During the construction of one Myanmar ship yard dry dock project，a part of wall of wells for pumping test collapsed. The local instability reasons comprise ground water dynamical action, compaction effect of pile foundation, pressure grouting. After taking some measures, including making using of ground water dynamical action, improving slurry performance, releasing the compaction effect of pile foundation and so on, there was no local instability happened, and the quality of wells was testified very good by pumping test.