SOIL DEFORMATION AND EROSION NEAR MOORING CHAINS IN CLAY BASED ON CYCLIC T-BAR TESTS

Soil deformation and erosion induced by anchor chain motion has a significant influence on the formation of trenches into the seabed near the touchdown area. However, the soil deformation and erosion are not well understood in the present trench formation, which limits the wide application in the prediction method. This paper presents a series of monotonic and cycle T-bar penetration tests to investigate the soil deformation and erosion phenomena at the seabed. Different soil undrained shear strengths were adopted, and a camera was used to record the soil deformation in real time. During the monotonic and the first penetration in the cyclic tests, the soil was displaced by the T-bar. In the cyclic tests, the degradation of soil resistance mainly appears in the first 20 cycles, and the final resistance is originated from the water replacement in the trench. The soil erosion near the T-bar mainly appears in the cracks formed during the initial penetration. When the water in the trench is replaced by the T-bar, water flows and erodes fine particles through the cracks. The trenches are initially caused by the T-bar penetration, and then the soil along the trench wall and bottom are eroded away during cyclic loading to form stable trench profiles.