Numerical Test Research on the Dilatancy of Irregular Columnar Jointed Rock Mass under Unloading Condition

In order to investigate the dilatancy of irregular columnar jointed rock masses (ICJRM) under unloading conditions, a series of three-dimensional discrete element numerical models of ICJRM with seven column dip angles were established, and the compressive strength typical failure characteristics and dilatancy evolution of ICJRM were obtained through numerical conventional triaxial compression tests under unloading confining pressure conditions. The results show that: The shape of peak deviatoric stress Δσ_1f vs. dip angle β_j curve resembled the letter “J”, where the peak deviatoric stress has the minimum value at β_j =60°, and reached its maximum value at β_j =90°, and the typical failure modes included splitting along the column and columnar joint surface, shear slipping along the columnar joint surface, and the compression-flexure destabilization of the columns; The dilatancy of irregular columnar jointed rock mass under unloading condition was closely related to the initial confining pressure and dip angle, and the corresponding volumetric strain increment obtained larger values when the dip angles ranged from 30° to 60° indicating a significant dilatancy.