Study on deformation and failure characteristics of overlying strata with thick loose layers and thin bedrock based on Hoek-Brown criterion

ThemechanicsparametersofrockmassinWulanmulunminearedeterminedonthebasisof theexperimentaldatameasuredinthelaboratoryandappliedHoek-Browncriterioninthispaper.On thisbasis the failure characteristics of overlying strata caused by coal mining are studied through FLAC3Dsimulationsoftware.Theresearchresultsshowthat:①Theoverlyingstrataundershallowburial depth until surface has been destroyed, and the skewness subsidence basin is formed on the
surface.Themaximumsubsidenceis2.1m,andthesubsidencerateis0.6.②Thestress-relaxedarea andthestress-increasedareaareformedinacertainrangeofthesurroundingboundaryofthemining area.Thestatepresents“externaltightinternalloosing”.Thedegreeofverticalstressconcentrationin frontofcoalwallisthehighest,andthestressconcentrationfactoris2.2.Thereisapressurearchseparatelyabovethecoalwallandtheopen-offcut,butthespan,thesizeofthearchfootandthedegree ofstressconcentrationaredifferent.③Theheightofthecavingzoneis18.9m,andtheheightofwater flowingfracturedzoneis62.5mof12403faceinWulanmuluncoalmine.