According to the characteristics of interfacial stress between surrounding rock and shotcrete support

mechanical model of composite curved beame for support system of tunnel surrounding rock and shotcrete lining was established

considering the interfacial deformation coordination and the effects of bearing arch of surrounding rock. Then from static equilibrium of two differential elements

the differential equations for the radial displacement of composite curved beam were obtained. All analytic formulas of both interfacial stress and internal forces between surrounding rock and shotcrete lining by arbitrary distribution load were derived. And thus the mechanical condition of interface zone and the stress concentration position were obtained

which is convenient to assess the stability of surrounding rock and predict the safety. Finally

the analysis of tunnel project excavated by bench method showed that shotcrete lining made the formation of compressive stress zone in surrounding rock by transferring stress from the interface between surrounding rock and shotcrete

which is beneficial to improve the stability of surrounding rock.