Abstract: The failure process of tunnel constructed in homogeneous rock is studied by using model test and discrete element method (DEM); and the laws of the stress of surrounding rock and their displacement during the failure process are analyzed. The results of model test match the results of numerical simulation perfectly. From the results some conclusions can be drawn. The surrounding rock of the arch crown deforms obviously after excavation. The failure of the surrounding rock initiates from the arch crown and develops upward progressively until a stable caving arch is formed. The radial stress and tangential stress in a given range of the surrounding rock decrease after excavation. The range in which tangential stress of the surrounding rock decreases expands outward during the tunnel failure process. The vertical stress of the arch bottom increases after collapse. The displacement increment from excavation to collapse is the biggest and that during the collapse is the smallest.

Key words: homogeneous rock, failure process, model test, discrete element method