循环加卸载条件下煤岩组合体力学响应及能量演化规律

Mechanical Response and Energy Evolution Law of Coal-Rock Combined Specimen under Cyclic Loading and Unloading Conditions

为研究煤岩组合体在外载荷作用下的力学响应及能量演化规律,设计了纯煤、煤岩组合体和纯岩试件单轴循环加卸载试验,分析了不同试件单轴抗压强度和弹性模量等力学响应特征,深入研究了煤岩组合体输入能密度、弹性能密度和耗散能密度演化规律,得到了不同试件的弹性能储存速率及储能能力的特性,建立并探讨了煤岩组合体能量破坏机理。结果表明:①煤岩组合体的力学参数更接近纯煤试件,其力学特性主要受煤体影响;②随外载荷增加,煤岩组合体输入能、弹性能和耗散能呈明显非线性增加趋势,其中弹性能占比远高于耗散能;③煤岩组合体能量破坏机理为外载荷作用使煤体和岩体同时开始储存弹性能,由于煤体弹性能储存速率较快,其内部弹性能率先达到储能极限,导致煤体破坏并向岩体释放弹性能,当达到岩体的储能极限时,岩体发生破坏。

Uniaxial cyclic loading and unloading experiments on pure coal,coal-rock assembly and pure rock specimens were designed and conducted to study the mechanical response and energy evolution law of coal-rock assembly under external load.The mechanical response characteristics such as uniaxial compressive strength and elastic modulus of test specimens were analyzed,and the evolution law of input energy density,elastic energy density and dissipated energy density of coal-rock assembly were examined in detail.The characteristics of elastic energy storage rate and energy storage capacity of different specimens were obtained,and the energy failure mechanism of coal-rock assembly were discussed.Results demonstrate that:1)The mechanical parameters of coal-rock combined specimens are closer to those of pure coal specimens,mainly affected by the coal.2)With the rise of external load,the input energy,elastic energy and dissipated energy of coal-rock combined specimen present obvious non-linear increase trends,in which the proportion of elastic energy is much higher than that of dissipated energy.3)Under external load,elastic energy is stored in coal and rock masses synchronously;but as elastic energy reaches the storage limit in coal earlier than that in rock,the coal mass breaks and releases elastic energy to the rock mass.When the storage limit in rock mass is reached,failure of rock mass occurs.