Abstract: To improve the accuracy of advanced geological prediction for tunnels by Ground Penetrating Radar (GPR), the GPR profiles of bad geological bodies (including horizontal fracture zone, inclined fracture zone, cavity and karst cave) were extracted by forward simulation in two-dimensional finite difference time-domain models. Case study on three karst tunnels of Anjiang Highway demonstrated the effectiveness of the forward simulation result. The result revealed that GPR is of obvious efficiency in identifying the location and horizontal development of fracture zone and karst cave, but has some limitations for vertical development and tilt angle of bad geological bodies. In conclusion, satisfactory result of advanced prediction can be obtained by analyzing measurement data through GPR profile based on detailed geological sketch.

Key words: tunnel, advanced tunnel prediction, geological radar, bad geological bodies, karst cave, fracture zone