白鹤滩拱坝初期蓄水库岸变形机理研究

Mechanism of reservoir bank deformation during initial impoundment of Baihetan arch dam

高拱坝蓄水期间均监测到一定程度的库岸变形,且变形量值和变形规律不一,这对超静定结构的高拱坝的工作性态和长期安全造成一定程度的影响。本文对白鹤滩拱坝的谷幅变形、坡体内部变形和库盘变形进行统计分析,研究了白鹤滩工程库岸变形的时空分布规律。通过建立谷幅变形的多元逐步回归模型,分离出水位分量、温度分量和时效分量。建立了有限元数值模型,基于裂隙岩体有效应力原理,利用弹塑性有限元方法,计算了白鹤滩拱坝初期蓄水到800 m高程时产生的谷幅变形。监测资料分析表明:大部分测线基本表现为收缩变形,且都与水位的上升具有一定的相关性;从顺河向方向来看,上游侧的谷幅变形值大于下游侧;从断面不同高程上的测线来看,谷幅收缩变形呈现自高而低依次减小的分布规律;坡体内部处于拉伸状态;库盘变形以下沉为主。多元回归分析和数值计算结果表明:谷幅变形监测值与800 m水位下有效应力计算值在上游侧的测线量值较为接近,两者在空间上也具有相同的分布规律,可以认为有效应力改变是初期蓄水库岸变形的主要影响因素。

For a high arch dam,significant reservoir bank deformation during its impoundment has been observed and it is diversified in magnitude and variation,which threatens its working condition and longterm safety owing to the nature of its statically indeterminate structure.This paper presents an analysis of the reservoir bank deformation and its spatial and temporal distributions through examining the data of valley width,slope interior and reservoir plate for the Baihetan dam.The components of water level,temperature and aging are separated by developing a multiple stepwise regression model of valley width deformation.An elastic-plastic finite element model is constructed using the effective stress principle of fractured rock mass;the valley deformation at the initial impoundment stage of 800m is calculated.The monitoring data show that most of the survey lines are basically in shrinkage deformation,and all of them have a certain correlation with the rise in the reservoir impounding stage.Along the river,the upstream sections feature a valley width deformation larger than that of the downstream ones.Survey data from high to low elevations of a valley section manifest a decreasing trend in the shrinkage deformation of valley width.The interior of the valley slope is in tension,and most of the reservoir plate undergoes subsidence.The results of multi-variate regression analysis and numerical calculations show that for the upstream sections,the calculated valley width deformation based on effective stress at the 800m stage are close to the measurements,and both are the same in spatial distribution patterns.It can be considered that the change in effective stress is the main factor affecting initial reservoir bank deformation.