阅读说明：本技术 一种可动态定向的三维矢量土压力传感器 (Three-dimensional vector soil pressure sensor capable of being dynamically oriented ) 是由 董彤 魏丽娟 刘引 陈晓 张雪研 于 2021-03-09 设计创作，主要内容包括：本发明属于应力测试领域,涉及一种可动态定向的三维矢量土压力传感器,包括球形基座、设置在球形基座上的若干个压力模块、设置在球形基座内的数据采集模块以及光纤；所述光纤与所述数据采集模块相连,所述数据采集模块上连接有若干导线,每个所述压力模块与一根所述导线相连,所述球形基座上还设有三轴倾角传感器,三轴倾角传感器通过一根所述导线连接至数据采集模块。本发明的以球形构造为基础,通过三轴倾角传感器,采用较低的成本便可以实现对应力方向的动态监测,真正实现对土体内一点处三维应力状态的实时矢量化描述,并同工程进行关联。(The invention belongs to the field of stress testing, and relates to a dynamically-oriented three-dimensional vector soil pressure sensor which comprises a spherical base, a plurality of pressure modules arranged on the spherical base, a data acquisition module arranged in the spherical base and an optical fiber, wherein the pressure modules are arranged on the spherical base; the optical fiber is connected with the data acquisition module, the data acquisition module is connected with a plurality of wires, each pressure module is connected with one wire, the spherical base is further provided with a three-axis tilt angle sensor, and the three-axis tilt angle sensor is connected to the data acquisition module through one wire. The invention is based on spherical structure, can realize dynamic monitoring of stress direction by a triaxial tilt angle sensor with lower cost, really realizes real-time vectorization description of three-dimensional stress state at one point in a soil body, and is associated with engineering.)

1. A three-dimensional vector soil pressure sensor capable of being dynamically oriented is characterized by comprising a spherical base, a plurality of pressure modules arranged on the spherical base, a data acquisition module arranged in the spherical base and an optical fiber; the optical fiber is connected with the data acquisition module, the data acquisition module is connected with a plurality of wires, each pressure module is connected with one wire, the spherical base is further provided with a three-axis tilt angle sensor, and the three-axis tilt angle sensor is connected to the data acquisition module through one wire.

2. The dynamically orientable three-dimensional vector earth pressure sensor of claim 1, wherein the pressure module comprises a mating pressure sensitive face and a silicon piezoresistive module, the pressure sensitive face facing outward of the spherical base.

3. The dynamically orientable three-dimensional vector soil pressure sensor of claim 1 wherein the spherical base has grooves for mounting pressure modules and three-axis tilt sensors, the pressure modules and three-axis tilt sensors each being disposed in a one-to-one correspondence in the grooves, the number of grooves being equal to or greater than the sum of the number of pressure modules and three-axis tilt sensors.

4. A dynamically orientable three-dimensional vector soil pressure sensor as claimed in claim 3 wherein said recess has a wire hole therein for a wire to pass through, said wire being disposed through said wire hole.

5. The dynamically orientable three-dimensional vector soil pressure sensor of claim 1, wherein the optical fiber comprises a cable shield and a cable insulation layer wrapped outside the cable shield.

6. The dynamically orientable three-dimensional vector soil pressure sensor of claim 1 wherein the wire comprises a core wire, a wire shield layer wrapped around the core wire, and a wire insulation layer wrapped around the wire shield layer.

7. The dynamically orientable three-dimensional vector soil pressure sensor of claim 1 wherein the pressure modules and three-axis tilt sensors have 9 set points, including 3 sets, the first set including 4 set points, evenly distributed on an axisymmetric plane of the spherical base, the second set including 1 set point, located at the end point furthest from the axis symmetric plane; the connecting line of the center of the spherical base and the set point in the second group is a Z axis, and an X axis and a Y axis are selected on an axial symmetry plane to form a Cartesian coordinate system; the third group comprises the other 4 set points, and the normal line positions of the set points are equal inclination lines of a Cartesian coordinate system.

8. The dynamically orientable three-dimensional vector earth pressure sensor of claim 7, wherein the third set of set points is located between the first set and the second set.

9. The dynamically orientable three-dimensional vector soil pressure sensor of claim 7 wherein said three-axis tilt sensors are disposed within a second set.

10. The dynamically orientable three-dimensional vector soil pressure sensor of claim 7 wherein there are at least 6 pressure modules.

Technical Field

The invention belongs to the field of stress testing, and relates to a three-dimensional vector soil pressure sensor capable of being dynamically oriented.

Background

In geotechnical engineering, the stress state of soil is extremely complex under the influence of complex external loads and actual engineering environment. However, as a porous multi-phase medium, the mechanical properties of soil are significantly affected by factors such as the magnitude of stress, the direction of stress, the stress path, and the history of stress. To characterize the stress state of the earth, the stress at a point is usually expressed as a vector. In three-dimensional space, a vector contains six degrees of freedom, so six independent variables are required to characterize the stress state of a point. In principal stress space, these six degrees of freedom are embodied as three magnitude quantities of principal stress and three directional quantities of a principal stress coordinate system. Therefore, the stress state can be depicted only by simultaneously and accurately acquiring the magnitude and direction of the stress of one point in the soil, and further, the geotechnical engineering safety and stability evaluation and the construction maintenance analysis are scientifically developed.

The three-axis tilt sensor can complete the positioning of the space relative direction under various postures, output the measured value to a computer, accurately measure the relation between the azimuth angle of the current three-dimensional posture of the sensor and the initial azimuth angle, and complete the three-dimensional depiction of the current posture under any coordinate through a calculation program. The FEC-100-3RS422 type triaxial tilt angle sensor produced by Beijing national warship sensing technology Limited can be selected.

In actual engineering, the accurate measurement of the three-dimensional stress state at a certain point is always a difficult point of the engineering, and the existing testing device has the following problems: the geometric shape of the device is irregular, the areas of all the surfaces are different, and the included angles between the surfaces are also different, so that the phenomenon of stress concentration and uneven stress distribution of the soil body can be caused, the accuracy of stress size testing is reduced, and the soil body can be even induced to be sheared and damaged along the plane of the surface of the device. In addition, the routing of the stress measurement ball consisting of a plurality of soil pressure cells is complex, and the line is arranged outside the measurement surface of the soil pressure cell, so that the soil pressure propagation rule is influenced, and the measurement precision is reduced. In addition, the existing schemes can only measure the magnitude of the three-dimensional stress state, and neglect the depiction of each stress direction, so that the direction of the measured stress is unclear, the measured stress state at one point cannot be associated with the actual engineering azimuth angle, and the stress state cannot be depicted in the engineering in a vector or tensor mode, and the stress state cannot be really used for describing the actual engineering stress state.

Disclosure of Invention

In view of this, the present invention provides a dynamically-oriented three-dimensional vector soil pressure sensor, which implements dynamic monitoring of a stress direction, truly implements real-time vectorization description of a three-dimensional stress state at one point in a soil body, and associates the three-dimensional vector soil pressure sensor with a project.

In order to achieve the purpose, the invention provides the following technical scheme:

a three-dimensional vector soil pressure sensor capable of being dynamically oriented comprises a spherical base, a plurality of pressure modules arranged on the spherical base, a data acquisition module arranged in the spherical base and an optical fiber; the optical fiber is connected with the data acquisition module, the data acquisition module is connected with a plurality of wires, each pressure module is connected with one wire, the spherical base is further provided with a three-axis tilt angle sensor, and the three-axis tilt angle sensor is connected to the data acquisition module through one wire.

Optionally, the pressure module comprises a pressure sensitive surface and a silicon piezoresistive module which are matched, and the pressure sensitive surface faces to the outer side of the spherical base.

Optionally, a groove for assembling the pressure module and the three-axis tilt angle sensor is formed in the spherical base, the pressure module and the three-axis tilt angle sensor are correspondingly arranged in the groove one by one, and the number of the grooves is greater than or equal to the sum of the number of the pressure module and the number of the three-axis tilt angle sensor.

Optionally, a wire hole for a wire to pass through is formed in the groove, and the wire passes through the wire hole.

Optionally, the optical fiber includes a cable shielding layer and a cable insulating layer wrapped outside the cable shielding layer.

Optionally, the wire includes a core wire, a wire shielding layer wrapped outside the core wire, and a wire insulating layer wrapped outside the wire shielding layer.

Optionally, there are 9 setting points of the pressure module and the three-axis tilt angle sensor, including 3 groups, the first group includes 4 setting points, which are uniformly distributed on an axisymmetric plane of the spherical base, and the second group includes 1 setting point, which is located at an end point farthest from the axisymmetric plane in a vertical distance; the connecting line of the center of the spherical base and the set point in the second group is a Z axis, and an X axis and a Y axis are selected on an axial symmetry plane to form a Cartesian coordinate system; the third group comprises the other 4 set points, and the normal line positions of the set points are equal inclination lines of a Cartesian coordinate system.

Optionally, the third set of set points is located between the first set and the second set.

Optionally, the three-axis tilt sensor is arranged in the second group.

Optionally, at least 6 pressure modules are provided.

Optionally, the arrangement direction of the optical fibers is opposite to the Z-axis direction.

Optionally, an optical fiber hole convenient for connecting an optical fiber is formed in the spherical base.

The invention has the beneficial effects that:

(1) the existing measuring device has irregular geometric shape, easily causes stress concentration and uneven stress distribution, reduces the accuracy of stress magnitude test, and even induces the soil body to generate shearing damage along the surface of the device. The spherical base is regular in geometric shape, and the phenomenon of uneven stress distribution caused by irregular shape of the testing device can be well weakened. The distance between each measuring plane is far and the distribution is uniform, and the measuring precision is improved to a certain extent.

(2) The stress direction measured by the existing device is uncertain. The three-axis inclination angle sensor is fixed on the spherical base and used for measuring the space attitude of the spherical base, on one hand, the three-axis inclination angle sensor is used for determining the embedding direction of the three-dimensional stress measuring device, and on the other hand, the attitude change condition of the spherical base after large deformation is monitored in real time. During specific implementation, an initial coordinate is given to the triaxial tilt sensor, so that the initial coordinate can be matched with a geomagnetic coordinate or an engineering coordinate for subsequent analysis. When the sensors are buried, the sensors can be placed at will according to the measuring point requirements, and after the burying is finished, the data of the three-axis tilt sensor is read, and a buried coordinate system is established. And in the loading and monitoring process, reading the data of the triaxial tilt sensor in real time and establishing a dynamic coordinate system. According to the basic operation relationship of mechanics, the stress conversion relationship under different coordinate systems can be obtained.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a three-dimensional isocline view of the present invention;

FIG. 2 is a three-dimensional elevation view of the present invention;

FIG. 3 is a three-dimensional top view of the present invention;

FIG. 4 is a cross-sectional view of the spherical base;

FIG. 5 is a cross-sectional view of the present invention;

FIG. 6 is a pressure module construction diagram.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

Referring to fig. 1-6, the reference numbers in the figures refer to the following elements: the pressure sensor comprises a pressure module 1, a three-axis tilt angle sensor 2, a data acquisition module 3, a spherical base 4, an optical fiber 5, an optical fiber hole 41, a wire hole 42, a groove 43, a conducting wire 10, a pressure sensitive surface 11 and a silicon piezoresistive element 12.

The invention mainly comprises a pressure module 1, a triaxial tilt angle sensor 2, a data acquisition module 3, a spherical base 4 and an optical fiber 5.

The spherical base 4 is provided with a fiber hole 41, a wire hole 42 and a groove 43. The pressure module 1 comprises a lead 10, a pressure sensitive surface 11 and a silicon piezoresistive element 12. The three-axis tilt angle sensor 2 is a mature product in the market, and can be subjected to appearance transformation on the basis of FNN-3400 type electronic compass produced by Shaanxi space great wall measurement and control Limited company, so that the three-axis tilt angle sensor is matched with the groove 43.

Assuming that the direction of the optical fiber 5 is the z direction, the x and y directions are selected on the equatorial plane perpendicular to z so as to together constitute a cartesian coordinate system. Three groups are divided into 1 group on the groove 43, the first group is symmetrical with the optical fiber hole 41 and is along the negative direction of the z axis; the number of the second group is 4, the second group is uniformly distributed along an x-y plane, and the normal direction is parallel to the x axis or the y axis; the third group is 4, and the normal line between the optical fiber hole 41 and the second group is an isoline of an x-y-z coordinate system. The three-axis tilt angle sensor 2 is arranged on one of the second group of grooves 43, and the pressure module 1 is directly arranged on the other 8 grooves 43 and is integrally packaged.

In order to minimize the influence of the sensor on the stress distribution, according to the prior art capabilities, the pressure module 1 has a diameter of about 25mm and the recess 43 is 3mm deep, whereby the spherical seat 4 has a diameter of about 60-70 mm.

The data acquisition module 3 is technically mature. The pressure module 1 is provided with a wire 10, one end of which is connected to the silicon piezoresistive element 12 inside the pressure module, and the other end of which is connected to the data acquisition module through a wire hole 42. The interior void of the spherical base 4 and the fiber holes 41 may be filled and sealed with a hot melt or glass adhesive to secure the internal components.

The spherical base 4 is a framework of the vectorization three-dimensional stress measuring ball, has the characteristics of high strength, good stability and the like in the spherical geometric shape, and is suitable for operation under deep soil layers and high additional loads. Two sets of eight cylindrical recesses 43 on the spherical base 4 are used to package the pressure module 1 and the triaxial tilt sensor 2. The wire 10 is used for transmitting the data measured by the pressure module 1 to the data acquisition module 3, and the other end of the wire passes through the wire hole 42 and is connected to the data acquisition module 3. The data acquisition module 3 collects and modulates the data of the triaxial tilt angle sensor 2 and the pressure module 1 and then transmits the data through the optical fiber 5. The three-axis tilt sensor 2 is fixed on the spherical base 4 and used for determining the real-time posture of the three-dimensional stress measuring device.

In the implementation process, the three-dimensional vector soil pressure sensor can be buried at a position where stress needs to be measured in a large-area excavating mode or a small-area excavating mode. When the three-dimensional vector soil pressure sensor is buried, the position of the three-dimensional vector soil pressure sensor can be randomly placed according to measurement requirements, and then soil is covered and tamped to finish the burying work of the three-dimensional vector soil pressure sensor. In the specific test process, the posture of the three-dimensional vector soil pressure sensor in a three-dimensional space can be obtained in real time through the triaxial tilt angle sensor 2, and then the direction of each pressure module 1 is determined through mathematical operation.

The specific calculation method is as follows:

the number of pressure modules 1 required for the test is selected according to the actual requirements. Taking six as an example, 10, 20, 30, 40, 50, 60, respectively, the measured stresses are σ₁₀、σ₂₀、σ₃₀、σ₄₀、σ₅₀、σ₆₀The normal direction of each pressure module is { alpha_i，β_i，γ_i10, 20, 30, 40, 50, 60. The measured three-dimensional stress state at the measurement point is then recorded in the initial coordinate system in the form of a matrix as:

{σ_ij}＝{σ_x σ_y σ_z σ_xy σ_yz σ_zx}

＝{σ₁₀ σ₂₀ σ₃₀ -σ₄₀ -σ₅₀ -σ₆₀} (1)

(1) three-dimensional stress state calculation method under any coordinate system

The three-dimensional stress state in any coordinate system can be calculated by the following formula:

σ_kl＝T_klijσ_ij (2)

where T is a coordinate transformation tensor between the measured coordinates and the desired coordinates.

This section is the basic calculation in the field and the details are not expanded.

(2) Method for calculating magnitude and direction of main stress in three-dimensional space

The part calculates the content of a multivariate linear function from linear algebra, and relates to a characteristic equation, a characteristic value and a characteristic vector, and the specific calculation process is as follows:

in the principal stress coordinate system, there is only a positive stress, and no shear stress, acting on each principal plane. Taking x-y-z as reference, setting the direction cosine of the main plane as l, m and n respectively, and calculating the magnitude and direction of the main stress according to vector operation, namely

The above formula can be rewritten as:

if a non-zero solution is required to exist in the homogeneous linear equation system with the above formulas l, m and n, the determinant of the coefficient must be zero according to the Cramer's law,

the characteristic equation of the stress is obtained by expansion

σ³-I₁σ²+I₂σ-I₃＝0 (6)

In the formula I₁、I₂And I₃Three stress independent variables.

Three roots of the unitary cubic equation are the magnitudes of three principal stresses, which are respectively recorded as sigma₁、σ₂And σ₃. The magnitudes of the three main stresses are respectively brought back to the formula (4) and are connected in parallel to form an identity

l²+m²+n²＝1 (7)

The eigenvector of each principal stress, i.e. the direction vector of the principal stress, can be found:

σ＝σ₁when n is greater than n₁＝(l₁,m₁,n₁)

σ＝σ₂When n is greater than n₂＝(l₂,m₂,n₂)

σ＝σ₃When n is greater than n₃＝(l₃,m₃,n₃)

The pressure module is integrally packaged, and a finished soil pressure box can be adhered to the three-dimensional base during specific implementation, so that the dynamic measurement of the three-dimensional attitude of the sensor is protected.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.