Research on the cuttings discharge in air cushion chamber of slurry shield based on CFD-DEM coupling method

Abstract

The rapid discharge of cuttings from the air cushion chamber is crucial for the construction safety and excavation efficiency of the slurry shield. Previous studies have mainly focused on the transport characteristics of cuttings in the slurry discharge pipe, while the complete process of cuttings entering the slurry discharge pipe from the air cushion chamber until they are discharged was often overlooked. Based on the CFD-DEM coupling method and combined with actual engineering, this paper established a numerical model that can more completely reflect the cuttings discharge process during slurry shield tunneling, and the effects of the slurry velocity at slurry gate and scouring pipes, inclination angle of slurry discharge pipe, cuttings diameter and shape coefficient were investigated by analyzing the variation in the mass flow rate, mass of discharged cuttings, and discharged ratio. The results revealed that increasing the slurry velocity can promote the discharge of cuttings. To keep the discharged rate at a high level, it is recommended that the slurry velocity at the slurry gate should be greater than 0.15 m/s. Reducing the inclination angle of the discharge pipe is conducive to the rapid discharge of cuttings. Cuttings with large diameter or small shape coefficient are more prone to accumulate in the air cushion chamber and cause clogging risk. The research results not only help to improve engineers' understanding of cuttings discharge in slurry shield, but also provide practical guidance for formulating relevant construction measures.