Water and sand inrush is one of the most serious threats in some shallow coal mines in China. In order to understand the process of sand inrush, experiments were performed to obtain the criterion for sand inrush. First, seepage tests were carried out to study the hydraulic properties of granular sandstone. The results indicate that seepage velocity has a linear relation with the porosity and particle-size distribution parameter. Then, sand inrush tests were conducted to investigate the critical conditions for sand inrush occurrence. It is determined that the sand inrush zone can be clearly distinguished based on the values of porosity and particle-size distribution parameter. Additionally, sand inrush tended to happen in the conditions of high porosity, high seepage velocity, and large particle-size distribution parameter. Further, general principles for preventing the water and sand inrush were proposed, such as reducing the porosity, improving the pore structure, and decreasing the seepage velocity. The proposed principles have been successfully used in situ to control the water and sand inrush.

Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column (SKCC) is a type of serious disaster in the underground coal extraction. Karst collapse column (KCC) developed in a confined aquifer occurs widely throughout northern China. A water inrush disaster from SKCC occurred in Taoyuan coal mine on February 3, 2013. In order to analyze the effect of the KCC influence zone’s (KCCIZ) width and the entry driving distance of the water inrush through the fractured channels of the SKCC, the stress, seepage, and impact dynamics coupling equations were used to model the seepage rule, and a numerical FLAC3D model was created to determine the plastic zones, the vertical displacement development of the rock mass surrounding the entry driving working face (EDWF), and the seepage vector and water inflow development of the seepage field. The hysteretic mechanism of water inrush due to SKCC in Taoyuan coal mine was investigated. The results indicate that a water inrush disaster will occur when the width of the KCCIZ exceeds 16 m under a driving, which leads to the aquifer connecting with the fractured zones of the entry floor. Hysteretic water inrush disasters are related to the stress release rate of the surrounding rocks under the entry driving. When the entry driving exceeds about 10 m from the water inrush point, the stress release rate reaches about 100%, and a water inrush disaster occurs.

The mining of shallow buried and thick coal seams may cause ground settlement, loss of surface water, and even soil desertification in arid–semi-arid climate zones. The key to protecting surface water resources through the technology of separated strata grouting is to study the evolution of the separation space under the key stratum (KS) with the change of strata. Aiming at the section of underground strata characteristics of F6202 and F6208 working faces, similar simulation tests under three typical geological conditions were carried out. Based on the experimental results, a theoretical calculation model was established, and the practice of separation grouting was carried out. The results show that, under the conditions of a thick coal seam with one KS, the structure formed by breaking strata below the KS was relatively unstable, and the separation space was relatively large, which is likely to cause serious ground settlement. More seriously, with the increase of the weakly consolidated layer and coal seam thickness, the increase of the ratio of rock to soil in the weakly consolidated layer, and the decrease of the thickness of the strata below the KS (two KS condition), the separation space was further increased. Based on the above analysis, combined with the real-time feedback data of the grout amount and pressure on hydraulic support, the position of the grouting borehole was determined, and the speed of mining advance was adjusted in time, thus effectively controlling the curvature of the ground settlement, protecting the integrity of the red clay layer near the surface, and consequently protecting water resources.

Geological structures of Sima coal mine in Shanxi Province were analyzed to understand the control effect of the geological structures on the occurrence of coalbed methane (CBM) in coal seam #3 of Sima coal mine. The CBM contents in the districts #2 and #3 of Sima coal mine were tested, and the effects of buried depth, fault and collapse column on the distribution of coalbed methane content are studied. The research results showed that: 1) The average content of CBM has a linear relationship with buried depth and overburden thickness, but in the smallscale range of buried depth, the dispersion between CBM and buried depth is very large. 2) Faults and collapse columns significantly affect the content of local CBM nearby, but from the largescale range such as the whole mining area, the average value of CBM content at a certain buried depth will not be affected by faults and collapse columns. 3) In the hanging wall of F29 normal fault, it is roughly estimated that the average escape rate of CBM near the fault is 13.9%, while in the footwall of F29 normal fault, this value is 0.7%–1.1%. The results show that there is a significant difference in the influence of the fault on the CBM content in the hanging wall and footwall. 4) The control effect of collapse column on CBM occurrence is related to the development height of collapse column, the cementation degree of collapse column, groundwater runoff conditions and other factors. It can be divided into three categories: aggregation action, escape action (such as collapse column X8) and no obvious effect (such as collapse column DX7).