冲击性煤体应力结构时间效应试验研究

Experimental study on time effect of stress structure in impact coal

煤矿工程中蕴含复杂的应力结构时间效应问题,与冲击地压灾害的发生与防治密切相关。针对冲击性煤体的应力结构时间效应开展试验研究,在陕西、甘肃以及内蒙古3个冲击地压矿井取得煤岩块体加工试件,通过煤单轴压缩动静载及蠕变试验研究加载速率的应力时间效应,采取长时分段试验方法研究煤原位解除条件下的应力时间效应,开展煤浸水以及煤岩组合试验研究结构时间效应。结果表明:煤体单轴抗压强度与加载速率具有正相关性,与原位解除时长和浸水时间具有负相关性,煤岩结构时间效应下的组合模式对其能量及强度属性有显著影响,冲击性煤体表现出应力与结构2个方面的时间效应。依据试验结果,提出塑限结构来解释应力作用下煤岩体的不可逆变形,再通过构建塑限结构时间效应模型,对比非弹性应变与不可逆应变的数值近似性,对冲击性煤体塑限应变特性进行了验证。

Coal mining engineering involves complex stress structure time effect issues,which are closely related to the occurrence and prevention of rock burst disasters.Therefore,this study conducts experimental research on the stress structure time effect of impact coal.Coal rock specimens were obtained from three coal mines in Shaanxi,Gansu,and Inner Mongolia.The stress-time effect of loading rate was studied through coal uniaxial compression static-dynamic load and creep tests.The stress-time effect under the condition of coal in situ release was investigated using a long-term segmented test method.Water immersion tests on coal and structural time-effect studies on coal-rock combinations were conducted.The experimental results indicate that there is a positive correlation between the uniaxial compressive strength of coal and the loading rate,and a negative correlation with the duration of in-situ relief and immersion time.The combined mode of coal-rock structure time effect significantly affects its energy and strength properties,while impact coal exhibits both stress and structural time effects.According to the experimental results,a plastic limit structure is proposed to explain the irreversible deformation of coal-rock mass under stress.Furthermore,by constructing a time-dependent model for plastic strain in coal under impact conditions and comparing the numerical approximations of non-elastic strain and irreversible strain,the plastic limit strain characteristics of shock-induced coal were verified.