Abstract:Because of the influence of karst caves,deformation characteristics of surrounding rock of tunnel in karst zone are different from those of common tunnel. Taking Baoshiyan tunnel in Dacheng high-speed railway as an example,the deformation characteristics of surrounding rock of the tunnel with a karst cave at side is studied by field monitoring and by finite difference software ,and the deformation characteristics of the surrounding rock of tunnel are obtained by field monitoring and by simulation analysis,which are mostly consistent. Results indicate that after the tunnel is excavated,the surrounding rock moves toward the karst cave and the tunnel. The surrounding rock between the karst cave and the tunnel deforms in opposite direction,and it is also the most dangerous zone. The displacements of the surrounding rock of the tunnel¢s representive positions near the karst cave are larger than those positions away from the karst cave,and the horizontal displacement of the left side wall is twice bigger than that of the right side wall. With the increase of the karst cave dimension,the settlement increment of the crown is the largest,and the horizontal displacement increment of the side wall is moderate and that of the hance is the least. The subsidence of the karst cave top and the horizontal displacement at the right position are larger,and those of other positions are little. Because the deformation of the surrounding rock of the tunnel appears unsymmetrical,deviation pressure will occur during excavation. The conclusion can be useful in design,construction and research of similar tunnels.