## 6 Conclusions  
1. Based on the slip line theory and the 'three zones' theory, the concept of damage fragmentation depth is proposed, and the interlayer rock mass structure is classified based on the damage fragmentation depth. When \(L\leq h_{m}+H_{\mathrm{dz}}\)', the thickness of the interlayer rock mass is less than or equal to the depth of complete damage and fragmentation, and the completely broken interlayer rock mass is formed. When \(L>h_{m}+H_{\mathrm{dz}}\)', the thickness of the interlayer rock mass is greater than the depth of complete damage and fracture, and the fracture-fracture superimposed interlayer rock mass is formed. When \(L\geq h_{m}+H_{\mathrm{dz}}\)', the thickness of the interlayer rock mass is greater than the sum of the floor failure depth and the water irnush fracture zone, and the broken-broken-broken combined interlayer rock mass is formed. A new method of structural division of water irnush disaster caused by damage of rock mass be tween close coal seams is proposed, which provides a basis for the study of water inrush disaster. 2. With the mining of the upper and lower coal seam working faces, the evolution law of the water inrush channel of the rock mass between the close coal seams shows that the water-conducting channel, the network water-conducting channel, and the boundary water-conducting channel appear in turn. In the process of upper coal seam mining, the interlayer rock mass water inrush is mainly based on the joint water inrush channel. In the process of lower coal seam mining, the interlayer rock mass water inrush is mainly based on the network water inrush channel and the boundary water inrush channel. The network water inrush channel undergoes an increase-decrease-constant change process, and the boundary water inrush channel undergoes an increase and then tends to be stable. The overall two-dimensional distribution of the water inrush channel of the interlayer rock mass is a positive trapezoid, the boundary water inrush channel is distributed on the side of the open-off cut, the side of the stop line of the working face, and the cracks in the whole interlayer rock mass are developed. The network water inrush channel and the bonding water inrush channel are distributed in the middle position of the inter-layer rock mass. The network water inrush channel runs through multiple inter-layer rock layers, and the degree of fracture development is smaller than that of the boundary water inrush channel. The bonding water inrush channel only runs through the single inter-layer rock layer, and the degree of fracture development is the smallest. The dynamic evolution process and distribution characteristics of water inrush channels in different inter-layer rock masses with the mining of working faces are revealed. Based on the evolution and distribution characteristics of water inrush channels, the water inrush process is transformed from qualitative analysis to quantitative research. 3. Combined with the characteristics of the water inrush channel in the inter-layer rock mass, the boundary water inrush crack has the characteristics of instantaneity and large water inflow. The network water inrush crack has the characteristics of horizontal and vertical flow equivalence. The joint water inrush crack has the characteristics of long action time and slow flow. Therefore, the boundary water inrush crack, the network water inrush crack, and the water movement in the joint water inrush crack are equivalently transformed into the flat plate flow state, the crack flow state, and the pore flow state movement, and the network-boundary, network-joint-boundary water inrush flow solid coupling calculation model is constructed. The fluid-solid coupling calculation model covers a variety of situations of water inrush from rock mass between close coal seams.