Abstract: Waterandsandinrushisoneoftheprincipalfactorsthatrestrictsafeandeffectiveproduction ofminingunderwaterbody.Thethreattosoftstratamineswithextremelythickcoalseamisespecially moreserious.Cavingzoneandfissurezone(jointname“two-zone”)heightsarethebasicparametersof waterinrush prediction.This paper observes the “two-zone” heights of extra-thick coal seam with slicingfull-mechanized caving mining in soft stratum with comprehensive measures of flushing fluid leakage,colorboreholeTVandcore-drilling,andresearchesthefracturefieldcharacteristicsofoverburdenfailurethroughdiscreteelementnumericalmethod.Theresearchresultsareasfollows:underthe
conditionofextra-thickcoalseamwithslicingfull-mechanizedcavingmininginsoftstratum,thestratum movementangleoftopslicingworkingfaceisabout75°,theratiois5.60~5.62betweencavingzoneand miningheight,theratiois11.67~12.20betweenfissurezoneandminingheight;theratiois 4.59~4.71 betweencavingzoneandminingheight,theratiois8.04~8.58betweenfissurezoneandminingheight inthebottomslicingworkingface;theheightofcavingzoneincreasesby49.41% ~50.85% andthe heightoffissurezoneincreasesby21.72% ~25.38%,butthe　 ratiobetweencavingzoneandmining heightdecreasesby16.19% ~18.33%,theratiobetweenfissurezoneandminingheightdecreasesby 29.67% ~34.10% whentheminingheightofthebottomworkingfaceis78.28% ~84.71% ofthetop workingface.Theresearchresultscanprovidereferenceforwaterdamagepredictionandtheheightof safetycoalandrockpillarinslicingfull-mechanizedcavingminingfaceunderlooseaquifer.