STUDY ON EFFECT OF FACTORS ON CRITICAL SHEAR STRESS OF COHESIVE BANK MATERIALS FOR COASTAL EROSION

The aim of this study is to investigate effect of sand-silt-clay content, moisture content, salinity, consolidation, and vegetation density on critical shear stress (tc) of cohesive bank materials for erosion processes of rivers and coastal regions. The authors used the non-vertical submerged jet test apparatus designed by Hanson et al. (2002) and reproduced by Deguchi et al. (2007) to carry out both laboratory and in situ measurements. The laboratory experimental results showed that the tc increased as the rate of clay content, salinity, consolidation, and vegetation density increased. The t c decreased as the moisture content increased. The in situ experimental results of five severely eroded sites of the Soai Rap river banks, southern Hochiminh City were similar to thoses of laboratory experiments. The erodibility (kd) of cohesive bank material can also be determined when the t c is measured.