岩体劣化对谷幅变形及高拱坝安全性的影响

Study of the influence of rock mass deterioration on valley deformation and high arch dam safety

拱坝建成蓄水后,水环境的变化会引起坝址区岩体力学性能的改变,进而引起谷幅收缩,影响大坝安全。针对锦屏一级拱坝蓄水初期出现的地基异常变形现象,基于岩体遇水劣化规律和非饱和渗流-应力耦合基本理论,建立岩体遇水劣化模型,采用非线性有限元数值分析方法,研究蓄水初期库区岩体劣化下的谷幅变形规律,进一步分析谷幅收缩对坝体结构的影响。研究表明:库岸岩体劣化对谷幅变形产生直接影响;岩体劣化程度越高,谷幅收缩越明显,坝体上游消落带区域的谷幅变形最为突出;随着水位升高,库岸岩体劣化范围扩大,坝体的最大顺河向位移、最大主拉应力和最大主压应力略有减小。因此,锦屏拱坝蓄水后由岩体劣化造成的谷幅变形不会影响坝体的整体安全。

After the arch dam is built and impounded,the change of water environment will change the mechanical properties of rock mass in the dam site area,and then cause valley shrinkage,affecting the safety of the dam.Aiming at the abnormal deformation of the foundation of JinpingⅠarch dam at the initial stage of impoundment,based on the law of rock mass deterioration in water and the basic theory of unsaturated seepage stress coupling,we established a model of rock mass deterioration in water,used nonlinear finite element numerical analysis method to study the valley deformation law under the rock mass deterioration in the reservoir area at the initial stage of impoundment,and further analyzed the impact of valley contraction on the dam structure.The study shows that the deterioration of rock mass on the reservoir bank has a direct impact on valley deformation.The higher the deterioration degree of rock mass,the more obvious the valley width shrinkage,and the valley deformation in the upstream fluctuation zone of the dam body is the most prominent.With the increase of water level,the deterioration range of reservoir bank rock mass expands,and the maximum displacement along the river,the maximum principal tensile stress and the maximum principal compressive stress of the dam body slightly decrease.Therefore,valley deformation caused by rock mass deterioration after impoundment of Jinping Arch Dam will not affect the overall safety of the dam.