Numerical Simulation of the Influence of Water Inrush on Underground Coal Mining Stability in Vietnam

The underground mining in Vietnam and around the world often face the water inrush and gas outburst that are the forms of special geological hazards even when having completely information about the current condition of the water bag appearance and accumulation of gas. It is difficult to predicte when water inrush and air outburst may occur in the process of mining. If the mining process is stopped too early for handling water or gas, it will cause useless expense for drilling. In contrast the catastrophe will happen before the drilling is undertaken. Therefore, it is necessary to study in order to forecast and identify the right time to stop exploiting for handling the so-called water bags and air bags. Assuming that gas outburst and water inrush will happen, if the destroyed area formed around the mining face and the water or gas bag is interconnected. So the mechanical model builded on this criteria allows the monitoring the failure process in the rock mass with regards to the mining process. The choice of time to halt exploiting for treatment of water inrush or gas outburst is the time before the next extraction round which leading to the formation of interdestroyed area. Numerical simulation (FLAC2D - Fast Lagrangian Analysis of Continua) based on the finite difference method was used to study the influence of water inrush on underground coal mining stability. The article introduces some of the results obtained from simulation studies.