Stability of bearing structure during soft roadway excavation-supporting

ZHAO Guangming; PENG Rui; MENG Xiangrui; ZHANG Xiaobo

Abstract：In order to study the mechanical bearing structure stability of soft surrounding rock of circular roadway nearby excavation face after "anchor-net-shotcrete" support,the surrounding rock of roadway was classified into crack zone,soften zone and elastic zone from inside to outside along radial direction of roadway according to surrounding rock deformation and mechanical features,among them the "anchor-net-shotcrete" support was mainly constructed in crack zone.Based on unified yield criterion,incremental constitutive equation and softened rock mechanical model,solutions of surrounding rock stress and deformation were obtained under the interaction of "surrounding rock-support".Taking the concentration of tangential stress and equivalent shear stress,and surrounding rock strength into account,mechanical bearing structure of the surrounding rock was classified into the "weak-main-strong" structure from inside to outside.The examples analysis shows that the bearing range,its deformation and shear stress of surrounding rock mechanical bearing structure is related to inter-row space of anchor bolt,softened modulus and excavation space effect.Based on "surrounding rock-support " mechanical bearing structure,the " anchor-net-shotcrete-grouting" support is designed,and engineering practice shows the support project can improve surrounding rock strength,reduce softened roadway deformation and ensure stability in the initial period of tunnel excavation.