Borehole Radar Forward Modeling And Applied Research

Borehole radar can detect the deep rock where conventional surface geophysical methods can not reach, providing a more complete and accurate information on the geological structure.It can provide an important geological information for the site selection of a major project, reduce project cost, ensure the quality of engineering and the safety of construction.The paper systematically discuss the main detection methods of borehole radar:Single-hole reflection survey,Cross-hole survey, Surface-Borehole Survey. We try to study the principles and applicability of the main detection methods, and study the factors which effect the efficiency of borehole radar's detection. Also, we analysised and calculated electromagnetic wave reflection's time-distance curve in the time profile of radar, if there were several typical interface underground,thenwe can get the characteristics of the images.Starting from Yee's algorithm, we derived the difference scheme of two-dimensional TM wave's electric field component and magnetic component of according to Maxwell curl equations. In the condition of using PML as the adsorbing boundary and using Ricker-wave as the excitation source, we write the two-dimensional TM wave FDTD calculation procedures. Then we get the corresponding two dimensional radar profiles.By comparing the different numerical simulation diagrams, we can verify the law of electromagnetic wave propagation; and through the numerical simulation of different geological abnormal body, we can get features of different geological abnormal body in the borehole radar images, then we can distinguish the geological abnormal body more easily.Finally, with combination of an engineering example, it is the guidance in distinguishing karst, caves and other abnormal body by summarized principles of borehole radar numerical simulation. It can enhance further understanding of the usefulness of borehole radar, and provide an intuitive understanding of the borehole radar technology' feasibility in the highway construction project...