三峡水库水位涨落条件下奉节南桥头滑坡稳定性分析

三峡大坝建成后，水库将分期蓄水抬高水位，蓄水后库区水位将上抬100多米。由于防洪的需要，库水位将在175～145m范围内变动。库水位的抬升和周期性涨落，将改变岸坡原有的水．岩作用环境与条件，有可能引起库岸边坡与滑坡的失稳。南桥头滑坡位于三峡库区奉节县长江公路大桥南岸，其稳定性直接关系到大桥的安全运行。应用FLAC^4.0对南桥头滑坡在不同水位及涨落条件下的渗流场与应力场进行分析，研究应力-渗流耦合作用下滑坡体的变形趋势与破坏特征：探讨了不同蓄水工况下滑坡稳定性的变化规律及其对桥基的影响。结果表明：南桥头滑坡在现状条件下处于基本稳定状态；三峡水库蓄水后，随着水位的抬升，滑坡整体稳定性逐渐恶化；滑带内塑性区全部连通，滑坡安全系数小于1．0，表明该滑坡在库水位抬升后有可能产生整体失稳。建议采取有效的工程治理措施，消除滑坡对大桥运行造成的安全隐患。

STABILITY ANALYSIS OF LANDSLIDE IN THE SOUTH END OF FENGJIE HIGHWAY BRIDGE WITH FLUCTUATION OF WATER LEVEL OF THREE GORGES RESERVOIR

After the TGP dam was built, the reservoir will be impounded gradually till the level ascends at least 100 m in about 10 years. As the need of flood prevention, the reservoir water level will fluctuate between 175 m and 145 m. The periodical rise and descent of water level will change the intrinsic water-rock interaction circumstance and condition, which maybe results in the instability of reservoir banks and slopes. Under the fluctuation of different water levels, the seepage-stress fields, the deformation trends and the failure process of landslide are analysed using FLAC~(4.0). In addition, the change of landslide stability and its influence on bridge foundation after water level fluctuations are discussed in this paper. All these research results will provide technical supports for the stability assess of bridge foundation and the design of project prevention.