Determination of the Critical Span for a Large-Caving above a Mined-out Area

An analytical model presented here was developed to determine the critical span for a large-caving that developed above the mined out area in Xiaowanggou Iron Mine. The model development is based on field observations measurements, examination of the characteristics of overlying rock masses, research on caving process and application of simple loading conditions in the gravitational field. Key input parameters were determined and utilized to predict the critical span for a large-caving. The difference between the predicted and measured values is less than ±3%. Results from the analytical model and field measurements have demonstrated that the proposed model can be used to predict the timing and crater location of large-caving and it forms the theoretical basis for mitigation of risk associated with a largecaving in a safe and economical manner.