pressure in the pressure vessel (2) decreases, some water in the air-water reservoir (4) flows into the pressure vessel (2) through the conduit. The air volume above the air-water reservoir (4) increases. The air-water reservoir (4) automatically absorbs the pressure fluctuation caused by the decrease in radial pressure. At the end of the test, the axial load and radial load slowly decreased, and the pressure in the pressure vessel (2) continued to decrease. According to the obtained differential pressure signal and pressure signal, the controller (12) first caused the valve core of the reversing valve (10) to move to the right through the digital output interface (11), and the gas flowed out from the air-water reservoir (4). Then the controller (12) output an analog signal through the D / A converter (15) and amplifier (18) to drive the electronic air pressure regulator (14). The electronic air pressure regulator (14) controlled the piston of the pressure booster valve to move to the right, and slowly reduced the pressure above the air-water reservoir (4).

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