Design and Construction of Banshengdong Underground V ertical Tanks

The paper introduces the design and construction of the underground storage in Banshengdong, Zhoushan City. This storage, buried in quartziferous porphyry, consists of several 5000 m³ tanks. According to the lithologic character, rock pillar thickness and geodynamics obtained through geological survey, it is pointed out that the rocks where tanks locate are of intemediate stability (mostty Class Ⅱ、Ⅲ), and are quite hard. The gunite support is tried as permanent supporting structure, thus one can treat the tank structure with a plan strain problem. With the help of rock mechanics, the paper analyzes computerized calculations for the two plans (four cases), and determines the law of cavern peridisplacement, the influence of initial rock stress field, the influence of fault on displacement, as well as the distribution of elastic areas. The reinforcing bar distribution pattern used in this project (1.5 m×2 m~2 m×2 m) is proved reasonable, and the safety margin for rock pillar thickness is 23~24 m. The screw excavation with a ring oblique channel running from the main leading pass to cap and pin of the tank, can speed up the project progress. Substitution of conventional integrated dome wall and separated dome vertical wall lined with gunite support as permanent support, and of bar bundle concrete gunite, result in high construction speed, lower raw material consumption and less construction cost.