Cavities and other adverse geological conditions are often encountered in the process of tunnel excavation,which seriously affect the safety and successful completion of tunnel construction.To accurately grasp the characteristics of ground penetrating radar reflection signal for cavities in front of the tunnel,forward simulation of different cavities in front of the tunnel was carried out by time-domain finite difference software.The time profile of GPR collected by model test was compared and analyzed.The results show that the GPR can detect the buried depth and depth dimension of cavities in...