Numerical Simulation Study on Effect of Lamprophyre in Water on Overburden Migration in Ultra-thick Coal Seam

In order to study the influence of lamprophyres intruding into different strata of roof of extra-thick coal seam on overlying rock migration before and after encountering water, a numerical simulation model of UDEC is established based on Datong Tashan Mine. The characteristics of overburden collapse failure and roof subsidence before and after the lamprophyre meets water are studied. The research shows that when lamprophyre intrudes into the top of coal seam in the case of water, the first collapse step distance of roof decreases and shows the characteristics of slow subsidence; when lamprophyre intrudes into the middle part of the direct roof, the upper direct roof strata collapse together with the lower direct roof, and the collapse step distance is obviously shortened; lamprophyres of different strata, whether they meet with water or not, only have direct influence on the activity rules of the direct roof strata in the initial mining stage, and the upper strata are mainly controlled by the basic roof.