Influence of Block Size and Shape on the Deformation Behaviour and Stress Development around Tunnels

Presence of various discontinuities such as bedding planes, foliation, faults, joints etc bring formation of blocks with different shapes and sizes. During tunnel excavation additional blocks are formed with propagation of existing fractures or due to new development under secondary stress conditions. Besides the strength properties of the discontinuities the size, shape, position of blocks and interaction between the blocks influence deformation characteristics (amounts, vector orientations and history) and stress development around the tunnel. The aim of this study is to evaluate the influence of the geological structure (block shape, block size and joint strength) on the deformation behaviour and stress development around the tunnel in blocky rock mass conditions by using numerical simulations with discrete element method and analyzing absolute displacement measurements. According to this evaluation, characteristics of different rock mass behaviours will be defined for various combinations of key parameters. System behaviour in blocky rock mass conditions will be analysed. The capability of the numerical simulations for modelling the anisotropic deformation behaviour of the tunnel excavation in discontinuous media will be investigated.