Experimental study on distribution law of residual fissure under multiple mining conditions

The developmental state of residual fissure in goaf is an important factor in the design of goaf filling and grouting. Under the conditions of multiple seams mining, this paper discusses the distribution of residual fissure in overlying strata by means of the similar material experiment. The results show that, after the end of mining, the distribution of residual fissure in goaf displays obvious characteristics in different zones. From both sides to the middle of goaf, it can be divided into three zones: residual fissure zone, compacted fissure zone, and surface tensile fissure zone. The fissure rate of the residual fissure zone generally varies from 19.45 % to 45.27 % while the fissure rate of the fissure compacted zone varies from 9.28 % to 19.33 %. The developmental height of interlayered fissure is decided by both mining width and total mining height. In both theory and practice, this study has the great importance in estimation of stability of the goaf, determining the range and depth of the goaf treatment, reasonable arrangement of the injected holes, and reasonable grouting amount of the single injected hole.