Abstract: The opening of chambers is a dangerous job with respect to the construction of earth pressure balance shield machines in mixed ground. This paper introduces the risk of chamber opening, discusses risk control methods, analyzes the geological and hydrological condition of the Shenzhen area concerning the issue of chamber opening, and presents risk prevention measures for site selection of chamber opening under various conditions. Additionally it discusses the experience of chamber opening in Lot 2222 of the Shenzhen Metro line 2.