Deformation Characteristic And Blasting Scheme Optimization For Tunnel With Horizontal Layered Surrounding Rock

Due to the extensive distribution of the layered rock mass and the specificity of its engineering properties,many stability problems for the layered rock mass are encountered in the tunnel design and construction.Therefore,it is of theoretical and practical importance to investigate the mechanical response of the layered surrounding rock mass.In this thesis,combining the finite difference software FLAC^3D and the finite element software LS-DYNA,the influences of the thickness of the layer,the joint parameters,the blast vibration and the support parameters on the tunnel stability are investigated.The main contents and conclusions are as follows:?1?Based on the engineering properties of the horizontal layered rock mass,the influence of the thickness of the layer on the tunnel stability is analyzed.When the thickness of the layer is small,the layered rock mass can be simulated with the ubiquitous-joint model.When the thickness of the layer is large,the layered rock mass can be simulated by combining the solid elements and the interface elements.By changing the joint parameters,the influence of the joint parameters on the stability of the surrounding rock mass are investigated.?2?According to the theory of the rock blasting,the full-time blasting speed curve is solved by LS-DYNA.Based on dynamic module in FLAC^3D,the curve is incorporated into FLAC^3D by the FISH language.The effect of the blasting load on the stress and strain of the rock mass is investigated,and the blasting scheme is optimized.In the middle between each pair of wedge holes,a hole is added,where the length of the hole and explosive quantity reduce.The blasting scheme optimization not only effectively maintains the drilling footage,but also lowers the vibration velocity around the vault and reduces the tensile failure.?3?The bolt support is chosen based on several different cases.The results indicate that:while the bolt length is within a critical value,the rock deformation can be effectively decreased,whereas the effect gradually weakens while the bolt length exceeds the value.The installation of the bolt at the side walls is beneficial for improving the rock stability;while the bolts are short and the distribution is intensive,the rock deformation can be controlled in a more effective manner,in contrast to when the bolts are long and the distribution is sparse.