Abstract: Sedimentation tank is one of the most important facilities in wastewater treatment engineering, and cracks and leakage problems often occur during the construction or use of sedimentation tank due to its huge plane size. The key to the design and construction of twelve 66-meter-diameter sedimentation tanks in a sewage plant was to solve the problems of cracks, soil liquefaction and soil bearing capacity. Compensation concrete and pre-stressed tendons were used respectively to eliminate or avoid the hydration heat temperature difference, shrinkage thermal stress and environmental thermal stress, so as to prevent shrinkage cracks and structure cracks. The liquefaction and bearing capacity problems of foundation soil were solved by using large diameter vibro-replacement stone column. After years of operation, the structure of sedimentation tank is still solid, proving its good application results

Key words: Sedimentation tank, Prestress, Crack, Soft soil, Vibro-replacement stone column