Numerical Simulation of Polarity Characteristics of Vector Elastic Wave of Advanced Detection in the Roadway

The high-order staggering grid Finite-Difference (FD) scheme based on first-order velocity-stress elastic wave equation has been deduced. The calculation method of PML boundary condition and stability condition established in this study can be used for numerical simulation of advanced detection of elastic wave in roadway, with the obtaining of high-precision seismogram. Then we systematically analyze the polarity of vector wave field in post-source observation system. The results indicate that the relationship between the vector wave field and the polarity of direct wave is related to reflection coefficient on the interface, while the polarity relationship between horizontal and vertical components of vector wave field is related to vertical position of the interface. During data processing for advanced detection of elastic waves, the sign of the reflection coefficient on the interface ahead can be determined based on the polarity relationship between reflected wave and direct wave from the seismograms; the soft and hard rock and other geological information on both sides of the interface is thus be determined. In addition, the direction of source wave depends on polarity relationship between horizontal and vertical components of reflected wave and is used to achieve the separation of up going and down going waves.