STUDY ON DEFORMATION AND INTERNAL FORCE OF SURROUNDING ROCKS AND INITIAL SUPPORT IN DAFENGYAKOU ROCK ROAD TUNNEL
大风垭口岩石公路隧道围岩及初期支护变形与内力研究

The long rock road tunnel named Dafengyakou in Yunnan province, a one-way and double lane tunnel with disjunctive up and down lines,is constructed by NATM. The tunnel is about 3 300 mlong. After analyzing the monitoring data,such as the convergence, crown displacement,internal displacement,internal force of the initial support, the laws for the changes of the internal force and deformation of the surrounding rocks and initial support including the creep of rock with time and excavation are studied. The creep deformation of sandstone in this tunnel is found to be agreement with the formula put forward by Evans. In the excavation of top and bottom bench,there is a simple linear relationship between the internal displacement of surrounding rocks and the radial distance to the inside of tunnel. During the excavation of top bench,there is also a linear relationship between the displacement rate and the logarithmic value of the distance between the face of top bench and the measured section. It is also shown that the disturbance of excavation of top bench on surrounding rocks is larger than that of bottom bench. The measured contact pressure between the initial lining and surrounding rocks at the crown is smaller than the calculated data by Chinese road tunnel code. The relationship between the internal force after the excavation of top bench and the reciprocal value of the distance between the face and section satisfies the exponential rule. All the obtained conclusions can guide the construction of the rock road tunnel.