Study On Mechanical Characteristics Of Filling Body In Goaf And Overburden Movement Law Under The Action Of Mine Water Erosion

Paste filling mining is an important means to improve the safety of mine production.Due to the influence of ground stress,groundwater erosion and mining disturbance,it has destroyed the original mechanical balance of overburden,formed a large number of cracks,and caused groundwater to enter the goaf,which is very easy to change the mechanical characteristics of the filling body,affecting the stability of the goaf and the safety of the mining area,Therefore,it is particularly important to carry out the mechanical property test and stability analysis of backfill under the action of mine water erosion for the safety of practical projects.Based on on-site sampling,indoor proportioning experiment,triaxial compression test and FLAC 3D numerical simulation,taking the filling mining in the South No.2 mining area of Xima Coal Mine in Liaoning Province as the engineering background,this paper analyzes the influence of different raw materials on the performance of the filling body,determines the optimal proportioning of the paste filling body,and studies the changes of mechanical properties of the filling body under different confining pressure levels,different corrosion ages,and different acid and alkali environments,The law of damage and deterioration of filling body under the action of mine water erosion is revealed,and the stability analysis of overlying strata and the law of surface deformation of filling body under different mining depths under the action of mine water erosion are proved.The main research results are as follows:(1)Based on the principle of mix proportion,determine the test raw materials.Through the performance test of backfill under different mix proportions,it is concluded that both fly ash and cement can improve its workability,but there is a threshold for fly ash to improve the compressive strength;The coal gangue can improve the compressive strength of the filling body but reduce the fluidity.The proper addition of water can improve the strength within a certain range.Finally,the optimal mix proportion is determined as follows: gangue: fly ash: cement: water=fly ash: cement:gangue: water=0.875:0.263:2.5:1,and the admixture accounts for 0.22% of the total mass.(2)Taking the filling material with the optimal mix ratio as the research object,through the uniaxial compression test under different acid-base properties and immersion time,the quality,wave velocity and strength deterioration law of the filling body under the corrosion effect is explored.Its mechanism is that the corrosion promotes the hydration reaction and dissolution reaction as acid>alkaline>neutral,and the stronger the acid(alkali)property,the more intense the reaction.(3)Through triaxial compression tests of backfill under different confining pressure levels,corrosion ages and acid-base environments,it is concluded that confining pressure levels can improve the ability of backfill to resist deformation and weaken the ability to resist elastic deformation;The plastic deformation,softening deformation,peak strength and residual strength increased first and then decreased with the increase of corrosion age;Acid erosion can increase the peak strength and residual strength of backfill,while alkaline erosion can increase the peak strength and reduce the residual strength of backfill.(4)Based on the triaxial compression test results of the backfill,the damage factor is introduced to determine the relationship equations between the compressive strength and the confining pressure level,the corrosion age,and the acid-base property respectively.The strength damage equation of the backfill under the combined erosion of the three factors is comprehensively established,and the rationality of the strength damage equation is verified by comparing the test value with the fitting value.(5)Combined with the engineering practice,the numerical models under different mining depths are established,and it is found that the maximum subsidence value and horizontal displacement of the ground surface increase first and then decrease with the mining depth.Through the numerical simulation of different filling body properties under the same opening depth,the stability of the overlying strata of the filling body under the action of mine water erosion and the law of surface deformation are explored,indicating that the surface control degree tends to a stable value after the filling body strength decreases to a certain extent.