Abstract: The roof of underground roadway (chambers) often breaks due to bending and delamination,and the location of the break is closely related to the geometric shape and position of the cracks. To reveal the impact of cracks on rock fracture, a three-point bending model of rock mass with offset oblique cracks was established. The offset coefficient and connectivity ratio of cracks were defined,and the relationship between the offset coefficient,inclination angle,and connectivity of cracks was analyzed. Based on the principle of mechanical equilibrium and the σ-K relationship derives the stress intensity factor K correlation between offset oblique cracks and offset vertical cracks. At the same time,the influence of crack inclination angle,connectivity, and offset coefficient on the stress intensity factor was analyzed. This method can provide a judgment basis for the tensile fracture of the roof of the roadway (chamber) under the influence of cracks.

Key words: three-point bending,stress intensity factor,rock mass,offset oblique crack,connectivity ratio