Abstract: Borehole radar can probe deep underground geoenvironment through arranging a dipole antenna in a borehole, and it is a good logging tool to obtain the electrical signals of geologic formation. According to the common point unfavorable geo-bodies in borehole radar exploration, such as cavities, karst caves and buried objects etc., the electrical response of the tool to point unfavorable geo-bodies of different geometry and buried depth is investigated. The application conditions and resolution response capabilities of the simulation models are analyzed. It reaches that the proper antenna frequency should be chosen according to the physical dimension of object-of-interest and resolution requirement of the exploration task; and that the radar cross section of geo-bodies with different geometry appears various characteristic. The resolution capacity of borehole radar antenna varies with the buried depth of geo-bodies; and the borehole radar with higher frequency antenna can obtain reflected signals of higher resolution. However, the reflected signals detected by the borehole radar with a higher frequency will attenuate faster than one with lower frequency antenna. The results provide visualized perceptual knowledge and abundant interpretation support for borehole radar using in geologic survey and potential disaster detection, and help to improve the accuracy of geological interpretation

Key words: borehole radar, finite difference time domain (FDTD), geometric effect, point unfavorable geologic bodies