Behaviour of the tunnel affected by adjacent slope excavation in a jointed rock mass

초록

1. INTRODUCTION When the rock slope is excavated adjacent to a railroad tunnel in order to construct a road or when the new parallel or crossed tunnel is constructed, the behavior of the existing tunnel would be greatly influenced by not only the joint condition but also the slope status. Therefore, safety of existing tunnel should be analyzed under the consideration of joint condition of rock mass and excavation conditions(slope, reinforcement method, etc.). However, it is difficult to find out any examples or studies on slope or tunnel excavation adjacent to an existing tunnel. Only a few studies could be found, but they are mostly limited to pertatining to homogeneous ground. In the jointed ground, therefore, construction is often undertaken based on the judgment of site engineer's experience at the on homogeneous ground. In this study,in order to invetigate the effects of joints on the behavior of the existing tunnel during the ground excavation close to a tunnel, large scale model tests were performed in the biaxial test facility (3.1m*3.1m*0.50m (width * height * length)). Test ground with regular joints were built with concrete blocks. Model tunnel in about 1/10 scale(0.6m in diameter) was built up. Joint dips were varied from vertical to horizontal (0°-90°), while the angle of excavated slope was varied 60°-90°. Behaviour of the existing tunnel was then analyzed under the consideration of joint dip, slope angle, and slope excavation.