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

Filling mining can effectively relieve safety and environmental problems caused by coal mining,which is one of the main technical ways of green coal mining.Filling materials and their mechanical properties have an important impact on reducing costs,improving technology and expanding are the application range of filling mining,which is one of the hot issues concerned and studied by the coal industry.In this paper,natural sand(soil),which is widely distributed in the west of China,is mixed with cement,silica fume and other cementitious materials to form slurry.After the foam is added,it is made into High sand high foam cement-based filling material(HSHFCFM).The systematic research is carried out on the strength and evolution characteristics of materials,the engineering mechanics characteristics of consolidation,the slurry pipeline transportation characteristics and the partial filling test of the top goaf of roadway.The main results are as follows:(1)Combined with the characteristics of high sand,low glue and high foam of Cement-based Filling Material,the mechanism of material formation was revealed,and the influence of sand cement ratio and foam addition on the strength and evolution characteristics of consolidation body was clarified.The strength and matrix strength,porosity and pore size parameters(equivalent mean pore size and variance)of consolidation material were defined.Based on the empirical formula of concrete material Ryshkewitch strength,a formula for calculating the strength of the consolidated body of the material is proposed.(2)The engineering mechanical properties of HSHFCFM were studied.The influence of particle size and dosage of gangue on the strength of HSHFCFM consolidating body was mastered.The strength change characteristics and mechanism of cement body under water immersion and corrosion environment were elucidated.The size effect of HSHFCFM consolidation strength is revealed,and the strength of three kinds of density class large filling consolidation body of 1000 kg/m~3,1200 kg/m~3and 1400 kg/m~3 was quantified.(3)The pipeline transportation characteristics of High sand high foam cement-based filling slurry(HSHFCFS)with different transport distance are expounded.Based on the rheological model of Bingham fluid,a calculation model of rheological parameters of HSHFCFS,such as yield stress and plastic viscosity,has been established.The volume loss test system for foamed slurry has been established.The foam loss of typical mixture(water binder ratio 0.6,sand cement ratio 3.5,micro silica powder ratio10%,aggregate fine sand II)has been obtained.A formula for determining the parameters of pipeline transportation system is proposed.(4)Based on the roof structure,roadway surrounding rock and bearing characteristics of the abandoned resources mining face in thick coal seam,and according to the requirements of cushioning roof dynamic load by filling cushion,the relevant technical parameters of filling body are determined,the underground pulping and pipeline transportation system is constructed,and the filling test of cement-based foam material is carried out.The stability and effectiveness of HSHFCFM are verified by borehole detection and field sampling.The research results can provide theoretical basis for the design of related technical parameters of cement-based foam filling materials in the application of coal mine underground filling,and have important reference significance for realizing coal mine safety and green mining.