Surrouding Rock Mechanical Response Study On Three-Lane Railway Tunnel With Large-Span

With the construction of high-speed railway in our country, the number of the large-span tunnel will increase gradually. The NATM(new Austrian tunneling method) is applied in design and construction of the large-span tunnel that will be developed and affirmed. Surrounding rock is the major bearing zone of the tunnel. It's very important that analyzing mechanical response of the surrounding rock with the construction dynamic process. In particular, studying the shape and stability of bearing zone in that process is beneficial to reasonably design and safely construct.Based on the basic principle of rock mechanics and theory of the NATM, this thesis builds a 3D model that accords with He Luo shan three-lane railway tunnel in DaLi-LiJiang railway and simulates the construction of the large-span tunnel using double side excavation method by elastic-plastic FEM analysis. The thesis reaches some useful conclusions that:Using the elastic-plastic theory and stress tensor tool, surrounding rock is classified to four zones (undisturbed zone elastic relaxation zone bearing zone plastic relaxation zone) by its stress status. These zones and adjacent border's logical formulations are concluded for differentiating in the computer process and designing primary support.Using data path which contains stress status, surrounding rock of the large-span tunnel is analyzed by stress tensor and those zones are identified by stress concentration in key position with the construction dynamic process.Using stress ratio which is defined by effective stress divided field stress, surrounding rock's strength increasing zone of the large-span tunnel are identified in key position with the construction dynamic process.Using plastic work theory, surrounding rock' plastic zone of the large-span tunnel are identified in key position with the construction dynamic process.