Mechanism and control of water seepage of vertical feeding borehole for solid materials in backfilling coal mining

To solve the problem of water seepage of vertical feeding borehole for solid materials, we established the fluid-solid coupling dynamic model of groundwater flowing in rock mass adjacent to the vertical feeding borehole. Combining with the engineering geological conditions, we built a numeral model to study the influence rule of the aquifer hydraulic pressure and seepage location of feeding borehole on the amount of seepage with finite element numerical method. The results show that the nonlinear relationship is presented among the amount of seepage, the seepage location and aquifer hydraulic pressure. The higher the aquifer hydraulic pressure is, the closer the distance between seepage location and aquifer is, and the faster the harmful levels of aquifer will grow. In practice, we calculated the allowable seepage of feeding borehole by the optimum moisture content and natural moisture content of backfilling materials, and then determined the protection zone of feeding borehole, so the moisture content of backfilling materials can be controlled within the scope of optimum moisture content.