三峡永久船闸采用直立岩坡贴壁式薄衬砌边墙，墙后外水压力是边墙稳定的重要荷载。船闸闸室水位变动频繁，当闸室水位突降，由室内渗出的外水即构成作用在边墙上的外水压力。考虑了墙内排水体系的作用，对非恒定渗流问题进行了多工况分析，给出极端最大外水压力值。 The permanent shiplock of the Three Gorges Project adopts an erected rock lining with thin lining wall, and the external water pressure behind the wall is an important load for the stability of the side wall. Frequent changes in the lock chamber water level, when the sudden drop in the water level in the lock chamber, the external water seepage from the room that constitutes the external water pressure on the wall. Considering the effect of the drainage system in the wall, a multi-condition analysis on the unsteady seepage problem is given, and the extreme maximum external water pressure value is given.