煤岩组合体峰后卸加载力学特性及支护作用机理

Mechanical characteristics and support mechanism of coalrock combined body under unloadloading conditions beyond peak strength

为深入研究煤岩组合体的峰后卸加载力学特性,采用PFC(Particle Flow Code)数值模拟软件对其进行了模拟试验,分析了不同卸载应力水平、卸载速率和支护方案对其强度、弹性模量、峰值轴向应变、冲击能量指数及声发射等特征的影响。结果表明:煤岩组合体在峰后阶段已经产生损伤,其峰后卸加载强度、弹性模量、冲击能量指数和最大声发射撞击计数均低于峰前常规单轴压缩的结果。在相同的卸载速率下,峰后卸载应力水平越高,煤岩组合体峰后卸加载强度越高。卸载速率对煤岩组合体峰后卸加载有整体强化和局部弱化两方面的作用。在相同峰后卸载应力水平条件下,随卸载速率的增加,煤岩组合体峰后卸加载强度呈“先增大、后减小”的演化特征。支护能够显著提高破碎煤岩组合体的强度和弹性模量,但只有稳定的支护方式才能够有效降低其冲击能量指数。为提高破碎煤岩体的稳定性和降低冲击风险,应当选择具有高强度、高可靠性和大变形能力的支护系统并增加护表面积。工程示例证明研究成果对现场工程实践具有指导意义。

To further investigate the mechanical properties of coalrock combined bodies under postpeak unloadloading conditions,simulation tests were conducted using PFC(Particle Flow Code)numerical simulation software.The study analyzed the strength,elastic modulus,peak axial strain,bursting energy index,and acoustic emission characteristics of coalrock combined bodies under different levels of postpeak unloading stress,unloading rates,and support schemes.The results indicated that the damage occurred in coalrock combined bodies during the postpeak phase,resulting in lower strength,elastic modulus,bursting energy index,and maximum AE counts compared to prepeak conventional uniaxial compression.Higher postpeak unloading stress levels led to increased postpeak unloadloading strength of coalrock combined bodies,under the same unloading rate.The unloading rate had two effects on the postpeak unloadloading strength:an overall strengthening effect and a local weakening effect.Consequently,under the same postpeak unloading stress level,the postpeak unloadloading strength of coalrock combined bodies exhibited a"first increasing,then decreasing"trend with increasing unloading rate.Support systems significantly enhanced the strength and elastic modulus of broken coalrock combined bodies.However,only stable support effectively reduced the bursting energy index.Therefore,to improve the stability of broken coalrock masses and mitigate the bursting risk,it was crucial to select support systems with high strength,high reliability,and ample deformation capacity,while also increasing the support surface area.The practical application of these research finding in an engineering example demonstrated their guiding significance for insitu engineering practice.