Research on the optimization design of primary support parameters of unsymmetrial loading tunnel based on the structure safety

According to the method deduced from the shear sliding theory,the primary support parameters of the typical unsymmetrial loading tunnel were optimized.The results show that the anchor can decrease effectively the deformation of the surrounding rock,and the longer the anchor,the better its supporting effects,but if the anchor is too long,the improving supporting effects become not so obvious;for the different unsymmetrial angles,the safety factors of vault and arch springing were more than 5,and the safety factor of hunch and the foot of wall are less than 1 on the some conditions.The hunch and foot of wall are the weak positions of supporting structure.