THREE-DIMENSIONAL STABILITY ANALYSIS OF DRILLING SITE IN DEEPWATER CONTINENTAL SLOPE AREA CONSIDERING VERTICAL HETEROGENEITY OF SOIL STRENGTH

To analyze the submarine stability in the deepwater continental slope area, a flow chart of submarine stability evaluation for deepwater drilling site in continental slope area is proposed. In this paper, the Lingshui X drilling site in the Qiongdongnan continental slope area is taken as the research area. A three-dimensional geometric model of the deepwater well site is constructed using the water depth data. Based on the geotechnical experiments and the seabed cone penetration tests, the undrained shear strength profile of the submarine soils is obtained. The factor of safety of three-dimentional slopes is calculated using strength reduction method and finite element method. Furthermore, the position and possible sliding direction of the potential landslide body at the well site are analyzed. The results show: (1) There is a piecewise linear relationship between the undrained shear strength and burial depth. Compaction is the main mechanism of the increase of soil strength with burial depth. Landslide or sediment environment can cause the sudden change of strength. (2) The maximum shear strain increment and velocity vector can be used to indicate the potential landslide bodies and slip direction, respectively. The predetermined well is not located in the potential landslide bodies or on the slip path. The minimum factor of safety is 1.23, which indicates that the seabed near the well is stable.