Yufeng Gao

Sedimentation Behavior of Four Dredged Slurries in China

Sedimentation model tests were carried out on four clays in China for investigating the sedimentation behavior of slurries. The sedimentary process can be divided into fluid state and consolidation state. The consolidation state of slurries can be divided into Non-Terzahi soil and Terzaghi soil. The void ratio responsible for the intersect point of fluid state and consolidation state is determined as 8.6 times the void ratio at liquid limit based on the difference of settling type which can be divide into Consolidation settling and Zone settling with the initial void ratio increase. According to the relationship between the stable void ratio (at the end of consolidation) and the initial void ratio, the suggested value of void ratio at the transition point from Non-Terzaghi soil to Terzaghi soil is 2.8 times its value at liquid limit.

Anisotropic Drained Deformation Behavior and Shear Strength of Natural Soft Marine Clay

The deformation behavior and shear strength of soft marine clays subjected to wave or traffic loads are different from that in triaxial loading due to the changes of major principal stress direction β and intermediate principal stress coefficient b. To investigate the anisotropy affected by β and b in natural soft marine clay, a series of drained tests were conducted by hollow cylinder apparatus. The principal stress direction relative to vertical direction were maintained constant under an increasing shear stress, with fixed intermediate principal stress coefficient b. The influence of the b and β on anisotropy of typically Wenzhou intact clay is discussed. It was found that octahedral stress–strain relationships expressed anisotropy with different b and β. The friction angle and deviator stress ratio with different b and β were presented to provide guidance for engineering projects in the coastal zone.

Compression Behavior of Dredged Slurries at High Water Contents

Oedometer tests were carried out using modified oedometer apparatuses on three different kinds of dredged slurries. Test results show that the compressibility of dredged slurries is influenced by initial water content when the initial water content is lower than upper limit water content. When the initial water content is higher than the upper limit water content, the compressibility is irrelevant with the initial water content. Result also shows that the upper limit water content is about three times their liquid limit. The compression curves of samples at the initial water content exceeding the upper limit water content overlap to a single curve. This compression curve is named as Top Compression Line (TCL) when it locates above the other compression curves of the same soil. At last, a normalized equation is obtained to normalize TCL of different soils.

Permeability Behavior of High-Moisture Content Dredged Slurries

In order to understand permeability behavior of high-moisture content dredged slurry in a storage yard, this article utilizes two modified oedometers to conduct consolidation and permeation tests on various kinds of high-moisture content dredged slurries in China. Experimental results show that although initial moisture content exerts a significant impact on the compression properties of dredged slurries, its impact on permeability property is relatively small, and the permeability coefficient has a one-to-one correspondence with the void ratio. In the coordinate system of e ∼ logk, the permeability coefficient of dredged slurry shows a nonlinear variance with void ratio. The permeability coefficient variability index C k is mainly distributed within 0.3 ∼ 0.7e and approximates to 0.5e. But in the coordinate system of loge ∼ logk, the permeability coefficient of dredged slurry shows a linear variance with the void ratio. Lastly, a e ∼ k quantitative method adapted to high-moisture content dredged slurry is proposed based on the normalized parameter e/e L .

Laboratory study on cement admixed marine silt bricks

ABSTRACT For the purpose of efficient utilization of sediments dredged from harbor, a new method was proposed in this study. Marine silt bricks were made by mixing sediments with cement and gypsum, placing it in a cubic mold with 240 mm in length, 115 mm in width, and 53 mm in height, and curing for certain days. To investigate the effects of cement and initial water content of soil on the mechanical behavior of marine silt bricks, unconfined compressive and flexural strength tests were carried out. Given the same curing time and cement content, the higher the initial water content, the lower the compressive and flexural strength. After 60 days of curing, the compressive strength of marine silt bricks with cement content = 20% and water content = LL (liquid limit) reached approximately 5 MPa. The flexural strength was relatively low. The flexural strength of marine silt bricks with 20% cement and water content = LL was around 1.5 MPa. The compressive and flexural strength decreased with the increase of water/cement ratio. As for the curing time, longer curing time had a positive impact on the compressive strength. The ratio of flexural to compressive strength varied slightly in the range of 0.4–0.5.

Rheological behavior of dredged slurries at high water contents

ABSTRACT Each year in the world, there is significant amount of dredged slurries generated during geotechnical jobs. In the slurry storage process, the rheological behavior is a key factor affecting the motion of dredged slurries. To gain better understanding on this behavior, experiments on dredged slurries with different liquid limits are conducted using rotary viscometer. It has been found that, as water content increases, slurry property can change from Bingham plastic fluids to Newtonian fluids. In log–log coordinates, their corresponding yield stress and plastic viscosity are in linear relationship with their water contents and the intersection of these two lines can be treated as the turning point which is 4.7 times the liquid limit. The yield stress and plastic viscosity of different dredged slurries can be normalized efficiently using normalized water content. So, in this paper, a new quantitative prediction method for yield stress and plastic viscosity is proposed, which is effective for use in alkined modes of motion, is proposed.

Effects of Column Diameter on Setting Behavior of Dredged Slurry in Sedimentation Experiments

This article investigates the influence of dimensions of a settling column on the settling mode and the settling rate. End conditions of the settling stage in the hindered settling were also analyzed. It was found that the settling mode in a column with a smaller diameter tends to be consolidation settling. The effect of a settling column wall decreases with increasing column diameter, and it can be ignored provided the column diameter is larger than 14.5 centimeters. For the difference in initial water content, the settling behavior of the slurry develops a different sensitivity to the diameter effect. The influence of column diameter reduces as the initial water content of the slurry becomes higher. It is suggested that the internal diameter of the column used in a sedimentation experiment should be 14.5 centimeters.