阅读说明：本技术 一种三维矢量压应力传感器 (Three-dimensional vector compressive stress sensor ) 是由 董彤 房雨雨 刘欣伟 魏丽娟 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,涉及一种三维矢量压应力传感器,包括球形基座,以及设置在球形基座上的若干个压力模块、以及多芯线缆；所述多芯线缆内设有与所述压力模块的数量相匹配的导线,每个所述压力模块与一根所述导线相连。本发明将压力模块整合在球形基座上,缩减了传感器尺寸；通过凹槽的形式,通过机械结构对压力模块进行安装,提高了连接强度,提高了固有频率,使其适用于测量爆炸冲击作用下土体内高频压应力的动态测量；通过球形基座和均匀分布的压力模块尽量避免应力集中的现象,提高测量精度；通过将所有导线整合在同一根线缆中降低了导线在基座内的布设难度。(The invention belongs to the field of stress testing, and relates to a three-dimensional vector compressive stress sensor which comprises a spherical base, a plurality of pressure modules and a multi-core cable, wherein the pressure modules and the multi-core cable are arranged on the spherical base; and the multi-core cable is internally provided with conducting wires the number of which is matched with that of the pressure modules, and each pressure module is connected with one conducting wire. The pressure module is integrated on the spherical base, so that the size of the sensor is reduced; the pressure module is installed through a mechanical structure in a groove form, so that the connection strength is improved, the inherent frequency is improved, and the dynamic measurement device is suitable for dynamic measurement of high-frequency pressure stress in the soil body under the action of explosive impact; the phenomenon of stress concentration is avoided as much as possible through the spherical base and the uniformly distributed pressure modules, and the measurement precision is improved; the difficulty of laying the wires in the base is reduced by integrating all the wires in the same cable.)

1. A three-dimensional vector compressive stress sensor is characterized by comprising a spherical base, a plurality of pressure modules arranged on the spherical base and a multi-core cable; and the multi-core cable is internally provided with conducting wires the number of which is matched with that of the pressure modules, and each pressure module is connected with one conducting wire.

2. The 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 three-dimensional vector compressive stress sensor according to claim 1, wherein the spherical base is provided with grooves for assembling pressure modules, the pressure modules are arranged in the grooves, and the number of the grooves is equal to or greater than the number of the pressure modules.

4. The three-dimensional vector compressive stress sensor of claim 3, wherein a wire hole for a wire to pass through is formed in the groove.

5. The three-dimensional vector compressive stress sensor of claim 1, wherein the multi-core cable comprises a cable shield and a cable insulation layer wrapped outside the cable shield.

6. The three-dimensional vector compressive stress 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 three-dimensional vector compressive stress sensor of claim 1, wherein the pressure modules have 9 set points, comprising 3 sets, a first set comprising 4 set points, evenly distributed on an axial symmetry plane of the spherical base, and a second set comprising 1 set point, located at the end point furthest from the vertical of the axial symmetry 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 three-dimensional vector compressive stress sensor of claim 7, wherein the third set of set points is located between the first set and the second set.

9. The three-dimensional vector compressive stress sensor of claim 7, wherein there are at least 6 pressure modules.

10. The three-dimensional vector compressive stress sensor of claim 7, wherein the multi-core cable is disposed in a direction opposite to the Z-axis direction.

Technical Field

The invention belongs to the field of stress testing, and relates to a three-dimensional vector compressive stress sensor.

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.

Compressive stress testing typically employs piezoresistive sensors. In general civil engineering, low-frequency loads such as long-term static loads, construction loads, traffic loads and the like are mainly measured. In special engineering, the method is mainly used for high-frequency loads of explosion and impact loads and earthquake loads. The latter has higher requirements on indexes such as integrity, rigidity, natural frequency and the like of the sensor.

The existing three-dimensional stress measuring device is generally special-shaped and has edges and corners, so that the existing three-dimensional stress measuring device has large interference on explosion shock waves; the movable soil pressure box is bonded on the base to be spliced, so that the strength is low and the movable soil pressure box is easy to scatter; the base natural frequency is lower.

Disclosure of Invention

In view of the above, the invention aims to provide a three-dimensional vector compressive stress sensor, which solves the problem of vector measurement of rock-soil three-dimensional dynamic stress under the action of high-frequency and high-strength dynamic loads such as explosion, earthquake and the like in engineering.

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

a three-dimensional vector compressive stress sensor comprises a spherical base, a plurality of pressure modules arranged on the spherical base and a multi-core cable; and the multi-core cable is internally provided with conducting wires the number of which is matched with that of the pressure modules, and each pressure module is connected with one conducting 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 modules is formed in the spherical base, the pressure modules are arranged in the groove, and the number of the grooves is greater than or equal to that of the pressure modules.

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

Optionally, the multi-core cable 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, 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, at least 6 pressure modules are provided.

Optionally, the arrangement direction of the multi-core cable is opposite to the Z-axis direction.

Optionally, an optical fiber hole convenient for connecting a multi-core cable is formed in the spherical base.

The invention has the beneficial effects that:

the pressure module is integrated on the spherical base, so that the size of the sensor is reduced; the pressure module is installed through the mechanical structure in the form of the groove, so that the problems of low rigidity and low inherent frequency when the cementing mode is fixed are solved, the connection strength is improved, the inherent frequency is improved, the problems that the cementing mode is easily damaged, cracked and dropped under the action of high-strength explosive load are solved, and the dynamic measurement device is suitable for dynamic measurement of high-frequency pressure stress in a soil body under the action of explosive impact; the phenomenon of stress concentration is avoided as much as possible through the spherical base and the uniformly distributed pressure modules, and the measurement precision is improved; the difficulty of laying the wires in the base is reduced by integrating all the wires in the same cable.

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 schematic view of the overall structure of the present invention;

FIG. 2 is a longitudinal axis cut-away view of the spherical base;

FIG. 3 is a longitudinal axis cut away view of the present invention;

FIG. 4 is a cutaway view of a erythroid plane of the present invention;

FIG. 5 is an exploded view of the erythroid plane of the present invention;

FIG. 6 is a cross-sectional view of a multi-core cable;

FIG. 7 is a schematic structural diagram of a pressure module;

fig. 8 is an exploded view of a pressure module.

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. 1-8, the reference numbers in the figures refer to the following elements: the pressure sensor comprises a spherical base 1, a pressure module 2, a multi-core cable 3, a cable hole 11, a groove 12, a cable hole 13, a pressure sensitive surface 21, a silicon piezoresistive module 22, a wire 23, a cable insulating layer 31, a cable shielding layer 32, a wire insulating layer 231, a wire shielding layer 232 and a core wire 233.

The invention relates to a three-dimensional vector compressive stress sensor which comprises a spherical base 1, a pressure module 2 and a multi-core cable 3. The spherical base 1 is provided with a cable hole 11, a groove 12 and a wire hole 13. The pressure module 2 consists of a pressure sensitive surface 21, a silicon piezoresistive module 22 and a lead 23.

The multi-core cable 3 comprises a cable insulating layer 31 and a cable shielding layer 32, at least 7 conducting wires 23 are contained in the multi-core cable, each conducting wire 23 is a four-core shielding cable, and the conducting wires 23 are respectively a conducting wire insulating layer 231, a conducting wire shielding layer 232 and a silver-plated core wire 233 from outside to inside.

The pressure module 2 is integrally encapsulated on the groove 12. Assuming that the direction of the cable hole 11 is the z direction, the x and y directions are selected on a equatorial plane perpendicular to z to jointly constitute a cartesian coordinate system. The grooves 12 can be divided into three groups, the number of the first group is 1, the first group is symmetrical to the cable hole 11, and the direction is negative along 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 lines of the third group are isolines of an x-y-z coordinate system between the cable holes 11 and the second group.

The multi-core cable 3 is threaded into the spherical base 1 through the cable hole 11, then the cable insulation layer 31 and the cable shielding layer 32 at the front end are stripped, and 7 wires 23 in the multi-core cable are respectively connected to the pressure module 2. The multi-core cable 3 is used for transmitting the piezoelectric signal of the pressure module to the acquisition end. In order to minimize the influence of the sensor on the stress distribution, according to the prior art capabilities, the pressure module has a diameter of about 25mm and the base recess has a depth of 3mm, whereby the spherical base 1 has a diameter of about 60-70 mm. The interior voids of the spherical base 1 and the reserved fiber holes (including the cable holes 11, the wire holes 13) may be filled and sealed with hot melt or glass glue to secure the internal components. The spherical measuring base is a framework of the vectorization three-dimensional stress measuring ball, the spherical geometry has the characteristics of high strength, good stability and the like, and the spherical measuring base is suitable for operation under deep soil layers and high additional loads. Three sets of 9 cylindrical grooves 12 on the spherical base 1 are used for packaging the pressure module.

In the implementation process, the vectorization three-dimensional main stress measuring ball is buried at a position where stress needs to be measured. When the embedded type can be embedded by adopting an excavating mode and manual positioning. If a drilling mode is adopted, the manual handheld sensor can be stretched into the hole to be placed and settled when the hole depth is shallow. If the hole depth is larger, the hole can be embedded by adopting an embedding auxiliary tool. For ease of operation and subsequent data analysis, the multi-core cable 3 is typically positioned directly above.

The specific calculation method after data acquisition is as follows:

and selecting the number of pressure modules required during testing according to actual requirements. Take six as examples, respectivelyDenoted as 10, 20, 30, 40, 50, 60, the measured stresses are σ, respectively₁₀、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 recorded as:

{σ_ij}＝{σ_x σ_y σ_z σ_xy σ_yz σ_zx}

＝{σ₁₀ σ₂₀ σ₃₀ -σ₄₀ -σ₅₀ -σ₆₀} (1)

subsequent calculations regarding stress are fundamental calculations in the art and details are not expanded. The size and the range of the pressure module can be selected or customized according to actual requirements, and the data cable can be selected or customized according to actual requirements.

The invention aims to protect the integrated packaging design of the pressure module and the integrated outgoing line design of the data cable.

Compared with the prior art, the invention has the following advantages:

(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 1 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) Too large a size: the sensor embedded in the rock-soil body has certain influence on the propagation of the blast-ground shock wave, and the influence is more obvious particularly when the size of the sensor is larger. In the prior art, the existing soil pressure cell finished product is assembled on a three-dimensional opposite base to realize the measurement of a three-dimensional stress vector. The finished fabricated connection allows functional overlap between the base and the earth pressure cell, resulting in a larger sensor size. The groove is arranged on the pressure sensor, so that the pressure module 2 is convenient to fix, and the size of the whole sensor can be reduced.

(3) The natural frequency is too low: in the prior art, the existing soil pressure cell finished product is assembled on a three-dimensional opposite base to realize the measurement of a three-dimensional stress vector. The assembly generally adopts a cementing mode, the base is made of polymer materials, the rigidity of a cementing material and the rigidity of the base are generally low, the inherent frequency is low, and the dynamic measurement method is difficult to be applied to the dynamic measurement of the high-frequency pressure stress in the soil body under the action of explosive impact. The invention has high natural frequency, and is suitable for dynamic measurement of high-frequency pressure stress in the soil body under the action of explosive impact.

(4) The overall strength is low: the cementing part of the measuring device manufactured by adopting the cementing assembly mode is a key weak part, and is easy to damage, crack and fall off under the action of high-strength explosive load, so that the overall testing precision is influenced. The pressure module 2 is installed through a mechanical structure, the whole structure is stable in connection, the strength is high, and the stability can be kept under the action of high-strength explosive load.

(5) The existing three-dimensional stress measuring device has irregular geometric shape, different area of each measuring surface and different included angle of each measuring surface, has obvious stress concentration phenomenon at local part, seriously influences the measuring precision, and even induces the soil body to generate shearing damage along the surface of the device. The invention avoids the phenomenon of stress concentration as much as possible by manufacturing the spherical shape.

(6) Each soil pressure cell all needs a wire, leads to soil pressure ball to need the circuit more than 6, and the degree of difficulty is great, efficiency is lower during practical application. According to the invention, multiple data cables are gathered into one cable for transmission through the multi-core cable, so that the efficiency is greatly improved; the cable fixing device is assembled and fixed through the same cable, integration of the whole device is facilitated, wiring efficiency of the whole device is improved, and structural stability is improved.

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.