CN105675179A - Tri-direction stress sensor with liquid metal antenna - Google Patents

Abstract

The invention discloses a tri-direction stress sensor with a liquid metal antenna. The stress sensor comprises a square hexahedral box (1), three surfaces sharing a vertex serve as stress surfaces (2) of the box, two organic polymer cylinders (3) are clamped between every stress surface (2) and an opposite surface thereof, each organic polymer cylinder (3) includes a spiral micro channel (5), each spiral micro channel (5) is full of liquid metal, and the liquid metal in the spiral micro channels (5) implements feeding via connected coaxial feed lines. Under the condition of tri-direction stress, the spiral micro channels (5)in the organic polymer cylinders (3) deform, so that the frequency of a device changes, an antenna frequency receiver measures the pressure of soil or rock, and thus, the pressure condition of the soil or rock is monitored and measured remotely. The tri-direction stress sensor has the advantages that stresses in three directions can be monitored in real time remotely, and the detection accuracy and reliability are improved.

Description

A kind of three-dimensional stress sensor with liquid metal antenna

Technical field

The invention belongs to Geotechnical Engineering stress test technical field, be specifically related to a kind of three-dimensional stress sensor with liquid metal antenna.

Background technology

In civil engineering, the triaxiality test of Rock And Soil or concrete bodies is a basic work in engineering, is the basis to engineering gps network and evaluation. Especially can accurately measure three-dimensional stress state and realize real-time remote monitoring, for infrastructure projects such as civil engineering, hydraulic engineering, traffic engineering, there is basic important function.

At present, in civil engineering stress test field, existing pressure test device great majority can only test the pressure in a direction, only minority pressure test device can test three-dimensional stress state, Chinese patent literature CN102620870A, CN104075944A disclose several three-dimensional stress sensor, have their own characteristics each. But find after Integrated comparative, there is Railway Project in existing three-dimensional stress sensor: 1, existing three-dimensional stress sensor is mainly all based on the sensor-type or native box body of type vibration wire, and this class testing device precision is not high enough, is subject to electromagnetic interference, range is big not, and long-time stability are poor; 2, existing three-dimensional stress sensor is all wired transmission test data, and MTD is deep not, it is impossible to remote testing; 3, existing three-dimensional stress sensor all can not for a long time, real-time remote monitoring.

Chinese patent literature CN104037495A discloses a kind of L-type liquid metal antenna for landslide monitoring on the 10th in JIUYUE in 2014, it includes elastic shell, L-type hollow pipe, micropump and feeding coaxial lines and ground strip, liquid metal is filled inside elastic shell, L-type hollow pipe is arranged on elastic shell top side, and connect inside elastic shell, L-type hollow pipe upwardly extends, micropump is installed on L-type hollow pipe top, being internally located at liquid metal overfall from L-type hollow pipe has feeding coaxial lines to draw, and the liquid metal at overfall place electrically connects with ground strip. This patent can carry out the state change on real-time remotely monitoring landslide, but, this device there is problems in that

1), this patent can only test a directional pressure, it is impossible to test triaxial pressure;

2), owing to micropump is installed on L-type hollow pipe top, this micropump is for evacuating gas to L-type hollow pipe, to maintain L-type hollow pipe air pressure balance, because the atmospheric pressure value in L-type hollow pipe cannot detect and keep constant, cause that the liquid metal flows relevant to atmospheric pressure value is subject to micropump control, so the liquid metal length of L-type hollow pipe can not truly reflect the stress deformation of elastic shell, cause the monitoring mistake that landslide displacement deforms;

3), L-type hollow pipe be arranged on elastic shell top side, elongated L-type hollow pipe intensity is relatively low, very weak with the intensity of elastic shell junction, easily snap off in actual use and damages.

Summary of the invention

For prior art Problems existing, the technical problem to be solved is just to provide a kind of three-dimensional stress sensor with liquid metal antenna, and it can in real time, remotely monitor triaxial pressure, and can improve the accuracy detected, reliability.

The technical problem to be solved is realized by such technical scheme, it includes box body, box body is square hexahedron, three faces wherein having common summit are stress surface, two organic polymer cylinders have respectively been clamped corresponding thereto between face at each stress surface, organic polymer cylinder has spiral type fluid channel, in spiral type fluid channel, is full of liquid metal, the coaxial feeder feed by connecting of the liquid metal in spiral type fluid channel.

Liquid metal in fluid channel constitutes liquid metal antenna. Liquid metal antenna on two organic polymer cylinders is concurrently accessed coaxial feeder and feeds, and forms the symmetrical dipole in antenna.

The operation principle of the present invention is: be embedded in rock mass by the present invention or after in soil, and three stress surfaces of box body start to be squeezed, the effect of being under pressure of the stress surface of box body, and produce deformation. Stress surface strains experienced passes to two compressible organic polymer cylinders, and organic polymer cylinder is compressed, and causes that the spiral type fluid channel in organic polymer cylinder produces longitudinal direction and transversely deforming. After deformation, the frequency receiving device reception is changing liquid metal after being fed by coaxial feeder.

Receiving the change of frequency thus extrapolating the soil pressure that device is subject to by receiving device, box case institute stress F is directly proportional to deflection Δ L, and relational expression is as follows:

F=K Δ L

In formula, K is the coefficient of elasticity of box body, Δ L=l₁-l₂, l₁For the liquid metal antenna length before pressure effect; l₂For the liquid metal antenna length after pressure effect.

According to " frequency reconfigurable antenna based on liquid metal is studied and design ", Xia Linyan, Chongqing Mail and Telephones Unvi's master thesis, the 34th page of formula (3.5), describe the frequency of liquid metal antenna and the relation of antenna length:

The frequency f of liquid metal antenna and the inversely proportional relation of the length l of liquid metal,Wherein c is the light velocity, and a is the coefficient of relationship between l and wavelength, ε_pIt it is organic polymer dielectric constant.

Thus, the three-dimensional stress state of rock mass to be measured or the soil body can be recorded according to the mutual relation of f-l-Δ L-F.

The present invention is when three received strength, the deformation of liquid metal spiral type fluid channel in organic polymer cylinder, make liquid metal antenna frequency change, receive device by antenna frequencies and record the pressure of the soil body or rock mass, it is achieved the remotely pressure condition of monitoring and the measurement soil body or rock mass. Owing to rock and soil pressure acts directly on organic polymer cylinder by box body panel, the liquid metal length in spiral type fluid channel is caused to change, the liquid metal flows deformation caused by pipeline air extracted out by the micropump avoiding L-type liquid metal antenna, the change of liquid metal antenna can truly reflect box body stress deformation, improves the accuracy of detection.It addition, the spiral type fluid channel being full of liquid metal is opened on the cylinder of polymeric cylinder, liquid metal antenna is attached on polymeric cylinder, and is arranged in box body, and its intensity is the intensity that box body is overall, improves the reliability of detection.

Compared with prior art, the invention have the advantage that can real-time remote monitoring triaxial pressure, improve the accuracy of detection, reliability.

Accompanying drawing explanation

The accompanying drawing of the present invention illustrates as follows:

Fig. 1 is the contour structures schematic diagram of the present invention;

Fig. 2 is the internal structure schematic diagram of the present invention;

Fig. 3 is the cylindrical structural representation of organic polymer of the present invention;

Fig. 4 is the contour structures schematic diagram of the Metal wire spiral column mould of the present invention;

Fig. 5 is the schematic block circuit diagram of the frequency measurement of the present invention;

Fig. 6 is the coordinate diagram that two present invention of application are corresponding.

In figure: 1. box body; 2. stress surface; 3. organic polymer cylinder; 4. coaxial feeder; 5. spiral type fluid channel; 6. Metal wire spiral column mould; 7. organic elastomer thin film.

Detailed description of the invention

Below in conjunction with drawings and Examples, the invention will be further described:

As depicted in figs. 1 and 2, the present invention includes box body 1, box body 1 is square hexahedron, three faces wherein having common summit are stress surface 2, two organic polymer cylinders 3 have respectively been clamped corresponding thereto between face at each stress surface 2, having spiral type fluid channel 5 on organic polymer cylinder 3, be full of liquid metal in spiral type fluid channel 5, the liquid metal in spiral type fluid channel 5 is fed by the coaxial feeder 4 connected.

Liquid metal selects the gallium-indium alloy of 3:1, tray interior filling gel. Box body stress surface is deformable steel membrane, non-stress face is indeformable steel plate.

Access coaxial feeder 4 in each spiral type fluid channel 5, pass from box body 1 summit. In this example, the often adjacent coaxial feeder 4 on three organic polymer cylinders 3 passes from adjacent vertex. External circuit is fed to liquid liquid metal by the coaxial feeder 4 accessed, and makes the liquid metal in every pair of spiral type fluid channel 5 constitute corresponding antenna, gives off electromagnetic wave.

As it is shown on figure 3, organic polymer cylinder 3 is provided with spiral type fluid channel 5. The manufacturing process of organic polymer cylinder 3 is as follows:

(1) as shown in Figure 4, prepare Metal wire spiral column mould 6, and prepare a cylindrical hollow mould;

(2) Metal wire spiral column mould is put into the hollow mould of cylinder, and Metal wire spiral column mould is close to hollow mould inwall is adhesively fixed, releasing agent is coated at Metal wire spiral column mould and hollow mould inwall, it is subsequently filled gluey organic polymer soln, after organic polymer solidifies, rotate by the hand of spiral and take out organic polymer cylinder, the cylindrical cylinder of organic polymer obtains a spiral type fluid channel groove;

(3) as shown in Figure 4, it is close to a circle organic elastomer thin film 7 on organic polymer cylinder 3 surface, makes spiral type fluid channel groove seal and form spiral type fluid channel 5;

(4) by spiral type fluid channel one end open to injecting liquid metal in fluid channel, after spiral type fluid channel fills full liquid metal, by fluid channel both ends open diaphragm seal, and perforate on the thin film of one end wherein;

(5) coaxial feeder is linked into thin film perforate;

(6) perforate is sealed.

Embodiment

Adopt the present invention to test three-dimensional stress, comprise the following steps:

Step 1, the present invention is laid in rock mass to be measured or the soil body

In rock mass to be measured or the soil body, boring is to presetting test point place, the triaxiality of two present invention is tested device and is fixed in connecting rod, deliver to default test point;The present invention is square shape, and three stress surfaces are mutually perpendicular to; Between the triaxiality test device of two present invention, at an angle, direction cosines can not be 1 to the normal direction of any two stress surface; Each stress surface can deform after being under pressure, thus change the present invention the frequency launched of liquid metal antenna.

Step 2, measure and receive the frequency of all directions

As it is shown in figure 5, swept signal source produces the sinusoidal electric signals of change frequency; The signal of telecommunication amplitude that amplitude measurement circuit records inputs automatic gain control circuit together with swept-frequency signal and compares, and is amplified through amplifying circuit by the signal after comparing; The signal of telecommunication of special frequency channel is by being converted into electromagnetic wave signal by signal transmission circuit after wave filter, it contains resonance coil and the liquid metal antenna connected by feeding coaxial lines, this special frequency channel signal of telecommunication is launched by liquid metal antenna, and receiving return signal by resonance coil, return signal and the former signal of telecommunication are overlapped; Resonance detecting circuit memory signal peak value, detects peak resonance point, in this, as interrupt signal; When electrical signal of the frequency a certain in special frequency channel is consistent with the own frequency of the liquid metal antenna deformed upon, resonance coil obtains the maximum signal of telecommunication, frequency counting circuit accurately measures frequency during the maximum signal of telecommunication passed through, and this frequency values is equal to the natural frequency value of liquid metal antenna. Amplitude measurement circuit records the amplitude of the signal of telecommunication in detecting circuit, sends automatic gain control circuit to as feedback signal;

The frequency that step 3, transmission are collected

Each class frequency value that receiver is collected by wireless transmitter is adopted to be transferred to PC end;

Step 4, data analysis

After PC termination receives frequency data, foundation more new database, and each group data of the different periods obtained are updated in test philosophy formula, thus calculating the three-dimensional stress constraint of test point.

The test philosophy derivation of equation of test point triaxiality is as follows:

As shown in Figure 6, two triaxiality test devices are designated as A, B respectively, and the space coordinates that wherein three stress surface normal direction of A are set up are oxyz; The space coordinates that three stress surface normal direction of B are set up are o ' x ' y ' z '. Record according to the description of number of patent application 201210096644.6:

If l_i、m_i、n_i(i=1,2,3) are x ', y ', z ' axle direction projection in oxyz coordinate system respectively; σ_x、σ_y、σ_zRespectively the surveyed normal pressure data of three stress surfaces of triaxiality test device A;Respectively triaxiality test device B the surveyed normal pressure data of tri-stress surfaces. Some stress states respectively (σ under oxyz and o ' x ' y ' z ' coordinate system_x、σ_y、σ_z、τ_xy、τ_yz、τ_zx) andWherein τ_xy、τ_yz、τ_zxIt is the shear stress components under oxyz coordinate system,It it is the shear stress components under o ' x ' y ' z ' coordinate system.

Then the stress tensor of oxyz and o ' x ' y ' z ' coordinate system subsequent point is respectively

$\[\mathrm{\σ}\]=\left[\begin{array}{ccc}{\mathrm{\σ}}_x& {\mathrm{\τ}}_{xy}& {\mathrm{\τ}}_{xz}\\ {\mathrm{\τ}}_{yx}& {\mathrm{\σ}}_y& {\mathrm{\τ}}_{yz}\\ {\mathrm{\τ}}_{zx}& {\mathrm{\τ}}_{zy}& {\mathrm{\σ}}_z\end{array}\right]$

$\[{\mathrm{\σ}}^{\′}\]=\left[\begin{array}{ccc}{\mathrm{\σ}}_x^{\′}& {\mathrm{\τ}}_{xy}^{\′}& {\mathrm{\τ}}_{xz}^{\′}\\ {\mathrm{\τ}}_{yx}^{\′}& {\mathrm{\σ}}_y^{\′}& {\mathrm{\τ}}_{yz}^{\′}\\ {\mathrm{\τ}}_{zx}^{\′}& {\mathrm{\τ}}_{zy}^{\′}& {\mathrm{\σ}}_z^{\′}\end{array}\right]$

Then there is [σ]=[L]^T[σ '] [L], wherein $\[L\]=\left[\begin{array}{ccc}{l}_1& m_1& n_1\\ l_2& m_2& n_2\\ l_3& m_3& n_3\end{array}\right],$ [L]^TTransposition for [L].

Three principal stress size σ of test point₁、σ₂、σ₃Can be in the hope of by the characteristic equation of three-dimensional stress constraint, equation is following formula such as:

In formula: J₁、J₂、J₃It is first, second, third invariant of stress tensor respectively:

J₁=σ_x+σ_y+σ_z

$J_2={\mathrm{\σ}}_x{\mathrm{\σ}}_y+{\mathrm{\σ}}_y{\mathrm{\σ}}_z+{\mathrm{\σ}}_z{\mathrm{\σ}}_x-{\mathrm{\τ}}_{xy}^2-{\mathrm{\τ}}_{yz}^2-{\mathrm{\τ}}_{zx}^2$

$J_2={\mathrm{\σ}}_x{\mathrm{\σ}}_y{\mathrm{\σ}}_z+2{\mathrm{\τ}}_{xy}{\mathrm{\τ}}_{yz}{\mathrm{\τ}}_{zx}-{\mathrm{\σ}}_x{\mathrm{\τ}}_{yz}^2-{\mathrm{\σ}}_y{\mathrm{\τ}}_{zx}^2-{\mathrm{\σ}}_z{\mathrm{\τ}}_{xy}^2$

The three-dimensional stress constraint obtaining test point must be calculated by these formula above-mentioned. (list of references: three-dimension geosciences modeling and Geology geomechanics analysis, Sun Weichun, Min Hong etc., Chinese Journal of Rock Mechanics and Engineering, in JIUYUE, 2008)

Two three-dimensional stress sensors of the present invention are placed at the test point place of body to be measured, the deformation of spiral type liquid metal fluid channel in compressible cylinder in three-dimensional stress sensor, the liquid metal antenna frequency making device changes, by antenna frequencies R-T unit, collect each frequency, thus indirectly recording all directions pressure of body to be measured, obtained the three-dimensional stress state of test point by formula operation, thus realizing remotely measuring and monitoring in real time.

Claims (2)

1. a three-dimensional stress sensor with liquid metal antenna, it is characterized in that: include box body (1), box body (1) is square hexahedron, three faces wherein having common summit are stress surface (2), two organic polymer cylinders (3) have respectively been clamped corresponding thereto between face at each stress surface (2), organic polymer cylinder (3) has spiral type fluid channel (5), being full of liquid metal in spiral type fluid channel (5), the liquid metal in spiral type fluid channel (5) is fed by the coaxial feeder 4 connected.

2. the three-dimensional stress sensor with liquid metal antenna according to claim 1, is characterized in that: coaxial feeder (4) passes from box body (1) summit.