Mechanical model of rock strata continuous bending movement under non-uniform load in backfill mining

In order to control the overburden continuous movement through gob filling and protect the ecosystemin the mining area,the “four zones” of the overburden movement of the filling mining are proposed:the backfill compression zone,the continuous subsidence zone,the key strata bearing zone and the ecological protection zone.The experiment has studied the compressive mechanical properties of gangue and fly ash with different ratios(2∶1,3∶1,4∶1,5∶1,6∶1),and the "stress-strain" relationship of the filling body is approximately Parabolic relationship.In the initial stage of compression (0～2 MPa),the backfill deforms rapidly,and in the later stage (>6 MPa),the deformation increases slowly,which indicates the initial compaction of the backfill plays an important role in controlling the deformation of the rock formation.The compression deformation resistance is the best when the proportion of gangue and fly ash is 4∶1.The key layer load-bearing protection mechanism of stress reduction and the linear recovery behind the working face is analyzed.The key layer load-bearing protection mechanism of stress reduction and the linear recovery behind the working face is analyzed.Based on the compression characteristics of the filling body and the non-uniform distribution of the stress behind the working face,the continuous bending mechanical model of the filling roof rock under the action of non-uniformly distributed load was established,and the mechanical conditions of the continuous bending deformation of the filling mining roof rock layer were obtained,andthe accurate judgment of the continuous bending movement of the roof in filling mining was realized.Numerical simulation analyzes the movement law of the overlying strata at different filling rates and it is known that when the filling rate is greater than 90%,the roof strata approximately undergoes continuous deformation and movement,and the simulation results of the direct roof and the maximum surface subsidence are very close to the theoretical predictions.