Analysis of cross-borehole pulse radar signatures on a half water-filled tunnel

The effect of the water collected in the bottom of an empty tunnel on cross-borehole radar signatures is analyzed using the finite-difference time-domain (FDTD) method. The cross-borehole pulse radar is represented by 3-dimensional model and B-scan images are calculated in two cases of fully air-filled and half water-filled tunnels. The first positive peak in the B-scan image appears in a later time and moves upward direction than the tunnel center as the water is collected in tunnel. To estimate the central position of the half water-filled tunnel, the first negative peak is adopted here and its utility is described clearly.