Mechanical Response Analysis On Granular Backfill Material Under Tamping Device

With the development of solid backfilling mining technology and application in the country,backfilling materials showed a trend of diversification,for example the aerolian sand,loess,gangue,fly ash and slag have been used as backfilling materials.Although they come from different places and their characteristics are unique,they all belong to granular materials.Based on the study of the mechanical properties of granular materials,the theoretical basis for improving backfilling mining effect has been established.This thesis focuses on the basic characteristics of granular materials and introduces the Discrete Element Method(DEM)to study the mechanical response of granular materials by numerical simulation.The EDEM software is chosen to carry out the tamping process in the gob to study the mechanical response of the granular backfilling material.The numerical simulation parameters are carlibrated from laboratory testing to reducing the errors.The results are as follows:(1)The restitutuion coefficient,dynamic friction coefficient and static friction coefficient have vital influences on the mechanical response of granular materials.However,due to the complex shapes of the granular material,there is only a low chance to obtain the parameters through laboratory experiments.Thus,it is necessary to carry out the numerical simulation parameter calibration.In the virtual test of gangue cylinder compaction test,the intrinsic parameters of gangue particles are obtained: The Poisson's ratio is 0.19,the density is 2670kg/m3,and elastic modulus of 15 GPa.In the virtual test of repose angle,it is concluded that the coefficient of restitution is 0.15,the static friction coefficient is 0.44,and the dynamic friction coefficient is 0.05.(2)As the angle of the tamping device increases continuously,the gap between the roof and the backfilling material will decreas first and then increase.When the tamping angle is 22°and 27°,the average dense degrees of backfilling materials are close and they are both larger than the dense degree of 32°.Therefore,during the process of tamping,the tamping head should bury into the backfilling pile so that the tamping head can work at the best condition.In the meantime,the tamping angle should not be too large,which will improve the tamping efficiency and effect.(3)As the particle sizes of the granular materials increase,the gap between the roof and the backfilling material will also increase,while the average dense degree will decrease.Besides,when the particle size distributions are small and medium,the average dense degrees are very close.So when preparing the backfilling materials in the coal mine,it is suggestesd to crack the gangue particles into medium size to increase the crack efficiency ad lower the cost.(4)With the increase of the tamping speed,the gap between the roof and the backfilling material shows a trend of linear increasing.While the dense degree behind the tamping device decreases slightly,which means that the tamping speed has a little influence o the dense degrees.Therefore,the tamping speed can be lowered to certain values to reduce the hydraulic pressure.