Mechanical Behaviour Of Gangue Backfill Material And Control Mechanism Of Strata Movement

Essentially,gangue backfill material is a non-continuum,under the effects of the stress of tamping system and pressure of overlying strata,gangue blocks will rotate,slip,occlude and break.The compaction deformation properties of backfill bodies should consider the influence of the main control factors such as gangue lithology,particle size grading and tamping stress,so as to provide a basis for the in-depth study of the strata movement mechanism controlled by gangue backfill materials.In this dissertation,based on the main control factors which affect the compaction deformation of the backfill bodies,a biaxial loading testing system for the granular backfill materials was developed,and based on comprehensive use of research methods such as theoretical analysis,experimental testing,numerical simulation,engineering practice,etc,the instantaneous and creep compaction properties of the gangue backfill materials were tested,the instantaneous compaction constitutive equation and creep compaction NMK constitutive model of gangue backfill materials subjected to multiple factors were constructed.In addition,the structural morphological evolution characteristics of compaction deformation of gangue backfill particles were analyzed,and the mesoscopic mechanisms of compaction deformation of gangue backfill materials were revealed.Moreover,the mechanical model of roof subsidence controlled by gangue backfill materials was constructed,and the mechanisms of strata movement controlled by backfill bodies were revealed.Then,a backfill mining design method of gangue materials was proposed.The following are the main innovative results achieved:(1)A testing method for the compaction mechanical properties of granular backfill materials was proposed,and a biaxial loading testing system for granular backfill materials was developed.Based on it,the relationships between four main control factors including lithology,particle size grading,lateral stress and lateral pressure times and the instantaneous compaction properties of gangue backfill materials were determined by experimental testing.Then,the constitutive equation of the instantaneous compaction deformation of gangue backfill materials subject to multiple factors was constructed.(2)The creep compaction properties of gangue backfill materials with different loading stress levels were tested,and the fractional creep compaction NMK constitutive model of gangue backfill materials was established.Then,three-dimensional creep equation of NMK constitutive model was deduced,and the parameters for NMK constitutive model was identified.Finally,the secondary development of creep compaction NMK constitutive model was realized.(3)The boundary contour properties of gangue blocks were analyzed,and a random generation method of gangue blocks was put forward.Moreover,the compaction deformation characteristics,the clump distribution and the structural morphological evolution characteristics of compaction deformation of gangue backfill particles were analyzed.Then,the mesoscopic mechanisms of compaction deformation of gangue backfill materials were revealed.(4)The mechanical model of roof subsidence controlled by gangue backfill materials was established,and the roof subsidence laws affected by main control factors were analyzed.Then,the mechanisms of strata movement controlled by backfill bodies were revealed.Meanwhile,a backfill mining design method of gangue materials was proposed and which has been analyzed in detail by the engineering case.Finally,the rationality of research results was validated.