Abstract:Small sludge discharge tanks are key structures in the sludge treatment system of waterworks, and their structural type selection directly affects the engineering economy and operational safety. At present, the design mostly relies on experience, lacking quantitative basis, and there is no clear optimal system guidance for working conditions. Based on the slice method, a parametric model (with a buried depth of 3~7 m and a width of 6~10 m) is established by using the finite element software Robot. The internal force laws of two types of tanks, namely open-top tank and covered tank, are analyzed, and the performances of three roof systems of flat slab type, slab-beam type and beam-column type of covered tanks are compared. The research results show that under the external soil condition, the critical buried depth of open-top tank is 5.0 m. When the buried depth ranges from 5.0 m to 7.0 m, the bending moment of the side wall of the tank increases by 248.6%, indicating that open-top tank is suitable for projects with a buried depth not larger than 5.0 m. The covered tank is constrained by the roof, and its side wall bending moment is significantly lower than that of the open-top tank. The roof bending moment of covered tank is sensitive to the span, with an increase of 256.9% when the span changes from 6 m to 10 m. For small-sized covered tank with a single span not larger than 6 m, the cost of the flat slab system is 9.2% lower than that of the beam-column system, demonstrating the optimal comprehensive advantages. Finally, a structural type selection adaptation table coupled with buried depth and width of the tank is established, which can make up for the deficiency of specifications in the optimization of working conditions.
