基于纳米压痕的煤系泥岩细观力学及断裂性能试验研究

Experiment on meso-mechanical and fracture characteristics of coal measures mudstone using nanoindentation

以口孜东煤矿煤系泥岩为对象,开展了纳米压痕试验,基于弹性接触理论以及能量原理,研究了泥岩岩样的细观力学性质及断裂力学特征,探讨了泥岩内部不同矿物成分之间的细观力学行为差异。研究结果表明:相同的最大压痕载荷条件下,泥岩表面压痕点深度变化不一,压痕点弹性模量约在2~114GPa范围内,而硬度在0~16GPa范围内变化,体现了泥岩的不均质性;基于弹性模量概率分布曲线,近似获得了泥岩三种主要的矿物成分,包括黏土类矿物(~7.83GPa)、绿泥石类矿物(~41.67GPa)以及石英矿物(~97.29GPa);黏土类矿物、绿泥石类矿物及石英矿物的断裂韧度分别约为0.09、0.91和1.95MPa·m^(1/2),而黏土类矿物断裂韧度所占比例较高(~70.0%),该矿物对泥岩宏观断裂力学性质起决定性作用。

Nanoindentation test was carried out on mudstone from Kouzidong Coal Mine. Based on the elastic theory and energy principle, the meso-mechanical properties and fracture characteristic were investigated. Furthermore, difference in meso-mechanical properties of main composition of mudstone was analyzed. The results showed that, under the same maximum load, the indentation depth on the mudstone surface varied differently. The elastic modulus ranged from 2 to 114GPa, and the hardness ranged from 0 to 16GPa, reflecting the heterogeneity of the mudstone. Based on the probability density distribution of modulus, three different main phases were identified, including clay minerals(~7.83GPa, including kaolinite and illite), chlorite(~41.67GPa) and quartz(~97.29GPa). Morever, the fracture toughness of clay minerals, chlorite and quartz was 0.09, 0.91 and 1.95MPa·m^(1/2), respectively. The fracture toughness of clay minerals accounted for the largest proportion(~70.0%), and the clay minerals played a significant effect in macro-fracture properties. With the obtained mesoscopic mechanical properties and fracture toughness of different phases of mudstone, it was useful to understand the macroscopic failure behaviour of mudstone.