Mechanical Characteristics of Backfill Under True Triaxial Compression and Unloading Conditions
For mines that adopt the filling mining method,the backfill is an important component of the underground stope.During the filling mining process of the first mining room and the pillars to be extracted after filling is completed,the backfill is disturbed and unloaded by the original geological stress and the excavation of the ore body.Based on the stress variation path during the filling mining process,the true triaxial compression and unloading experiments on backfill were carried out,the instability failure process and acoustic emission response characteristics of backfill were analyzed,and the mechanical properties of backfill were studied.The results are concluded as follows.Firstly,under true triaxial compression conditions,the failure mode of the backfill specimens is mainly tensile failure,exhibiting better elasticity.The peak strength and elastic modulus increase with the increase of curing time and confining pressure.Secondly,under unidirectional unloading conditions,the peak strength of the backfill specimens decreases by about 17.74％compared to the peak strength under true triaxial compression conditions.The peak strength increases with the increase of confining pressure,the elastic modulus decreases with the increase of confining pressure,and the Poisson's ratio firstly increases and then decreases with the increase of confining pressure.Thirdly,under bidirectional unloading conditions,the backfill specimens rapidly lose stability and fail,with a peak strength decrease of about 17.76％compared to the peak strength under true triaxial compression conditions.The peak strength,elastic modulus,and Poisson's ratio of the backfill specimens all increase with the increase of confining pressure.Finally,the backfill specimens undergo greater deformation and lower failure strength under bidirectional unloading conditions than under unidirectional unloading conditions.
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维普
