Crushed Rock Filling For Tight Roof Control Mechanism

Hard roof is common in coal mines.It is typically characterized with high rock strength,large overhanging area and high bearing capacity,therefore,it is generally hard to be controlled.Rock burst,cola-gas outburst,goaf hurricane and many other dynamic hazards could be easily induced when mining in such roof condition,which cause a serious impact on mine production safety.As a green mining technology,in recent years,solid backfill mining technique achieves better results in mining “three under coal”.Theory and practice have proved that,it can effectively control the strata movement and deformation,as well as weaken the strata behavior.In this dissertation,solid mining backfill is used to study the control of backfill mining technique on the hard roof dynamic hazards by intergrated methods of theoretical analysis,laboratory test,numberical simulation.Characteristic energy dissipation of solid backfill material is tested and evolution of the hard roof deformation energy characteristics and prevention methods are analyzed;the interrelation between backfill body and hard roof,energy variation control,hazard prevention,roof deformation and energy distribution rules under different roof-controlled backfilling ratios in the backfill workface are systematically studied.The dissertation also gives the simulation of solid backfill mining by FLAC3D numerical simulation software.The main achievements are as follows:Through laboratory tests on the characteristic energy dissipation of solid backfill material to obtain the relationship between particle size,loading velocity and initial loading stress on the energy dissipation characteristics.The energy variation in compaction process may be clarified into three stages: slow dissipation stage,speed-up dissipation stage and rapid dissipation stage.This dissertation reveals energy evolution rules during the roof deformation and the causes of dynamic hazards,and the process of energy accumulating,transforming and releasing from the first exposure of hard roof to breaking down,reducing the accumulation and release of energy is found to be key factor to prevent dynamic hazards.Based upon the hard roof deformation of solid backfill mining,this dissertation establishes a non-uniform segmented model of a beam on elastic foundation,the equations of energy distribution and releasing before and after the hard roof breaking down are given.The interaction between the backfilling body and the roof of under different backfilling ratios is studied by changing the elastic foundation coefficient.The effect of backfilling on deformation of hard roof and energy variation in workforce are analyzed.Using FLAC3D numerical simulation software,the stress and energy distribution is surrounding rock mass under different roof-controlled backfilling ratios are analyzed.This dissertation develops a method of preventing hard roof dynamic hazards by solid backfill mining,which Optimizes backfill mining system.