Application of Rosenblueth method in evaluating stability reliability of anchor-shotcrete net support system for soft-fractrue surrounding rock

The characteristic of soft-fractrued rock mass is that its component is complex,fissure is well developed and there is dilatant mineral.Underground pressure of surrounding rock mass of roadway in soft-fractrue rock mass is mainly deformation pressure.Underground pressure emerges that side wall rock mass of roadway swells to be a wedge and is squeezed out at first.The phenomenon basically is in accordance with shear slide theory proposed by Rabcewicz.The most effective support to soft-fractured rock mass is anchor-shotcrete net support,but there is uncertainty in parameters and failure mechanism of anchor-shotcrete net support structure due to the characteristic and complexity of soft-fractrued rock.The reliability method that can take uncertainty into account is the most appropriate way to analyze stability of the support structure.With the reliability equation established,load bearing structure of anchor-shotcrete net is divided into two sub-structure according to underground pressure of the soft-fractrued rock mass,and general limit state equation is established based on deformation of sub-structure and its load bearing condition.Since the general limit state equation established is based on circular section,four calculation methods with section of roadway changed into equivalent circle section are put forward.An engineering example is also given.