A Case Study of Rock Failure and Water Inrush from the Coal Seam Roof

According to the hydrogeological conditions of No.6 mining area of Jining Ⅲ coal mine,instable rock failure process of coal roof under mining was simulated by using the RFPA2D(Rock Failure Process Analysis) and the relationship between rock failure of coal roof and water inrush was discussed.The numerical simulation results show that the first roof weighting occurs when 30 m of the coal seam is mined and the overlying strata of the seam begins breaking.Then the periodic roof weighting occurs about every 22 m.When the mined coal seam is up to 140～150 m long,the height of failure will reach the highest.This result corresponds to the in-situ measured value.During excavation in No.6 mining area,20 times of water-inrush from overlying sandstone have happened.Generally,groundwater bursts out from the overlying aquifers when the periodic weighting happens or when the working face is advanced for every 140~150 m.As a matter of fact,water inrush is obviously associated with the roof failure process.