高拱坝蓄水期谷幅时效变形机理分析

Analysis of mechanism of valley creep deformation of high arch dam during impoundment

针对国内某高拱坝工程蓄水期间出现的谷幅收缩问题,分析了谷幅变形监测资料,获取了谷幅变形的时空分布规律。在此基础上,通过建立谷幅变形的统计回归模型,对各个监测点的谷幅变形过程进行了回归分析,分离出库盘水压变形分量、气温变形分量及时效变形分量。基于回归分析成果,采用有限元方法研究了库盘水压以及渗流场变化过程中所引起的渗流力作用、基岩温度变化、材性变化以及有效应力降低等因素对谷幅变形的影响。结果表明,渗流力和基岩温度变化会引起一定的谷幅收缩变形,但变形量值和变形规律与实际不符,并非拱坝谷幅变形的主要诱发因素。谷幅变形主要是由近坝区水文地质条件的改变所触发的岸坡蠕变变形,数值模拟的谷幅变形过程与实测结果吻合较好。

The regression analysis of the valley deformation process at each monitoring point of Xiluodu arch dam was carried out, so valley deformation is decomposed as deformation caused by instantaneous change in water level, deformation caused by temperature and time effect deformation. Based on the results of the regression analysis, the effects of reservoir pressure, bedrock temperature and hydrogeological condition on valley deformation were studied respectively with finite element method. The research shows that changes of hydraulic pressure and bedrock temperature could cause a certain valley deformation, which is much smaller than the measured deformation, and is not the main cause of valley deformation of Xiluodu arch dam. Valley deformation is largely the time effect deformation caused by the change of hydrogeological conditions in the near dam area, which presents as the creep deformation of the structural surface along the interlayer fault zone.The valley deformation process of numerical simulation is good agreement with the measured results.