Research On The Laws Of Overlying Rock And Support Resistance Of Yushuwan Coal Mine In Yushen Coal Area

The coal mining under the condition of the thick loose beds and the thin base rock in Shenfu and Yushen coal area in the north of Shaanxi Province of China, cuases the strata behavior severely, such as the overlying strata fall out and sink along coal wall, and appears step surface subsidence, and needs the yield with big working resistance to control the roof. However the studies of the strata behavior with thick soil layer and thick rock are less. In this paper, the law of the appearance of strata pressure, overlying strata movement and reasonable force of the supports under this new conditions are studied in details with the methods as following: Similar material simulating experiments, numerical simulation and theoretical analysis.Proceeding with the geological physics and mechanics character of the laterite and loess, and then connect with the geological conditions of the first fully mechanized coal mining working face in Yushuwan coal mine, two similar material simulating experiments(5m and 3m) are established. Concluded the laws of overlying strata movement under the condition of the thick soil layer and rock, especially expatiated the laws of strata behavior and roof movement when the mining-induced fissere is run through the roof. The relationship between the support and the surrounding rock is simulated and the reasonable support resistance is got. Through analyzing the supporting resistance, influence of laterite on the main roof structure and falling height of overlying rock, it is revealed that the overlying strata don't fall out and sink along coal wall. However the overlying strata structure is"three zones"which are caving zone, fractured zone and sagging zone.Theoretical Analysed the roof structure with the stratum theory for strata control under thick soil layers and rock of Yushuwan coal mine, explain the small periodic weighting is single key stratum fractured and huge periodic weighting is two or more key starum fractured. By study on equilibrium condition of key rockin the fractrue rock-pillar, the mechanical model of key rock structure is established. And theoretical formulas of therational support resistance in fully mechainzed coal mining face under thick soil layers and rock is gained at the same time.Applying the numerical simulations program RFPA2D to analyze the laws of strata pressure appearance under the mining condition of thick soil layers and rock, the overlying strata structure is at the distributing of"three zones". Due to the soil cohesion of the clay layer, the bed separation of the above rerrane develop up to the siol stratum along with the advance of the working face, then rupture cranny develop to the surface speedly. And the cracks are appeared in different length about 40～60m far from the working face. There is some isolated zones about 30m on the dip and 18m on the strike.The strata behavior is not very severely as the one under the conditon of the thick loose beds and the thin base rock in Shenfu coal area in the north of Shaanxi Province. At a certain advancing distance, the overlying strata don't fall out and sink along coal wall to the surface, so the results of the similar simulation test are proved to be correct.