Abstract: This paper discusses some geomechanics problems in block caving.In order to reduce the fluctuation of the RQD obtained in the same situ on a rock mass, a new NRQD（Normal Rock Quality Designation） is recommened, which is obtained by statistics of discontinuities carried out at the vertical direction to the main group of discontinuities.The statistics data on the discontinuities of a rock massare will not be in consistent with practical facts if the investigation is only carried out at horizontal level.The space investigation is recommended.A new supp-ositeion is presented that not only the size of rock and ore reduces,but their shap get more and more homogeneous in the course of caving and drawing as well.