卸荷条件下岩石破坏能量演化试验研究进展

岩石在变形破坏过程中不断与外界交换着物质和能量，是一个能量耗散的损伤演化过程，岩石破坏的实质是能量驱动下的状态失稳现象。综合介绍了在开挖瞬间，迅速增大的轴向应力随着时间增长逐渐趋于稳定和围压瞬间卸载的应力重分布情况，目前主要采用轴压升高、围压降低而轴压不变、围岩降低的室内试验方案。结果表明:岩石卸荷破坏具有明显的围压效应，总应变能、弹性应变能和耗散能与初始围压呈正相关关系；随着卸荷速率的增加，能量转化速率不断减小，岩石容易产生瞬间动态破坏；不同卸荷水平下能量演化存在明显的差异；碎屑岩块分形维数越大，扩容现象越明显，穿晶、沿晶裂纹越发育，消耗能量越多。基于现有的研究成果，提出完善试验系统、采用与工程实际相符合的应力路径、开展微细观裂纹研究、深入能量转化敏感阶段研究的发展趋势。

Test Study Progress of Rock Failure Energy Evolution Under Unloading Condition

The deformation and fracture of rocks are an evolution process with the exchange of energy and mass between rocks and outer exotic environment. Rock failure is a state failure phenomenon driven by energy. The axial stress increases rap-idly during excavation and it tends to be stable with the increasing of time,but confining pressure is unloaded instantaneously. At present,indoor test scheme mainly adopts increasing axial pressure and reducing confining pressure at the same time or keeping axial pressure constant and reducing confining pressure. The experimental results show that:the confining pressure effect of rock failure is significant,the total strain energy,elastic strain energy and dissipation energy are positively correlated with the initial confining pressure;with the increasing of the unloading rates,the energy conversion rates is decreased continu-ously,and the phenomenon of transient dynamic failure can be appeared easily;the difference of energy evolution is significant under the different unloading levels;the larger the fractal dimension,the more obvious dilatancy,the more developed of trans-granular and intergranular cracks and the more energy is consumed. Based on the existing study results,the development trend of testing system improvement,adopting the stress path in accordance with engineering practice,study of micro-meso crack and further study of the sensitive stage of energy conversion are proposed as the further study directions.