Abstract: A model of analyzing the mechanics of hydraulic tunnel with gently dipped layered jointed rock with long span and high sidewall was established using UDEC based on the non-continum theory. The wave velocity characters, displacement distribution, stress distribution and plastic zone distribution, as well as the stability of surrounding rock at different positions of the tunnel under seismic action were analyzed. The response of surrounding rock during earthquake action was acquired. Results revealed that under sine shear seismic wave in vertical direction, the dynamic characteristic of monitoring points in vertical direction were more apparent than that in horizontal direction; in the initial stage of seismic wave action, the displacement of sidewall was larger than that of the roof, and the displacement of bottom surrounding rock was largely affected by seismic action as time went by; after the seismic action, the stress of monitoring points all increased slightly; and plastic zone in the tunnel’s sidewall and the bottom surrounding rock enlarged obviously. The results provide references for further analysis on the deformation and failure mechanism of surrounding rock under seismic load.

Key words: jointed rock, hydraulic tunnel, universal distinct element code, seismic load, dynamic characteristic