Abstract: The characteristics of construction, structure and material, operation of cofferdam on thick overburden were analyzed. The challenges in cofferdam design and research, and the overall aims of seepage control system were discussed. The main content, technical route and important conclusions of studies on the safety of seepage control system and structures of cofferdam on thick overburden were presented.

Key words: cofferdam , overburden  ,   seepage control ,    impervious body ,    deformation  ,   safety