Study on damage-crack criterion of bedding limestone based on ultimate tensile strain

The ultimate tensile strain can be used as the criterion to assess material damage. However, typical sedimentary rocks contain structural planes arranged in various directions, resulting in anisotropy of the tensile properties. Determining the ultimate tensile strain of rock with bedding of different dip angles is the fundamental problem. According to the limit analysis method, the endpoint of the elastic stage was taken as the critical state to judge splitting, and the ultimate tensile strain and directions of rock with different bedding angles were determined. Based on the Weibull distribution of the rock element strength and the Lemaitre principle of strain equivalence, the evolution equation of the damage variable was derived with increasing tensile strain. The tensile criterion and the calculation method of damage stress were established based on the ultimate tensile strain, and the numerical simulation program with the tensile damage was constructed in Fast Lagrangian Analysis of Continua (FLAC^3D). Finally, this model was applied to stability analysis for excavated surrounding rock in an ideal circular tunnel. The damage evolution has a negative exponential relationship with the first principal strain. The plastic zone, displacement field, stress field, and damaged zoneare all in accordance with the general law. The results can provide a basis for examining the tensile characteristics of a layered rock mass.