Evolution Characteristics of Overburden Strata Structure for Ultra-Thick Coal Seam Multi-Layer Mining in Xinjiang East Junggar Basin

The efficient and safe extraction of ultra-thick coal seam in the Xinjiang East Junggar Basin has been a major focus in the future of mining in China. This paper systematically studied the overburden strata fracturing process and the structure evolution characteristics based on a typical ultra-thick coal seam condition in Xinjiang, using both physical and numerical modeling studies. The interactions between shields and the roof strata were also examined, from the perspective of ground support. The results indicated that roof structure was mainly in the form of voussoir beam at the early mining stage, where overburden stability was affected by the rock mass properties and mining parameters. The support load mainly included top coal and immediate roof gravity load and the load caused by main roof rotary consolidation. As a result of mining disturbance and strata movement, the overlying strata re-fractured in the later mining stage. The roof structure changed from beam to arch gradually and propagates upwards with the increase of multi-layer mining times. The support load was mainly the gravity load of the friable rock mass within compression arch. The results will provide a guideline for the improvement of roof stability under similar mining conditions in Xinjiang.