| Before excavating a tunnel in rock, the rock is at initial stress state. Excavation causes the redistribution of stress and the displacement towards the centre of the tunnel in rock, and thus forms a new stress field, known as the second rock stress state. If the rock at the second stress state cannot maintain long-term stability, we must set up retaining structures in order to impose the constraints on the surrounding rock within the tunnel, control the rock deformation, improve the stress state and make the rock stable, which is known as the third stress state. Obviously, it is the key to a reasonable and reliable design and construction of the tunnel in rock to find and know the stress and displacement in the surrounding rock within the tunnel at each construction stage.In this thesis, a systematical study was made on the distributions of the stress and displacement in the surrounding rock within the tunnel at different construction stage by using elasto-plastic theory and FLAC3D on the basis of the relevant work so far available. The main contributions of the thesis include:1. The basic principles and main features of FLAC3D were introduced briefly.2. Based on the assumption that the initial stress in rock is isotropic, some analytical expressions were summarized and derived for the distributions of stress and displacement in the rock of circular tunnel at the second elastic and plastic states and at the third plastic state, respectively.3. The stress and displacement in rock of circular tunnel at each state were stimulated with FLAC3D, and the results were compared with the ones obtained by analytical expressions.4. The distribution characteristics and the influencing factors of the stress and displacement in rock of circular tunnel were analyzed and illustrated.5. By using FLAC3D, the influence of dilatancy on the stress and displacement of rock in circular tunnel was analyzed and the effect of coefficient of earth pressure at rest on the shape and range of plastic zone in the rock surrounding tunnel investigated.The study made in the thesis may provide some guidance and valuable references to the design and construction of tunneling. |
