Prediction of Deep Rock Mass Quality and Spatial Distribution Law of Open-pit Gold Mine Based on 3D Geological Modeling

Changshanhao open-pit gold mine in Inner Mongolia is the largest gold heap leach mine in North China. Recently, the mining depth and scale have increased, due to depletion of shallow resources. Since deep mining and steep slope mining have begun at Northeast stope of Changshanhao gold mine, landslides and instabilities of different scales occurred at many areas, constituting severe threat to both personnel and equipment. In order to comprehensively evaluate the slope stability of the Northeast stope and provide guidance for the division of dangerous areas in the stope, the 3D geological model of the Northeast stope of Changshanhao open-pit gold mine was established by using 3D digital modeling technology. Following, the rock quality designation (RQD) value of deep rock in the stope was estimated, based on RQD sample data of deep rock extracted from borehole and geostatistics method, while the distribution characteristics in three-dimensional space of rock mass quality of the open-pit slope were revealed. Ultimately, through the comparative analysis of the integrity investigation results outcrop rock mass and the prediction results of deep rock mass, the feasibility of three-dimensional geological modeling method and the reliability of the calculation results based on geostatistics method were verified, providing reference for safe mining of the high and steep slope within the open pit. The comparative analysis results indicated that: (1) the overall rock mass quality grade of current slope at the Northeast mining area was poor; (2) the rock mass at the north side of the upper part of the east U-shaped mouth was quite fractured, further reinforcement, monitoring and prevention are needed; (3) in the final state of design, the influence of mining disturbance will further degrade the quality of slope rock mass.