Dewatering effect on dredged slurry clay by different types of drainage materials

Abstract

Kumamoto slurry clay has high water content and organic
content. From the preliminary test, it was found that
improvement effect of this clay by adding hardening agent such
as cement is very small. It was also suggested that dewatering
of the clay is important for improvement. In this work, several
types of drainage materials were installed in the slurry clay in
the field and laboratory test conditions, respectively. A simple
dewatering method of soft clay using geotextile as drainage
materials was proposed based on the dewatering test results.
The effect of the drainage materials on the slurry clay were
evaluated by ratio of 7 day water content and initial water
content of the slurry clay (w7/w0). The ratio of w7/w0 in the
samples with string and cloth was 0.55 under the effective
drainage condition in the laboratory test. The values of w7/w0 on
the field dewatering tests with the drainage materials (string and
cloth) are below 0.75. In the laboratory and field dewatering
tests, 25 and 35 kPa vacuum pressure can be obtained,
respectively. It is indicated that the drainage materials are
effective for reducing the water content of the slurry clay without
applying external force of energy.