结合南水北调中线工程河北段南沙河预应力混凝土倒虹吸结构的设计，采用有限元分析方法，研究了各种设计工况下地基条件变化对倒虹吸结构的受力性能影响规律。结果表明：地基不均匀对倒虹吸结构整体在正常使用阶段的受力状态具有较大影响，采用换填土方式改善地基均匀性对改善倒虹吸结构整体受力性能特别是底板受力状态具有显著作用。

In combination with the prestressed concrete structure design of inverted siphon down across the Nansha River of the Center Route Project of Water Transfer from South to North, the three dimensional finite element analysis method was used to study the effects of foundation changes on the behaviors of inverted siphon structure under several design conditions. The calculated results show that the regularity of foundation has more influence on the behaviors of inverted siphon under unevenness state, and that the marked improvement to the behaviors of inverted siphon can be obtained by displacing soil adjusting the regularity of foundation, especially to the behaviors of bottom slab of inverted siphon.