Excavation Scheme Analysis for Shallow Bias Tunnels

The mechanics numerical simulation of different construction sequence has been studied for shallow bias tunnels using the method of CRD.The displacement,stress,and early supporting internal force of the surrounding rock are also analyzed and compared for different excavating sequences.The results show that the best excavating sequences should be upper bench of shallow side-upper bench of deep side-lower bench of shallow side-lower bench of deep side,under which stress and displacement will be minor in the excavating process.The lateral wall and the tunnel crown are key places that must be noticed.