Study On Physical And Mechanical Properties Of High Sand And High Foam Cement-based Filling Material

Filling mining can effectively alleviate the waste of abandoned resources and surface subsidence caused by mining process,which is one of the important means to achieve green mining in mines.Research and development and application of filling materials is a hot issue in mining industry.In this paper,the natural sand,which is widely distributed on the northwest surface,is used as aggregate.It is mixed with ordinary portland cement,micro silica fume and other gel materials,and mixed with foam made of composite foaming agent.Cement filled backfill material with high sand and high foam is prepared.The fluidity,thixotropy,micro-pore characteristics and mechanical properties of slurry are systematically studied.The main research results are as follows:(1)Combining with the characteristics of the filling material,the physical and chemical properties of the main raw materials such as natural sand,cement and micro silicon powder were studied.The hydration process of the gel material was analyzed.The advantages of HTQ-1 composite foaming agent in physical foaming were mastered,and the formation and failure mechanism of the foam were revealed.According to the strength principle of the material,a reasonable range of material proportioning was calculated.Based on Bingham fluid theory,the rheological properties and thixotropic properties of the foamed slurry were studied.The calculation models of yield stress,viscosity coefficient,shear rate and shear stress were established.The setting time and influencing factors of foamed slurry were determined.The factors affecting the rheological characteristics of slurry were determined.The increase of water binder ratio increased the free water content and diluted the gel material.The flocculation structure reduces the friction resistance of aggregate particles and their friction,reduces thixotropy and increases rheological properties.The addition of smooth foam can enhance slurry fluidity.(2)The pore formation mechanism of material consolidation was studied,the preparation of filling material was expounded,and the pore characteristics of material consolidation and its influencing factors were analyzed.With the increase of sand binder ratio,the porosity,average pore size,pore size variance and roundness of the consolidation body increased.The ratio of sand to cement had a more significant effect on the pore characteristics of the larger foam samples.When the water binder ratio was 0.6,the pores formed were more uniform;when the mixing time and the stirring rate increased,the average pore size,variance and pore size of the consolidated body could be reduced.(3)The mechanical properties of cementitious filling materials with high sand and foam were studied.The influencing factors of strength and the failure characteristics of the cementitious filling materials were analyzed.The increase of sand binder ratio decreases the strength of the consolidation body and reduces the brittleness of the consolidation body.The strength of the specimen with 800 kg/m3 and 1000 kg/m3 density of the matrix decreases by 35.4%,57.8% and 53.1% respectively.The ratio of sand to cement has a more significant effect on the mechanical properties of the larger foam sample.The alkaline environment can enhance the strength of the consolidation body,and the corrosion of the acidic environment consolidation body is stronger,which can reduce the material strength.(4)The numerical analysis of filling effect of high-sand and high-foam cement-based filling material shows that the stress distribution of roadway surrounding rock can be improved and the deformation of roadway surrounding rock can be effectively controlled by goaf filling.The industrial test with this material has been carried out to verify the effectiveness of filling effect.The research results can provide reference for the application of high sand and high foam cement-based filling materials and safe,efficient and green mining in mines.