不同加载刚度下煤体冲击倾向性测试及评价指数分析

Bursting liability test and evaluation index analysis of coal under different loading stiffnesses

煤矿冲击地压是顶板–巷帮系统动力失稳破坏的工程灾变问题,顶板作用下的巷帮冲击破坏研究更符合井下原位地质与工程条件。利用研制的多级可调刚度加载装置,研究不同试验机加载刚度下煤体冲击倾向性指数测试结果,并根据建立的巷道围岩供能冲击表征模型,提出评价巷帮冲击危险性的冲击供能指数。研究表明:随着试验机–试件刚度比的减小,煤体峰后破坏速度加快,破坏形式由块体开裂和剥离转化为碎块崩裂和弹射,碎块分形维数增大,试件破碎程度增强;煤体单轴抗压强度、弹性能量指数的测试值与刚度比相关性很小,动态破坏时间与刚度比呈幂函数正相关的关系,冲击能量指数与刚度比呈幂函数负相关的关系;顶板供能与巷帮煤体释放弹性能叠加是造成巷帮冲击破坏的重要原因,随着顶板–巷帮刚度比的减小,顶板对巷帮供能增加,冲击危险性增强。提出的考虑顶板刚度与供能的巷帮冲击供能指数,可作为评价不同顶板与巷帮组合刚度条件下巷帮冲击危险性的重要指标。

Coal burst is an engineering dynamic failure of roof and sidewall system.The research of sidewall bursting failure under the action of roof is more suitable for in-situ geological and engineering conditions in coal mining.By using the developed multi-level changeable stiffness loading test device,the test results of coal bursting liability index under different loading stiffness of the test device were studied.According to the energy supply burst characterization model of the roadway surrounding rock,the bursting energy supply index for bursting risk evaluation was proposed.The results show that with the decrease of the device-specimen stiffness ratio,the post-peak failure velocity of coal is accelerated,and the failure mode of coal is transformed from block cracking and peeling to fragment ejection.The fragment fractal dimension and fracture degree of specimens increase.Testing value of the uniaxial compressive strength and elastic strain energy index have little correlation with the stiffness ratio.The duration of dynamic fracture is positively correlated with the stiffness ratio in a power function,while the bursting energy index is negatively correlated with the stiffness ratio in a power function.The roof supply energy,together with the coal released elastic energy,is an important cause of coal burst.With the decrease of roof-sidewall stiffness ratio,the roof supply energy increases,and the coal bursts more easily.The proposed bursting energy supply index can be used as an important indicator to evaluate coal burst risk under different roof and sidewall stiffness conditions.