EXPERIMENTAL STUDY ON DISTRIBUTION LAW OF RESIDUAL FISSURES IN OVERLYING STRATUM UNDER MULTIPLE SEAM MINING

The developmental state of residual fissures in goaf is an important factor in the design of goaf filling and grouting. Under the conditions of multiple seam mining,this paper discusses the distribution of residual fissures in overlying stratum by means of simulated experiment of similar materials. The test results show that after the end of mining the distribution of residual fissures in goaf has obvious characteristics in different zones. From both sides to the middle of goaf,it can be divided into three zones: residual fissure zone,fissure compacted zone,and surface tensile fissure zone. The fissure rate of residual fissure zone generally varies from 19.54% to 45.27% while the fissure rate of fissure compacted zone varies from 9.28% to 19.33%. The developmental height of separated strata 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 construction site on the goaf,determining the range and depth of goaf management,reasonable arrangement of injected hole,as well as reasonable computation of grouting amount for single injected hole．