绿片岩剪切流变及破坏试验研究

Shear rheological test and failure analysis of green schist

为揭示高应力状态下绿片岩的剪切流变及其破坏特性,针对雅砻江锦屏一级水电站坝址区超埋深、高地应力等显著特征,采用排孔切割等特殊方法制备试样,利用岩石剪切流变仪对绿片岩试样开展了剪切流变试验。试验结果表明:①在大多数应力水平下,剪切变形在历时48 h后基本趋于稳定。②当试验进行到最高一级剪切载荷后,片理面出现大位移滑动而迅速破坏,各试件从最后一级加载到出现大位移破坏经历的时间差异较大;根据最后一级剪切的剪应力-剪切位移-时间关系曲线的特点,可划分为两种破坏曲线类型。③绿片岩的极限长期强度与瞬时强度相比有较明显的降低,强度效应主要表现在c值的降低,而对f值影响相对较小。④强度比τ∞/τ与法向应力有明显相关性,随着法向应力的增加,该比值越来越大。

To reveal shear rheology and failure characteristics of green schist under high stress, special methods such as row-hole cutting were used to prepare samples and the shear creep test machine was used to carry out shear rheological test on the green schist sampled from the dam site of Jinping I Hydropower Station that is featured with ultra-embedding depth and high geo-stress. The test results showed that: ① the shear deformation tended to be stable after 48 hours loading under highest stress levels. ② When the shear load reached the highest level, large displacement appeared on the schist surface and the sample was destroyed rapidly. The duration of the highest level loading until destruction varied with different samples. Failure of samples could be divided into type A and type B according to the characteristics of the curves of shear stress-shear displacement-time. ③ Compared with the instantaneous strength, the long-term strength of the green schist decreased significantly, namely the cohesion decreased notably but the friction decreased a little. ④ The strength ratio τ∞/τ had a significant relationship with the normal stress σ. As the normal stress σ increased, the value of τ∞/τ became larger and larger.