Abstract: Qiyueshan expressway tunnel site area is well-developed with strong catastrophic concealed karst caves. In order to study change laws for influence of concealed karst cave on the displacement of tunnel rock, two geological factors (tunnel depth, surrounding rock grade) and two morphological factors (karst cave size, the distance between tunnel and karst cave) are selected for numerical experiments. The influence of support on the displacement of the surrounding rock was discussed, and the influence of concealed karst caves at top on deformation of tunnel rock in different directions was analyzed. The influence law for different factors effect on top karst caves was systematically studied. The results show that: (1) The affects of top karst cave on rock deformation in vertical and horizontal directions are opposite. In vertical direction, the top karst cave slows down the convergence effect at crown and arch bottom; In the horizontal direction, the top karst cave intensifies the convergence effect at arch waist, and the influence of top karst cave on displacement of the crown, arch bottom, and arch waist decreases in turn. (2) With the increase of rock grade, tunnel depth, and size of karst cave, and the decrease of distance between karst cave and tunnel, the effect of the top karst cave on tunnel rock deformation becomes more obvious. Within the range of design factors, the influence of each factor on top karst cave is obviously different.

Key words: expressway tunnel; concealed karst cave, displacement monitoring, numerical simulation