Effects of Initial Concentration on Flocculation Size and Settling Velocity of Marine Hydraulic Fill Clay

Yang Shen,Yinghao Zhu,Dongdong Ge,Xue Shen

doi:10.1007/s41208-016-0016-8

Yang Shen, Yinghao Zhu + Show 2 more

Open Access

https://doi.org/10.1007/s41208-016-0016-8

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Abstract

Using marine hydraulic fill clay to reclaim land is the main mean to deal with land supply and demand in coastal area. Detecting the soil’s settling velocity, which is mainly affected by initial concentration of clay, is significant for filling projects. In this paper the marine clay of the East China Sea was used for tests to study the floc size and the settling velocity properties with different initial concentrations. According to SEM tests, it can be found that the typical floc size is about 17.5 μm in suspensions of different initial concentrations, so by using the Stokes’ formula the typical floc’s theoretical velocity is calculated. Then the settling column tests were carried out, and the formation of suspension-water interface was found related to initial concentration. When the initial concentration is 120 g L−1, the interface’s settling velocity is a little smaller than the theoretical value. As the initial concentration increased, the interface’s settling velocity reduced at a decreasing rate. Finally a modified semi-empirical formula is established to calculate the interface’s settling velocity of constant settling stage in different initial concentrations, which is significant for the study of hindered settling and the design of hydraulic fill elevation.

Highlights

As the rapid development of coastal areas and the increasing population, the contradiction of land supply and demand is more and more serious
In spite of the importance of the settling velocity, it is nearly impossible to obtain its actual value in situ, and in most cases it is obtained from laboratory experiments or predicted by empirical formulas
This paper presents a study on the characteristics of floc size and suspension-water interface in dilute clay-water mixtures

Summary

Introduction

As the rapid development of coastal areas and the increasing population, the contradiction of land supply and demand is more and more serious. Using hydraulic fill for land reclamation is undoubtedly a fast and effective method to fill a large area of land in coastal areas. In the past decades the studies on the properties and behavior of sedimentation of clay-water mixtures has increased gradually, motivated by the awareness of the importance of hydraulic fill in coastal areas. As a study (Kynch 1952) shown, the formation of suspension-water interface and its settling velocity are two of the key characteristics in the study of clay-water sedimentation. Few researches have been published on the properties of the formation of suspension-water interface and its settling velocity. This paper presents a study on the characteristics of floc size and suspension-water interface in dilute clay-water mixtures. A modified semi-empirical formula is established to calculate the settling velocity of suspension-water interface with different initial concentrations

Material and Methods

Results and Discussion

Conclusions