(1. College of Civil Engineering and Architecture，Zhejiang University，Hangzhou，Zhejiang 310027，China； 2. College of Civil Engineering and Architecture，Central South University，Changsha，Hunan 410075，China)
Abstract：The lateral displacements of anti-slide piles are monitored using inclinometer. The internal forces of anti-slide piles were estimated through back analysis of the lateral displacement and then compared with the design internal forces. The operation state of the anti-slide piles could be deduced from the internal forces，which may be divided into the stable state，the limit security state and the instable state. In the stable state，the anti-slide pile still contains certain margin of safety；in the limit state，the anti-slide pile fully plays its role，and it is in the critical state of invalidation；in the instable state，the anti-slide piles cannot meet the required standard，which may lead to the failure of the anti-slide，therefore，the monitoring should be strengthened and the new reinforcement measure is needed. The anti-slide piles in project are in the stable state by back analysis based on data.
