Abstract: Disturbance cracks or fractures are generated in the surrounding rock mass of mining face in the process of coal mining. Among these cracks or fractures, some experience the opening process. Due to the fact that there is no substance in these opened cracks or fractures to transmit force, the stresses in the zone near to these cracks or fractures will decrease to a small value from their initial gravity-induced large stress values but not necessarily reach 0. After these cracks or fractures are generated, the stresses in the zone near to them would adjust and cause vibration due to stress redistribution. Accordingly, these cracks or fractures would be closed again, they could even bear great shear stresses. Based on the described phenomenon that the stress in the zone near to disturbance cracks or fractures have experienced the process of stress unloading from large to small values, a method referred to as “dynamic stress tracing method” is developed to identify the range and height of disturbance factures/cracks zone. The No.3 coal seam mining of Shizuishan in Ningxia province is given as a case. The discrete element software package UDEC is applied to determine the stress distribution during the process of coal mining. Based on the proposed dynamic stress tracing method, the range and height of the disturbance fractures/cracks zones are estimated using the post-processing package TecPlot. It is indicated that the proposed dynamic stress tracing method for identifying the height of coal mining disturbance fractured/cracks zone is feasible, and owns good suitability.

Key words: underwater seam mining, dynamic stress tracing method, mining disturbance fractures/cracks zone, discrete element method, Ningxia Shizuishan coal mine