Abstract

Long-distance transportation of coarse-grained dredging materials might be a formidable task. Researches on conveying properties of coarse-grained soil are mostly based on indoor small/medium-sized pipes, few demonstration analysis and researches with field test of large-scaled pipes. Conveying properties of dredging coarse sand are studied after a field test of large-scale pipes with an improved data analysis method. Formulas for friction resistance and practical minimum velocity are established, which are more accurate and optional than existing empirical formulas. The maximum conveying distance of 1 Cutter Suction Dredger(CSD) with steel/polyurethane pipe scheme are about 4.3km, and 4.6km respectively. For the transportation requiement of 5.5km in length, the schemes of 1 CSD with 1 boost pump with steel pipe, and 2 CSDs in parallel connection with steel or polyurethane pipe, are optional, with the production capacity 1890m3/h, 1350m3/h, and 2060m3/h respectively.

INTRODUCTION

Cutter Suction Dredger is a popular construction ship type in dredging and reclamation projects. The soil on the riverbed/seabed to be dredged is cut and agitated by the rotating cutter device, and transported to the disposal area or reclamation area by slurry pumps and pipelines. Due to its properties of continuous operation of excavation-transportationunloading, high efficiency and low cost,CSDs have been widely used in coastal and inland waterway construction and maintenance, river and lake dredging, environmental dredging and other projects. The conveying system, composed of slurry pumps and their driving system, pipelines and auxiliary devices, is the core equipment to transport dredged soil. Its operation performance is the key factor determining construction efficiency and energy consumption of CSDs (Xiong et al., 2015; Li et al., 2017). Usually, CSDs are equipped with one submerged pump and one or two deck/cabin pumps to meet different requirements. Different pump combination modes are adopted due to different conveying distance requirements, and the energy consumption of conveying system can reach more than 80% of the total energy consumption of the whole CSD (Bi et al.,2008; Li et al., 2017). In cases of short conveying distance, a necking at the outlet might be necessary, so as to avoid excessive discharge and low efficiency of slurry pumps; in cases of ultra long conveying distance, installation of boost pumps is the most common scheme in engineering (Song et al., 2017).

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