Experimental Study On Mechanical Properties Of Different Grade Paste Filling Bodies Of Coal Gangue

Based on the mining and filling of Sima Coal mine as the background,this paper adopts mechanical test and acoustic emission detection methods to explore the influence law and energy evolution law of the three influencing factors,the dosage of each filling material in Sima,the loading rate selected in the test process and the coal gangue grading in the filling material on the physical characteristics,failure characteristics,acoustic emission ringing count of paste filling.In addition,FLAC^3Dsoftware was used to conduct numerical modeling based on actual mining hydrogeology,and the influence law of filling step distance and advancing distance of working face on surface movement and deformation was analyzed when paste filling body with optimized ratio and grading was used for filling.The main research methods and results are as follows:（1）The control variable method was used to design the dosage of each filling material,and mechanical tests were conducted on standard cylindrical specimens made according to the designed ratio scheme to analyze the influence law of the dosage of each filling material on the physical characteristics of paste filling;Slump and bleeding rate were tested with the same ratio scheme.The results show that increasing the mass concentration and the amount of coal gangue,fly ash,cement and admixture can effectively improve the compressive performance of backfill,but the amount of fly ash can not be increased without limit.When the amount of fly ash reaches400kg/m³,the compressive strength of backfill will be reduced.Increasing the mass concentration and the content of coal gangue and admixture,reducing the content of fly ash and cement will reduce the slump of filling body;Increasing the mass concentration and the dosage of each filling material will reduce the bleeding rate.Considering the test results of compressive strength,slump and bleed rate of filling body,coal gangue:fly ash:cement:water:admixture=2.75:1:0.25:1:0.01 is finally selected as the filling ratio scheme of Sima Coal mine.（2）The Taibo theory was introduced into Sima filling ratio scheme to design the gradation of coal gangue in filling materials,and the mechanical properties of filling specimens under five different loading rates after gradation design were analyzed.The results show that with the increase of loading rate,the compressive strength and elastic modulus of each grade of backfill have a linear increase trend.With the increasing decline coefficient of intermediate distribution of Taibo theory,the compressive strength and elastic modulus of backfill at each loading rate increase first and then decrease.When the decline coefficient of gradation is 0.5,the compressive performance of backfill is the best.By fitting the test data,the expressions of the loading rate,the gradation decline coefficient and the relationship between them and the compressive strength and elastic modulus of the filling body were obtained.（3）Failure characteristics of paste filling body were analyzed according to loading rate and coal gangue grade.The results show that with the increase of loading rate,the filling body mainly reflects the change of failure form,which evolves from tensile failure to shear failure.With the increasing of the gradation decline coefficient,the filling body is mainly reflected in the change of failure degree,which evolves from small crack to long crack.（4）The acoustic emission detection system was introduced into the uniaxial compression test system to analyze the damage evolution process of paste backfill through the acoustic emission collection and cumulative ringing count.The results show that with the increase of loading rate,the acoustic emission ringing count decreases linearly,and the crack initiation and damage stress of filling body increase linearly.The cumulative acoustic emission ringing count,crack initiation and damage stress of backfill increased first and then decreased with the increase of gradation decreasing coefficient.By fitting the test data,the relationship expressions of loading rate and gradation decline coefficient with acoustic emission cumulative ringing count,crack initiation and damage stress of filling body were obtained.（5）The evolution law of total strain energy,elastic strain energy and dissipated energy of paste filling body was analyzed by energy calculation principle.The results show that with the increasing of the loading rate,the filling energy volume presents a nearly linear increasing trend.With the increasing of the gradation decreasing coefficient,the filling energy increased first and then decreased.By fitting the data,the expressions of the relationship between the loading rate and the gradation decline coefficient and the filling energy were obtained.When the ratio of elastic energy to dissipated energy is close to 0.5,the filling body will fail and become unstable.（6）FLAC^3Dmodeling was used to analyze the surface movement and deformation law of Sima Coal Mine.The results show that the surface movement and deformation increase with the increase of filling step distance and the advance of working face,but the increment of surface movement and deformation decreases continuously.Origin software was used to fit the monitoring data,and the expression of the relationship between filling step distance and advancing distance of working face and surface movement and deformation was obtained.This paper has 73 figures,20 tables and 72 references.