Soil pressure sensor based on lever structure

Abstract

The invention relates to the technical field of soil pressure sensors, and discloses a lever structure-based soil pressure sensor, which comprises a shell, a bearing plate, a constant-strength cantilever beam, a force transmission lever and a measurement optical fiber, and is characterized in that the shell is internally provided with a containing cavity with an upward opening, the bearing plate is arranged at the top of the shell, and one end of the constant-strength cantilever beam is arranged on the side wall of the containing cavity; the force transmission lever is rotationally arranged in the accommodating cavity, and the measuring optical fiber is arranged at the bottom of the equal-strength cantilever beam; the equal-strength cantilever beam guarantees equal strain in the axial direction, micro deformation of the force bearing plate is amplified and transmitted to the equal-strength cantilever beam through the force transmission lever, deformation is converted into optical signals through the measuring optical fiber, and an anti-electromagnetic interference optical fiber measuring mode and an external collecting and demodulating technology are combined. Not only is small-size design and high sensitivity realized, but also interference on the original structure and stress distribution of the soil body is reduced, and the measurement precision in a complex rock-soil environment is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pressure sensors, in particular to a soil pressure sensor based on a lever structure. BACKGROUND

[0002] In geotechnical engineering, accurate measurement of soil pressure is the cornerstone of ensuring the safe operation of the project. Deviation in soil pressure measurement usually has significant negative effects. Underestimating soil pressure often leads to excessive deformation of the engineering structure or even structural instability, while overestimating soil pressure usually results in greater design redundancy, increasing the cost of engineering construction and operation. Therefore, accurate measurement of soil pressure is the key to ensuring the safe service and economic design of the project.

[0003] Existing soil pressure sensors mainly include resistance type and vibrating string type. Resistance type usually converts elastic deformation caused by soil pressure into resistance value, and then converts it into electrical signal through circuit. The vibrating string type uses steel string as the sensing element. The change in tension of the steel string caused by soil pressure affects its vibration frequency, and the soil pressure is inversely deduced by measuring the frequency change. However, the existing sensor needs to be designed with a larger size to facilitate deformation or vibration, and then capture the small changes brought by soil pressure. However, due to the large size of the soil pressure sensor, it also forms a rigid support in the soil body after being buried, which seriously damages the soil structure and significantly affects the stress distribution in the soil body, resulting in large measurement error.

[0004] In view of this, the existing technology still needs to be improved and developed. SUMMARY

[0005] In view of the shortcomings of the prior art described above, the purpose of the present application is to provide a soil pressure sensor based on a lever structure, which aims to solve the problem that the existing soil pressure sensor has a large size and forms a rigid support in the soil, causing large disturbance to the soil and affecting the measurement data.

[0006] The technical solution adopted by the present application to solve the technical problems is as follows: A soil pressure sensor based on a lever structure, comprising: a shell having an accommodating cavity with an opening facing upwards inside; a load plate arranged on the top of the shell to close the opening of the accommodating cavity; an equal strength cantilever beam arranged at one end on the side wall of the accommodating cavity and suspended at the other end; a force transmission lever rotatably arranged inside the accommodating cavity; one end of the force transmission lever is connected with the load plate, and the other end is connected with the suspended end of the equal strength cantilever beam; A measuring optical fiber is arranged at the bottom of the uniform strength cantilever beam, and one end of the measuring optical fiber is provided with a connecting wire which penetrates through the shell and is connected with an external collecting device.

[0007] Further, the fixed end of the uniform strength cantilever beam is connected with the inner wall of the accommodating cavity, the width of the fixed end to the overhanging end of the uniform strength cantilever beam gradually decreases to form a fan-shaped structure, and the bottom wall of the uniform strength cantilever beam is arranged in parallel and with a gap to the bottom wall of the accommodating cavity.

[0008] Further, the overhanging end of the uniform strength cantilever beam is provided with a rectangular plate which is connected with the force transmission lever.

[0009] Further, the length of the measuring optical fiber is smaller than the length of the uniform strength cantilever beam, and the measuring optical fiber is located on the middle line of the lower surface of the uniform strength cantilever beam.

[0010] Further, the shell and the accommodating cavity are both cylindrical, and the thickness of the bottom wall of the shell is greater than the thickness of the bearing plate.

[0011] Further, the force transmission lever comprises: A force receiving rod is arranged at the bottom of the bearing plate and located at the middle position of the bearing plate; A support rod is arranged at the bottom of the force receiving rod and rotationally arranged inside the accommodating cavity; the support rod is at a certain angle with the force receiving rod; A force transmission rod is arranged at the end of the support rod away from the force receiving rod; the force transmission rod is at a certain angle with the support rod, and the force transmission rod is connected with the uniform strength cantilever beam.

[0012] Further, a support frame is arranged inside the accommodating cavity, and the support rod rotationally cooperates with the support frame.

[0013] Further, the support frame is a U-shaped support frame, the top of the support frame is provided with a rotation groove, and the support rod is located in the rotation groove.

[0014] Further, the measuring optical fiber is pasted to the bottom wall of the uniform strength cantilever beam by epoxy resin.

[0015] Further, it further comprises: A temperature compensation optical fiber is arranged at the inner wall of the accommodating cavity and connected with the connecting wire.

[0016] Compared with the prior art, the present application has the following beneficial effects: In the present application, the protection and installation reference are provided by the shell, the external pressure is received by the elastic steel sheet bearing plate, the deformation linearity is guaranteed by the equal strength cantilever beam, the small displacement of the bearing plate is amplified and transmitted to the equal strength cantilever beam by the force transmission lever, the deformation is converted into an optical signal by the measurement optical fiber pasted at the bottom of the equal strength cantilever beam, the measurement precision in the complex rock-soil environment is improved by combining the optical fiber measurement mode and the external collection demodulation technology, the measurement error problem caused by the large size of the traditional sensor is effectively solved, and reliable data for accurate monitoring of the earth pressure in the rock-soil engineering is provided. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the earth pressure sensor of the present application.

[0018] Figure 2 It is a schematic diagram of the equal strength cantilever beam and the force transmission lever structure of the present application.

[0019] Figure 3 It is a sectional view of the earth pressure sensor of the present application.

[0020] The numbers in the figure indicate that: 1, shell; 11, annular support body; 12, base; 2, containing cavity; 3, bearing plate; 4, equal strength cantilever beam; 5, force transmission lever; 6, measurement optical fiber; 7, support frame. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0022] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0023] In the description of the present application, it should be noted that unless otherwise expressly specified and limited, the terms "mounting", "connection", "linking" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] In view of the deficiencies of the prior art, the present embodiment provides a soil pressure sensor based on lever structure, which can be specifically referred to as follows: As shown in the accompanying Figure 1 and the accompanying Figure 3 A soil pressure sensor based on lever structure includes a shell 1, a bearing plate 3, an equal strength cantilever beam 4, a force transmission lever 5 and a measurement optical fiber 6. The shell 1 is internally provided with an accommodating cavity 2 with an opening facing upward, which provides protection and mounting space for internal components; the bearing plate 3 covers the top of the shell 1, closes the opening of the accommodating cavity 2, and directly bears external pressure; the equal strength cantilever beam 4 is fixed at one end to the side wall of the accommodating cavity 2 and suspended at the other end, which can produce elastic deformation under external load; the force transmission lever 5 is rotatably arranged in the accommodating cavity 2, connected at one end to the bearing plate 3 and at the other end to the suspended end of the equal strength cantilever beam 4, to realize the transmission and amplification of the strain of the bearing plate 3; the measurement optical fiber 6 is attached to the bottom of the equal strength cantilever beam 4 and connected to external collection equipment through an optical cable penetrating the shell 1, to convert strain into optical signals.

[0025] Among them, the shell 1 is made of stainless steel, which provides structural support for the sensor; the bearing plate 3 can be a stainless steel disc, which can deform to transmit soil pressure; the equal strength cantilever beam 4 is the core deformation element, which is made of stainless steel, gradually narrows away from the side wall of the accommodating cavity 2 along the central axis, ensuring that the surface strain of the beam is equal in the direction of the central axis; the force transmission lever 5 amplifies the strain at the center of the bearing plate 3 through the principle of lever, improving the measurement sensitivity and reducing the size of the pressure sensor itself.

[0026] Specifically, when the soil pressure acts on the bearing plate 3, the bearing plate 3 deforms downward, pushing the force transmission lever 5 to rotate around the rotation point. The force transmission lever 5 transmits the small strain to the suspended end of the equal strength cantilever beam 4 through the force arm amplification effect, causing the equal strength cantilever beam 4 to bend and deform. The measurement optical fiber 6 at the bottom of the equal strength cantilever beam 4 produces a grating wavelength shift, which is transmitted to the external collection equipment through the optical cable and converted into a pressure value by a demodulator. Throughout the process, the shell 1 protects the internal elements from soil erosion, and the accommodating cavity 2 provides a stable installation reference for each component.

[0027] Compared with the prior art, the traditional resistance type or vibrating wire type sensor needs a larger size to capture a slight deformation, and is easy to damage the soil structure after being buried; the scheme can reduce the overall size of the sensor through the amplification effect of the force transmission lever 5, and reduce the disturbance to the soil structure. At the same time, the optical fiber measurement method has the advantages of anti-electromagnetic interference, is suitable for complex rock-soil environment, and can significantly improve the measurement accuracy.

[0028] Through the above technical scheme, the application realizes the balance of small size design and high sensitivity, and solves the measurement error problem caused by the oversize of the traditional sensor. The combination of the lever amplification structure and the optical fiber sensing not only ensures the accuracy of the soil pressure measurement, but also reduces the disturbance to the original structure of the soil, and is suitable for precise monitoring of soil pressure in geotechnical engineering, and provides reliable data for engineering safety and economic design.

[0029] As shown in the accompanying drawings, Figure 3 The shell 1 includes a ring-shaped support body 11 and a base 12, the ring-shaped support body 11 is cylindrical, and the base 12 is disc-shaped and detachably arranged at the bottom of the ring-shaped support body 11 to provide a supporting force.

[0030] In this embodiment, as shown in the accompanying drawings, Figure 3 The fixed end of the equal-strength cantilever beam 4 is connected with the inner wall of the accommodating cavity 2, the width from the fixed end to the free end of the equal-strength cantilever beam 4 gradually decreases, forming a fan-shaped structure, and the bottom wall of the equal-strength cantilever beam 4 is arranged in parallel with the bottom wall of the accommodating cavity 2 with a gap. The fixed end of the equal-strength cantilever beam 4 is rigidly connected with the inner wall of the accommodating cavity 2, the width from the fixed end to the free end gradually decreases, and the whole is fan-shapedly distributed; the thickness of the equal-strength cantilever beam 4 is uniform, the bottom wall is parallel to the bottom wall of the accommodating cavity 2, and the gap therebetween is controlled within a certain range to avoid contact with the cavity wall during deformation.

[0031] The fan-shaped structure makes the bending stress of each section of the equal-strength cantilever beam 4 equal, the width gradually changing design makes the strain of the upper and lower surfaces of the equal-strength cantilever beam 4 along the axial direction equal, compared with the equal-width cantilever beam, and the strain sensing range of the measurement optical fiber 6 can be improved; the parallel gap arrangement reserves sufficient deformation space for the equal-strength cantilever beam 4, avoiding mechanical interference affecting the measurement accuracy.

[0032] Specifically, when the force transmission lever 5 pushes the free end of the equal-strength cantilever beam 4, the fan-shaped structure makes the stress uniformly distributed in the whole equal-strength cantilever beam 4. Since the bottom wall is kept parallel to the bottom wall of the accommodating cavity 2, the measurement optical fiber 6 is always in the same plane during the deformation process, ensuring the linear correspondence between the wavelength drift and the strain. This structure design makes the equal-strength cantilever beam 4 produce greater deformation under the same pressure, and cooperates with the lever amplification effect to further improve the sensitivity of the sensor.

[0033] Through the above technical solutions, this application ensures deformation linearity through a fan-shaped structure and avoids base interference through a parallel gap design, providing a structural foundation for high-precision measurement of the sensor and adapting to the wide-range earth pressure monitoring needs in geotechnical engineering.

[0034] In this embodiment, as shown in the appendix Figure 2 As shown, a rectangular plate is provided at the cantilever end of the equal-strength cantilever beam 4, and the rectangular plate is connected to the force transmission lever 5. The rectangular plate is made of the same spring steel as the equal-strength cantilever beam 4 and is connected to the cantilever beam through an integral molding process; the upper surface of the rectangular plate is connected to the end of the force transmission lever 5.

[0035] The rectangular plate increases the contact area between the equal-strength cantilever beam 4 and the force transmission lever 5, preventing excessive local stress from damaging the equal-strength cantilever beam 4; the one-piece molding process ensures connection strength and eliminates the impact of assembly gaps on force transmission.

[0036] Specifically, when the lever rotates, the force is transmitted vertically to the center of the rectangular plate through contact. The rectangular plate evenly distributes the concentrated force to the cantilever end of the equal-strength cantilever beam 4, making the overall force on the fan-shaped equal-strength cantilever beam 4 balanced.

[0037] Through the above technical solution, this application achieves uniform force transmission through a rectangular plate, and the contact structure ensures accurate force transmission, further optimizing the structural reliability and measurement stability of the sensor.

[0038] In this embodiment, as shown in the appendix Figure 3 As shown, the length of the measuring fiber 6 is less than the length of the equal-strength cantilever beam 4, and the measuring fiber 6 is located on the central axis of the equal-strength cantilever beam 4.

[0039] The design, which is shorter than the beam length, ensures that the optical fiber only covers the main deformation area of ​​the cantilever beam; the arrangement along the axis ensures that the optical fiber bears pure bending strain, and the strain on the upper and lower surfaces of the beam is equal everywhere along the axis, which facilitates the measurement of experimental data.

[0040] Specifically, when the equal-strength cantilever beam 4 bends, the measuring optical fiber 6 deforms along with the beam, and the grating wavelength drifts linearly with strain. Since the strain on the surface of the equal-strength cantilever beam 4 is equal along the axial direction, the measurement accuracy of the optical fiber can be improved.

[0041] Through the above technical solution, this application ensures the accuracy and stability of strain measurement by optimizing the fiber optic arrangement, and provides a high-quality optical signal source for accurate demodulation of pressure signals.

[0042] In this embodiment, as shown in the appendix Figure 1 As shown, both the outer shell 1 and the receiving cavity 2 are cylindrical, and the thickness of the bottom wall of the outer shell 1 is greater than the thickness of the load-bearing plate 3. The outer shell 1 is cylindrical in shape and made of 304 stainless steel; the receiving cavity 2 is a concentric cylinder.

[0043] The cylindrical structure makes the shell 1 bear force uniformly, adapts to the isotropic pressure environment of the soil body, and avoids stress concentration caused by structural heterogeneity; the thickened bottom wall improves the overall rigidity of the shell 1, and ensures that the bottom does not produce additional deformation when the sensor is buried; the thinning design of the force bearing plate 3 improves its sensitivity to pressure, facilitating the transmission of small soil pressure.

[0044] Specifically, when the sensor is buried in the soil body, the cylindrical shell 1 can uniformly bear the soil pressure around, avoiding structural deformation caused by excessive local stress; the thickened bottom wall ensures that the bottom of the sensor remains stable under the buried pressure, without affecting the initial position of the internal elements; the thin-walled force bearing plate 3 produces a small bending under the action of soil pressure, and the deformation is amplified and transmitted to the equal strength cantilever beam 4 through the force transmission lever 5. This structural design can reduce the interaction area between the sensor and the soil body, effectively reducing the interference with the original stress field.

[0045] Through the above technical solutions, the present application adapts to the soil pressure environment through the cylindrical design, and takes into account rigidity and sensitivity through thickness differentiation design, further reducing the interference with the original structure of the soil body and improving the measurement accuracy.

[0046] In this embodiment, as shown in the accompanying drawings, Figure 2 The force transmission lever 5 includes a force receiving rod, a support rod and a force transmission rod. The force receiving rod is arranged at the bottom center of the force bearing plate 3 and connected to the force bearing plate 3 by welding, hinging or abutting; one end of the support rod is connected perpendicularly to the bottom of the force receiving rod, forming a 90° angle with the force receiving rod; the force transmission rod extends from the end of the support rod away from the force receiving rod, forming a 90° angle with the support rod, and the end is connected to the rectangular plate of the equal strength cantilever beam 4 by welding, hinging or abutting.

[0047] The three-section structure realizes pressure amplification through the force arm ratio, amplifies the small deformation of the force bearing plate 3 and transmits it to the equal strength cantilever beam 4; the angle design ensures that the force transmission direction is perpendicular to the force bearing plate 3 and the equal strength cantilever beam 4, making the measurement result more accurate.

[0048] Specifically, when the force bearing plate 3 is pressed to move downward, it drives the force receiving rod to push the support rod to rotate around the rotation shaft, and the force transmission rod at the other end of the support rod is lifted upward, causing the equal strength cantilever beam 4 to deform. Since the force arm of the force transmission rod is several times that of the force receiving rod, it realizes amplification of small strain. This structure makes the sensor can sense small pressure, and the sensitivity is improved by more than several times compared with the structure without lever.

[0049] Through the above technical solutions, the present application realizes pressure amplification and directional transmission through the three-section lever structure, provides high sensitivity protection for small size sensors, and adapts to the monitoring needs of weak soil pressure changes in geotechnical engineering.

[0050] In this embodiment, as shown in the accompanying drawings, Figure 1As shown, the inside of the accommodating cavity 2 is provided with a support frame 7, and the support rod is rotationally matched with the support frame 7.

[0051] Wherein, the support rod and the support frame 7 are both cylindrical structures, the support rod is directly overlapped on the support frame 7, the support frame 7 provides a stable rotation fulcrum for the lever, and ensures that the force arm ratio is constant; the low-friction rotation matching reduces the energy loss when the lever rotates.

[0052] Specifically, the support rod of the force transmission lever 5 is sleeved on the rotating shaft of the support frame 7 through the shaft hole, when the force rod is stressed, the support rod rotates flexibly around the rotating shaft, and drives the force transmission rod to push the equal strength cantilever beam 4. The fixed position of the support frame 7 ensures that the rotating shaft is at the force arm node of the force rod and the force transmission rod, and ensures that the magnification is stable. The low-friction design makes the lever rotate under the action of a small force, ensuring the response speed of the sensor to small pressure.

[0053] Through the above technical solutions, the present application provides a stable low-friction fulcrum through the support frame 7, ensures the accuracy of pressure amplification, and improves the sensitivity and long-term reliability of the sensor.

[0054] In this embodiment, as shown in the accompanying drawings, Figure 2 As shown, the support frame 7 is U-shaped, the top is provided with a rotating groove, and the support rod is located in the rotating groove. The support frame 7 is U-shaped, the bottom is fixed to the bottom wall of the accommodating cavity 2 by two bolts; the top of the support frame 7 is provided with a rotating groove, and the support rod of the force transmission lever 5 is placed in the groove to form a linear contact rotation matching.

[0055] Wherein, the U-shaped structure provides bilateral support for the lever, avoiding radial deviation when rotating; the rotating groove replaces the traditional shaft hole matching through linear contact, reducing the contact area and further reducing the friction; at the same time, the rotating groove also limits the movement of the force transmission lever 5.

[0056] Specifically, the support rod of the force transmission lever 5 is placed in the groove of the U-shaped support frame 7 at both ends, when the lever rotates, the support rod slides along the circular arc surface of the groove, and the linear contact mode makes the contact stress concentrate at the lowest point of the groove, ensuring the stability of the rotating center. The bilateral constraint of the U-shaped structure prevents the support rod from swinging horizontally when stressed.

[0057] Through the above technical solutions, the present application provides constraint and rotation through the U-shaped support frame 7, and the linear contact groove reduces friction, further improving the accuracy of pressure transmission and the flexibility of lever rotation.

[0058] In this embodiment, the measurement optical fiber 6 is pasted to the bottom wall of the equal strength cantilever beam 4 by epoxy resin.

[0059] Specifically, when the equal strength cantilever beam 4 is bent to generate strain, the epoxy layer uniformly transmits the deformation of the beam body to the measurement optical fiber 6, so that the optical fiber grating is deformed to cause wavelength drift. The low modulus characteristic of the epoxy resin ensures that the adhesive layer does not generate additional stress when the beam body deforms, ensuring the consistency of the optical fiber strain and the beam body strain.

[0060] Through the above technical solution, the application optimizes the bonding process to ensure accurate strain transmission, improve the measurement accuracy of the sensor and the environmental adaptability.

[0061] In this embodiment, the soil pressure sensor based on the lever structure further comprises a temperature compensation optical fiber. The temperature compensation optical fiber is of the same model as the measurement optical fiber 6, adopts a fiber grating structure, and is bonded to the side wall of the accommodating cavity 2 by epoxy resin; the compensation optical fiber and the measurement optical fiber 6 are connected in parallel and connected to the same connection line, and are transmitted to the external collection device synchronously.

[0062] Among them, the same model optical fiber only senses the change of the ambient temperature; the parallel transmission realizes the synchronous collection of the measurement signal and the compensation signal, which is convenient for real-time temperature correction.

[0063] Specifically, when the temperature of the geotechnical environment changes, the measurement optical fiber 6 will be affected by both strain and temperature, while the temperature compensation optical fiber is only affected by temperature. The external collection device compares the wavelength difference between the two to eliminate the interference of temperature on the measurement optical fiber 6, and obtains the strain signal caused only by pressure.

[0064] Through the above technical solution, the application realizes real-time correction of the ambient temperature through the temperature compensation optical fiber, further improves the measurement accuracy of the sensor in a complex temperature environment, and adapts to the wide temperature range monitoring requirements of geotechnical engineering.

[0065] Based on the thin plate theory, the deflection of the total stress force plate under the action of the total stress force plate and the lever force rod The calculation formula is as follows: ; Among them is the total stress of the total stress bearing plate 3 acting on the outer side of the total stress bearing plate 3, is the radius of the sensor, and are the elastic modulus and Poisson's ratio of the bearing plate 3, is the thickness of the total stress bearing plate 3, is the force acting on the center of the bearing plate 3.

[0066] Specifically, the fixed end of the equal strength cantilever beam 4 is connected with the shell 1, and the free end is connected with the force transmission lever 5. The lever ratio of the force transmission lever 5 is . Based on the principle of lever, the force acting on the bearing plate 3 and the force acting on the free end of the cantilever beam satisfy the following relationship: ; wherein represents the force acting on the inside center of the force bearing plate 3, represents the force acting on the connection between the force transmission lever 5 and the equal strength cantilever beam 4, respectively represent the distance from the connection between the force transmission lever 5 and the force bearing plate 3 to the lever fulcrum beam, represents the distance from the connection between the force transmission lever 5 and the free end of the equal strength cantilever beam 4 to the lever fulcrum beam.

[0067] Specifically, the free end of the equal strength cantilever beam 4 is connected to the sensor shell 1, and the free end is connected to the force transmission lever 5. The width of the equal strength cantilever beam 4 gradually decreases from the fixed end to the free end, ensuring that the strain of the equal strength cantilever beam 4 is equal along the length direction after being stressed, thereby improving the measurement accuracy. Under the action of the force transmission lever 5, the deflection of the free end of the equal strength cantilever beam 4 is The calculation formula is as follows: ; wherein is the length of the equal strength cantilever beam 4, is the effective width of the fixed end of the equal strength cantilever beam 4 (the effective width refers to the distance between the two end points of the arc-shaped section of the fixed end of the equal strength cantilever beam 4), is the thickness of the equal strength cantilever beam 4. The deflection of the free end of the equal strength cantilever beam 4 and the strain satisfy: ; Based on the deformation compatibility principle and the lever principle, the deflection of different components inside the sensor satisfies the following formula: ; Therefore, the soil pressure can be calculated according to the following formula: ; Specifically, the measurement optical fiber 6 is pasted below the equal strength cantilever beam 4 by using epoxy resin, and the equal strength cantilever beam 4 deforms under the action of the soil pressure, thereby causing the wavelength of the optical fiber to drift. In addition, a temperature compensation optical fiber is also included, which is used to correct the measurement error caused by the temperature change inside the sensor. It should be noted that the temperature compensation optical fiber is not shown in the drawings. The wavelength shift of the temperature compensation optical fiber under the action of temperature and strain satisfies the following formula: ; wherein and are respectively the coefficients of the strain and the temperature of the optical fiber, and are respectively the initial state wavelength and the wavelength drift caused by the strain or the temperature, is the temperature inside the sensor during measurement.

[0068] Therefore, the formula for calculating the earth pressure by the optical fiber is: ; Specifically, the measurement optical fiber 6 and the temperature compensation optical fiber are connected by an optical cable, and form optical connection and data communication with an external optical fiber demodulation system, so as to realize real-time measurement of the earth pressure.

[0069] Specifically, the small earth pressure sensor based on the lever structure is buried in the soil, and the upper part is subjected to the earth pressure, which is transmitted to the force transmission lever 5 in the sensor through the bearing plate 3, and then transmitted to the equal strength cantilever beam 4 through the force transmission lever 5, so as to exert an upward force on the equal strength cantilever beam 4. The equal strength cantilever beam 4 deforms, causing the wavelength of the measurement optical fiber 6 to change, which is transmitted to the optical fiber demodulator (external acquisition device) through the optical cable, so as to measure the earth pressure in real time. It should be noted that the optical fiber demodulator is not drawn.

[0070] Specifically, in a certain small earth pressure sensor, the radius is , the thickness of the bearing plate 3 and the equal strength cantilever beam 4 is , the length of the equal strength cantilever beam 4 is approximately equal to 2 times the radius of the pressure sensor, and the effective width of the fixed end of the equal strength cantilever beam 4 is . At this time, the formula for calculating the earth pressure is: ; Let and satisfy the following relationship: ; ; The formula for calculating the earth pressure can be transformed as: ; When the radius of the pressure sensor becomes of the original, to keep and unchanged, the following conditions should be met: ; where is the changed lever ratio. Since , the internal lever ratio before and after the change of the radius of the pressure sensor satisfies the following relationship: ; Therefore, the pressure sensor can adjust its lever ratio and the radius of the bearing plate 3, amplify the strain of the equal strength cantilever beam 4 inside the sensor, ensure the measurement accuracy, reduce the sensor volume, reduce the disturbance to the soil body during embedding, and realize accurate measurement of soil pressure.

[0071] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the features disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

Claims

1. A soil pressure sensor based on a lever structure, characterized by, The utility model relates to a kind of temperature sensor, including: Shell, internally with the containing cavity of opening upwards; Force plate, set to the top of the shell, to close the opening of the containing cavity; Equal strength cantilever beam, one end is set to the side wall of the containing cavity, and the other end is in suspension; Force lever, rotation is set to the inside of the containing cavity;One end of the force lever is connected with the force plate, and the other end is connected with the suspension end of the equal strength cantilever beam; Measuring optical fiber, set to the bottom of the equal strength cantilever beam;One end of the measuring optical fiber is provided with connecting wire, and the connecting wire is connected with external acquisition equipment by penetrating the shell.

2. The soil pressure sensor based on a lever structure according to claim 1, characterized in that, The fixed end of the equal strength cantilever beam is connected with the inner wall of the containing cavity, the width of the fixed end to the suspension end of the equal strength cantilever beam gradually decreases, forming a fan structure, and the bottom wall of the equal strength cantilever beam is parallel to the bottom wall of the containing cavity and arranged with a gap.

3. A soil pressure sensor based on a lever structure according to claim 2, characterized in that, The suspension end of the equal strength cantilever beam is provided with a rectangular plate, and the rectangular plate is connected with the force lever.

4. The soil pressure sensor based on lever structure according to claim 1, characterized in that, The length of the measuring optical fiber is less than the length of the equal strength cantilever beam, and the measuring optical fiber is located at the middle line of the lower surface of the equal strength cantilever beam.

5. The soil pressure sensor based on lever structure according to claim 1, characterized in that, The shell and the containing cavity are both cylindrical, and the thickness of the bottom wall of the shell is greater than the thickness of the force plate.

6. The soil pressure sensor based on lever structure according to claim 1, characterized in that, The force lever includes: Stress rod, set to the bottom of the force plate and located at the middle position of the force plate; Supporting rod, set to the bottom of the stress rod and rotationally set to the inside of the containing cavity;The supporting rod and the stress rod form a certain angle; Force rod, set to the end of the supporting rod away from the stress rod;The force rod and the supporting rod form a certain angle, and the force rod is connected with the equal strength cantilever beam.

7. A soil pressure sensor based on a lever structure according to claim 6, characterized in that, The inside of the containing cavity is provided with a support frame, and the supporting rod is rotationally matched with the support frame.

8. A soil pressure sensor based on a lever structure according to claim 7, characterized in that, The support frame is a U-shaped support frame, the top of the support frame is provided with a rotating groove, and the supporting rod is located in the rotating groove.

9. The soil pressure sensor based on lever structure according to claim 1, characterized in that, The measuring optical fiber is pasted to the bottom wall of the equal strength cantilever beam by epoxy resin.

10. The soil pressure sensor based on lever structure according to claim 3, characterized in that, It also includes: Temperature compensation optical fiber, set to the inner wall of the containing cavity and connected with the connecting wire.

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