Study On The Damage Evolution Law Of The Filling Body In The Wide Scale Of Fine Macro Instability

As a kind of heterogeneous composite material,there are a lot of initial micro cracks in the filling body.The distribution and content of these initial damages determine the macroscopic mechanical properties of the filling body.In the past,the research on the failure mechanism of backfill mainly focused on the single scale of macro or micro,and ignored the internal initial damage,so it is difficult to reveal the evolution rule of internal damage from micro scale to macro scale.Based on this,through the macro mechanical test and micro pore distribution test,the corresponding numerical simulation is carried out to study the whole process of damage cross-scale evolution leading by micro crack growth in the filling body,and reveal the damage evolution law in the process of filling body instability.The specific research results are as follows:1)Carry out the uniaxial acoustic emission test of filling body with different ash sand ratio.By using the method of time-frequency analysis,the precursory information of the failure of filling body is explored.Before the peak stress,the low frequency signal decreases,and the high and medium frequency signals increase,which can be used as the precursor information of the filling failure.2)Based on the distribution characteristics of acoustic emission parameters(RA,AF)in the process of loading,the macroscopic failure forms of filling body with different ash sand ratio are revealed.The tensile failure occurs first and then the shear failure occurs in the 1:6 filling body,with the same proportion;the tensile failure is the main failure mode of the 1:10 filling body,supplemented by the shear failure;the tensile failure occurs in the whole process of the 1:15 filling body.3)By carrying out the experiment of filling resin with different ash sand ratio,the thin section of the casting was analyzed by microscope.The average pore diameter and face ratio of the filling body with different lime sand ratio decreased first and then increased,and both of them reached the minimum value in the compaction stage.4)Based on the results of the micro analysis of the filling casting slice,the heterogeneous model with the initial damage was established with porosity as the initial damage variable,and the micro numerical simulation was carried out.With the increase of porosity,the peak stress of the same ash sand ratio filling body decreased.The peak stress of the three filling body specimens with 1:6 porosity of 7%,9% and 11% was 2.8MPa,2.6MPa and 2.4Mpa respectively.Figure60;Table10;Reference 82...