Research On Waveform Change Law And Its Application As Wavelet Propagated In Structure Planes Of Rock Mass

Since being transformed and re-transformed in different periods and different sizes oftectonic movements, the rock mass formed different scale of structural planes. Becausedifferent structural planes in rock mass have different mechanics properties, its simplifiedmodel is also different. The type of structural plane played an important role in the stresswave propagated in rock mass. When the stress wave propagated in the actual rock mass, thechange of wavelet’s waveform can response the mechanics properties of the structural planedirectly. So that study the waveform change rule of wavelet propagation in the joint has animportant significance to the wave field forward modeling and inversion.In this paper, firstly established three different joint rock mass models, there are a thinviscoelastic joint model, a thick viscoelastic joint model and a layered rock mass contained asoft interlayer. Then used the Ricker wavelet as the incident wave to oblique incidence threedifferent joint rock mass models, and get the transmission wave after the wavelet propagationthe three different models. By using the correlation coefficient of waveform and the variationcoefficient of waveform to quantified the waveform change of the incident wave and thetransmission wave, and study the influence rule of the transmission waveform change bychanging the thickness of the joint, viscosity coefficient, stiffness, thickness of the softinterlayer, elastic modulus, angle and the peak frequency of the incident wavelet, get theconclusions as follows:(1)In the process of wavelet propagation in the viscoelastic joint, the waveform change isrelated to the dynamic characteristics of the joint and the angle and the peak frequency of theincident wavelet. It showed that the greater the viscosity coefficient of the joint, the waveformchange is larger; the smaller the stiffness of the joint, the greater the waveform changed; thegreater the thickness of the joint, the greater the waveform changed. Meanwhile, the peakfrequency increases, the greater the change in the waveform. In the thin viscoelastic jointmodel, the waveform change smaller as the incidence angle is larger, while in the thickviscoelastic joint model, the waveform change greater when the incidence angle is larger. Bycomparing the two viscoelastic joint models found that when the thickness of joint is less than0.1meters used the thin viscoelastic joint model to calculate, while the thickness of joint ismore than0.1meters, choose the thick viscoelastic joint model to calculate.(2)In the process of wavelet propagation in a layered rock mass contained a soft interlayer,when the elastic modulus of the both sides is same, the elastic modulus of the soft interlayer is smaller, the greater the waveform change is. The greater the thickness of the soft interlayer,the greater the waveform change is; the greater the incidence angle the greater the waveformchange is.(3)Using the filed test data taken in Dengxing Copper into the wavelet propagated in thethick viscoelastic joint model to get the transmission coefficient and the reflection coefficient.Then calculated the calculating incident waveform from the test transmission waveform,compared the test incident waveform and the calculating incident waveform to get the elasticmodulus of the joint, found the result is reasonable.