## 1 Introduction  
With the increase in coal mining depth, there are some water inrush accidents caused by separation seepers after mining [1; 2]. As the working face advances, the different strata in the overburden may subside unevenly, thus forming a large number of transverse separation voids. Once these voids are recharged gradually by the surrounding weak aquifer, more and more water will accumulate in the separation layer. Some aquiclude of certain thickness exists between the separation seeper and caving fracture zone. When the pressure of the separation seeper exceeds the critical pressure value of the aquiclude, water inrush from the separation layer would occur. This kind of water inrush is characterized by its sudden, instantaneous, and large water inflow, but it declines fast, for it is mainly from static reserves. The formation of a separation seeper is the main reason for the increase in water inflow in the working face. This kind of disaster poses severe challenges to the safety production of the working face. However, due to the large workload, the prevention and control of a separation seeper is very hard. [PERSON] et al. studied the bed separation distribution and development in the process of strata movement [3]. Theoretical analysis, numerical simulation, and borehole drilling were used to study the mechanism of large-scale water inrush events [4]. [PERSON] et al. studied the prevention and mechanism of bed separation water inrush for thick coal seams [5]. Strata behavior monitoring was carried out using remote-type geotechnical instruments during the extraction of pillars in one of the panels [6]. The theoretical pattern of ground movement observed in flat terrains was modified by surface topography and geological structures [7]. Using the 'three maps-two predictions' method, an index model of water abundance (yield) of the overlying aquifers was constructed and overlain on a map that indicates potential fractured zone connections to the overlying aquifers [8]. The presence of spatially discrete, stiff roof units is one feature that has been linked to dynamic failure events [9]. An analysis of spatial differences in permeability based on sedimentary and structural features of the sandstone aquifer overlying coal seams was undertaken [10]. Three coal mines in the Ordos Basin were selected for a detailed evaluation of the water in-brush risk [11]. Zones of interconnected fractures and separate horizontal fractures were studied with vertical wells drilled from the ground surface down to active underground workings [12]. The locations of mining-induced horizontal fractures along rock interfaces in the overburden were identified using an original experimental device [13]. [PERSON] et al. categorized bed separations and indicators of threatening situations and analyzed the morphological evolution of bed separation [14]. Hydrogeological Classification and Water Inrush Accidents in China's Coal Mines were made [15]. Injecting grout into the bed separation in the overburden was proposed as an effective control measure against surface subsidence during longwall mining [16]. Through engineering geology investigation and theoretical analysis, the mechanism of abnormal water inrush in the roof of the working face under the condition of giant thick igneous rock cover in Haizi mine is researched [17]. [PERSON] et al. made a prediction of the height of the destressed zone above the mined panel roof in longwall coal mining [18]. The water-resistant key strata stability has been detected by optic fiber sensing in shallow-buried coal seams [19]. A new estimating approach for vertical bedding separation, which uses the ratio between current and average vertical bedding separation was proposed [20]. A water-resistant key strata model of a goat floor prior to main roof weighting was developed to explore the relationship between water inrush from the floor and main roof weighting [21].