Elastic-plastic unified solutions for stresses and displacements of deep buried circular hydraulic tunnel

Taking the integrated influences of seepage volumetric force, intermediate principal stress, principal stress orders, rock strain softening and shear dilation into account, some assumptions are brought for the elastic-plastic analysis of a deep buried circular hydraulic tunnel. Based on these assumptions, the elastic-plastic unified solutions for stresses and displacements of the circular tunnel both in construction and operation periods are derived. The solutions in operation period involve two conditions that surrounding rock is elastic or elastic-plastic in construction period. The unified solutions have a wide applicability, which can naturally reduce to many existing results. With the analysis of an engineering example, the influences of the ratio of osmotic coefficient between surrounding rock and lining, unified strength theory parameter, strain softening characteristic parameter and shear dilation characteristic parameter on the tangential stress and displacements are discussed. It is shown that the effects of overall parameters in construction period are more profound than those in operation period. The influences of the ratio of osmotic coefficient between surrounding rock and lining, cohesion softening characteristic parameter on the tangential stress and displacements both in construction and operation periods are significant. The latent potentialities of surrounding rock are brought due to considering the intermediate principal stress. The shear dilation characteristic parameter is important for the displacements of tunnel.