Measurements of undrained shear strength during natural drying
Résumé
Considering protection of the environment and environmental regulations, the great volumes of dredged low and/or high sediments should be treated. Because of the types of dredgers and the presence of fine particles of the sediments, they have high moisture content. So it’s necessary to carry out the treatments of dehydration and drying for decreasing the wa-ter content. The objective of this study is to follow the natural drying evolution of the sediments by their mechanical characterization. Through the analysis of the physical and chemical properties (grading nature, moisture content, limits of Atterberg and organic matter content) of studied sediments, characterization of shear strength was carried out taking account the influence of water content. The relatively long process of natural drying is depending on the time and by the relation of Su-W which is established by two methods of testing in laboratory. This paper consists of the presentation of results performed with fall-cone test (FCT) and vane shear test (VST) on dam and marine sediments. Relationship between water content and undrained shear strength obtained from fall cone and from vane shear test is evaluated and given. Finally, the relationship is discussed regarding the two testing procedures and a pro-posed correction for FCT could be suggested for dam and marine sediments. But measurements of Su with FCT and VST pose problem due to their principle and their procedure of testing. FCT test is applied only on top of sediment layer and VST test gives discrete measures along the vertical depth layer. Considering these limitations, a continuous Su testing will be preferable. Applicability of T-Bar test to sediments is examined. T-Bar test may be a suitable method to calculate the undrained shear strength of sediments. However, the applicability of T-Bar test (TBT) is not evaluated yet.