Catastrophic mechanism and its prevention and control of seepage deformation and failure of mining rock mass Ⅲ: a review of water retention bulkhead

The types of seepage instability of water retention bulkhead are divided according to the analysis of typical cases of leakage instability of water retention bulkhead in mines in China. The seepage instability criterion of water retention bulkhead is reviewed, and an expression of the critical hydraulic gradient against seepage failure of water retention bulkhead and surrounding rocks is recommended. The scientific and technological issues that need to be further researched, and the contents and ideas that need to be tackled urgently are discussed. The results show that the seepage instability of water retention bulkhead can be divided into three categories, namely, the seepage instability of the surrounding rock fracture and the interface between bulkhead and surrounding rock due to seepage, the deformation and instability of surrounding rock and water retention bulkhead caused by water pressure, and the deterioration and instability of surrounding rock caused by water immersion. The parameter sensitivity analysis was carried out for the safety factor of the seepage stability in bulkhead and surrounding rock, and the results showed that the rock mass integrity coefficient and the water-conducting pathway penetration coefficient of the surrounding rock were the main influencing factors. In the design and construction, enhancing the integrity of the surrounding rock mass and improving the impermeability of the surrounding rock water pathway is the key to ensuring its anti-seepage stability. For the calculation of the critical hydraulic gradient against seepage failure of water retention bulkhead, the integrity of the rock mass, the adhesion strength between the surrounding rock and the bulkhead, the fault fracture zone, the ground stress and hydraulic environment, and the deterioration performance of the surrounding rock immersion should comprehensively be considered. The parameter sensitivity analysis shows that these factors are all highly sensitive factors, and the key parameters are the water immersion damage factor and the water-conducting pathway penetration coefficient of the rock mass; therefore, when determining the critical hydraulic gradient, it is necessary to focus on finding out the important basic data such as the hydraulic properties, the strength of structural surface strength of the surrounding rock and the water pressure applied to the retention bulkhead. The evolution mechanism of seepage field under the multi-field coupling conditions of the water retention bulkhead and surrounding rock combination, the stabilization mechanism of seepage failure at the intersection of the bulkhead-surrounding rock and the discontinuities of the surrounding rock structure are two key scientific problems that need to be solved urgently. In the next step, the geological model of the bulkhead -surrounding rock combination and its geological environment evolution, the seepage mechanism and instability criterion with high water pressure, the life-cycle safety and stability control methods should be studied.