向家坝水电站坝基挤压带岩石三轴蠕变试验及非线性黏弹塑性蠕变模型研究

STUDY OF TRIAXIAL CREEP TESTS AND ITS NONLINEAR VISCO-ELASTOPLASTIC CREEP MODEL OF ROCK FROM COMPRESSIVE ZONE OF DAM FOUNDATION IN XIANGJIABA HYDROPOWER STATION

基于岩石常规三轴蠕变试验成果,研究向家坝水电站坝基挤压破碎带砂岩蠕变力学特性,分析岩石轴向和侧向蠕变规律。在低应力水平下,岩石仅发生衰减蠕变和稳态蠕变,而且稳态蠕变阶段的应变速率为非零常数,蠕变量不可忽视,岩石变形满足Burgers蠕变模型。当应力达到一定水平时,岩石经过衰减蠕变和稳态蠕变之后发生加速蠕变破坏。不同围压下蠕变破坏特征不同,尤其是加速蠕变启动时间的差别较大,据此提出加速蠕变启动元件。通过将加速蠕变启动元件与Burgers模型串联,建立一个新的岩石六元件非线性黏弹塑性蠕变模型,并从理论上对其蠕变力学特性进行讨论。推导三维应力状态下的岩石蠕变本构模型公式,研究蠕变参数辨识方法。通过与试验曲线的比较,显示所建非线性蠕变模型的正确性与合理性。

Based on the results of rock triaxial test,the creep mechanical properties of the sandstone from the compressive rupture zone in Xiangjiaba Hydropower Station are investigated,and the laws of axial and lateral creep of rock are also analyzed.In the low stress level,the rock only appears decay creep and steady creep.The steady creep strain rate is non-zero constant,and the creep deformation cannot be ignored.The creep of rock is consistent with Burgers model.When the stress reaches a certain level,the accelerated creep damage of rock occurred after the decay creep and steady creep.The characteristics of rock creep failure under different confining pressures are different,especially the starting time of accelerated creep.According to the feature,the startup component of accelerated creep is proposed.By connecting the startup component and Burgers model in series,a new six-component nonlinear viscoelasto-plastic creep model of rock is constructed.The creep property of the nonlinear model is carried out based on the theoretical analysis.The creep constitutive equation in three-dimensional stress state is deduced.The creep parameter identification method is investigated.The comparison between nonlinear creep model and experimental curve shows that the proposed nonlinear viscoelasto-plastic creep model is available and reasonable.