大岗山水电站坝区辉绿岩流变特性的三轴试验研究

为解决大岗山水电站坝基的辉绿岩的流变力学问题,利用RLW-1000三轴流变仪进行了不同应力路径下的三轴流变试验,得到了各工况下的应力-应变-时间曲线。结果表明：辉绿岩是典型的硬脆性岩石,存在明显的流变门槛值,破坏时表现为突发性的脆性破裂。在破裂应力水平下表现出减速蠕变、等速蠕变和加速蠕变,减速蠕变和加速蠕变历时都十分短暂。临近破裂时的横向蠕变速率均不同程度的大于轴向,这是导致岩石扩容的主要原因。由于流变过程中损伤不断发展,导致岩石整体强度下降,因此流变破坏强度普遍低于常规三轴压缩试验瞬时破坏强度。辉绿岩存在一定的蚀变现象,蚀变矿物呈细鳞片状集合体。由于蚀变带的存在,使得岩块的强度受到影响,岩石破裂极易发生在结晶程度较差的矿物颗粒部位或胶结程度较差的两种矿物接触部位。

Triaxial Test Research into Rheological Properties of Diabase in Dagangshan Hydropower Station Dam Site

The rheological properties of soft rock have been studied deeply, but the rheological characteristics of hard-brittle rock still remain largely unexplored. In order to study the long-term mechanical properties of the diabase in Dagangshan hydropower station dam site, triaxial rheological tests under different stress paths are carried out on RLW-1000 rheology testing machine, and the stress-strain-time curves under different conditions are obtained. The results show that the diabase is typical hard-brittle rock which has obvious rheological threshold, and sudden brittle fracture is shown at failure of specimen. Shortly prior to failure, each specimen experienced transient creep, steady-state creep and tertiary creep stage in the fracture stress level, but the transient creep and tertiary creep stage maintained short time. When the applied stress level is closed to the fracture stress, the circumferential creep rates are higher than those of axial which are the main reason induced the volume dilatancy phenomenon of specimen. The continuous development of damage in rheological process causes decrease of whole strength of rock mass, so the rheological failure strength is lower than the instantaneous failure strength by the triaxial compression test. There is some degree of alteration in the diabase of Dagangshan hydropower station dam site, the altered minerals show fine scale-like aggregation. The strength of rock is impaired by the existence of alerted strip, the rupture of rock can occur easily in the interface of poorly crystallized mineral grains and the poorly cemented ones.