Shearing strength parameter detection device and detection method based on piezoelectric ceramic piece

Abstract

The invention discloses a shearing strength parameter detection device based on piezoelectric ceramic pieces and a detection method. The device comprises a main body frame, a compression plate, a screw rod, a nut, a first piezoelectric ceramic piece, a second piezoelectric ceramic piece, a support column and a fixed seat, the first piezoelectric ceramic piece and the second piezoelectric ceramic piece are fixed in the container through nuts and are buried in the sample soil body; sample soil in the main body frame is compressed to a preset confining pressure condition through the compression plate by screwing the nut, a piezoelectric signal under the confining pressure condition is measured through the piezoelectric ceramic piece and external electronic equipment connected with the piezoelectric ceramic piece, wavelet packet decomposition is carried out on the piezoelectric signal, and a decomposed piezoelectric signal is obtained; establishing a relation curve between the piezoelectric signal change degree and the shear strength parameter according to the decomposed piezoelectric signal, and completing the detection; the soil compaction device is easy to operate, the compression plate is adjusted by rotating the nut to compact soil, and the soil compaction degree of the compression plate can be observed in real time through the scale marks on the main body framework.

Description

Technical Field

[0001] The present invention relates to the field of soil parameter detection, and specifically to a shear strength parameter detection device and detection method based on piezoelectric ceramic sheets. Background Art

[0002] In the field of civil engineering, the determination of soil mechanical parameters is of great significance for ensuring the safety and stability of engineering structures and preventing the occurrence of geological disasters. These parameters not only reflect the basic physical properties of the soil, but also directly affect the safety, stability and durability of engineering structures. Confining pressure refers to the pressure acting on the surrounding of the soil, which will have a significant impact on the stress state, deformation characteristics and shear strength of the soil.

[0003] At present, there are many mainstream detection methods for shear strength parameters, such as direct shear method, triaxial compression test and ring shear test, etc. The above measurement methods and means for shear strength parameters are complex in operation and expensive in equipment, and cannot realize the real-time monitoring of soil mechanical parameters. Monitoring means such as strain gauges and displacement sensors have the disadvantages of low sensitivity, slow response speed and susceptibility to environmental interference, and are difficult to meet the high requirements for real-time monitoring of shear strength parameters. Therefore, developing a new type of shear strength parameter detection device and method, realizing advantages such as high sensitivity, fast response and low cost, and being able to overcome the deficiencies of traditional monitoring methods to achieve rapid measurement of shear strength parameters and improve the monitoring efficiency has become the top priority. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a shear strength parameter detection device and detection method based on piezoelectric ceramic sheets.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions: In a first aspect, an embodiment of the present application provides a shear strength parameter detection device based on piezoelectric ceramic sheets, which comprises: A main frame, the main frame is a cubic frame, and a compression plate that fits its skeleton and compresses or relaxes into the cubic frame is provided on each of the six faces of the main frame; A first lead screw is arranged on the bodies of two mutually parallel compression plates, and its two ends respectively penetrate through the two compression plates and are threadedly connected with two first nuts that fit the outer walls of the two compression plates; A second lead screw is arranged on the bodies of the other two mutually parallel compression plates, and its two ends respectively penetrate through the other two compression plates and are threadedly connected with two second nuts that fit the outer walls of the other two compression plates; The third lead screw and the fourth lead screw are arranged at intervals on the bodies of the remaining two parallel compression plates. The two ends of the third lead screw and the fourth lead screw respectively penetrate through the remaining two compression plates and are threadedly connected with two third nuts that are in contact with the outer walls of the remaining two compression plates; On the rod bodies of the third lead screw and the fourth lead screw, a first piezoelectric ceramic sheet and a second piezoelectric ceramic sheet are respectively arranged opposite to each other. The first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet are located inside the main frame, their orientations are opposite to each other, and their respective central points are on the same horizontal line.

[0006] In the implementation of this embodiment, soil samples are added to the container formed by the main frame and the compression plates in multiple times and compacted successively. The first nut, the second nut, and the third nut are respectively tightened using a torque wrench to drive the six compression plates to be compressed to be consistent with the confining pressure conditions of the indoor triaxial compression test. The computer controls the signal amplifier to generate an electrical signal and transmit it to the first piezoelectric ceramic sheet. After the first ceramic sheet receives the electrical signal, it generates a stress wave and transmits it to the second piezoelectric ceramic sheet. After the second piezoelectric ceramic sheet receives the stress wave, it generates electrical signal data and transmits this data to the data collector. The data collector transmits the electrical signal data to the computer. The computer establishes a relationship curve between the change degree of the piezoelectric signal and the shear strength parameter according to the returned electrical signal data to complete the detection.

[0007] The advantage of this solution is that, different from the current mainstream shear strength parameter detection means, such as strain gauges, displacement sensors, etc., this device has high sensitivity. By using piezoelectric ceramic sheets combined with a computer as the technical means for detecting shear strength parameters, it can quickly respond to the changes in shear strength parameters; it can achieve a tight combination with the soil body and can also be conveniently arranged at the positions where measurement is required; it has good long-term stability and durability and is also applicable to various soil bodies; in addition, through the cooperation of the main frame with the compression plates, lead screws, and nuts, different soil confining pressure conditions can be achieved, and the operation is simple and convenient; therefore, the shear strength parameter detection system provided by this embodiment can detect different types of soil bodies without being affected by the types of soil bodies.

[0008] As a further solution of the present invention, the main frame is connected with a fixed seat through a support column.

[0009] The advantage of this solution is that the connection between the main frame and the fixed seat can effectively avoid the problem of the entire device tipping over unstably during the process of compressing the compression plates using a torque wrench, increasing the stability of the entire device.

[0010] As a further solution of the present invention, scale lines along the moving direction of the compression plates are also arranged on the skeleton of the main frame for recording the moving data of the compression plates.

[0011] The advantages of this solution are as follows: by observing the scale lines, the operator can observe the moving distance of the compression plate relative to the main frame in real time, so as to achieve quantitative control of the compression process; at the same time, setting scale lines on the framework can make the compression process more visual, so as to more intuitively understand the degree of compression, rather than relying solely on feeling and estimation; in addition, the benefit of setting scale lines is that it has good repeatability and standardization. When different operators perform compression operations under the same preset confining pressure conditions, through the standardized guidance of the scale lines, consistent confining pressure results can be achieved.

[0012] As a further solution of the present invention, the third lead screw and the fourth lead screw are respectively provided with a fourth nut and a fifth nut that can move along the screw body, and the fourth nut and the fifth nut are respectively connected to the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet.

[0013] The advantages of this solution are as follows: by adjusting the fourth nut and the fifth nut, the orientations of the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet can always be opposite to each other, and the centers of the two always remain on the same straight line, ensuring the accuracy of the detection effect; in addition, fixing the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet to the fourth nut and the fifth nut respectively can effectively prevent the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet from deforming due to pressure during the compression process or the centers of the two not being on the same straight line, increasing the stability of the structure.

[0014] As a further solution of the present invention, reserved grooves for burying wires are provided on the screw bodies of the third lead screw and the fourth lead screw.

[0015] The advantages of this solution are as follows: by opening guiding reserved grooves on the screw bodies of the third lead screw and the fourth lead screw, the wires connected to the piezoelectric ceramic sheets can be well fixed on the screw bodies of the third lead screw and the fourth lead screw, and it can prevent the wires from breaking due to pressure during the compression process.

[0016] As a further solution of the present invention, a pressure sensor is provided on the inner wall of the compression plate.

[0017] The advantages of this solution are as follows: by providing a pressure sensor on the inner wall of the compression plate, the change of soil pressure can be monitored in real time during the compression process of the soil sample; in addition, by quickly transmitting the data collected by the pressure sensor to external detection equipment, the detection time can be effectively shortened.

[0018] As a further solution of the present invention, reserved holes for connecting wires are opened on the plate body of the compression plate.

[0019] The advantages of this solution are as follows: by opening reserved holes on the plate body of the compression plate, it is convenient to connect the pressure sensor and the strain box, so as to obtain the corresponding soil confining pressure parameters.

[0020] Second aspect, the embodiments of the present application also provide a shear strength parameter detection method based on piezoelectric ceramic sheets based on the above shear strength parameter detection device, which includes the following steps: S1: Perform a triaxial compression test to determine the control shear strength parameters under different confining pressure conditions; S2. Fix the compression plate on the main frame, add soil samples into the main frame to a preset thickness, and at the same time keep the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet placed in the main frame; S3: Connect the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet to an external electronic detection device using wires; S4: Use a torque wrench to compress the compression plate to a preset confining pressure condition by tightening the first nut, the second nut, and the third nut; S5: When the preset confining pressure condition is reached, measure the piezoelectric signal under this confining pressure condition; S6: Perform wavelet packet decomposition on the piezoelectric signal to obtain a decomposed signal; S7: According to the decomposed signal, establish a relationship curve between the change degree of the piezoelectric signal and the shear strength parameter; S8: According to this relationship curve, calculate the shear strength parameter values of the soil under each confining pressure and complete the detection.

[0021] The advantage of this solution is that different confining pressure conditions can be achieved by adjusting the tightening or loosening degree of the first nut, the second nut, and the third nut, which is very convenient and simple; at the same time, the pressure sensors arranged on the inner wall of the compression plate can detect the soil confining pressure in all directions in real time, and quickly control the compression plate to be compressed to the preset confining pressure condition through the mutual cooperation of the four; in addition, the computer controls the signal amplifier to generate an electrical signal and transmit it to the first piezoelectric ceramic sheet. After receiving the electrical signal, the first piezoelectric ceramic sheet generates a stress wave and transmits it to the second piezoelectric ceramic sheet. After receiving the stress wave, the second piezoelectric ceramic sheet generates electrical signal data and transmits this data to the data collector. The data collector transmits the electrical signal data to the computer, and the computer establishes a relationship curve between the change degree of the piezoelectric signal and the shear strength parameter according to the transmitted electrical signal data. This detection method relying on piezoelectric ceramic sheets to detect stress changes is very efficient and rapid, and can effectively shorten the detection time.

[0022] Specifically, step S2 specifically includes: Place the compression plate on the skeleton of the main frame; Pass one end of the third screw rod and the fourth screw rod through the compression plate, and install the fourth nut and the fifth nut in the middle of the rod bodies of the third screw rod and the fourth screw rod, and keep the first piezoelectric ceramic sheet and the second piezoelectric ceramic sheet facing each other, and the centers of the two are on the same line; Pass another compression plate through the other ends of the third screw rod and the fourth screw rod, and make it fit on the framework of the main body frame. Keep the two compression plates parallel. Use the third nuts to threadedly connect to the two ends of the third screw rod and the fourth screw rod respectively, and make the third nuts closely adhere to the outer walls of the two compression plates respectively; Place the remaining compression plates on the framework of the main body frame; Pass the first screw rod through the other two mutually parallel compression plates, threadedly connect the two first nuts to the two ends of the first screw rod respectively, and make them closely adhere to the outer walls of the other two compression plates; Pass the second screw rod through the remaining two mutually parallel compression plates, threadedly connect the two second nuts to the two ends of the second screw rod respectively, and make them closely adhere to the outer walls of the remaining two compression plates.

[0023] The advantage of this solution is that the operation is simple. Only by the cooperation of the screw rods and nuts can the compression plates be fixed on the main body frame. At the same time, the compression of the soil material can be adjusted by rotating the nuts. The degree of compression of the soil material by the compression plates can be observed in real time through the scale lines on the framework of the main body frame. Description of the Drawings

[0024] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not constitute a limitation to the embodiments of the present invention. In the drawings: Figure 1 is the overall schematic diagram of the detection device; Figure 2 is the schematic diagram of the third screw rod and the fourth screw rod; Figure 3 is the schematic diagram of the reserved groove structure of the third screw rod and the fourth screw rod; Figure 4 is the relationship curve between the change degree of the piezoelectric signal and the internal friction angle of the soil body; Figure 5 is the relationship curve between the change degree of the piezoelectric signal and the cohesion of the soil body; Figure 6 is the flow chart of the detection method.

[0025] The names corresponding to the reference numerals in the drawings are: 1 - Main body frame; 2 - Compression plate; 3 - First screw rod; 4 - First nut; 5 - Second screw rod; 6 - Second nut; 7 - Third screw rod; 8 - Fourth screw rod; 9 - Third nut; 10 - First piezoelectric ceramic sheet; 11 - Second piezoelectric ceramic sheet; 12 - Fourth nut; 13 - Fifth nut; 14 - Reserved groove; 15 - Support column; 16 - Fixed seat; 17 - Reserved hole. Detailed Embodiments

[0026] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0027] Please refer to Figures 1 to 3 , the first embodiment of the present invention provides a shear strength parameter detection device based on piezoelectric ceramic chips, which comprises A main body frame 1, the main body frame 1 is a cubic frame, and a compression plate 2 that fits its skeleton and compresses or relaxes into the cubic frame is provided on each of the six faces of the main body frame 1; A first lead screw 3 is arranged on the bodies of two mutually parallel compression plates 2, and its two ends respectively penetrate through the two compression plates 2 and are threadedly connected with two first nuts 4 that are in contact with the outer walls of the two compression plates 2; A second lead screw 5 is arranged on the bodies of the other two mutually parallel compression plates 2, and its two ends respectively penetrate through the other two compression plates 2 and are threadedly connected with two second nuts 6 that are in contact with the outer walls of the other two compression plates 2; A third lead screw 7 and a fourth lead screw 8 are arranged at intervals on the bodies of the remaining two mutually parallel compression plates 2. The two ends of the third lead screw 7 and the fourth lead screw 8 respectively penetrate through the remaining two compression plates 2 and are threadedly connected with two third nuts 9 that are in contact with the outer walls of the remaining two compression plates 2; First piezoelectric ceramic chips 10 and second piezoelectric ceramic chips 11 are respectively arranged oppositely on the rod bodies of the third lead screw 7 and the fourth lead screw 8. The first piezoelectric ceramic chips 10 and the second piezoelectric ceramic chips 11 are located inside the main body frame 1, their orientations are opposite to each other, and their respective center points are on the same horizontal line.

[0028] When this embodiment is implemented, the first lead screw 3, the second lead screw 5, the third lead screw 7 and the fourth lead screw 8 are the same in terms of material, size and shape. At the same time, the first nut 4, the second nut 6, the third nut 9, the fourth nut 12 and the fifth nut 13 are the same in terms of material, size and shape; two of the six compression plates 2 are respectively provided with threaded holes for the third lead screw 7 and the fourth lead screw 8 to pass through, and the remaining four compression plates 2 are respectively provided with at least one threaded hole for other lead screws to pass through; the first piezoelectric ceramic chips 10 and the second piezoelectric ceramic chips 11 are circular ceramic chips, and the two are respectively nested in a copper shell (wrapped by the copper shell).

[0029] In the implementation of this embodiment, soil samples are added to the container formed by the cubic frame 1 and the compression plate 2 in multiple times and compacted successively. The first nut 4, the second nut 6, and the third nut 9 are respectively tightened using a torque wrench to drive the six compression plates 2 to be compressed to be consistent with the indoor triaxial confining pressure condition. By setting the torque value of the torque wrench and calculating the corresponding axial pre-tightening force according to the combination of the torque coefficient and the thread specification, and then combining with the reading of the pressure sensor, the pressure applied by the compression plate to the soil body can be accurately controlled. The computer controls the signal amplifier to generate an electrical signal and transmit it to the first piezoelectric ceramic sheet 10. After receiving the electrical signal, the first ceramic sheet 10 generates a stress wave and transmits it to the second piezoelectric ceramic sheet 11. After receiving the stress wave, the second piezoelectric ceramic sheet 11 generates electrical signal data and transmits this data to the data collector. The data collector transmits the electrical signal data to the computer. The computer establishes a relationship curve between the change degree of the piezoelectric signal and the shear strength parameter according to the transmitted electrical signal data to complete the detection.

[0030] The advantage of this solution is that, different from the current mainstream detection means for shear strength parameters, such as strain gauges, displacement sensors, etc., this device has high sensitivity. By using piezoelectric ceramic sheets combined with a computer as the technical means for detecting shear strength parameters, it can quickly respond to the changes in shear strength parameters; it can achieve a tight combination with the soil body and can also be conveniently arranged at the positions where measurement is required; it has good long-term stability and durability and is also applicable to various soil bodies; in addition, through the cooperation of the main body frame 1, the compression plate 2, the lead screw, and the nut, different soil confining pressure conditions can be achieved, and the operation is simple and convenient; therefore, the shear strength parameter detection system provided by this embodiment can detect different types of soil bodies and is not affected by the types of soil bodies.

[0031] As a further solution of the present invention, the main body frame 1 is connected with a fixed seat 16 through a support column 15.

[0032] The advantage of this solution is that the connection between the main body frame 1 and the fixed seat 16 can effectively avoid the problem of the entire device tipping over unstably during the process of compressing the compression plate 2 using a torque wrench, and increases the stability of the entire device.

[0033] As a further solution of the present invention, scale lines along the moving direction of the compression plate 2 are also provided on the skeleton of the main body frame 1 for recording the movement data of the compression plate 2.

[0034] The advantage of this solution is that by observing the scale lines, the operator can observe in real time the moving distance of the compression plate 2 relative to the main body frame 1, thereby realizing quantitative control of the compression process; at the same time, setting scale lines on the framework can make the entire compression process more visual, so as to more intuitively understand the degree of compression, rather than just relying on feeling and estimation; in addition, the advantage of setting scale lines is that it has good repeatability and standardization. When different operators perform compression operations under the same preset confining pressure conditions, through the standardized guidance of the scale lines, consistent confining pressure results can be achieved.

[0035] As a further solution of the present invention, the third lead screw 7 and the fourth lead screw 8 are respectively provided with a fourth nut 12 and a fifth nut 13 that can move along the screw body, and the fourth nut 12 and the fifth nut 13 are respectively connected to the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11.

[0036] The advantage of this solution is that by adjusting the fourth nut 12 and the fifth nut 13, the orientations of the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 can always be opposite to each other, and the centers of the two always remain on the same straight line, ensuring the accuracy of the detection results; in addition, fixing the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 to the fourth nut 12 and the fifth nut 13 respectively can effectively prevent the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 from deforming due to pressure and / or shear force during the compression process, or the centers of the two not being on the same straight line, increasing the stability of the structure.

[0037] As a further solution of the present invention, reserved grooves 14 for burying wires are reserved on the screw bodies of the third lead screw 7 and the fourth lead screw 8.

[0038] The advantage of this solution is that by opening the reserved grooves 14 on the screw bodies of the third lead screw 7 and the fourth lead screw 8, the wires respectively connected to the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 can be well fixed on the screw bodies of the third lead screw 7 and the fourth lead screw 8, and it can prevent the wires from breaking due to pressure during the compression process.

[0039] As a further solution of the present invention, a pressure sensor is provided on the inner wall of the compression plate 2.

[0040] The advantage of this solution is that by providing the pressure sensor on the inner wall of the compression plate 2, the change of soil pressure can be monitored in real time during the compression process of the soil sample; in addition, the data collected by the pressure sensor is quickly transmitted to external detection equipment, which can effectively shorten the detection time.

[0041] As a further solution of the present invention, a reserved hole 17 for connecting a wire is provided on the plate body of the compression plate 2.

[0042] The advantage of this solution is that by providing the reserved hole 17 on the plate body of the compression plate 2, it is convenient to connect the pressure sensor and the strain box, so as to obtain the corresponding soil confining pressure parameters.

[0043] Please refer to Figures 4 to 6 , the second embodiment of the present invention is based on the above embodiment, and provides a method for detecting shear strength parameters based on piezoelectric ceramic chips, which includes the following steps: S1: Conduct a triaxial compression test in a geotechnical laboratory to determine the control shear strength parameters under different confining pressure conditions; S2. Fix the compression plate 2 on the main body frame 1, add soil samples into the main body frame 1 to a preset thickness, and at the same time keep the first piezoelectric ceramic chip 10 and the second piezoelectric ceramic chip 11 in the main body frame 1; S3: Connect the first piezoelectric ceramic chip 10 and the second piezoelectric ceramic chip 11 to an external electronic detection device using wires; S4: Use a torque wrench to compress the compression plate 2 to a preset confining pressure condition by tightening the first nut 4, the second nut 6 and the third nut 9; S5: When the preset confining pressure condition is reached, measure the piezoelectric signal under this confining pressure condition; S6: Perform wavelet packet decomposition on the piezoelectric signal to obtain a decomposed signal; S7: According to the decomposed signal, establish a relationship curve between the change degree of the piezoelectric signal and the shear strength parameters; S8: According to this relationship curve, calculate the shear strength parameter values of the soil under each confining pressure and complete the detection.

[0044] When implementing this embodiment, a triaxial compression test is carried out. By adding confining pressure, the principal stress difference and axial strain are recorded, and the failure stress circles under multiple confining pressure conditions are drawn to obtain the corresponding shear strength parameters under different confining pressure conditions, namely the internal friction angle φ and the cohesion c; when adding soil samples into the main body frame, it is necessary to first determine the soil sample type, dry density, water content and density, calculate the preset soil sample mass through calculation with the soil sample volume, and then add the soil samples into the main body frame in multiple portions. After each addition, the surface of the soil sample needs to be hammered with a compaction hammer. The above-mentioned electronic detection device includes a signal amplifier respectively connected to the first piezoelectric ceramic chip, a data collector connected to the second piezoelectric ceramic chip, and a signal amplifier and a computer connected to the data collector.

[0045] The advantages of this solution are as follows: different confining pressure conditions can be achieved by adjusting the tightening or loosening degrees of the first nut 4, the second nut 6, and the third nut 9, which is very convenient and simple; meanwhile, the pressure sensors arranged on the inner wall 2 of the compression plate can detect the soil confining pressure in all directions in real time, and quickly control the compression of the compression plate 2 to the preset confining pressure condition through the mutual cooperation of the four; in addition, the computer controls the signal amplifier to generate an electrical signal and transmit it to the first piezoelectric ceramic sheet 10. After receiving the electrical signal, the first piezoelectric ceramic sheet 10 generates a stress wave and transmits it to the second piezoelectric ceramic sheet 11. After receiving the stress wave, the second piezoelectric ceramic sheet 11 generates electrical signal data and transmits this data to an external data collector. The data collector transmits the electrical signal data to the computer. The computer establishes a relationship curve between the change degree of the piezoelectric signal and the shear strength parameter according to the transmitted back electrical signal data, that is, the relationship curve between the change degree of the piezoelectric signal and the internal friction angle of the soil and the relationship curve between the change degree of the piezoelectric signal and the cohesion of the soil. This detection method relying on piezoelectric ceramic sheets to detect stress changes is very efficient and rapid, and can effectively shorten the detection time.

[0046] Specifically, fixing the compression plate 2 to the main body frame 1, and the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 being located inside the main body frame 1 specifically include: Placing the compression plate 2 on the skeleton of the main body frame 1; Using one end of the third lead screw 7 and the fourth lead screw 8 to pass through the compression plate 2, and installing the fourth nut 12 and the fifth nut 13 to the middle parts of the rod bodies of the third lead screw 7 and the fourth lead screw 8, and keeping the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 facing each other, and the center points of the two being on the same line; Passing another compression plate 2 through the other ends of the third lead screw 7 and the fourth lead screw 8, and making it fit against the skeleton of the main body frame 1, keeping the two compression plates 2 parallel, using the third nut 9 to threadedly connect to the two ends of the third lead screw 7 and the fourth lead screw 8 respectively, and making the third nut 9 respectively in close contact with the outer walls of the two compression plates 2; Placing the remaining compression plate 2 on the skeleton of the main body frame 1; Passing the first lead screw 3 through the other two mutually parallel compression plates 2, threadedly connecting the two first nuts 4 to the two ends of the first lead screw 3 respectively, and making them in close contact with the outer walls of the other two compression plates 2; Passing the second lead screw 5 through the remaining two mutually parallel compression plates 2, threadedly connecting the two second nuts 6 to the two ends of the second lead screw 5 respectively, and making them in close contact with the outer walls of the remaining two compression plates 2.

[0047] The advantage of this solution is that the operation is simple. Only by the cooperation of the lead screw and the nut can the compression plate be fixed on the main frame. At the same time, the compression plate can also be rotated to adjust the compaction of the soil material. The degree of compaction of the soil material by the compression plate 2 can be observed in real time through the scale line on the skeleton of the main frame 1.

[0048] For a better understanding and implementation of this embodiment, the above detection method will be further explained and described below in combination with specific embodiments. Specific embodiments: A method for detecting shear strength parameters based on piezoelectric ceramic chips, the steps of which include: S1: Conduct a triaxial compression test in a geotechnical laboratory to determine the control shear strength parameters under different confining pressure conditions; When specifically implementing this step, prepare the instrument and equipment required for the triaxial compression test, prepare the soil sample, and adopt the non-consolidated non-drained scheme for the test method; install the specimen on the base of the pressure chamber, add a confining pressure of 700 kPa to 800 kPa as the starting confining pressure, with a loading interval of 50 kPa, and finally load to 1000 kPa, adopt a shear rate of 0.8 mm / min, and record the principal stress difference and axial strain during this period; draw the relationship curve between the principal stress difference and the axial strain, and take the peak value of the principal stress difference on the curve as the failure point. When there is no peak value, take the principal stress difference corresponding to 20% axial strain as the failure point. Draw the damaged stress circles under multiple confining pressure conditions to obtain the corresponding shear strength parameters under each confining pressure condition, that is, the internal friction angle φ and the cohesion c.

[0050] S2. Fix the compression plate 2 on the main frame 1, add soil sample into the main frame 1 to a preset thickness, and at the same time keep the first piezoelectric ceramic chip 10 and the second piezoelectric ceramic chip 11 in the main frame 1; In this step, please combine Figures 1 to 3 , the main frame 1 is composed of 12 steel bars with a cross-section of 15 mm × 15 mm and a length of 120 mm for the cube skeleton; the support columns 15 are 4 steel bars with a cross-section of 15 mm × 15 mm and a length of 90 mm; the compression plate 2 is a high-strength steel plate part with a size of 90 mm × 90 mm and a thickness of 5 mm; the first lead screw 3, the second lead screw 5, the third lead screw 7 and the fourth lead screw 8 are all threaded rods with a diameter of 10 mm; the first nut 4, the second nut 6, the third nut 9, the fourth nut 12 and the fifth nut 13 are all hexagonal nuts with an outer diameter of 15 mm, an inner diameter of 10 mm and a height of 10 mm; the fixing seat 16 is a square plate part with a size of 120 mm × 120 mm, and the fixing seat 16 is welded to the 4 support columns 15 of the main frame 1.

[0051] In the specific implementation of this step, please combine with Figures 1 to 3 , first paste the pressure sensor on the inner wall of the compression plate 2; use two of the first lead screws 3 and the first nuts 4 to fix the two compression plates 2 on the main body frame 1 along the x-axis direction; use two of the second lead screws 5 and the second nuts 6 to fix the other two compression plates 2 on the main body frame 1 along the y-axis direction; rotate the fourth nut 12 and the fifth nut 13 to the middle of the rod bodies of the third lead screw 7 and the fourth lead screw 8 respectively, and keep the first pressing piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 facing each other, and the center points of the first pressing piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 are on the same straight line; use the third lead screw 7 and the fourth lead screw 8 and the third nut 9 to fix one compression plate 2 on the bottom surface of the main body frame 1 along the z-axis; add the sample soil into the container formed by the main body frame 1 and the compression plate 2 in multiple times and hammer the soil body to make the soil sample reach the preset mass; use the third lead screw 7 and the fourth lead screw 8 and the third nut 9 to fix the last compression plate 2 on the top surface of the main body frame 1 along the z-axis.

[0052] S3: Connect the first piezoelectric ceramic sheet 10 and the second piezoelectric ceramic sheet 11 to an external electronic detection device using wires; In the implementation of this step, the first piezoelectric ceramic sheet 10 is connected to a signal amplifier, the second piezoelectric ceramic sheet 11 is connected to a data collector, and the signal amplifier and computer connected to the data collector.

[0053] S4: Use a torque wrench to compress the compression plate 2 to the preset confining pressure condition by tightening the first nut 4, the second nut 6, and the third nut 9; In the implementation of this step, use a torque wrench to tighten the nuts in contact with the compression plate 2 in the x-axis, y-axis, and z-axis directions to drive the compression plate 2 to compress the soil body, and combine the scale lines on the main body frame 1 and the pressure sensor to compress the soil body to the preset confining pressure condition.

[0054] S5: When the preset confining pressure condition is reached, measure the piezoelectric signal under this confining pressure condition; In the specific implementation of this step, the computer controls the signal amplifier to generate an electrical signal and transmit it to the first piezoelectric ceramic sheet 10. After receiving the electrical signal, the first piezoelectric ceramic sheet 10 generates a stress wave and transmits it to the second piezoelectric ceramic sheet 11. After receiving the stress wave, the second piezoelectric ceramic sheet 11 generates piezoelectric electrical signal data and transmits this data to an external data collector. The data collector transmits the piezoelectric electrical signal data to the computer, and the computer receives the transmitted piezoelectric electrical signal data.

[0055] S6: Perform wavelet packet decomposition on the piezoelectric signal to obtain decomposed signals. When specifically implementing this step, use MATLAB software to perform wavelet packet decomposition on the obtained piezoelectric signal to obtain decomposed signals.

[0056] S7: Based on the decomposed signals, establish a relationship curve between the degree of change of the piezoelectric signal and the shear strength parameters, and the detection is completed.

[0057] When specifically implementing this step, after performing wavelet packet decomposition on the measured piezoelectric signal, calculate the energy of the decomposed signals, specifically as follows:

[0058] In the formula, E ij represents the energy of the decomposed signal in the jth frequency band under the ith group of confining pressure conditions; L js represents each sampling point of the decomposed signal in the jth frequency band; m represents the number of sampling points, and n is the number of wavelet packet decomposition layers, taking 3.

[0059] At this time, the total energy under the ith group of confining pressure conditions can be written as:

[0060] Write the energy of the generated swept-frequency excitation signal as E start , and the energy obtained by finally applying the confining pressure as E end , establish a normalization relationship as follows:

[0061] Substitute the energies under different confining pressure conditions into the above formula to obtain the energy values of each decomposed signal under different confining pressure conditions. After non-linear fitting, plot the relationship curve between the degree of change of the piezoelectric signal and the internal friction angle of the soil, and the relationship curve between the degree of change of the piezoelectric signal and the cohesion of the soil.

[0062] The above specific implementation manners have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above is only the specific implementation manners of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A shear strength parameter detection device based on piezoelectric ceramic sheets, characterized in that: A main frame (1), the main frame (1) being a cubic frame, and each of the six faces of the main frame (1) being provided with a compression plate (2) which fits the frame and compresses or relaxes the inside of the cubic frame; The first screw rod (3) is arranged on the plate bodies of the two mutually parallel compression plates (2), and its two ends respectively penetrate the two compression plates (2) and are threadedly connected with two first nuts (4) that are in contact with the outer walls of the two compression plates (2); The second screw rod (5) is arranged on the plate bodies of the other two mutually parallel compression plates (2), and its two ends respectively penetrate the other two compression plates (2) and are threadedly connected with two second nuts (6) that are in contact with the outer walls of the other two compression plates (2); The third screw rod (7) and the fourth screw rod (8) are arranged at intervals on the plate bodies of the remaining two mutually parallel compression plates (2); the two ends of the third screw rod (7) and the fourth screw rod (8) respectively penetrate the remaining two compression plates (2) and are threadedly connected with two third nuts (9) that are in contact with the outer walls of the remaining two compression plates (2); A first piezoelectric ceramic sheet (10) and a second piezoelectric ceramic sheet (11) are respectively arranged on the rod bodies of the third screw rod (7) and the fourth screw rod (8) in opposition to each other; the first piezoelectric ceramic sheet (10) and the second piezoelectric ceramic sheet (11) are located in the main frame (1), the two are oriented in opposite directions, and their respective center points are located on the same horizontal line.

2. A shear strength parameter detection device based on a piezoelectric ceramic sheet according to claim 1, characterized in that: The main frame (1) is connected to a fixing seat (16) via a support column (15).

3. The shear strength parameter detection device based on piezoelectric ceramic sheets according to claim 1, characterized in that: The skeleton of the main frame (1) is also provided with scale lines along the moving direction of the compression plate (2), which are used to record the movement data of the compression plate (2).

4. The shear strength parameter detection device based on piezoelectric ceramic sheets according to claim 1, characterized in that: The third screw rod (7) and the fourth screw rod (8) are respectively provided with a fourth nut (12) and a fifth nut (13) movable along the rod body; the fourth nut (12) and the fifth nut (13) are respectively connected to the first piezoelectric ceramic sheet (10) and the second piezoelectric ceramic sheet (11).

5. The shear strength parameter detection device based on piezoelectric ceramic sheets according to claim 1, characterized in that: A reserved groove (14) for embedding a conductive wire is reserved on the rod bodies of the third screw rod (7) and the fourth screw rod (8).

6. The shear strength parameter detection device based on piezoelectric ceramic sheets according to claim 1, characterized in that: The inner wall of the compression plate (2) is provided with a pressure sensor.

7. The shear strength parameter detection device based on piezoelectric ceramic sheets according to claim 1, characterized in that: A reserved hole (17) for connecting a wire is provided on the body of the compression plate (2).

8. A detection method for a shear strength parameter detection device based on a piezoelectric ceramic sheet according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Conduct triaxial compression tests in the geotechnical laboratory to determine the control shear strength parameters under different confining pressure conditions; S2, fixing the compression plate (2) on the main frame (1), and adding soil samples into the main frame (1) to a preset thickness, while keeping the first piezoelectric ceramic sheet (10) and the second piezoelectric ceramic sheet (11) in the main frame (1); S3: connecting the first piezoelectric ceramic sheet (10) and the second piezoelectric ceramic sheet (11) to an external electronic detection device using a wire; S4: using a torque wrench to tighten the first nut (4), the second nut (6) and the third nut (9) to compress the compression plate (2) to a preset confining pressure condition; S5: When the preset confining pressure condition is reached, measuring the piezoelectric signal under the confining pressure condition; S6: performing wavelet packet decomposition on the piezoelectric signal to obtain a decomposed signal; S7: establishing a relationship curve between the piezoelectric signal change degree and the shear strength parameter according to the decomposed signal; S8: Based on the relationship curve, the shear strength parameter value of the soil under various confining pressures is calculated and the test is completed.

9. The detection method according to claim 7, characterized in that: Step S2 specifically includes: S21: placing the compression plate (2) on the skeleton of the main frame (1); S22: using one end of the third screw rod (7) and the fourth screw rod (8) to pass through the compression plate (2), and installing the fourth nut (12) and the fifth nut (13) to the middle of the shaft of the third screw rod (7) and the fourth screw rod (8), and keeping the first piezoelectric ceramic sheet (10) and the second piezoelectric ceramic sheet (11) facing each other, and keeping their center points on the same line; S23: Passing another compression plate (2) through the other end of the third screw rod (7) and the fourth screw rod (8), and making it fit on the skeleton of the main frame (1), keeping the two compression plates (2) parallel, using the third nut (9) to be respectively threadedly connected to the two ends of the third screw rod (7) and the fourth screw rod (8), and making the third nut (9) fit closely to the outer walls of the two compression plates (2); S24: placing the remaining compression plates (2) on the skeleton of the main frame (1); S25: passing the first screw rod (3) through the other two mutually parallel compression plates (2), and threading the two first nuts (4) to the two ends of the first screw rod (3) respectively, and making them close to the outer walls of the other two compression plates (2); S26: Pass the second screw rod (5) through the remaining two mutually parallel compression plates (2), and thread the two second nuts (6) onto the two ends of the second screw rod (5) respectively, and fit them firmly against the outer walls of the remaining two compression plates (2).

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