水电站坝的砂层地基地震液化可靠度研究

对四川地区江河上数座水电站坝基砂层的26组动力三轴试验资料进行了统计分析,基于动剪应力比法的液化判别方法推导了的地震液化的极限状态方程,使用蒙特卡洛随机抽样的方法计算了砂层液化的失效概率,并对某水电站的厂房地基砂层的液化可靠度进行了计算分析。研究表明,统计按粉砂样总体和中细砂样总体划分较为合理;砂层的动剪应力比可采用正态分布;电站砂层地基地震液化的最危险工况为,闸坝盖重加稳定的向上渗流及遭遇Ⅶ度地震荷载,为高液化风险,其液化概率随埋深加大而增大,最危险部位为砂层底板,对坝基砂层应进行抗液化处理。

RELIABILITY ANALYSIS OF LIQUEFACTION OF THE SAND-LAYER FOUNDATION AT A DAM OF HYDROELECTRIC POWER STATION

In this paper, authors established a critical state equation for liquefaction of soil based on the ratio of seismic shear stress and pressure stress methods (RSC) and liquefaction probability through Monte-Carlo simulation using shear strength results of 26 groups of cyclic tri-axial tests from hydroelectric power stations in Sichuan Province. The reliability of liquefaction of soil layer of one hydropower station was then evaluated using the method. The results showed that it is reasonable to classify soil as slit and sand groups for statistical analysis. The ratio of shear stress and consolidation stress (RSC) follows normal distribution. The most dangerous case is a small dam with seepage suffering grade under VII magnitude of earthquake. The liquefaction venture increases as the depth of the sand-layer increases. The most vulnerable location in soil profile is the up-side of sand-layer. Therefore, treatment measures were recommended to strengthen the foundation of the dam to prevent liquefaction.