The Aqueous Media Structure And Mining Failure Feature Of The Jurassic-cretaceous In Yushen Mining Area

Yushen mining area in northern Shanxi is the essence of Jurassic-Cretaceous coalfield,which is one of the most important large coal production bases in China.The Jurassic-Cretaceous is of the main coal-rich strata in the western China's coal-rich area,which differs greatly from the Carboniferous-Permian coal field in the eastern of China,and has its own distinctiveness in the structure of the aquifer and the characteristics of mining failure,It has a great influence on the evaluation of mine water filling condition.Based on the geological background of Yushen mining area,X-ray diffraction,scanning electron microscopy and mercury intrusion test,combined with the geological depositional environment and the evolution of the study area,were used to analyze the structure and micro-pore structure of Jurassic–Cretaceous system in Yushen mining area from the aspects of mineral composition,pore structure and rock mechanics characteristics;Secondly,the Yushuwan coal mine geological condition was taken as the prototype.Through numerical simulation and similar materials simulation,the characteristics of overburden failure on typical stratigraphic structures are studied.And then by analyzing the Jurassic-Cretaceous distribution and stratigraphic structure,the law of occurrence and migration of groundwater in the mining area and the hydrogeological significance of the water filling in the coal mine was studied,and the water-engineering practice case about coal mining under water-containing was presented.The main contents and achievements of this paper are as follows:(1)The Jurassic-Cretaceous in the Yushen mining area had experienced a complex and special diagenetic stage and a relatively transient sedimentary evolution process.The result of X-ray diffraction,electron microscopy and mercury intrusion tests showed that the Jurassic-Cretaceous had the characteristics of low intensity,weak cementation,high porosity and permeability and so on.For example,the porosity of the rock samples from Zhiluo group was 15.53%,which was much higher than that of the Carboniferous-Permian sandstones in eastern China,which was 1.1~2%.(2)Similar material simulation test and numerical simulation method were used to study failure features of overburden strata and the evolution rule of water flowing fracture zone in the Yushuwan coal mine.The simulation of the mining of No.2 coal seam was stratified at 5m,and the deformation and failure of the overburden strata was gentle,therefore abscission layer and flat arch shape was finally formed respectively with 55 meters and 49 meters in height.The difference of values between the simulated and the empirical formula was obvious,which showed the particularity of the Jurassic-Cretaceous overburden failure.(3)The macroscopic distribution of the Jurassic-Cretaceous in this area,which,according to the lithologic facies and distribution characteristics,was mainly grouped into three water-bearing rock formations—direct water source Jurassic-Cretaceous bedrock confined water,roof water channel bedrock fissure zone and primary structural surface cracks and other water channels,characterized the overall groundwater runoff with a from-northwest-to-southeast flow tendency.Water-filled strength factors and the effect of fissure closure on water filling were analyzed in the given example of typical water inrush coal mine—Jinjie coal mine.(4)The water flowing fracture zone of Yushuwan coal mine,in which stratified coal mining method was used,had not do damage to phreatic aquifer.That had confirmed the overburden failure law of the experimental simulation,and provided a practical reference to coal mining under water-containing for the coal mines in this area with similar mine geological conditions.