CN106323158A - Device for testing three-dimensional strain state inside soil mass and testing method - Google Patents

Abstract

The invention provides a device for testing a three-dimensional strain state inside a soil mass. Six common strain gauges of the device are sequentially fixed onto strain gauge bases on six surfaces with uncorrelated normal vectors of a rhombic dodecahedron, and lead holes leading to the center of the rhombic dodecahedron are formed in centers of the six surfaces with the uncorrelated normal vectors of the rhombic dodecahedron and connected with a data acquisition system through measuring leads. Besides, the invention further provides a testing method of the device for testing the three-dimensional strain state inside the soil mass. The device has the advantages that the three-dimensional strain state of a certain position of the soil mass is more accurately tested, linear strain in a maximum main strain direction can be obtained, among six strain gauge testing values, testing precision of three main strain gauges is 1.22 rho, testing precision of three shearing strain gauges is 0.71 rho, average testing precision is 0.97 rho, strain gauge testing precision in a single direction is improved, and the limitation of only testing surface strain at inaccurate testing positions in the past is changed. The device visually reflects the deformation state inside the soil mass, and safety stock of engineering construction is improved.

Description

For testing device and the method for testing of inside soil body three dimensional strain state

Technical field

The invention belongs to the deformation in engineering and strain testing technical field, being specially one test inside soil body three-dimensional should The device of change state and method of testing, by six incoherent of normal vectors on this device acquisition granatohedron Line strain, is computed just can obtaining testing the three dimensional strain state at the soil body.

Background technology

The deformation of object and strain testing are basic works in civil engineering, hydraulic engineering and traffic engineering Make.It is by engineering health monitoring and quantifies the premise of mechanical analysis.Deeply recognize the mechanical property of material, answering of the research soil body Power, strain, accurately understand its stress and working condition, is quality evaluation and the key of reinforcing maintenance in engineering construction.

Generally, unidirectional strain testing and the pure stress test of beaer can be counted by foil gauge and stress Become.When studying a certain strain determined on direction or during stress, can use arrange in the direction foil gauge, stressometer or its The mode of his sensor obtains the mechanics parameter in the direction.For plane stress and strain problems, can be by body surface The strain rosette pasting conventional foil gauge composition records.Conventional strain rosette is made up of three foil gauges, can only record in a certain plane Strain conditions, and strain and stress epidemic situation comparison within Rock And Soil is complicated in Practical Project, it is difficult to be reduced to one-dimensional or The simple state of two dimension.Generally require the three dimensional strain state obtained within jobbie.

Three dimensional strain state within Rock And Soil there is no widely used effective way at present, and its Patent " is used for testing The test device of three dimensional strain state and method of testing thereof " (publication No.: CN104482913A) be based on six ribs of positive tetrahedron Three dimensional strain embossing device.This device is less with soil body contact surface, and the skeleton pasting foil gauge is easily sent out along with the deformation of the soil body Change shape, is not fixed easily its position in beaer, thus causes its test orientation to there is deviation, it is impossible to Accurate Determining ground The a certain three dimensional strain state determining position in body.The material selection elastic modelling quantity of this device pedestal is less than beaer material to be measured Shaft-like plastics, this device is placed in beaer and use after stress deformation, can not be repeated, belong to disposable apparatus.Material Waste is serious, disagrees with the environmental protection concept advocated.In order to obtain authentic and valid strain regime, it is necessary to inside soil body Strain regime carry out the most stable test.In such as base pit engineering, the stress of the various location soil body, strain regime Different, and depend on the impact of the factors that form of construction work, construction progress, weather conditions etc. are difficult to quantify.Therefore, add The accurate measurements of beaer internal strain state under the conditions of strong three-dimensional state, not only to ensureing construction quality and construction safety very Important, also it is the basic demand to information civil engineering construction.

Summary of the invention

It is an object of the invention to provide a kind of device for testing inside soil body three dimensional strain state and method of testing, with The three dimensional strain state realizing test inside soil body any point is tested directly and accurately.

For achieving the above object, the technical solution used in the present invention is: provide one test inside soil body three dimensional strain shape The device of state.Wherein this device includes that granatohedron, six common foil gauges, measure traverse line, center of area wire guide, wires converge Total hole, foil gauge pedestal.Six common foil gauges are fixed on the strain of incoherent of six normal vectors of granatohedron On sheet pedestal, the measure traverse line of six common foil gauges passes through center of area wire guide, collects from the centre of form wire of granatohedron Hole is connected with foil gauge data collecting system after deriving, and forms three dimensional strain state testing device.Utilize data collecting system The reading of six foil gauges of test, determines with each foil gauge direction cosines value according to the reading of foil gauge on six different directions And the relationship between transition matrix, and then it is calculated the three dimensional strain state of any point in the soil body.

The method of testing of a kind of device for testing inside soil body three dimensional strain state is provided simultaneously.

The effect of the present invention is: this device uses granatohedron to be the base pasting foil gauge, granatohedron Manufacture method convenient, be directly to be intercepted acquisition by square, and granatohedron be made up of 12 complete equal faces, each The vector that foil gauge direction is pasted in face is the most equal and unique with the angle of face normal.Therefore using granatohedron as the present invention Base, test can be made directly perceived and test position accurately, overcome that single foil gauge measuring accuracy is the highest, test position exists Deviation, measurement direction are single, cannot obtain the technology limitations such as three dimensional strain state.Additionally the method Computing Principle is clear and definite, calculates Precision is higher.The precision assuming common foil gauge is ρ, and the strain testing precision in calculated three principal strain directions is respectively Being 1.22 ρ, the measuring accuracy of three shear stress is 0.71 ρ, and average test precision is 0.97 ρ, and precision is improved, more accurate Really, deformation state within testee, and this device intuitively can reuse, composite green environmental protection concept, and carrying The safety stock of high engineering construction, provides new thinking and approach for strain testing technical field correlational study.

Accompanying drawing explanation

Fig. 1 is the direction vector of the foil gauge of the present invention；

Fig. 2 is the making figure of the granatohedron of the present invention；

Fig. 3 is the granatohedron of the present invention；

Fig. 4 is the granatohedron skeleton laying foil gauge of the present invention；

Fig. 5 is the top view of the three dimensional strain test device of the present invention；

Fig. 6 is the three dimensional strain test device design sketch of the present invention.

In figure:

1. granatohedron 2. foil gauge 3. measure traverse line

4. center of area wire guide 5. wire collects hole 6. foil gauge pedestal

Specific embodiment

In conjunction with accompanying drawing, device for testing inside soil body three dimensional strain state of the present invention a kind of and method of testing are added To describe in detail.

The present invention is that this device includes rhombus 12 for testing the apparatus structure of inside soil body three dimensional strain state 1, six foil gauges 2 of face body, measure traverse line 3, center of area wire guide 4, wire collect hole 5, foil gauge pedestal 6；By six foil gauges 2 Being fixed on the foil gauge pedestal 6 of incoherent of 1 six normal vectors of granatohedron, wherein foil gauge pedestal uses elasticity Modulus is less than soil body material to be measured.The measure traverse line 3 of six common foil gauges passes through center of area wire guide 4 from granatohedron Centre of form wire collects after hole 5 is derived and is connected with foil gauge data collecting system, forms three dimensional strain state testing device；Utilize The reading of data collecting system six foil gauges of test, according to the reading of foil gauge on six different directions and each foil gauge direction Cosine value determines the relationship between transition matrix, and then is calculated the three dimensional strain shape of any point in the soil body State.

Comprise the following steps for testing the method for testing of the device of soil body three dimensional strain state:

(1) first by measure traverse line 3 from the beginning of each foil gauge 2 bottom surface, through center of area wire guide 4 at granatohedron Collected hole 5 by wire after converging at the centre of form to draw；Each foil gauge 2 is fixed on six foil gauge pedestals, then by poly-ammonia The press-in of ester foam gap filler is filled and is collected in hole 5 to wire, for the space between filling measure traverse line and wire guide, is formed and surveys The device of examination inside soil body three dimensional strain state, and this device is placed in the tested soil body.

(2) with centre of form O of granatohedron as initial point, with OO₁、OO₂、OO₃Three-dimensional coordinate is set up for x-axis, y-axis, z-axis System.

(3) coordinate system set up according to step (2) tries to achieve α₁、α₂、α₃、α₄Four face foil gauges direction vector (1, 0,1), (0,1,1), (-1,0,1), (0 ,-1,1) and face β₁、β₂Foil gauge direction vector (1,1,0), (-1,1,0) linear nothing Close, i.e. these six faces are incoherent of direction vector.

(4) according to the axis direction of six common foil gauges and x-axis, y-axis, the direction of each foil gauge of angle calcu-lation of z-axis Cosine l, m, n, and thereby determine that matrix A.

(5) reading of data collecting system six foil gauges (2) of test is utilized, according to foil gauge on six different directions Reading and each foil gauge direction cosines value determine the relationship { ε between transition matrix_j}=A^-1{ε_i, and then calculate Obtain the three dimensional strain state of any point in the soil body.

{ε_j}=A^-1{ε_i} (1)

Wherein A^-1For

$A^{-1}=\left\{\begin{array}{cccccc}0.5& -0.5& 0.5& -0.5& 0.5& 0.5\\ -0.5& 0.5& -0.5& 0.5& 0.5& 0.5\\ 0.5& 0.5& 0.5& 0.5& -0.5& -0.5\\ 0& 0& 0& 0& 1& -1\\ 0& 1& 0& -1& 0& 0\\ 1& 0& -1& 0& 0& 0\end{array}\right\}---\left(2\right)$

Device and the method for testing of the test inside soil body three dimensional strain state of the present invention are achieved in that

1, the granatohedron carcasing of foil gauge is laid:

At the circular hole of six centrally disposed a diameter of 1cm in face pasting foil gauge, this circular hole vertically leads to rhombus dodecahedro The centre of form of body, selects the face not pasting foil gauge of granatohedron 1 and opens a diameter of 2cm thereon and lead to the circle of the centre of form Hole, to accommodate the passage of six common foil gauge measure traverse lines.It is face incoherent of six normal vectors of granatohedron α₁、α₂、α₃、α₄Dough-making powder β₁、β₂Paste foil gauge on the foil gauge pedestal of center, bottom foil gauge, smear bonding with side if desired Agent is to ensure foil gauge uniform force.

2, the assembling process of three dimensional strain test device:

First by measure traverse line 3 from the beginning of each foil gauge 2 bottom surface, through center of area wire guide 4 in granatohedron shape Collected hole 5 by wire after converging at the heart to draw；Each foil gauge 2 is fixed on six foil gauge pedestals, then by polyurethane Foam gap filler press-in is filled to wire and is collected in hole 5, for the space between filling measure traverse line and wire guide, formed based on The three dimensional strain state testing device of foil gauge 2.

3, this device is embedded in the position to be measured of the soil body, records six principal strain directions by strain data acquisition system Strain value, obtain conventional three-dimensional strain regime according to formula (1).

Three dimensional strain state testing device based on common foil gauge and granatohedron, calculates pushing away of theoretical formula (1) Lead process as follows:

Assume the straight line OA in three dimensions, as shown in Figure 1.Then this straight line direction cosines l in x, y, z direction, M, n are respectively

N=cos σ (5)

In formula, σ is the angle of straight line and z-axis,Angle for the projection in plane xOy of this straight line Yu x-axis.If known one The strain regime of point is ε_j={ ε_x,ε_y,ε_z,ε_xy,ε_yz,ε_zx, then the line strain in OA direction is:

ε_n=ε_xl²+ε_ym²+ε_zn²+ε_xylm+ε_yzmn+ε_zxnl (6)

That is, if it is known that the strain regime of a bit, then the line strain of any direction all can be passed through formula (6) and obtains.Accordingly , if the line strain on known six different directions, then can also obtain its conventional strain method for expressing.If known six differences Line strain on direction is respectively as follows:

${\mathrm{\ϵ}}_i={\mathrm{\ϵ}}_x{l}_i^2+{\mathrm{\ϵ}}_y^2{m}_i^2+{\mathrm{\ϵ}}_z{n}_i^2+{\mathrm{\ϵ}}_{xy}{l}_i{m}_i+{\mathrm{\ϵ}}_{yz}{m}_i{n}_i+{\mathrm{\ϵ}}_{zx}{n}_i{l}_i---\left(7\right)$

Wherein i=1,2,3,4,5,6, the mapping relations of general strain regime to different directions line strain be:

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\\ {\mathrm{\ϵ}}_3\\ {\mathrm{\ϵ}}_4\\ {\mathrm{\ϵ}}_5\\ {\mathrm{\ϵ}}_6\end{array}\right\}\left\{\begin{array}{cccccc}{l}_1^2& m_1^2& n_1^2& l_1{m}_1& m_1{n}_1& n_1{l}_1\\ l_2^2& m_2^2& n_2^2& l_2{m}_2& m_2{n}_2& n_2{l}_2\\ l_3^2& m_3^2& n_3^2& l_3{m}_3& m_3{n}_3& n_3{l}_3\\ l_4^2& m_4^2& n_4^2& l_4{m}_4& m_4{n}_4& n_4{l}_4\\ l_5^2& m_5^2& n_5^2& l_5{m}_5& m_5{n}_5& n_5{l}_5\\ l_6^2& m_6^2& n_6^2& l_6{m}_6& m_6{n}_6& n_6{l}_6\end{array}\right\}\left\{\begin{array}{c}{\mathrm{\ϵ}}_x\\ {\mathrm{\ϵ}}_y\\ {\mathrm{\ϵ}}_z\\ {\mathrm{\ϵ}}_{xy}\\ {\mathrm{\ϵ}}_{yz}\\ {\mathrm{\ϵ}}_{zx}\end{array}\right\}---\left(8\right)$

Or it is abbreviated as { ε_i}=A{ ε_j, wherein j=x, y, z, xy, yz, zx.And have

$A=\left\{\begin{array}{cccccc}{l}_1^2& m_1^2& n_1^2& l_1{m}_1& m_1{n}_1& n_1{l}_1\\ l_2^2& m_2^2& n_2^2& l_2{m}_2& m_2{n}_2& n_2{l}_2\\ l_3^2& m_3^2& n_3^2& l_3{m}_3& m_3{n}_3& n_3{l}_3\\ l_4^2& m_4^2& n_4^2& l_4{m}_4& m_4{n}_4& n_4{l}_4\\ l_5^2& m_5^2& n_5^2& l_5{m}_5& m_5{n}_5& n_5{l}_5\\ l_6^2& m_6^2& n_6^2& l_6{m}_6& m_6{n}_6& n_6{l}_6\end{array}\right\}---\left(9\right)$

Being obtained by Fig. 2, the direction vector of each foil gauge is as shown in table 1

The direction vector of table 1 each foil gauge of dodecahedron

Therefore

$A=\frac{1}{2}\left\{\begin{array}{cccccc}1& 0& 1& 0& 0& 1\\ 0& 1& 1& 0& 1& 0\\ 1& 0& 1& 0& 0& -1\\ 0& 1& 1& 0& -1& 0\\ 1& 1& 0& 1& 0& 0\\ 1& 1& 0& -1& 0& 0\end{array}\right\}---\left(10\right)$

So

{ε_i}=A{ ε_j} (11)

Wherein i=1,2,3,4,5,6.Therefore

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\\ {\mathrm{\ϵ}}_3\\ {\mathrm{\ϵ}}_4\\ {\mathrm{\ϵ}}_5\\ {\mathrm{\ϵ}}_6\end{array}\right\}=\frac{1}{2}\left\{\begin{array}{cccccc}1& 0& 1& 0& 0& 1\\ 0& 1& 1& 0& 1& 0\\ 1& 0& 1& 0& 0& -1\\ 0& 1& 1& 0& -1& 0\\ 1& 1& 0& 1& 0& 0\\ 1& 1& 0& -1& 0& 0\end{array}\right\}\left\{\begin{array}{c}{\mathrm{\ϵ}}_x\\ {\mathrm{\ϵ}}_y\\ {\mathrm{\ϵ}}_z\\ {\mathrm{\ϵ}}_{xy}\\ {\mathrm{\ϵ}}_{yz}\\ {\mathrm{\ϵ}}_{zx}\end{array}\right\}---\left(12\right)$

The inverse matrix A of A^-1For

$A^{-1}=\left\{\begin{array}{cccccc}0.5& -0.5& 0.5& -0.5& 0.5& 0.5\\ -0.5& 0.5& -0.5& 0.5& 0.5& 0.5\\ 0.5& 0.5& 0.5& 0.5& -0.5& -0.5\\ 0& 0& 0& 0& 1& -1\\ 0& 1& 0& -1& 0& 0\\ 1& 0& -1& 0& 0& 0\end{array}\right\}---\left(13\right)$

Therefore, it can obtain three dimensional strain state be:

{ε_j}=A^-1{ε_i} (14)

Calculating derivation for above-mentioned narration, test result is calculated by existing citing, it is assumed that record answering of six faces Become and be respectively as follows: 320,260,370,400,500,350 (μ ε).

That is:

${\mathrm{\ϵ}}_{\mathrm{\ξ}}=\left\{\begin{array}{c}{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\\ {\mathrm{\ϵ}}_3\\ {\mathrm{\ϵ}}_4\\ {\mathrm{\ϵ}}_5\\ {\mathrm{\ϵ}}_6\end{array}\right\}=\left\{\begin{array}{c}320\\ 260\\ 370\\ 400\\ 500\\ 350\end{array}\right\}---\left(15\right)$

Obtain according to three dimensional strain state computation formula (1) and (2), (3), (4) formula:

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_x\\ {\mathrm{\ϵ}}_y\\ {\mathrm{\ϵ}}_z\\ {\mathrm{\ϵ}}_{xy}\\ {\mathrm{\ϵ}}_{yz}\\ {\mathrm{\ϵ}}_{zx}\end{array}\right\}=\left\{\begin{array}{cccccc}0.5& -0.5& 0.5& -0.5& 0.5& 0.5\\ -0.5& 0.5& -0.5& 0.5& 0.5& 0.5\\ 0.5& 0.5& 0.5& 0.5& -0.5& -0.5\\ 0& 0& 0& 0& 1& -1\\ 0& 1& 0& -1& 0& 0\\ 1& 0& -1& 0& 0& 0\end{array}\right\}\×\left\{\begin{array}{c}{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\\ {\mathrm{\ϵ}}_3\\ {\mathrm{\ϵ}}_4\\ {\mathrm{\ϵ}}_5\\ {\mathrm{\ϵ}}_6\end{array}\right\}---\left(16\right)$

That is:

$\begin{array}{c}{\mathrm{\ϵ}}_x=0.5{\mathrm{\ϵ}}_1-0.5{\mathrm{\ϵ}}_2+0.5{\mathrm{\ϵ}}_3-0.5{\mathrm{\ϵ}}_4+0.5{\mathrm{\ϵ}}_5+0.5{\mathrm{\ϵ}}_6\\ {\mathrm{\ϵ}}_y=-0.5{\mathrm{\ϵ}}_1+0.5{\mathrm{\ϵ}}_2-0.5{\mathrm{\ϵ}}_3+0.5{\mathrm{\ϵ}}_4+0.5{\mathrm{\ϵ}}_5+0.5{\mathrm{\ϵ}}_6\\ {\mathrm{\ϵ}}_z=0.5{\mathrm{\ϵ}}_1+0.5{\mathrm{\ϵ}}_2+0.5{\mathrm{\ϵ}}_3+0.5{\mathrm{\ϵ}}_4-0.5{\mathrm{\ϵ}}_5-0.5{\mathrm{\ϵ}}_6\\ {\mathrm{\ϵ}}_{xy}=1{\mathrm{\ϵ}}_5-1{\mathrm{\ϵ}}_6\\ {\mathrm{\ϵ}}_{yz}=1{\mathrm{\ϵ}}_2-1{\mathrm{\ϵ}}_4\\ {\mathrm{\ϵ}}_{zx}=1{\mathrm{\ϵ}}_1-1{\mathrm{\ϵ}}_3\end{array}---\left(17\right)$

In the soil body, the three-dimensional microstrain at test position is:

${\mathrm{\ϵ}}_j=\left\{\begin{array}{c}{\mathrm{\ϵ}}_x\\ {\mathrm{\ϵ}}_y\\ {\mathrm{\ϵ}}_z\\ {\mathrm{\ϵ}}_{xy}\\ {\mathrm{\ϵ}}_{yz}\\ {\mathrm{\ϵ}}_{zx}\end{array}\right\}=\left\{\begin{array}{c}440\\ 410\\ 250\\ 150\\ -140\\ -50\end{array}\right\}.$

Device and the method for testing for testing inside soil body three dimensional strain state of the present invention, it is possible to obtain more accurately Real strain regime at inside soil body certain point to be measured, to strengthen the stability monitoring of the strain regime to inside soil body.This The bright feature possessed is: the granatohedron base of employing is made up, therefore more than the material of the soil body to be measured of elastic modelling quantity This base does not deforms because of earth stress deformation so that test position is more stable.Foil gauge on granatohedron Pedestal is made up, so that foil gauge deforms together along with the stress soil body, more less than the material of the soil body to be measured of elastic modelling quantity The dependent variable that the reaction stress soil body produces exactly.Additionally granatohedron is directly intercepted by square and forms, simple for production. And 12 surfaces of this granatohedron are the most equal, each the vector pasting foil gauge direction is the most equal with the angle of face normal And it is unique, because these granatohedron measuring accuracies are higher than other dodecahedron base.

Claims (2)

1. for testing a device for inside soil body three dimensional strain state, this device is connected with data collecting system, and it is special Levy and be: this test device includes base granatohedron (1), six foil gauges (2), measure traverse line (3), center of area wire guides (4), wire collects hole (5), foil gauge pedestal (6)；Six foil gauges (2) are separately fixed at granatohedron (1) six On the foil gauge pedestal (6) of uncorrelated of normal vector, the measure traverse line (3) of six foil gauges passes through center of area wire guide (4) from Pedicellus et Pericarpium Trapae Shape dodecahedral centre of form wire collects after hole (5) is derived and is connected with foil gauge data collecting system, forms three dimensional strain shape State test device.

The method of testing of a kind of device testing inside soil body three dimensional strain state the most according to claim 1, this device Method of testing comprise the following steps:

(1) first by measure traverse line (3) from the beginning of each common foil gauge (2) bottom surface, through center of area wire guide (4) at rhombus ten Collected hole (5) by wire after converging at the dihedron centre of form to draw；Six common foil gauges (2) are separately fixed at normal vector not phase On the foil gauge pedestal (6) in six faces closed, then cranny filler of polyurethane foam press-in filling is collected in hole (5) to wire, For the space between filling measure traverse line and wire guide, formed based on common foil gauge (2) and the three of granatohedron (1) Dimension strain regime test device, and this device is placed in the tested soil body；

(2) with centre of form O of granatohedron as initial point, with OO₁、OO₂、OO₃Three-dimensional system of coordinate is set up for x-axis, y-axis, z-axis；

(3) coordinate system set up according to (2) tries to achieve α₁、α₂、α₃、α₄Foil gauge direction, four faces vector (1,0,1), (0, 1,1), (-1,0,1), (0 ,-1,1) and face β₁、β₂The vector (1,1,0) in foil gauge direction, (-1,1,0) linear independence, i.e. this Six faces are incoherent of direction vector；

(4) according to the axis direction of six common foil gauges and x-axis, y-axis, the direction cosines of each foil gauge of angle calcu-lation of z-axis L, m, n, and thereby determine that matrix A；

(5) reading of data collecting system six foil gauges (2) of test is utilized, according to the reading of foil gauge on six different directions And each foil gauge direction cosines value determines the relationship { ε between transition matrix_j}=A^-1{ε_i, and then be calculated The three dimensional strain state of any point in the soil body.

{ε_j}=A^-1{ε_i} (1)

Wherein A^-1For

$A^{-1}=\left\{\begin{array}{cccccc}0.5& -0.5& 0.5& -0.5& 0.5& 0.5\\ -0.5& 0.5& -0.5& 0.5& 0.5& 0.5\\ 0.5& 0.5& 0.5& 0.5& -0.5& -0.5\\ 0& 0& 0& 0& 1& -1\\ 0& 1& 0& -1& 0& 0\\ 1& 0& -1& 0& 0& 0\end{array}\right\}---\left(2\right)$