Rock mass characteristic of Suanjingzi section in the Beishan Preselected Site of China’s high-level radioactive waste disposal

Abstract

Rock mass characteristic is a key influence factor for site selection and site suitability evaluation of high-level radioactive waste disposal engineering. In this paper, rock mass characteristic including geological characteristic, geometric features of joint, and quality evaluation of rock mass was studied for the Suanjingzi section in the Beishan preselected site of China’s high-level radioactive waste (HLW) disposal. Site investigation, mathematical statistics, and probability analysis were applied to study geometric features of joint. The statistics results showed that there are four optimal joint sets in the Suanjingzi section, the occurrence of each joint set obeys Fisher distribution, and the spacing of each set is fitted by negative exponential distribution. Tangent circular sampling window was used to study the trace length and the trace midpoint density, and wide spacing, long trace length, and small trace midpoint density are the main characteristic of Suanjingzi section. Considering the importance of joint in high-level radioactive repository, joint structure rating (JSR) was used to evaluate the quality of rock mass. The results indicated that the Suanjingzi area in the Beishan preselected site was suitable for China’s HLW disposal repository.