Stability Analysis and Monitoring Method for the Key Block Structure of the Basic Roof of Noncoal Pillar Mining with Automatically Formed Gob-Side Entry

Abstract

Thekeyblockofthebasicroofisthemaincontributortothestructuralstabilityofaroadway.Researchonthestabilityofthekey block structure is of great significance for the promotion of noncoal pillar mining with automatically formed gob-side entry (GEFANM)technology.ThispaperissetintheengineeringcontextoftheGEFANMexperimentattheNingtiaotaCoalMine.The study fully considered the differences in the gob roof caving on the roof-cutting-line side, and the range of rotation angles to maintainastablekeyblockwasdetermined.Basedonthisrangeofrotationangles,therangeofsafebulkingcoefficientsofgangue wascalculated.Thebulkingcoefficientofthegangueonthegravelsideoftheroadwaywasusedasthemetricinanewmonitoring methodandinthecalculationofthefieldparameters.Therangeofsafebulkingcoefficientswasdeterminedtobe1.40–1.37.Field monitoringwasconductedtoobtaintheganguebulkingcoefficientonthegravelside.Combiningtheroofandfloorconvergence data,whenthebulkingcoefficientfellwithinthesaferange,theconvergencewas95–113mm.Inthisstage,thekeyblockstructure wasstable.Whentheganguebulkingcoefficientfelloutsidethesaferange,theconvergencewaslarger,andcrackswereobserved. Thekeyblockmaybevulnerabletoinstability.Theresultsaffirmedthattheganguebulkingcoefficientcanbeusedasamonitoring metric to study the stability of key block structures.