地震作用下渗流对平原水库土石坝稳定的影响

INFLUENCE OF SEEPAGE ON STABILITY OF EARTH-ROCK DAM IN PLAIN AREA UNDER SEISMIC LOADING

平原水库的土石坝在坝基中普遍存在着可液化的土层,地震作用下坝基液化问题及其对大坝稳定的影响是一个人们普遍关注的问题。为此,以天津尔王庄水库这一典型平原水库为工程背景,在室内和现场试验的基础上,对土层液化可能性进行判别,对土层的动力特性进行研究,同时对渗流场在地震作用下的变化进行初步探讨。试验结果显示,在研究区域内的可液化土层在7度地震烈度下有发生液化的可能性。此外,模型试验显示渗流场在地震作用下会发生变化,但在本次计算条件下,渗流场的变化不大。根据室内试验得到的各种参数,利用数值计算方法对渗流在地震作用下所起的作用进行分析。分析结果显示,计算所得到的液化区域深度与试验结果相符。土层的分布对液化区域大小与位置的影响明显,考虑和不考虑渗流对液化区域的影响不大;但是,考虑渗流会使迎水坡的安全系数提高,背水坡的安全系数下降。同时,在一定区域内,在考虑渗流的情况下,土体的水平位移也有增大的趋势。

The soil layers with liquefaction characteristics can be often found in the foundation of earth-rock dam in plain area. The soil liquefaction under seismic loading and its influence on the stability of the dam are important issues. The Erwangzhuang reservoir dam, a typical earth-rock dana in plain area, is chosen as an example to study the problem. Based on the indoor and in-situ tests, the liquefaction possibility of the soil layers, the dynamic properties of soil and the change of seepage field in the soil under earthquake are all concerned. The in-situ test results show that under seismic loading with magnitude 7, some in-situ soil layers could be liquefied. The results of indoor model tests show that the seepage field in the soil is changed under vibration; but the change of seepage field is not obvious. Utilizing the soil parameters obtained by indoor tests, the dynamic numerical analysis is performed with/without considering seepage. The numerical results show that the depth of liquefied zone agrees with the results of tests. The size of liquefaction region in the foundation is affected by the distribution of soil layers remarkably; yet the seepage influence is not obvious. When considering seepage, the factor of safety of upstream increases and the factor of safety of downstream will decrease. The influence of the seepage on the horizontal displacement can also be found at the same time.