In order to solve the problem of large error between the coase sand pipeline transportation resistance calculated by Durand Formula and the measured value, a field test was carried out in a certain project. Based on the measured data, combined with the mathematical statistical analysis method, the optimization of Durand formula has been realized. The conclusions are given: the optimized formula can well characterize the pipeline transportation characteristics of the coarse sand, achieve high-precision & real-time prediction on the construction site, and the calculation method of the critical flow velocity with minimum friction is given.
In the land reclamation engineering, CSD and TSHD are mainly used to the filling construction. And the pipeline transmission is an important link, and the loss of pipeline pressure is an important research content of pipeline transportation characteristics. The current methods used for pipeline transportation resistance prediction is mainly based on three different theories (Fei, 1994, Fei, 1986): diffusion theory, gravity theory and energy theory. The representative empirical formulas based on the above methods are Durand formula, Wasp formula, Wilson formula, Fei Xiangjun formula, Wang Shaozhou formula, Chen Wenguang model, etc., and all have certain limitations and scope of application (Li, 2014, Durand, 1952, Wasp, 1977, Wilson, 2004, Wei, 2015). Among them, the classic Durand formula has been tested by years of construction experience (Ministry of Transport of the People's Republic of China, 2012), and it can basically predict the transportation resistance of common materials such as silt, silt and fine sand in large-diameter pipelines (such as DN750 and DN850). At the same time, some scholars have carried out a series of studies on the influence of different particle shapes on the transportation resistance of straight pipelines and vertical pipelines (Chung, 1998, Chen, 2020).
In recent years, the filling medium in the expansion projects of Xiamen Airport and Hong Kong Airport is mainly medium and coarse sand. According to the situation of on-site construction, the pipeline transportation resistance is greater. However, the Durand formula in the dredging specification is mainly obtained through theoretical analysis and experimental data with small diameters, and cannot very accurately represent the characteristics of pipeline transportation under the conditions of large diameters, large flows and high concentrations. Therefore, it is not suitable for DN850-Q235 pipeline transportation of coarse sand, which brings difficulties to the friction size, row spacing and output of coarse sand in pre-side pipeline transportation.
