Experimental Study On Modified Property Of Coal Mine Filling Material With Different Admixtures

The property of filling materials is the key of material filling technology.The method of coal filling put forward many requirements on filling materials in working properties,mechanical properties,deformation properties and pumping properties.While the existing research results and the field application shows that most of coal mining appears the problem of shortage of raw materials if full mining according full filling.The stripe filling or structure filling can save raw materials,but they put forward new requirements on the performance of the filling material.This paper is focused on the special requirements of material filling material in the coal filling mining technology,taking optimization design and making test with different kinds of the additive in its rheology,water bleeding,compressive strength and shrinkage to explore the effect of admixture on filling material.And different boundary conditions are studied to reveal their influences on pipeline pressure loss of filling material by using numerical simulation.Using different testing methods of filling material to optimize its performance based on the combination between macro and micro.Macro aspect,making slump test and rheology test to evaluate the rheology of filling material.The water-reducing effect of water reducer was investigated according to the bleeding rate test.Compressive strength and drying shrinkage were taken test to measure cube compressive strength and dry shrinkage under different age of filling material with different admixtures.Microcosmic aspect,thermal field emission scanning electron microscopy(FEXEM)was used to observe 28 d microstructure of the specimens with different water reducer,the impact on the mechanical behavior of macroeconomic as the change of microstructure was explored with different water reducer.28 d mainly hydration products of the specimen with different water reducer were identified by spectrum analysis method.Hydration products of 28 d specimens were respectively analyzed by X-ray diffraction(XRD)technology only mixed water reducing agent,early strength agent and expansion agent,and reddish-brown powder material at the interface of racking specimen was analyzed as well.Combining fluid mechanics,rock mechanics and the theory of surface chemistry knowledge,comparing test in the process of research to analyz and discuss the results.Results showed that the water reducer could effectively improve the mass concentration and different age(especially the early)compressive strength of material,could improve the material rheology,could decrease bleeding water.There were more obviously effects of poly carboxylic acid water reducer than naphthalene series water reducer at the same cost,and was more environmentive.Using Early strength agent only Na2SO4,Ca(OH)2 respectively or mixed were not ideal for early strength of material material,the effect of Na2SO4 is obvious relatively among them.Using early strength agent only MgO or Ca(OH)2 respectively,making rheology abate,and the compressive strength had no obvious improvement.Not only no reduction effect,drying shrinkage had increased on the contrary,but its rate was less than 0.2%.Combining calculation fluid dynamics(CFD)software FLUENT on the numerical simulation for the pipeline pressure loss of material filling in coal mines under different parameters,using the rheological theory combined with rheological parameters(plastic viscosity)to study the water reducer on the impact of filling material pumping,discussing the effects of other different parameters on the pumping properties of filling material during pipeline pressurization process.The results showed that the pipeline pressure loss was bigger with the bigger inlet velocity.The pressure loss increased almost exponentially with the higher slurry viscosity.The change role of filling material pressure loss in bend and straight pipe with the various parameters were basically same,but the pressure loss was bigger in the curved pipe.Geometry of pipe greatly influenced the distribution of velocity field and density field when the material was pumping,density increasesd and speed reduced in the bend pipe.Through these research,the performance of the optimized coal mine filling material the reasonable range had beed summarized.