Study On Mechanical Properties Of Superhigh-water-gangue Cement Backfill

In order to solve the problem of"three"coal pressing and promote the utilization of gangue solid waste,promote the safe and efficient green mining.As an important part of green mining system,backfill mining can effectively solve the problem of"three-down"coal mining to protect the ecological environment.This thesis studies a new type of filling material formed by the mixture of ultra-high water material as cementing material and gangue as aggregate.By combining laboratory experiments,theoretical analysis and numerical simulation,the optimal ratio of gangue and ultra-high water filling body is determined,and the mechanical properties and fracture evolution of the meso level of the filling body as well as the control effect of filling mining on overburden migration and surface subsidence are studied.Draw the following conclusions.（1）Laboratory uniaxial compression tests are carried out on gangue and ultra-high water filling materials with different particle sizes and gangue content,and the stress-strain curve and the variation law of uniaxial ultimate strength with gangue ratio are obtained.The ratio of filling body to gangue and gangue particle size are determined to be 1:3,and the ultimate strength of the single axis is the highest at 15～20mm.（2）The crack propagation of ultra-high water-gangue cemented filling in uniaxial compression process was monitored by acoustic emission test.The AE characteristics of mixed consolidated backfill are divided into four types:the first type is gentle stage-transition stage-steep increase stage,the second type is gentle stage-steep increase stage,the third type is steep stage-gentle stage-steep increase stage,and the fourth type has a steady increase in the cumulative ringing times during the whole uniaxial compression process.The AE characteristics of mixed cemented backfill are obviously different from those of brittle materials.The sharp increase of acoustic signal occurs in the residual strength stage of stress-strain curve.（3）By using PFC^2D numerical simulation software,the parallel bond model and rigid cluster were selected to simulate uniaxial and biaxial compression tests of ultra-high water-gangue cemented filling body respectively,and the stress-strain curve and crack evolution law were obtained.Under biaxial compression,the stress-strain curve will show periodic changes with the failure-reconstruction of gangue structure.Compared with gangue with large and small grain sizes,the crack growth rate of filling body is slow under uniaxial compression.Failure characteristics of mixed cemented backfill in numerical simulation of uniaxial compression can be divided into three categories:"X"conjugate shear failure,single inclined plane shear failure and multi-inclined plane shear failure.（4）FLAC^3D numerical simulation software was used to simulate the control effect of gangue-ultra-high water cement filling mining on overburden migration and surface movement.With the progress of filling mining,the subsidence of direct roof,basic roof and surface gradually increases and eventually tends to be stable.The maximum subsidence eventually tends to be 82.78,82.72 and 79.30 mm.The maximum horizontal movement,inclined deformation and horizontal deformation are 16.53 mm,3.57 mm/m and 0.93 mm/m,respectively.The damage of surface buildings is basically in theⅠdamage range.（5）The elastic modulus of gangue-ultra-high water material cemented backfill was used to define the damage variable of the backfill,and the piecewise damage constitutive equation of mixed cemented backfill with different gangue contents under uniaxial compression was established and verified.Based on the damage evolution constitutive equation of mixed cemented backfill and the mechanical criterion of energy absorption and release of mixed cemented backfill,the energy evolution law of the backfill in the numerical simulation of gangue-ultra-high water cemented backfill was obtained.There are 51 figures,23 tables and 89 references in this thesis.