Upper Bound Analysis Of Slope Stability For Tunnel Entrance

ABSTRACT:With the rapid development of our country’s economy and investment increasing infrastructure. There are more and more tunnels in the engineering construction. And the slope stability of tunnel entrance is related to the whole tunnel project can be smoothly carried. And the geological condition of tunnel entrance is complex with landslides and other phenomena. How to guarantee the safety and quality of tunnel portal section construction has become a hot research topic.Base on the geological conditions of the tunnel slope and engineering practical significance, this paper used the theory of limit analysis upper limit to analyze the stability of the tunnel slope:(1) In this paper, the maximum limit analysis method is adopted to analysis the slope stability of the tunnel entrance. The logarithmic spiral failure mechanism of the tunnel entrance slope was set up. And the critical height solving of tunnel slope was made into nonlinear programming mathematical problems. The gravity work power and internal energy dissipation power of slope is derived and the expression of the critical height is obtained. The calculation results agree well with the existing results, which shows the validity of method in this paper.(2) The earthquake force load and pore water pressure influence were integrated into the limit analysis upper theory. The safety factor of complex tunnel slope was calculated based on limit analysis combined with strength reduction technology the excavation scope of slope tunnel is under the slope. The influence of different parameters on soil stability of tunnel slope is analyzed.(3) The discrete sliding surface method was used to research the stability of inhomogeneous slope. When the number of these points is larger enough, the approximate, composed by the straight line between these key points, is quiet similar with the analytical surface. The external and internal work rate of the approximate was computed, and then the tunnel slope critical height can be obtained.(4) According to Jiutiaoling tunnel slope engineering located of Inner Mongolia-Central China coal transport channel and the landslide engineering of Daganxi tunnel slope in Xiangxi, based on the analysis of sliding model, the strength parameter was back analyzed by tunnel slope inclination data. Furthermore, the safety factor was obtained by upper bound theorem. There are35figures,5tables and97references in this paper.