Vacuum preloading and electro-osmosis consolidation of dredged slurry pre-treated with flocculants

Abstract

To improve the consolidation of dredged slurry, a combined method of vacuum preloading and electro-osmosis consolidation was applied to a dredged slurry pre-treated with flocculants. In this study, the optimal mixing ratio of two conventional inorganic flocculants was determined by conducting a settling column test. A vacuum preloading and electro-osmosis test was then carried out on the dredged soil after flocculating the soil particles. During the test, the drainage mass and surface settlement were monitored. After the test, the soil moisture content, shear strength, and soil particle size were measured. The test results show that the inorganic flocculant FeCl3 has a better flocculation effect than Al2(SO4)3, and its optimum value is 0.75% in terms of the soil dry weight. The addition of flocculants effectively increased the soil particle size, alleviated the clogging of drainage channels and PVDs (plastic vertical drains), and accelerated the drainage rate. Moreover, the electrical conductivity and electro-kinetic dewatering were improved, thereby increasing the shear strength and soil uniformity.