CN105738479A - Method and device for testing small strain viscoelasticity parameter of geotechnical engineering material through bending elements - Google Patents

Abstract

The invention discloses a method and device for testing the small strain viscoelasticity parameter of a geotechnical engineering material through bending elements. The process comprises the steps of firstly, preparing a column type sample, and conducting measurement to obtain the density of the sample; placing the column type sample on a foaming rod, connecting the excitation bending element and the receiving bending element to the two ends of the column type sample respectively, and inserting piezoelectric ceramics of the two bending elements into the same depth in the column type sample; exciting a pulse signal through the excitation bending element, wherein the signal is transmitted and reflected by the column type sample and recorded and received by the receiving bending element, and processing a transmitted excitation signal and a received signal, so that the viscoelasticity parameters containing the elastic parameter and the damping ratio are obtained. Compared with an existing material viscoelasticity parameter test method, the method and device can be used for testing the strain viscoelasticity parameter and have the advantages that the test device is simple, test efficiency is high, and the physical relation is definite.

Description

The method of flexure element test geomaterial small strain viscoelastic parameters and device

Technical field

The present invention relates to material parameter method of testing and device, be specifically related to method and the device of a kind of flexure element test geomaterial small strain viscoelastic parameters, obtained its small strain viscoelastic parameters by geomaterial wave testing and analyzing and processing.

Background technology

When carrying out Dynamic Analysis of Foundation or dynamic model test, the dynamic stress-strain relationship of geomaterial is often reduced to desirable viscoelastic model, and its mechanical characteristic is characterized by elastic modelling quantity and damping ratio；The accuracy of material viscoelasticity parameter testing will directly affect the degree of reliability of dynamic analysis or test.For the material (such as complete rock) that uniformly continuous and rigidity are bigger, the test of viscoelastic parameters can adopt cantilever beam vibratory drilling method, and clear and definite and test result test sample frequency of vibration and amplitude the impact of this method boundary condition is less.And soil body material is owing to being discrete multiphase medium, and inapplicable cantilever method, when its small strain, viscoelastic parameters test need to by resonant column test or free vibration column test.The testing procedure relative complex of resonant column test, it is necessary to obtain sample resonant frequency by the mode of frequency sweep, calculates the elastic parameter of sample material；When finding resonant frequency, sample is had the effect of encryption of shaking in advance by frequency sweep, and test material elastic modelling quantity test result can be caused bigger than normal；Resonant column test boundary condition is failed to understand, the vibration characteristics of excitational equipment itself can affect test result.And free vibration column test is only to sample single static loading, obtaining its resonant frequency by sample self-vibration characteristic, method of testing is convenient compared with resonant column test；Not shaking in advance encryption effect, the impact of sample is less, and measuring accuracy relatively resonant column test is high.But free vibration column test still exists the shortcoming that boundary condition is not clear, its test result needs to be modified.In summary, geomaterial test of viscoelastic parameters when small strain still lacks a kind of method unified, easy, reliable.

Summary of the invention

In order to solve Problems existing in background technology, the present invention proposes method and the device of a kind of flexure element test geomaterial small strain viscoelastic parameters: only by a wave testing, can the viscoelastic parameters of analytical calculation geomaterial, simplify the test mode method of geomaterial parameter；Assay device is simple, it is only necessary to flexure element corollary apparatus can complete test.

The technical solution used in the present invention is as follows:

One, the method for a kind of flexure element test geomaterial small strain viscoelastic parameters, comprises the following steps:

1) preparing column type geomaterial sample, by weighing, surveying, volume obtains its density of material；

2) fixing column type geomaterial sample, is connected to the two ends of cylindrical sample by excitation flexure element and reception flexure element, and the piezoelectric ceramics of two flexure elements is inserted into same depth in column type geomaterial sample；

3) signal generator produces pulse voltage signal as pumping signal, it is divided into two-way, wherein a road is sent to oscillograph recording after power amplifier amplifies, excitation flexure element is led on another road, column type geomaterial sample motivates elastic body wave, bulk wave is approximate one-dimensional propagation in column type test sample, the shearing wave that energy is higher is met styletable free boundary and can be reflected, the fluctuation producing reflection in test process in sample is received flexure element successively reception, it is converted into voltage signal after charge amplifier amplifies as receiving signal, it is sent to oscillograph recording.

4) analyze reception signal, by perfect elastic body wave theory and one-dimensional wave theory, calculate and obtain geomaterial small strain viscoelastic parameters.

Described elastic parameter specifically calculates acquisition in the following ways: according to reaching signal time difference at the beginning of pumping signal and elastic body wave, obtain the bulk wave velocity of wave that in column type test sample, signal is propagated, being solved, according to perfect elastic body wave theory, the elastic parameter obtaining this column type test sample material by below equation again, elastic parameter includes modulus of shearing, Young's modulus and Poisson's ratio:

$E=\frac{(1-2\mathrm{\μ})(1+\mathrm{\μ}){{\mathrm{\ρV}}_p}^2}{1-\mathrm{\μ}}$

G=ρ V_s ²

$\mathrm{\μ}=\frac{2-{\left(\frac{V_p}{V_s}\right)}^2}{2-2{\left(\frac{V_p}{V_s}\right)}^2}$

Wherein, G represents that modulus of shearing, E represent that Young's modulus, μ represent that Poisson's ratio, ρ represent density of material, V_pFor geomaterial compressional wave spread speed, V_sFor geomaterial shearing wave spread speed.

Described geomaterial compressional wave spread speed V_pWith geomaterial shearing wave spread speed V_sIt is respectively adopted below equation to calculate:

$V_p=\frac{L-2l}{T_p-T_0-t_0}$

$V_s=\frac{L-2l}{T_s-T_0-t_0}$

Wherein, T₀For the take-off time point of pumping signal, T_pFor the first passage time point of compressional wave, T_sFor the first passage time point of shearing wave, t₀For testing the system delay of circuit between excitation flexure element and reception flexure element, L is the length of column type test sample, and l is the insertion depth of flexure element piezoelectric ceramics.

Described elastic parameter specifically calculates acquisition in the following ways: analyzes and receives the attenuation successively arriving shearing wave in signal, in conjunction with the propagation distance of shearing wave, adopts below equation to calculate the damping ratio obtaining geomaterial material:

$\mathrm{\δ}=\frac{{\mathrm{SV}}_s}{2\mathrm{\π}}$

Wherein, V_sGeomaterial shearing wave spread speed, S represents attenuation quotient (α^f) with slope at main energy frequency range place of the relation curve of frequency (f).

Described attenuation quotient (α^f) adopt below equation to calculate with the relation curve of frequency (f) slope S at main energy frequency range place:

$S=\frac{{\mathrm{\Δ\α}}^f}{\mathrm{\Δ}f}$

Wherein, Δ α^fFor the shearing wave variable quantity at main energy frequency range attenuation quotient, the section that Δ f is shearing wave main energy frequency range is long.

Keep described cylindrical sample unsettled during test, it is prevented that transmission occurs bulk wave in communication process, causes calculated damping ratio bigger than normal as far as possible.

Described pulse signal can adopt square wave or sine wave.

Two, the device of a kind of flexure element test geomaterial small strain viscoelastic parameters:

Including test sample, receive flexure element, excitation flexure element, foam rods, signal generator, power amplifier, charge amplifier and oscillograph, test sample is placed in the plane by foam rods, the two ends of test sample are connected to reception flexure element and excitation flexure element, the piezoelectric ceramic piece receiving flexure element and excitation flexure element is inserted in test sample, receive flexure element to be connected with oscillograph through charge amplifier, excitation flexure element is connected with oscillograph through power amplifier, and power amplifier is connected with signal generator.

Described reception flexure element is identical with the degree of depth that the piezoelectric ceramic piece of excitation flexure element is inserted into test sample.

Described test sample is column, and Ratio of long radius to short radius is more than 3.The draw ratio of column type test sample relatively big should regard one-dimensional propagation as ensureing that bulk wave can be similar in the sample.

Described column test sample is propped by two foam rods, two 0.2 times away from end face be of position of the fulcrum respectively test sample two ends bulk sample strong points, to ensure that suffered by column test sample, peak value moment of flexure is minimum, and then reduce the sample Stress non-homogeneity distribution impact on test result.

Flexure element is as the element of test Rock And Soil shear wave velocity, and its development has ten several years, the also comparative maturity of the application in soil test.Nowadays, it has had good popularization, and is not only present in Scientific Research in University Laboratory.Flexure element test based on wave theory relatively complete, its application for many years also has better effect, is current laboratory test wave velocity testing element comparatively reliably.

The main material of flexure element of the present invention is piezoelectric ceramics, and it can produce cubic deformation under the excitation of voltage.Excitation flexure element, under the excitation of voltage, both can produce shearing wave, and also can produce compressional wave.In conventional flexure element application process, often to eliminate the near-field effect that compressional wave causes, in order that obtaining shearing wave signal clearly.But, near-field effect also reflects the compression velocity of wave of sample material conversely speaking,.The restriction of meta structure form by bending, the shearing wave energy of its generation is significantly larger than compressional wave.Compressible ripple is propagated fast, arrives prior to shearing wave and receives flexure element, so being prone to differentiate at the compressional wave arriving signal receiving signal Small Amplitude.As for shearing wave, its energy exceeds one order of magnitude of compressional wave, and the existence of compressional wave has no effect on its differentiation just reaching signal.In this way, it is possible to by analysis to received signal, it is thus achieved that the compression velocity of wave of test material and shear wave velocity.By perfect elastic body wave theory it can be seen that bulk wave velocity of wave and the Young's modulus of material, modulus of shearing, Poisson's ratio are relevant, consider the relation of equal quantity that three elastic parameters are inherent, it becomes possible to three equations of row simultaneously, solve three unknown quantitys.

Method of testing of the present invention need to first prepare column type geomaterial sample, selects compared with big L/D ratio to ensure that bulk wave is similar to one-dimensional propagation in the sample.The excitation end of flexure element and receiving terminal, insert the both sides of sample respectively.Being produced pulse voltage signal by signal generator during test, make excitation flexure element motivate elastic body wave (shearing wave and compressional wave) in column type test sample, bulk wave is propagated along specimen length direction, is received flexure element by the other end and receives.The shearing wave that energy is higher simultaneously, decay is slower runs into free boundary back reflection at the column test sample other end, continues at sample internal communication.Experimentation ensures sample is unsettled, reduces shearing wave transmission on the contact surface, makes internal damping become the main cause causing bulk wave to decay as far as possible.Receiving terminal flexure element can obtain multiple shearing wave reflected signal in once excitation, by these signal difference crest place amplitudes are analyzed, it is possible to obtain ripple attenuation in communication process, thus the damping ratio according to flight distance calculation material.

Beneficial effects of the present invention:

This invention simplifies the method for testing of geomaterial parameter.

Meaning of the present invention, without the experimental apparatus of many set costlinesses, is achieved with geomaterial small strain viscoelasticity two only with flexure element relevant apparatus and overlaps index, reduce testing cost.

In process of the test, by the excitation of sample bending two ends unit and reception, one group of fluctuation signal has just comprised the relevant information of geomaterial small strain viscoelastic parameters；Eliminate originally complicated test procedure, workable, save the testing time；During signal analysis, the perfect elastic body wave theory of foundation is easily understood, explicit physical meaning.

The inventive method is tested based on bulk wave, is the acquisition material parameter when geomaterial is lossless.So, same sample can the retest when difference control, eliminate the uncontrollable impact that sample preparation again is likely to bring.Experiment proves that, adopt result acquired by the inventive method to have higher reliability.

Accompanying drawing explanation

Fig. 1 is the inventive method test device schematic diagram；

Fig. 2 is embodiment high polymer column sample wave testing signal；

Fig. 3 is that embodiment high polymer tests first three arrival shearing wave signal Fourier spectrum；

Fig. 4 is the relation curve of embodiment high polymer shearing wave attenuation quotient and frequency.

In figure: 1, test sample；2, receive flexure element；3, encourage flexure element；4, piezoelectric ceramic piece；5, foam rods；6, signal generator；7, power amplifier；8, charge amplifier；9, oscillograph；10, compressional wave first passage time point；11, shearing wave first passage time point；12, first time arrives shearing wave；13, second time arrives shearing wave；14, third time arrives shearing wave；15, bulk wave actuation duration point.

Detailed description of the invention

Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.

This method tests device based on flexure element, analyzes, by what bulk wave velocity of wave and bulk wave were decayed, the viscoelasticity index obtaining test material.

This method test device includes receiving flexure element 2, excitation flexure element 3, foam rods 5, signal generator 6, power amplifier 7, charge amplifier 8 and oscillograph 9, test needs to prepare the cylindrical sample that major diameter is relatively larger, and it being shelved in foam rods 5 with as far as possible few contact area, position of the fulcrum is each indentation 0.2L in sample two ends.During test, sample one end flexure element motivates pulse signal, and this signal includes compressional wave and shearing wave composition, and it is received flexure element record by the other end after propagating in sample.Contrast signal excitation receives time difference can obtain the velocity of wave of two kinds of bulk waves, thus calculated the elastic parameter of the soil body by perfect elastic body wave theory.Meanwhile, the shearing wave that energy is higher, decay is slower occurs reflection to continue to propagate at styletable free boundary place, and the shearing wave relatively successively arrived can be grasped the shearing wave situation with range attenuation, estimate the damping ratio of sample material whereby.

Specifically, the concrete operations principle process of the inventive method is as follows:

Step 1: preparation is the column type geomaterial sample of L in column length, and the density p of test sample.The draw ratio of sample should be greater than 3, regards one-dimensional propagation as ensureing that bulk wave can be similar in the sample.

Step 2: determine the system delay t of test circuit₀, it is determined that flexure element receives the initial take-off direction of signal.

Step 3: as shown in Figure 1, for preventing bulk wave from transmission occurring in communication process, cause calculated damping ratio bigger than normal, need to the test sample 1 in column be placed in the plane by foam rods 5 during test, position of the fulcrum is the indentation of sample two ends 0.2L, L is the total length of column sample.The two ends of test sample 1 are connected to reception flexure element 2 and excitation flexure element 3, and the piezoelectric ceramic piece 4 receiving flexure element 2 and excitation flexure element 3 is inserted in test sample 1, records the insertion depth l of each flexure element piezoelectric ceramics.

Step 4: circuit connects such as Fig. 1, signal generator produces pulse signal, and after power amplifier, this signal is divided into two-way: a road excitation flexure element 3, makes piezoelectric ceramics vibrate in the sample, simultaneously generation shearing wave and compressional wave；Oscillograph 9 is linked on another road, records pumping signal.The bulk wave that excitation flexure element 3 evokes is propagated along specimen length direction, is received flexure element 2 at the other end and receives, is converted into the signal of telecommunication.The shearing wave that energy is higher simultaneously is met styletable free boundary and can be reflected, and causes shearing wave to carry out travel back in sample.

Step 5: the excitation recording transient state and the wave signal successively arrived.The take-off time point of pumping signal is calculated as T₀, receive in signal, what arrive at first belongs to compressional wave, using first voltage fluctuation as the first passage time point T of compressional wave_p.Shearing wave energy is more than compressional wave, so with in the voltage magnitude section of significantly increasing, first balance of voltage position consistent with flexure element initial take-off direction is as the first passage time point T of shearing wave_s.The first passage time of bulk wave deducts the systematic error of test device again, is the actual propagation time in the sample of bulk wave, considers further that propagation distance just can calculate compressional wave in sample and propagate velocity of wave V_pVelocity of wave V is propagated with shearing wave_s.Computing formula is as follows:

$V_p=\frac{L-2l}{T_p-T_0-t_0}---\left(1\right)$

$V_s=\frac{L-2l}{T_s-T_0-t_0}---\left(2\right)$

Step 6: according to elastic wave prorogation theory it can be seen that there is following relation between elastic parameter and bulk wave velocity of wave:

$E=\frac{(1-2\mathrm{\μ})(1+\mathrm{\μ}){{\mathrm{\ρV}}_p}^2}{1-\mathrm{\μ}}---\left(3\right)$

G=ρ V_s ²(4)

$\mathrm{\μ}=\frac{2-{\left(\frac{V_p}{V_s}\right)}^2}{2-2{\left(\frac{V_p}{V_s}\right)}^2}---\left(5\right)$

G modulus of shearing；

E Young's modulus；

μ Poisson's ratio；

ρ density of material.

After obtaining bulk wave velocity of wave, the elastic parameter of test material can calculate either directly through formula 3～5.Step 7: owing to, in the pulse signal that excites, the energy of compressional wave is less, so arriving again at the bulk wave receiving flexure element to be after reflection mainly shearing wave.In sample, shearing wave is approximate regards one-dimensional propagation as, and communication process geonetrical attenuation can be ignored.And sample is almost unsettled when testing, will not there is transmission in bulk wave, so causing the main cause that shearing wave is decayed is exactly the material damping of geomaterial sample.

During analysis, the shearing wave successively arrived after first distinguishing reflection from the time-domain signal received, and each signal is taken wait long duration to pass through discrete Fourier transform method migration in frequency domain.Because in communication process, the attenuation of different frequency fluctuation is different, will be calculated by following formula so successively arriving the energy attenuation situation of each frequency of vibration in shearing wave

${\mathrm{\α}}^f=\frac{1}{2(j-i)L}ln\frac{\stackrel{\‾}{A_i^f}}{\stackrel{\‾}{A_j^f}}---\left(6\right)$

I & lt arrives shearing wave signal amplitude corresponding to each frequency f in a frequency domain；

Jth time arrives shearing wave signal amplitude corresponding to each frequency f in a frequency domain；

α^fThe attenuation quotient of the corresponding fluctuation of each frequency f.

I, j represent the ordinal number successively arriving receiving terminal shearing wave.

Step 8: the attenuation quotient corresponding to different frequency can be obtained according to formula 6, its corresponding relation is reflected as frequency-attenuation quotient curve in coordinate diagram, and its slope is:

$S=\frac{{\mathrm{\Δ\α}}^f}{\mathrm{\Δ}f}---\left(7\right)$

S is attenuation quotient (α^f) and frequency (f) relation curve slope at main energy frequency range place, Δ α^fFor the shearing wave variable quantity at main energy frequency range attenuation quotient, the section that Δ f is shearing wave main energy frequency range is long.

Step 9: considering that the damping of general geomaterial is smaller, damping ratio can be calculated by following formula:

$\mathrm{\δ}=\frac{{\mathrm{SV}}_s}{2\mathrm{\π}}---\left(8\right)$

In formula, δ is the damping ratio of geomaterial.

Embodiments of the invention and specific implementation process thereof are as follows:

Earth and rockfill dam core walling material (two-pack foamable polyurethane, hereinafter referred high polymer) as test object, is carried out the test of material small strain viscoelastic parameters by the present embodiment.

Step 1: preparation is long is 15cm, and diameter is the column type high polymer sample of 5cm, weighs, and the density calculating sample is 169kg/m³。

Step 2: will encourage, receive the directly contact of flexure element front end piezoelectric ceramic piece, by comparing excitation, receiving signal, it is determined that the system delay of flexure element test is 24 μ s, it is determined that the initial take-off of flexure element reception signal is downwardly.

Step 3: high polymer sample 1 is placed in the plane by foam rods 5, the two ends of test sample 1 are connected to reception flexure element 2 and excitation flexure element 3, the piezoelectric ceramic piece 4 receiving flexure element 2 and excitation flexure element 3 is inserted in test sample 1, records the insertion depth 1cm of each flexure element piezoelectric ceramics.

Step 4: as Fig. 1 connects circuit, signal generator produces the sine pulse voltage of 10kHz, and after power amplifier amplifies, a-road-through, to oscillograph, records the actuation duration；Excitation flexure element is led on another road, makes flexure element vibrate in the sample, motivates elastic body wave.Bulk wave is similar to one-dimensional propagation in the sample, and the shearing wave that energy is higher can reflect in styletable free boundary, and in test process, the fluctuation receiving end flexure element of sample receives, and is converted into voltage signal, and amplifies through charge amplifier, by oscillograph recording.

Step 5: the type signal that the present embodiment test obtains is as in figure 2 it is shown, in figure, the voltage receiving signal occurs fuctuation within a narrow range at first, and the compressional wave that this is little by energy, velocity of wave is fast causes, and fuctuation within a narrow range beginning is compressional wave first passage time point 10；Subsequently, receiving signal and substantially fluctuation occurs, voltage magnitude increases.Because judge the initial take-off of flexure element downwardly before, so with the substantially section of fluctuation voltage regulation once decline place for shearing wave first passage time point 11；Pumping signal is sinusoidal voltage pulse, and its ski-jump is bulk wave actuation duration point 15.

Step 6: each calculating parameter value can be obtained from Fig. 2, and calculate acquisition bulk wave velocity of wave.The reading of each time point and velocity of wave result of calculation such as table 1 in the present embodiment.

High polymer material small strain viscoelastic parameters test result in table 1 the present embodiment

Step 7: receive signal back segment and be clearly present the shearing wave signal that several different time arrives, iris out by dotted ellipse in Fig. 2.According to receiving the sequencing arrived that fluctuates in signal, it is possible to being classified as first time arrival shearing wave 12, second time arrives shearing wave 13, and third time arrives shearing wave 14.

Step 8: by first three time arrive wave signal take respectively wait long duration 1.024ms analyze (totally 1024 sampled points): by time-domain signal pass through discrete Fourier transform method migration to frequency domain, result is as it is shown on figure 3, the fundamental frequency of signal is 976Hz.Except the DC component that 0Hz frequency is corresponding, three curves all occur in that peak value near 8000Hz frequency.Thus in the present embodiment, the main energy frequency range of shearing wave signal is 6836Hz to 8789Hz.Then, calculate first three time according to following formula and arrive shearing wave signal between any two, the attenuation quotient that each frequency is corresponding

${\mathrm{\α}}^f=\frac{1}{2(j-i)L}ln\frac{\stackrel{\‾}{A_i^f}}{\stackrel{\‾}{A_j^f}}$

I & lt arrives shearing wave signal amplitude corresponding to each frequency f in a frequency domain；

Jth time arrives shearing wave signal amplitude corresponding to each frequency f in a frequency domain；

α^fThe attenuation quotient of the corresponding fluctuation of each frequency f.

I, j represent the shearing wave ordinal number successively arriving receiving terminal flexure element.

Step 9: result of calculation can plot three curves in attenuation quotient-frequency coordinate system, it is thus achieved that the slope S at main energy frequency range place, as shown in Figure 4.Having irised out, with dashed rectangle, the data point that main energy frequency is corresponding in Fig. 4, in frame, three curves all have close slope, wherein Δ α^fTaking in dashed rectangle the difference of two frequency correspondence attenuation quotients of 8789Hz and 6836Hz on each curve, length Δ this example of f of main energy frequency section is 1953Hz.

Finally calculate and obtain damping ratio, wherein previously recorded the V of shear wave velocity_sTake 253m/s.Result of calculation is as shown in table 2 below:

Table 2 high polymer damping ratio test result

From embodiment, the inventive method device is simply effective, merely with flexure element and test equipment accordingly, only by the excitation of a signal and reception, so that it may obtain geomaterial small strain viscoelastic parameters.Explicit physical meaning, by the wave theory of perfect elastic body and one-dimensional wave theory, set up the relation between wave signal and geomaterial small strain viscoelastic parameters, obvious technical effects highlights, it is applicable to the Non-Destructive Testing of multiple geomaterial small strain viscoelastic parameters, applied range.

Claims (10)

1. a method for flexure element test geomaterial small strain viscoelastic parameters, is characterized in that comprising the following steps:

1) preparing column type geomaterial sample, by weighing, surveying, volume obtains its density of material；

2) fixing column type geomaterial sample, is connected to the two ends of cylindrical sample by excitation flexure element and reception flexure element, and the piezoelectric ceramics of two flexure elements is inserted into same depth in column type geomaterial sample；

3) signal generator produces pulse voltage signal as pumping signal, it is divided into two-way, wherein a road is sent to oscillograph recording after power amplifier amplifies, excitation flexure element is led on another road, column type geomaterial sample motivates elastic body wave, the fluctuation producing reflection in sample is received flexure element successively reception, is converted into voltage signal after charge amplifier amplifies as receiving signal, is sent to oscillograph recording.

4) analyze reception signal, calculate and obtain geomaterial small strain viscoelastic parameters.

2. the method for a kind of flexure element according to claim 1 test geomaterial small strain viscoelastic parameters, it is characterized in that: described elastic parameter specifically calculates acquisition in the following ways: according to the time difference reaching between signal at the beginning of pumping signal and elastic body wave, obtain the bulk wave velocity of wave that in geomaterial sample, signal is propagated, being solved, according to perfect elastic body wave theory, the elastic parameter obtaining this sample material by below equation again, elastic parameter includes Young's modulus, modulus of shearing and Poisson's ratio:

$E=\frac{(1-2\mathrm{\μ})(1+\mathrm{\μ}){{\mathrm{\ρV}}_p}^2}{1-\mathrm{\μ}}$

G=ρ V_s ²

$\mathrm{\μ}=\frac{2-{\left(\frac{V_p}{V_s}\right)}^2}{2-2{\left(\frac{V_p}{V_s}\right)}^2}$

Wherein, G represents that modulus of shearing, E represent that Young's modulus, μ represent that Poisson's ratio, ρ represent density of material, V_pFor geomaterial compressional wave spread speed, V_sFor geomaterial shearing wave spread speed.

3. the method for a kind of flexure element according to claim 2 test geomaterial small strain viscoelastic parameters, is characterized in that: described geomaterial compressional wave spread speed V_pWith geomaterial shearing wave spread speed V_sIt is respectively adopted below equation to calculate:

$V_p=\frac{L-2l}{T_p-T_0-t_0}$

$V_s=\frac{L-2l}{T_s-T_0-t_0}$

Wherein, T₀For the take-off time point of pumping signal, T_pFor the first passage time point of compressional wave, T_sFor the first passage time point of shearing wave, t₀For testing the system delay of circuit between excitation flexure element and reception flexure element, L is the length of cylindrical sample, and l is the insertion depth of flexure element piezoelectric ceramics.

4. the method for a kind of flexure element according to claim 1 test geomaterial small strain viscoelastic parameters, it is characterized in that: described elastic parameter specifically calculates acquisition in the following ways: analyze signal in cylindrical sample and propagate the attenuation successively arriving shearing wave, in conjunction with the propagation distance of shearing wave, below equation is adopted to calculate the damping ratio obtaining cylindrical sample:

$\mathrm{\δ}=\frac{{\mathrm{SV}}_s}{2\mathrm{\π}}$

Wherein, V_sFor geomaterial shearing wave spread speed, S represents attenuation quotient α^fWith the relation curve of the frequency f slope at main energy frequency range place.

5. the method for a kind of flexure element according to claim 4 test geomaterial small strain viscoelastic parameters, is characterized in that: described attenuation quotient α^fBelow equation is adopted to calculate with the relation curve of the frequency f slope S at main energy frequency range place:

$S=\frac{{\mathrm{\Δ\α}}^f}{\mathrm{\Δ}f}$

Wherein, Δ α^fFor the shearing wave variable quantity at main energy frequency range attenuation quotient, the section that Δ f is shearing wave main energy frequency range is long.

6. the method for a kind of flexure element according to claim 1 test geomaterial small strain viscoelastic parameters, is characterized in that: keep described cylindrical sample unsettled during test as far as possible.

7. for implementing the device of a kind of flexure element test geomaterial small strain viscoelastic parameters of the arbitrary described method of claim 1～6, it is characterised in that:

Including test sample (1), receive flexure element (2), excitation flexure element (3), foam rods (5), signal generator (6), power amplifier (7), charge amplifier (8) and oscillograph (9), test sample (1) is placed in the plane by foam rods (5), the two ends of test sample (1) are connected to reception flexure element (2) and excitation flexure element (3), the piezoelectric ceramic piece (4) receiving flexure element (2) and excitation flexure element (3) is inserted in test sample (1), receive flexure element (2) to be connected with oscillograph (9) through charge amplifier (8), excitation flexure element (3) is connected with oscillograph (9) through power amplifier (7), power amplifier (7) is connected with signal generator (6).

8. the device of a kind of flexure element according to claim 7 test geomaterial small strain viscoelastic parameters, it is characterised in that: the degree of depth that described reception flexure element (2) is inserted into test sample (1) with the piezoelectric ceramic piece (4) of excitation flexure element (2) is identical.

9. the device of a kind of flexure element according to claim 7 test geomaterial small strain viscoelastic parameters, it is characterised in that: described test sample (1) is in column, and Ratio of long radius to short radius is more than 3.

10. the device of a kind of flexure element according to claim 7 test geomaterial small strain viscoelastic parameters, it is characterized in that: described column test sample (1) is propped by two foam rods (5), 0.2 times away from end face be of two position of the fulcrum respectively test sample (1) two ends bulk sample strong point.