Device for measuring change in strength performance of soil mass under lightning impulse and measuring method thereof

Abstract

The present invention provides a device and a measuring method for determining the change in the strength performance of soil under lightning shock. The device of the present invention mainly includes an impulse current generator, an upper specimen box, a lower specimen box, a grounding electrode, a permeable stone, a pressure plate, a pressure piston, a pressure sensor, a differential displacement gauge, a hydraulic system, and a computer data acquisition system. The impulse current generator can be used to generate lightning impulse current. The upper specimen box and the lower specimen box can be used to accommodate soil and the grounding electrode. There are two grounding electrodes. One grounding electrode is electrically connected to the current output terminal of the impulse current generator, and the other grounding electrode is grounded. The specimen box can be used to conduct direct shear tests and unidirectional compression tests to measure the change in the mechanical strength of the soil. The device of the present invention can well simulate the change in the mechanical strength of the soil caused by lightning shock, thereby providing a reference for exploring the mechanism of soil lightning disasters.

Description

Technical Field

[0001] The present invention relates to the field of environmental geotechnical engineering, and particularly to a device for measuring the change of the strength performance of soil under lightning impact and a measuring method thereof. Background Art

[0002] Lightning is a natural phenomenon that exists ubiquitously on the earth. There are a total of 1.4 billion lightning strikes globally every year on average, with a frequency of about 45 times per second. More than half of these lightning strikes occur within clouds. Although cloud-to-ground lightning only accounts for one-third of the lightning strikes, it has the greatest impact on the surface environment. Cloud-to-ground lightning has characteristics such as instantaneity, suddenness, and high danger. It is actually a process in which a powerful lightning current releases energy to the ground. Each cloud-to-ground lightning strike involves 10 9 -10 10 J of energy. Although most of this energy is consumed during air conduction to produce thunder, hot air, light, and radio waves, when it hits the ground, about 108 J of energy is still released into the ground, and its peak current can still reach dozens of kiloamperes, or even hundreds of kiloamperes, lasting for dozens of microseconds. The huge energy will cause a significant mechanical impact effect on the soil.

[0003] At present, a large number of studies only focus on the lightning impact characteristics of grounding devices, but the research on the impact of lightning impact on soil is very lacking. It should be noted that, first of all, whether it is the use of grounding devices or other lightning protection measures, the huge energy of the final lightning current will be discharged into the soil, which will inevitably cause certain strength damage to the soil; secondly, in the lightning protection design of grounding devices, the transient characteristics of the grounding device have a great impact on the lightning protection effect. However, the grounding device buried in the soil and the soil are a closely contacted whole, and the transient characteristics and lightning protection effect of the grounding device will be directly affected by the surrounding soil; finally, for the existing research devices and methods for soil under lightning impact, the scope and depth of the cross-research on lightning and geotechnical engineering are still far from enough. For example, in the patent of "Device for Measuring Electrical Response of Soil under Lightning Impact" with the application number 201310202692.3, the main disadvantage of this patent is that it can only measure the current waveform and pore water pressure in the soil under lightning impact, and cannot obtain some mechanical strength performance change data of the soil under lightning impact. Moreover, using two electrode plates as the electrodes of the grounding system does not conform to the actual situation, and the measured current waveform and other data have little value for the geotechnical engineering field that focuses on mechanical properties. Therefore, for the lack of existing research on the impact of lightning on soil devices and technologies, especially the research on the characteristics such as the change of the mechanical strength performance of the soil caused by lightning impact still has many immature points. It is of great significance to develop and design a device and method that can measure the change of the mechanical strength performance of the soil under lightning impact. Summary of the Invention

[0004] The object of the present invention is to provide a device and method for measuring the change in the mechanical strength performance of soil before and after lightning strikes.

[0005] To achieve the above object, the present invention provides a device for measuring the change in the strength performance of soil under lightning strike, including a sample box, two grounding electrodes, a direct shear module for soil, a one-way compression module for soil, a computer acquisition system, and an impulse current generator;

[0006] The sample box is composed of an upper sample box and a lower sample box symmetrically arranged up and down; the interior of the sample box is filled with a soil sample, and the two grounding electrodes are embedded in the soil sample, one of the grounding electrodes is electrically connected to the impulse current generator, and the other grounding electrode is grounded;

[0007] The top of the upper sample box is a through hole, and the one-way compression module for soil applies pressure to the internal soil sample through the through hole; the direct shear module for soil is connected to the upper sample box and pushes the upper sample box to displace relative to the lower sample box;

[0008] The direct shear module for soil, the one-way compression module for soil, and the impulse current generator are all connected to the computer acquisition system by signals.

[0009] Furthermore, it further includes a bracket and a base;

[0010] The sample box is fixed to the base by bolts, and the direct shear module for soil and the one-way compression module for soil are arranged around the outer periphery of the sample box through the bracket.

[0011] Furthermore, in the sample box, a permeable stone layer is laid on both the top surface and the bottom surface of the soil.

[0012] The top of the upper sample box is provided with a drainage hole; the side surfaces of the upper sample box and the lower sample box are provided with holes for external connection of the grounding electrode; after the upper sample box and the lower sample box are butt-jointed and matched, they are fixed into a box by bolts.

[0013] Furthermore, the one-way compression module for soil includes: a vertical differential displacement gauge, a vertical pressure sensor, a vertical piston, and a hydraulic system;

[0014] The vertical piston is arranged above the sample box and is driven by the hydraulic system to press the soil. The vertical differential displacement gauge records the deformation amount of the soil, the vertical pressure sensor is connected to the hydraulic system by signals and records the pressure; both the vertical piston and the vertical differential displacement gauge are connected to the computer acquisition system by signals.

[0015] Furthermore, the direct shear module for soil includes a horizontal differential displacement gauge, a horizontal piston, a horizontal pressure sensor, and a hydraulic system;

[0016] The horizontal piston is arranged on the side of the upper specimen box through the hydraulic system. The horizontal differential displacement meter records the displacement distance of the upper specimen box. The horizontal pressure sensor is signal-connected to the hydraulic system to record the horizontal pressure. Both the horizontal differential displacement meter and the horizontal pressure sensor are signal-connected to the computer acquisition system.

[0017] The present invention also provides a method for measuring the change in the mechanical strength performance of soil under lightning impulse action, including the following steps:

[0018] S1): Determine the test parameters;

[0019] S2): Install the experimental device according to the test parameters;

[0020] S3): Conduct the direct shear test and unidirectional compression test of the soil before lightning impulse; obtain the mechanical parameter indexes of the soil sample before lightning impulse action: cohesion X1, internal friction angle Y1, and compression modulus Z1;

[0021] S4): Conduct the lightning impulse discharge test;

[0022] S5): Conduct the direct shear test and unidirectional compression test of the soil before lightning impulse, and obtain the mechanical parameter indexes of the soil after lightning impulse: cohesion X2, internal friction angle Y2, and compression modulus Z2;

[0023] S6): Analyze the test results; through the calculation formulas and obtain the magnitude of the change in the mechanical strength of the soil under various lightning current parameters and soil sample parameters, providing important data support for the lightning-induced disaster mechanism of the soil and the evolution law of mechanical properties.

[0024] Further, in S1), the test parameters include: soil moisture content, salt content, pH value, the size and arrangement distance of the grounding electrode, lightning current amplitude and waveform parameters, and multiple groups of designed soil samples are made.

[0025] Further, in S2), calculate the amount of soil material according to the size of the specimen box and the initial porosity of the set soil, fill in the soil material and the grounding electrode according to the design requirements of the grounding electrode arrangement distance, compact the soil material to the top surface of the upper specimen box, and install multiple groups of devices.

[0026] Further, in S3), start the hydraulic system to apply different vertical pressures to each group of tests through the vertical piston. After the soil sample is stable, start the horizontal piston and push the upper sample box to the right at a constant speed to start the shear test until the soil sample fails. During the shear process, the computer data acquisition system obtains the shear-displacement curve of the soil sample. Through data processing, the cohesion and internal friction angle strength parameters of the soil body of each group of samples can be obtained, and their average values are taken as the soil strength parameters under the conditions of this soil sample. Start the hydraulic system to sequentially apply different levels of vertical pressure to the soil sample through the vertical piston. Each level of vertical pressure increases in sequence. Each time, it is necessary to wait for the deformation to be stable before applying the next level of vertical pressure. The computer data acquisition system will record the readings of the vertical differential displacement gauge at each pressure level. Through data processing, deformation parameters such as the compression modulus of the soil body can be obtained, and their average values are taken as the soil deformation parameters under the conditions of this soil sample;

[0027] In step S5), the same operating steps as in step S3) are adopted.

[0028] Compared with the prior art, the advantages of the present invention are as follows: In the device and method of the present invention, since the impulse current generator adopted can simulate lightning currents of arbitrary waveforms and amplitudes, and this device can regulate parameters such as the moisture content, salt content, and pH value of the soil body and parameters such as the size and arrangement distance of the grounding electrode, it can well simulate the mechanical impact effect of lightning on the soil body. Through direct shear tests and one-way compression tests, the changes in the mechanical strength performance of the soil body before and after lightning strikes and the influence laws of various parameters can be effectively evaluated, and it is simple, easy to implement, and low in cost, which can provide important data support for the lightning disaster mechanism and mechanical property evolution law of the soil body. Description of the Drawings

[0029] Figure 1 It is a schematic structural layout diagram of the device for measuring the change in strength performance of the soil body under lightning strike of the present invention;

[0030] Figure 2 It is a side view of the sample box of the present invention;

[0031] Figure 3 It is Figure 1 the sectional view taken along A-A of

[0032] Figure 4 It is the principle wiring diagram of the impulse current generator of the present invention;

[0033] In the figure: 1 upper specimen box, 2 lower specimen box, 3 grounding electrode, 4 permeable stone, 5 pressure plate, 6 drainage hole, 7 horizontal differential displacement gauge, 8 vertical differential displacement gauge, 9 vertical pressure sensor, 10 vertical piston, 11 horizontal piston, 12 horizontal pressure sensor, 13 hydraulic system, 14 computer data acquisition system, 15 impulse current generator, 16 base, 17 bracket, 18 soil sample, 19 hole, 20 bolt, 21 pulse capacitor bank, 22 protective resistor, 23 control system, 24 silicon stack, 25 wave tuning resistor, 26 wave tuning inductor, 27 electric ignition sphere gap, 28 step-up transformer, 29 specimen. Detailed implementation manner

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be further described below.

[0035] Embodiment 1

[0036] As Figure 1 shown. A device for measuring the change of strength performance of soil under lightning impact includes an upper specimen box 1, a lower specimen box 2, a grounding electrode 3, a permeable stone 4, a pressure plate 5, a drainage hole 6, a horizontal differential displacement gauge 7, a vertical differential displacement gauge 8, a vertical pressure sensor 9, a vertical piston 10, a horizontal piston 11, a horizontal pressure sensor 12, a hydraulic system 13, a computer data acquisition system 14, an impulse current generator 15, a base 16, a bracket 17, and a soil sample 18.

[0037] Among them, both the upper specimen box 1 and the lower specimen box 2 are made of tempered glass and have a hollow structure inside. The length is 500 mm, the width is 500 mm, and the height is 200 mm. The internal structure is used to accommodate the soil sample 19 and the grounding electrode 3. The top surface of the lower specimen box is open, and there are two bolt holes at both the upper and lower ends of the left and right sides. The upper end is connected to the upper specimen box through a bolt 20, and the lower bottom surface is fixed on the test platform base 16 and is provided with a drainage hole 6. Both the upper and lower surfaces of the upper specimen box are open. The left side is connected to the external horizontal piston 11 and is provided with a horizontal pressure sensor 12. The right side is provided with a horizontal differential displacement gauge 7, which can be used to obtain the shear load-displacement curve of the soil during the direct shear test before and after lightning impact and obtain the shear strength index of the soil. Permeable stones 4 with the same size as the internal dimensions of the specimen box are arranged on both the upper and lower sides of the specimen box. The soil sample 18 and the grounding electrode 3 are filled in the middle area. A pressure plate 5 is arranged on the top surface. A vertical piston 10 is provided above the pressure plate 5, and a vertical pressure sensor 9 and a vertical differential displacement gauge 8 are respectively arranged, which can be used to obtain deformation indexes such as the compression modulus of the soil during the unidirectional compression test before and after lightning impact.

[0038] The hydraulic system 13 provides the vertical pressure and horizontal thrust required for the direct shear test and the unidirectional compression test.

[0039] Five groups of this sample box should be installed. The soil samples 18 in the sample box are soil bodies with water contents of 0%, 5%, 10%, 15% and 20% respectively, so as to study the influence law of the water content of the soil body on the change of the mechanical strength performance of the soil body under lightning impulse.

[0040] There are two grounding electrodes 3, both made of copper, with a circular cross-section of a radius of 5 mm and a length of 300 mm. During the test, the two grounding electrodes 3 are respectively buried in the soil samples 18 of the upper sample box 1 and the lower sample box 2, at a distance of 100 mm from the vertical interface of the upper and lower sample boxes. Both ends of the two grounding electrodes 3 are 100 mm away from the left and right side faces of the sample box, and the distances from the front and back side faces of the specific sample box are equal, and they are at the center of the front and back box faces of the sample box.

[0041] The horizontal pressure sensor 12, the vertical pressure sensor 9, the horizontal differential displacement gauge 7 and the vertical differential displacement gauge 8 are all connected to the computer data acquisition system 14 through acquisition signal lines to obtain test data. The direct shear test and the one-way compression test methods in the "Standard for Geotechnical Test Methods" (GB / T 50123 - 2019) are used to analyze the collected data to obtain the strength change of the soil body.

[0042] As Figure 2 is the side view of the sample box of the present invention. The upper sample box 1 and the lower sample box 2 are connected by bolts 20, and the lower sample box 2 is connected to the base 16 by bolts. There is a hole 19 with a radius of 5 mm at the center of the left side faces of the upper sample box 1 and the lower sample box 2. During the installation of the device, the current injection end of the grounding electrode 3 in the upper sample box 1 is electrically connected to the current output end of the impulse current generator through the hole 19, and the grounding electrode 3 in the lower sample box 2 is grounded through the hole 19.

[0043] Figure 3 For Figure 1 is the sectional view of A - A. During the installation process of this device, first place a permeable stone 4 with a size of 500 mm * 500 mm * 8 mm at the bottom of the lower sample box 2. Calculate the amount of soil material according to the initial porosity of the soil body, fill the sample box with soil samples 18 with different water contents to a position 100 mm away from the bottom of the lower sample box 2, install the grounding electrode 3 in the lower sample box 2, and then continue to fill the soil sample 18 to the center of the upper sample box 1. At this time, the top of the soil sample is 300 mm away from the bottom of the lower sample box, install the grounding electrode 3 in the upper sample box, continue to fill the soil sample 18 until it is 10 mm away from the top of the upper sample box, place the permeable stone 4 on the soil sample 18, and finally place the pressure plate.

[0044] Figure 4This is the schematic wiring diagram of the impulse current generator 15 of the present invention, including a pulse capacitor bank 21, a protection resistor 22, a control console 23, a silicon stack 24, a wave-shaping resistor 25, a wave-shaping inductor 26, an electric ignition spark gap 27, and a step-up transformer 28. The input end of the impulse current generator 15 is connected to the 220V mains through a cable, and the current output end is electrically connected to the current injection end of the grounding electrode 3 in the upper sample box. The wavefront time and the wave tail time of the output lightning current waveform can be controlled by adjusting the wave-shaping inductor 26 and the wave-shaping resistor 25 of the impulse current generator, and the amplitude of the output lightning current can be controlled by adjusting the charging voltage of the pulse capacitor bank 21, so as to generate a lightning impulse current waveform with an amplitude of 8 - 200kA, a wavefront time of 1.2 - 20us, and a wave tail time of 20 - 1000us. In this embodiment, a current waveform with an amplitude of 20kA and a waveform of 10 / 350us is adopted. The control system 23 of the impulse current generator 15 is connected to the electric ignition spark gap 27 through an optical fiber. After the pulse capacitor bank 21 is charged, the control system 23 transmits a trigger signal to the electric ignition spark gap 27 through the optical fiber to generate an electric spark between the gaps, thereby generating a lightning current acting on the soil sample 18 to complete the discharge process.

[0045] When this device measures the change in the strength performance of the soil before and after lightning strikes, multiple repeated tests need to be carried out, and the average value of the strength measurement results of each test is taken as the soil strength value under the action of this lightning impulse current to reduce the influence of external environmental factors on the results.

[0046] Embodiment 2

[0047] A device for measuring the change in the strength performance of soil under the action of lightning strikes is the same as that in Embodiment 1. Among them, the internal space dimensions of the upper sample box 1 and the lower sample box 2 are both 600mm * 600mm * 300mm. The cross-section of the grounding electrode 3 is a circle with a radius of 8mm and a length of 400mm. The arrangement distance between the two grounding electrodes is 300mm, and they are placed at the center of the sample box. The soil samples 18 in the sample box are soils with salt contents of 0%, 2%, 4%, 6%, and 8% respectively, and a lightning current waveform with an amplitude of 20kA and a waveform of 10 / 350us is adopted.

[0048] Embodiment 3

[0049] A device for measuring the change in the strength performance of soil under the action of lightning strikes is the same as that in Embodiment 1. Among them, the internal space dimensions of the upper sample box 1 and the lower sample box 2 are both 600mm * 600mm * 300mm. The cross-section of the grounding electrode 3 is a circle with a radius of 8mm and a length of 400mm. The arrangement distance between the two grounding electrodes is 300mm, and they are placed at the center of the sample box. The water content and salt content of the soil sample 18 in the sample box are both 0%. Tests are carried out respectively with lightning current waveforms with amplitudes of 20kA, 40kA, 60kA, 80kA, and 100kA and a waveform of 10 / 350us.

[0050] A method for measuring the change in the mechanical strength performance of soil before and after lightning strikes. By determining test parameters, installing test equipment, conducting direct shear tests and unidirectional compression tests on the soil before lightning strikes, conducting lightning strike discharge tests, conducting direct shear tests and unidirectional compression tests on the soil before lightning strikes, and analyzing test results, etc., the change in the mechanical strength performance of the soil before and after lightning strikes is obtained. The specific steps of the method are as follows

[0051] S1) Determine test parameters.

[0052] Including the moisture content, salt content, and pH value of the soil 18, the size and layout distance of the grounding electrode 3, the lightning current amplitude and waveform parameters, and making multiple groups of designed soil samples.

[0053] ① Determine the lightning current amplitude and waveform parameters. By adjusting the wave-shaping resistor 25 and wave-shaping inductor 26 of the impulse current generator 15, the front time and tail time of the output lightning current waveform are controlled, and by adjusting the charging voltage of the pulse capacitor bank 21, the amplitude of the output lightning current is controlled. Its reference value can be determined through simulation software or calculation formulas before adjustment.

[0054] ② Determine soil parameters. According to the test requirements, determine the moisture content, salt content, pH value, etc. of the soil. First, clean the soil sample to remove soluble salt components, dry it after cleaning to remove moisture, and then add a preset mass of water and salt according to the test requirements to make multiple groups of soil samples.

[0055] S2) Install the test equipment.

[0056] Calculate the amount of soil material according to the size of the sample box and the set initial porosity of the soil, fill in the soil material 18 and the grounding electrode 3 according to the design requirements of the layout distance of the grounding electrode 3. The current injection end of the grounding electrode 3 in the sample box 1 is electrically connected to the current output end of the impulse current generator through the hole 19, and the grounding electrode 3 in the lower sample box 2 is grounded through the hole 19. Compact the soil material 18 to the top surface of the upper sample box 1 and install multiple groups of the device of the present invention.

[0057] S3) Conduct direct shear tests and unidirectional compression tests on the soil before lightning strikes.

[0058] Adopt the methods of direct shear tests and unidirectional compression tests in the "Standard for Geotechnical Test Methods" (GB / T 50123 - 2019) to measure the strength parameters and deformation parameters of the soil before lightning strikes.

[0059] ① Conduct a direct shear test. Start the hydraulic system 13 to apply different vertical pressures to each group of tests through the vertical piston 10. After the soil sample is stable, start the horizontal piston 11 and push the upper sample box 1 to the right at a constant speed to start the shear test until the soil sample fails. During the shear process, the computer data acquisition system 14 obtains the shear-displacement curve of the soil sample. Through data processing, the strength parameters such as the cohesion and internal friction angle of the soil body of each group of samples can be obtained, and their average values are taken as the soil strength parameters under the conditions of this soil sample.

[0060] ② Conduct a one-way compression test. Start the hydraulic system 13 to apply different levels of vertical pressure to the soil sample in sequence through the vertical piston 10. The vertical pressure at each level increases in sequence. Each time, it is necessary to wait for the deformation to be stable before applying the next level of vertical pressure. The computer data acquisition system 14 will record the readings of the vertical differential displacement gauge 7 at each pressure level. Through data processing, the deformation parameters such as the compression modulus of the soil body can be obtained, and their average values are taken as the soil deformation parameters under the conditions of this soil sample.

[0061] S4) Conduct a lightning impulse discharge test.

[0062] After the impulse current generator 15 is adjusted, by pressing the "Trigger" key of the control system 23 of the impulse current generator 15, the electric ignition sphere gap 27 transmits a trigger signal to generate an electric spark between the sphere gaps, thereby generating a lightning current acting on the soil sample 18 to complete the discharge process.

[0063] S5) Conduct a direct shear test and a one-way compression test on the soil body before the lightning impulse.

[0064] Use the method described in S3) to conduct a direct shear test and a one-way compression test on the soil sample 18 after the lightning impulse, and obtain the strength parameters such as the cohesion and internal friction angle of the soil body after the lightning impulse and the deformation parameters such as the compression modulus at this time.

[0065] S6) Analysis of test results. For the mechanical parameter indexes of the soil sample before the action of the lightning impulse: cohesion X1, internal friction angle Y1, and compression modulus Z1, and the mechanical parameter indexes of the soil body after the lightning impulse: cohesion X2, internal friction angle Y2, and compression modulus Z2, they are processed according to the following expressions (1)-(3), and the magnitude of the change in the mechanical strength of the soil body under the conditions of each lightning current parameter and soil sample parameter can be obtained, which can provide important data support for the mechanism of soil lightning disaster and the evolution law of mechanical properties.

[0066]

[0067]

[0068]

[0069] The above are only the preferred embodiments of the present invention and do not impose any limitation on the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification and other changes to the technical solution and technical content disclosed by the present invention, which are all within the content of the technical solution of the present invention and still fall within the protection scope of the present invention.

Claims

1. A device for measuring the change in strength properties of soil under lightning impulse, It is characterized in that It includes a sample box, two grounding electrodes, a soil direct shear module, a soil unidirectional compression module, a computer acquisition system and an impulse current generator; The sample box is composed of an upper sample box and a lower sample box symmetrically arranged in the upper and lower parts; the sample box is filled with a soil sample, and two grounding electrodes are pre-buried in the soil sample, one of the grounding electrodes is electrically connected to the impulse current generator, and the other is grounded to the grounding electrode; The top of the upper sample box is a through hole, and the soil unidirectional compression module applies pressure to the internal soil sample through the through hole; the soil direct shear module is connected to the upper sample box to push the upper sample box to move relative to the lower sample box; The soil direct shear module, the soil unidirectional compression module and the impulse current generator are all connected to the computer acquisition system signal.

2. The device for measuring the change of strength properties of soil under lightning impulse according to claim 1, It is characterized in that Also includes a stand and base; The sample box is fixed on the base by bolts, and the soil direct shear module and the soil unidirectional compression module are arranged around the periphery of the sample box by the bracket.

3. The device for measuring the change of strength properties of soil under lightning impulse according to claim 1, It is characterized in that In the sample box, the top and bottom surfaces of the soil body are both paved with permeable stone layers; The top of the upper sample box is provided with a drainage hole; the sides of the upper sample box and the lower sample box are provided with holes for external connection of the grounding electrode; the upper sample box and the lower sample box are fixed into a box by bolts after being butt-jointed.

4. The device for measuring the change of strength properties of soil under lightning impulse according to claim 1, It is characterized in that The soil unidirectional compression module comprises: a vertical differential displacement meter, a vertical pressure sensor, a vertical piston and a hydraulic system; The vertical piston is arranged above the sample box and is driven by the hydraulic system to press the soil. The vertical differential displacement meter records the deformation of the soil. The vertical pressure sensor is connected to the hydraulic system signal to record the pressure. The vertical piston and the vertical differential displacement meter are both connected to the computer acquisition system signal.

5. The device for measuring the change of strength properties of soil under lightning impulse according to claim 1, It is characterized in that The soil direct shear module comprises a horizontal differential displacement meter, a horizontal piston, a horizontal pressure sensor and a hydraulic system; The horizontal piston is arranged on the side of the upper sample box through the hydraulic system, the horizontal differential displacement meter records the displacement distance of the upper sample box, the horizontal pressure sensor is connected with the hydraulic system signal to record the horizontal pressure; the horizontal differential displacement meter and the horizontal pressure sensor are both connected with the computer acquisition system signal.

6. A method for measuring the change in mechanical strength properties of soil under lightning impulse, using the device for measuring the change in strength properties of soil under lightning impulse as claimed in any one of claims 1 to 5, It is characterized in that The following steps are involved: S1): Determine the test parameters; S2): Install the experimental device according to the test parameters; S3): Conduct direct shear tests and one-way compression tests on the soil before lightning strikes; obtain the mechanical parameter indexes of the soil samples before lightning strikes: cohesion X1, internal friction angle Y1, and compression modulus Z1; Start the hydraulic system to apply different vertical pressures to each group of tests through the vertical piston. After the soil sample is stable, start the horizontal piston and push the upper sample box to the right at a constant speed to start the shear test until the soil sample fails; during the shear process, the computer data acquisition system obtains the shear-displacement curve of the soil sample. Through data processing, the cohesion and internal friction angle strength parameters of the soil body of each group of samples can be obtained, and their average values are taken as the soil strength parameters under the conditions of this soil sample; start the hydraulic system to apply different levels of vertical pressures to the soil sample in turn through the vertical piston. Each level of vertical pressure increases in turn. Each time, the next level of vertical pressure needs to be applied after the deformation is stable. The computer data acquisition system will record the readings of the vertical differential displacement gauge at each pressure level. Through data processing, deformation parameters such as the compression modulus of the soil body can be obtained, and their average values are taken as the soil deformation parameters under the conditions of this soil sample; S4): Conduct lightning strike discharge tests; S5): Conduct direct shear tests and one-way compression tests on the soil after lightning strikes, and obtain the mechanical parameter indexes of the soil after lightning strikes: cohesion X2, internal friction angle Y2, and compression modulus Z2; S6): Analysis of test results; through the calculation formula , and , the magnitude of the change in the mechanical strength of the soil under various lightning current parameters and soil sample parameters is obtained, providing important data support for the lightning disaster mechanism of the soil and the evolution law of mechanical properties.

7. The method for measuring the change in the mechanical strength performance of soil under lightning strike according to claim 6, wherein, in S1), the test parameters include: soil moisture content, salt content, pH value, the size and arrangement distance of the grounding electrode, lightning current amplitude and waveform parameters, and multiple groups of designed soil samples are made.

8. The method for measuring the change in the mechanical strength performance of soil under lightning strike according to claim 6, wherein, in S2), calculate the amount of soil material according to the size of the sample box and the designed initial porosity of the soil body, fill in the soil material and the grounding electrode according to the design requirements of the grounding electrode arrangement distance, compact the soil material to the top surface of the upper sample box, and install multiple groups of devices.

9. The method for measuring the change in the mechanical strength performance of soil under lightning strike according to claim 6, wherein, in step S5), the same operation steps as in step S3) are adopted.

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