软弱破碎围岩分次压实力学特性试验分析

Experimental analysis on fractional compaction mechanical characteristics of soft and broken rock

由于煤矿再生岩体围岩结构和成分进行了重组,其力学特性将发生本质变化。根据再生岩体压实成岩过程中破碎岩体多次受压的实际情况,采用广西州景煤矿再生顶板破碎围岩进行有侧限条件的分次压实试验。结果表明:分次压缩过程可分为压实破碎、压实应力记忆和压密固结3个阶段。在第1次压缩时,压实特性曲线呈线性变化,后续压实特性曲线逐渐向指数形式转变,而"压实应力记忆"阶段表现为多项式变化。在侧限压缩条件下,提出以最小势能原理作为判定不规则岩样挤压破碎判据。破碎岩样压缩特性受压实次数和装岩高度的影响,破碎岩样分次压实次数越多,累积压缩应变越大,后续压缩时的应力增量越大。装岩高度越大,压缩至相同压应力时,累积总应变越大。压实应力达到一定程度,不同粗粒径破碎岩样的粒径分布规律趋于一致,据此建立了破碎岩样粒径分布与工程中破碎岩体压实程度之间的相关关系。

The mechanical properties of the regenerated rock mass are intrinsically changed due to the reorganisation of the structure and components in the coal mine. In this study, the fractured rock mass was repeatedly compressed during the compaction and diagenesis process of the regenerated rock mass. Then the fractional compaction test under confined conditions was carried out using the broken surrounding rock of the regenerated roof of the Zhoujing coal mine in Guangxi. The results show that the process of fractional compression can be divided into three stages: compaction crushing, compaction stress memory and compaction consolidation. At the first compression, the compacting characteristic curve changes linearly, and the subsequent compaction curve gradually changes to an exponential form, while the stage of compaction stress memory shows a polynomial change. Under the confined compression condition, the criterion of minimum potential energy is used to determine the crushing fracture of irregular rock samples. The compression characteristics of fractured rock samples are influenced by the number of compaction and the height of rock mass. When the times of compaction are larger, the cumulative compression strain is greater, and the stress increment in the subsequent compression is higher. As the loading height is higher, the cumulative total strain is greater at the same compressive stress.When the compaction stress reaches a certain degree, the grain-size distribution of the broken rock samples with different coarse-grained sizes tends to be consistent. Therefore, the correlation between the size distribution of broken rock samples and the compaction degree of the regenerated rock mass is established.