Damage mechanics and its application for the design of an underground theater

Abstract

This paper presents a damage mechanics method for the evaluation of the elastic damage of jointed rock mass and its application in predicting damage distribution in the jointed rock mass in the excavation for an underground structure in the framework of continuum damage mechanics. The damage variable is a second-order damage tensor which is assumed to describe the damage effect of jointed rock mass. The elasticity tensor defined in the model is verified by employing laboratory cement mortar specimens with various cases of joint distribution. The same specimen is analyzed using the developed damage mechanics method as well as the normal FE method, which employs joint elements to simulate jointed cracks. In order to apply the developed damage elasticity theory to three-dimensional damage analysis in underground structure excavation, a three-dimensional grouted rockbolt element is introduced, which considers the resistance of the grout to the relative shear displacement between the bolt and the rock mass around it in the axial direction. Plastic behaviors of the steel bar and the grout of the grouted bolt are considered in the model by using various constitutive laws. Finally, an engineering example for damage analysis is presented, namely an underground theater assumed to be excavated in a geological environment of jointed rock.