Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

Reflection energies of electromagnetic waves radiating from a dipole antenna vary with not only boundary conditions between subsurface and an object but also antenna orientation relative to the strike of the target. To investigate GPR responses depending on the target property and geometry, we have conducted numerical simulation using the three-dimensional finite difference time-domain modeling algorithm considering a thin-wire dipole antenna. We used an antenna with 0.74 m in length, and its main frequency in the air is 200 MHz. We made a homogeneous half-space model containing a steel pipe or a void plastic pipe to compare the differences to the electromagnetic properties. We chose a cylinder or a box as the shapes of the objects, and two transmitting antenna orientations. We have visualized the main electric field distributions as a snapshot when the direction of the transmitting antenna was both parallel and perpendicular to the strike of the target. The reflection from the void pipe was not sensitive to either the orientation of the antenna or the shape of the pipe. For the case of buried steel pipe, however, reflection energy was sensitive to both its shape and the antenna direction relative to its strike. The reflection accompanied wiggles when the antenna orientation is orthogonal to the cylindrical steel pipe.