Abstract: The strength of rock mass is controlled by structural plane. On the basis of theoretical analysis on stress distribution and failure mechanism of single structural plane in surrounding rock, the influences of dip angle of structural plane and distance from structural plane to tunnel center on the failure mechanism of jointed rock mass are researched. The results are concluded as follows: 1) discontinuities are more likely to occur when structural plane is closer to the excavation contour line; 2) the position where structural plane first destructs is affected by the angle of structural plane. Furthermore, the deformation of 18 groups of rock masses with different combinations of discontinuity distribution, rock strength and discontinuity strength are calculated and compared in three-dimensional element code (3DEC), and the failure mechanisms of surrounding rock with various discontinuities distribution are analyzed. The contribution of structural plane’s mechanical properties to rock failure is also studied: the distribution of structural plane determines the location of the first failure; and the failure of structural plane does not necessarily lead to the failure of surrounding rock.

Key words: deep tunnel, jointed surrounding rock, discontinuities, geometric parameters, discrete element, failure mechanism