Abstract: The deformation and failure of tunnel's surrounding rock is closely related to factors such as rock strength, characteristics of structural plane, groundwater and geostress. The geometric parameters (spacing and inclination) of the controlling structural plane affect the macro-integrity of the surrounding rock and the stress distribution after excavation, and furthermore, control the plastic deformation of the surrounding rock and the shear-slipping of structural plane. In order to study the control effect of structural plane's geometric parameters on the stability of tunnel's surrounding rock, we analyzed the deformation and failure of surrounding rock of Xiangjiawan tunnel in Zhengzhou-Wanzhou high-speed railway as a case study using UDEC based on regional geo-environmental investigation, geologic sketch of tunnel face, and test of the rock physical and mechanic parameters. Results demonstrated that the spacing and inclination of structural plane have a significant influence on the deformation and failure of surrounding rock. The stability of surrounding rock should be relatively superior during the tunnelling construction when the spacing of the structural plane was greater than 1/10 diameter and the inclination of the structural plane was in the range from 0° to 30°. The research finding has practical guiding significance for the safety construction of similar tunnels.

Key words: tunneling engineering, controlling structural plane, stability of surrounding rock, UDEC discrete element software, spacing between structural plane, inclination of structural plane