Safety Assessment of Abandoned Stope,Method and Practice

The disposal of abandoned stope is a problem of technological difficulty in the mining field in China.A large abandoned-stope without disposal poses a potential danger of sudden large-scale roof fall.A regular safety assessment of an abandoned stope is among necessary measures to insure safe production in underground mines where the open-stopping method is adopted.This paper discusses the methods used in the safety assessment of abandoned stopes and their applications.They include 3-D simulation of a large-scale roof fall,the calculation and assessment of the pillar distribution,the design against air shock waves and the assessment.The 3-D simulation involves some modification of ANSYS.The plastic strain variations and tensile fractures are considered.The new pillar strength theory,the conception of stress release,and the statistical classification of rock falling are adopted in the method for assessing the pillar distribution.Air dynamics of underground mining and crack growth are taken into account in the design against air shock waves and the assessment.The results show it is technologically feasible to accurately,simply and efficiently evaluate the stability of abandoned stopes and related engineering environment with these methods.And the methods have been applied successfully to safety evaluation or safety acceptance evaluation in gold mines,phosphorite mines,iron mines,plumbum and zinc mines,coal mines,vanadium mines and strontium mines.