级配破碎煤岩体压实过程中再破碎特征研究

Re-crushing characteristics in the compaction process of graded crushed coal rock mass

为研究承压破碎煤岩体压实与再破碎特征,根据破碎煤岩体的力学特征与孔隙结构的稳定性将破碎煤岩体的压实变形过程分为塑性失稳、应力恢复与类原岩应力3个阶段,再通过获有专利权带侧限的破碎煤岩体压缩实验系统以分级加载的方式对不同Talbol指数n的破碎煤样进行压实试验。研究表明:在整个压实过程中,由煤样颗粒位移重组引起的变形大于由破碎填充引起的变形;随着应力的增大,各组试样中小粒径的颗粒不断大幅增加,其中M-4组试样增幅最大,增加了389.4 g,其余大粒径的颗粒不同程度的减少,4组试样承载后的粒度分布均趋近于同一种稳定的级配结构;分形维数轴向应力间符合幂函数关系,且应力一样时,n越大,混合破碎煤样的分形维数变化率越大;给出破碎煤岩体承压过程中压缩模量的计算公式,并发现相同应力条件下n越大,破碎率变化率越大,混合破碎煤岩体的稳定性越差,为采空区安全治理与预防地表沉降提供了有力的理论指导。

In order to study compaction and re-crushing characteristics of crushed coal body,compaction and deformation process of crushed coal body was divided into three stages:plastic instability,stress recovery,and primary rock-like stress according to mechanical characteristics of crushed coal body and the stability of the pore structure,and then the compaction test was carried out on crushed coal samples with different Talbol indices n by patented crushed coal body compression test system with side limit and graded loading.The study has shown that throughout the compaction process,deformation caused by the displacement reorganization of the particles was larger than that caused by crushing and filling;as the stress increases,the particles of small and medium size in each group increase greatly,with the largest increase of 389.4 g in the M-4 group,and remaining particles of large size decreased in different degrees,and particle size distribution of all four groups was close to the same stable grade.The formula for calculating compression modulus of crushed coal body under pressure is given,and it is found that the greater the value of n under the same stress condition,the greater the rate of change of crushing rate and the poorer the stability of mixed crushed coal body,which provides a strong theoretical basis for safe management of mining area and prevention of ground settlement.