巷道垮落煤体的宏观剪切特性

Macro shear mechanical properties of granular coal from collapsed roadway

为研究巷道垮落煤散体力学性质对在垮落体内快速安全再造应急救援通道的影响,利用岩石力学直剪试验装置开展了4种法向应力和3种剪切速率下的直剪试验,分析其宏观力学特性与剪切前后颗粒级配变化,引入相对破碎率定量研究煤散体的破碎程度,在此基础上拟合得到了颗粒破碎率随法向应力和剪切速率变化的数学模型。结果表明:随着法向应力增加,剪切应力-应变曲线有从应变软化型向硬化型转化的趋势;煤散体抗剪强度和剪切模量均随法向应力增加而线性增大,均随剪切速率的增加而线性减小;随剪切速率的增加,内摩擦角及相对破碎率均减小,黏聚力增加。颗粒破碎率与法向应力正相关、与剪切速率负相关,三者之间满足二元一次函数关系。

This paper manages to investigate the influence of mechanical properties of granular coal collapse on the rapid and safe reconstruction of emergency rescue channel in collapse body. The investigation is accomplished by applying the direct shear test facility of rock mechanics to conduct the direct shear tests under 4 normal stresses and 3 shear rates and analyzing the variation rules of macro-mechanical properties;studying the breakage degree of the granular coal with the relative breakage ratio by analyzing the particle distribution variation before and after shearing, and on the basis of this study, obtaining the maths model, which changes its partical breakage rate along with the change of normal stress and shearing rat.The test results show that with the increase of normal stress, the shear stress-strain curve tends to change from strain softening to hardening;both the shear strength and shear modulus of granular coal increase linearly with the normal stress increasing, and decrease linearly with the shear rate decreasing;the internal friction angle and the relative breakage rate both decrease linearly, while the cohesion increases linearly with the increase of the shear rate. Breakage rate of particle is positive correlated with normal stress and negative correlated with shear rate, and thus, the mathematical relationship among the three factors accords with bivariate primary function.