Experimental Study On Aeolian Sand Paste Filling Material

Paste filling is an important part of coal mine green mining technology.Filling materials are the core of filling technology and are the main factors that determine filling quality,filling cost and filling effect.Based on the problems of serious waste of coal resources and surface subsidence caused by strip mining in Shanghe Coal Mine of Yulin City,a new type of paste-like filling material with aeolian sand as aggregate,fly ash and cement as binder is developed.The remaining coal pillars are mined by filling the goaf with the material.In this paper,we selected the aeolian sand in the Maowusu desert of Yuyang area,fly ash of coal-fired power plant and ordinary portland cement as experimental materials.Their micro-morphology and main components were analyzed by scanning electron microscope(SEM)and X-ray diffraction analysis(XRD).The results show that the surface of aeolian sand has many points and holes,with uniform particle size,good sortability,low compression ratio,and good compactability.Its main components is AI2O3 and SiO2;the surface of fly ash whose main components is SiO2,AI2O3,Fe2O3 is bead structure and porous;Chemical composition of ordinary portland cement(32.5#)is CaO,SiO2,Fe2O3,AI2O3.The factors affecting the pumpability of aeolian sand-like paste-filling pastes are mainly composed of the components of the paste slurry.By controlling a single variable,the slump,diffusion,and bleeding rate are tested at various levels.It is concluded that the mass concentration has the greatest effect on the pumpability of the paste slurry,followed by the cement and fly ash,and the aeolian sand has the smallest effect on the pumpability of the paste slurry.The factors affecting the strength of aeolian sand-like paste filling bodies mainly are the composition of paste-like filling materials and the curing time of test blocks.By controlling a single variable,a multi-level uniaxial compressive strength test was conducted.The influence of each factor on the strength of backfill is obtained.The greatest impact on backfill strength is the cement content,and the slurry concentration has a great influence on the early strength,and the fly ash content has a great influence on the later strength.Through the above experiments,the optimal pumping performance and mechanical properties of the aeolian sand-like paste filling materials were studied by multi-factor and multi-level optimization.The best ratio was obtained.Through the on-site filling test at No.3216 working face of Shanghe Coal Mine,it was not found that the aeolian sand-like slurry slurry had blocked pipe and pipe cracking during the pipeline pumping process.The filling surface worked well and the strength of the filling body was satisfactory.The design requirements have achieved good economic and social benefits.