双向加载煤岩变形与声发射特性颗粒流研究

CHARACTERISTICS OF COAL'S STRENGTH DEFORMATION AND ACOUSTIC EMISSION UNDER BIAXIAL LOADING WITH PARTICLE FLOW CODE

为了明确煤岩双向应力状态下的强度和损伤特性,通过煤岩的单轴试验测得其力学参数,然后利用颗粒流和fish程序结合试验结果获得煤岩细观力学参数,进行了煤岩双向加载下的强度、变形和损伤声发射特征的研究。获得以下主要结论:双向加载煤岩变形破坏过程中,中间主应力对屈服阶段影响最显著,而对峰后软化阶段基本没有影响,这与三向加载下围压对峰后软化阶段的影响不同,从而表明双向加载条件下煤岩峰后基本不存在脆性-延性转化的特征。双向加载下煤岩的体变经历线性体缩、非线性扩容和线性扩容阶段,中间主应力对非线性扩容阶段影响显著,而对其他两个阶段基本没有影响。煤岩损伤破坏过程中,在弹性阶段声发射呈线性增加趋势但增速较小,屈服阶段声发射进入非线性快速增加阶段,在峰值附近增速最快,峰后初期达到最大强度,随后声发射强度急剧减小。声发射最大强度有一定的滞后效应,随着中间主应力的增大,最大声发射强度的滞后效应相对减弱,且随着中间主应力的增大,声发射最大强度持续时间段明显延长。

This paper investigates coal strength and damage charateristics under bidirectional loading,obtains the mechanical parameters by testing the coal under uniaxial compression,then gets coal mesomechanical parameters through particle flow code( PFC) and fish program combined with the uniaxial experimental results. It conducts the research on coal strength,deformation and acoustic emission under biaxial loading. The main research results are reached as follows. In coal deformation and failure process under bidirectional loading,intermediate principal stress has the most significant effect on the yield stage,but no effects on the post-peak softening stage,which is different from the effects confining compression on the post-peak softening stage under triaxial loading. This result shows that coal under biaxial loading basically does not have the features of brittle converting ductile in post-peak stage. Coalvolumetric strain under biaxial loading shows the three stages of linear volumetric strain decrease,nonlinear expansion and linear expansion. Intermediate principal stress has the most significant effects on nonlinear expansion stage,but no effects on other two stages. In coal damage and failure process,acoustic emission linearly increases at elastic stage,but the growth rate is smaller,nonlinearly rapidly increases at yield stage. It has the fastest growing near peak,reaches the maximum intensity at post-peak initial stage. Then the acoustic emission intensity decreases sharply. Acoustic emission maximum intensity lags behind the peak stress. The lag effect of acoustic emission maximum intensity relatively weakens along with the increasing of intermediate principal stress. Acoustic emission maximum intensity duration becomes longer with the increase of intermediate principal stress.