Research On Overlying Strata Hydrological Characteristics Induced By Top Coal Caving In Extremely Thick Coal Seam

Fushun mining area's geological structure is complex, the largest coal seam thickness is110m and average thickness is59.58m, it is rare in the world; the hydrological conditions become complicated as multi-mining area mining and slice mining nested with each other. A large water inrush accident happened at Laohutai73003#mining face on March10,2007, and then another two water inrush happened in2011, for the actual project situation and the problems faced by Laohutai, the paper studies the overlying strata hydrological evolution law after top coal caving in extremely thick coal seam.The key findings and conclusions are as follows:(1) This paper puts Laohutai E6200profile as main section, uses three-dimensional numerical analysis method, simulates the superimposed effect of new and old mining areas overlying rock mass movement and deformation and damage after fully-machanized sublevel caving, reveals the overlying rock mass's movement and deformation range and the damage height increase as superimposed effect increase, According to the simulation results established a relationship between the height of water flowing fractured zone H and mining thickness M1.(2) Studying the evolutionary characteristics of height of water flowing-fracture zone of fault zone in the case of fully-machanized sublevel caving. According to the simulation results reveal the evolved features of the fault zone hydraulic conductivity height, the height at fault F25increase20.7%to123.2%, the height at fault F18increase26.99%to81.93%.(3) According to the simulation results and actual engineering data, the sources of inrush-water mainly include: Hunhe water, atmospheric precipitation, the seeper of land subsidence basin, gravel aquifer, the seeper of separated strata, water in the old mining area and old lane, water in the faults. Reveals the formation process of the water inrush channels.The evolution of water inrush is the height of water flowing fractured zone increased and faults activated inform the water inrush channels and contact with gravel aquifer, the seeper of separated strata and other water sources, ultimately lead to water inrush accident.(4) Proposed prevention measures of water burst of roof and work face at the Laohutai mine according to water supply relationship.