Experimental study on coarsely water-bearing sandstone in roof of Jurassic coal seam

The similar simulation experiment has always been an essential method to study water-preserved mining, during which the similarity between simulation materials and rock properties is the most significant issue. Ningdong coalfield is a typically ecological-fragile mining area where a special sandstone contains a large amount of low maturity and clay minerals. This sort of sandstone represents the soft-rock properties under mining influence and water absorb- drying process. It was confirmed that this is coarsely argillaceous arkose which is formed in quickly emerging sedimen- tary environment in accordance with its composition and structure. The sandstone is comprised of clay,quartz and feld- spar by the quantified analysis of X-ray diffraction. The clay incorporates enormous mont-morillonite,illite smectite mixed layer and chlorite and all of these materials are water swelling. The study of triaxial compressive strength and permeability of the sandstone by MTS Servo demonstrates that the sandstone samples have plastic-failure characteris- tics. The permeability of water-saturated sandstone has mutational points,after which it is approximately constant be- fore increasing to the maximum at failure. In addition,the uniaxial compressive strength and elastic modulus have a negative relation with moisture content.