An Improved Vulnerability Assessment Model for Floor Water Bursting from a Confined Aquifer Based on the Water Inrush Coefficient Method

Pressurized confined water below coal seams are serious threats to mining. The conventional water inrush coefficient method fails to accurately assess the risk of floor water inrush under some specific conditions, such as high water pressure and low water yield in the source aquifers. Large amounts of water inrush data including water inrush flow rate, water inrush coefficient (T (s) ), floor aquiclude thickness (M), and water abundance, were collected and statistically analyzed. The results indicated that inrushes mostly occurred when M was less than 30 m and that the critical T (s) increased linearly with M. The occurrence of a water inrush and water inrush yield amount (Q in L/s) were related to both the values of T (s) and the unit water inflow (q in L/(s m)). In addition, 97.7% of the large- and medium-sized inrush events occurred when q > 2 L/(s m) and only a small proportion (3.2%) of the small-sized inrushes happened when q < 0.1 L (s m). T (s) , M and q were comprehensively analyzed and used to evaluate vulnerability to floor water inrush. By analyzing the distribution of water inrush points and the scale of water inrush events, the vulnerability was divided into four levels (safe, moderately safe, potentially dangerous, and highly risky) based on T (s) -M and T (s) -q models. Successful application of these models in the Huaibei mining area proved that they are feasible in practice. The T (s) -M and T (s) -q charts can be used independently or jointly. These new methods should improve the accuracy of predictions and evaluations during deep exploitation where the aquifers are often characterized with high pressure but low water abundance. The results could also help reduce the amount spent on mine water prevention and control.