页岩卸荷能量演化特征试验研究

隧道、硐室和矿井等地下空间,应力卸荷是导致岩体破坏的主要原因之一。因此,为研究卸荷条件下的岩石破坏行为,以页岩为研究对象,开展恒定轴压卸围压三轴压缩试验。基于能量耗散与释放原理,分析试验不同阶段能量演化规律及临界围压对试样吸收的总能量和耗散能的影响,探讨卸荷条件下岩石破坏条件。研究结果表明,卸荷试验能量变化主要分为能量聚集阶段、能量耗散阶段和能量释放3个阶段:(1)外力对试样做的功主要以弹性能形式存在;(2)外力所做的功主要耗散于微裂纹形成、扩展,岩石强度降低,此阶段耗散能迅速增加而弹性能基本保持不变;(3)当岩石强度降低到一定程度时,弹性能瞬间释放,岩石破坏。

Experimental Study on the Energy Evolution of Shales Unloading Failure

Unloading pressures is one of the major reasons that result in the damage of rock in underground spaces, such as tunnel, chamber and mine. Therefore, in order to investigate the failure of rock, Longmaxi formation shales are taken as the research object. And triaxial compression tests, the axial stress is constant and radial stress is unloaded, were carried out. The variation rule of energy at different stages and the influence of the critical confining pressure on total energy and dissipated energy were investigated, and the critical condition of rock failure was explored. The results show that the variation of energy is distributed into three stages: energy-accumulating stage and energy-dissipating stage and energy-releasing stage. The work produced by axial force is stored in the form of elastic energy at the energy-accumulating stage; The work produced by axial force are consumed by the formation and extension of cracks at the energy-dissipating stage, which would lead to strength decrease, and dissipated energy rapidly increases and elastic energy remains about the same; Elastic energy release results in rock failure when strength of rock fall below a certain point.