破碎矸石侧限承载条件下的宏-细观尺寸效应研究

Study on Macro-Micro Size Effect of Broken Gangue Under Confined Load Condition

矸石充填体在承压过程中力学性能受充填体尺寸的影响较大,实验室力学参数测试结果很难反映工程实际情况。为研究破碎矸石充填体侧限承压条件下的力学性能尺寸效应,借助实验室试验和颗粒流数值模拟,从宏-细观尺度分析了破碎矸石试件的直径与径高比对其承载性能的影响。结果表明:试件直径对其宏观力学性能影响显著,随着试件直径增大其抗变形能力明显减弱;破碎矸石的孔隙率变化量随试件直径增大而增加;其压缩过程中试件两侧的矸石块发生挤压破碎,细颗粒逐步填充至试件中部,颗粒配位数随试件的可变形空间增加而增大;在应力加载阶段,颗粒逐渐破碎,颗粒力链由“环状力链”演化为“柱状力链”,平均接触力变化率表明体积大的试件更易达到抗压缩变形能力极限;矸石试件主要以拉伸破坏为主,矸石块的破碎程度随试件尺寸增加而增大。研究成果对矿山充填开采的充填物料选择具有重要意义。

The mechanical properties of gangue backfill are greatly affected by the size of the backfill during the pressure bearing process,and the mechanical parameter testing results in laboratory are difficult to reflect the actual engineering situation.In order to study the size effect of mechanical properties of broken gangue backfill under confined pressure,laboratory tests and grain flow numerical simulation were used to analyze the influences of diameter and diameter-height ratio of broken gangue specimens on its bearing capacity from macro-meso scale.The results are concluded as follows.Firstly,the diameter of the specimen has a significant impact on its macroscopic mechanical properties,and its deformation resistance decreases significantly with the increase of the specimen diameter.Secondly,the change in porosity of broken gangue increases with the increase of specimen diameter.Thirdly,during compression,the gangue blocks on both sides of the specimen are crushed,and the fine particles are gradually filled into the middle of the specimen.The coordination number of particles increases with the increase of the deformable space of the specimen.Fourthly,in the stress loading stage,the particles gradually break up,and the particle force chain evolves from a‘ring force chain’to a‘column force chain’.The average change rate of contact force indicates that the larger the specimen is,the easier it is to reach the limit of compression deformation resistance.Finally,the gangue specimens are mainly subjected to tensile failure,and the degree of fragmentation of the gangue blocks increases with the increase of specimen size.The research results are of great significance for the selection of filling materials in backfill mining.