拱坝坝肩岩石流变力学特性试验研究及其长期稳定性分析

EXPERIMENTAL STUDY OF RHEOLOGICAL MECHANICAL PROPERTIES OF ARCH DAM ABUTMENT ROCK AND ITS LONG-TERM STABILITY ANALYSIS

采用岩石全自动三轴流变伺服仪,对小湾水电站两岸山体的蚀变岩进行三轴流变力学试验,得到岩石典型的流变全程曲线。流变试验结果表明:较高应力水平条件下,蚀变岩具有较为显著的流变特性,流变变形量大,流变速率快。基于试验结果,研究蚀变岩在不同应力水平下流变变形随时间的变化规律,分析试样的流变破裂形式与机制,掌握了蚀变岩三轴流变的基本特性。采用Cvisc流变模型对蚀变岩流变试验曲线进行辨识,得到相应的流变力学参数;基于三维非线性数值分析方法,采用黏弹塑性流变本构模型,模拟小湾水电站长期运营条件下的流变力学行为,并与弹塑性计算条件下进行对比分析。结果表明:小湾水电站拱坝及坝肩岩体长期流变变形明显大于弹塑性变形;考虑岩石流变作用使得应力场随时间增长发生重分布,局部应力集中现象有所缓解;坝肩岩体受力初期表现出较为显著的流变特性,流变一定时间后,流变速率变得恒定平稳,流变变形趋于稳定。

In order to understand the rheological properties of alteration rock specimen of two banks of Xiaowan hydropower station,triaxial compression rheological experiments on alteration rock specimens are carried out by the rock servo-controlled rheological testing machine. The test results show that the rheological properties of alteration rock are very significant,and the rheological deformation of specimens is large. Based on the triaxial rheological experimental results,the variation law of axial strains of alteration rock specimens with time is investigated. At the same time,the variation tendency of axial rheological rates under different stress levels is discussed in detail;the rheological failure mechanism is analyzed;and the triaxial rheological law of alteration rock specimen is obtained. Cvisc rheological model is used to fit the rheological test curves,and the constitutive relationships of Cvisc model and its parameters are obtained. Based on the optimal rheological model of rock,the rheological mechanical behaviors of rock mass on two banks are simulated by using 3D nonlinear numerical method. Throughout the analysis of the calculated results,the long-term stability of arch dam and abutment are estimated by studying the displacement and stress. The results show that the rheological effect of Xiaowan hydropower station is very remarkable. The rheological deformations of arch dam and two banks are larger than the elastoplastic deformations. Considering the rock rheological behavior,the stress field will redistribute with the increase in time;and the phenomenon of local stress concentration will decrease. The abutment rock mass expresses explicit rheological characteristics at the beginning of loading,and then,the rheological rate and rheological deformation of arch dam and abutment tend to stability.