Study On The Reasonable Retainning Of The Waterproof Coal Pillar Of Steep Medium & Thick Coal Seam With Hard Roof

Mining under surface water is a marginal subject involving several fields, such as mining, geology, hydrological geology, geophysical exploitation, rock mechanics, mining survey and calculation mathematics etc. It is a very sophisticated work about many related principles and modern exploitation technique that include the failure laws of overburden rock, characteristics of water-proof pillar, the dynamic laws of under surface water, characters of aquifer, safety production and technical measures of working face, the technology of retaining waterproof pillar and the evaluation of economical and social effectiveness etc. Hard and careful efforts are required to correctly assess the safety of coal mining under surface water, especially to improve the safety of upper limit of coal mining in order to promote mining under surface water, and assure the safety of workers as well as miner.The failure laws of the coal and rock masses are the important factors to determine the safety mining over-limit. It must has rational and credible methods in order to determine the failure law after mining. In this paper, after analyzing the current situation and the results of mining under surface water home and abroad, it uses many methods including similar simulating experiment, geologic radar detect, locale test on cavern basic point, numerical simulation and theory analysis to analysis the crack height, the loads of the water proof pillar and the stability of the steeply middle and thick coal which has hard over rock masses.In this paper, it takes the 112 gob areas of Tie Shannan coal of Si Chuan Da Zhu Mining Bureau as an example, According to the stress distribution of waterproof pillar on basis of test on equivalent materials, and combining with technology of detect on geologic radar, This paper studies on the destructive rule of coal or cock, then gets the characteristics of breach fracture zone of coal or rock, and confirm the reasonable width of waterproof pillar in K21 coal floor. Using way of three-dimensional finity cell, and 3D-σprocedure software , this paper conducts numerical simulation and calculation toward waterproof pillar, then, on the basis of theories analysis , it proves the suitable width leaving for safety waterproof pillar and the reasonability of upper limit of mining in 112 mining area. then checking up mining practice, analyzing the observation and prediction data of dripping water amount and effusing water amount throughout mining. It is obvious from the research that the definitive width of waterproof pillar...