Stability,Analysis Of Submarine Slope In The Yellow River Estuary

The stability of submarine slope in the modern Yellow River Delta threatens the safety of oil and gas engineering facilities. However, the stability of submarine in this area is complex and hard to predict.There are many factors cause this phenomenon, such as the stratigraphic texture which formed by the huge Yellow River sediment load and its frequent diversions in history, the dynamic effects which contain waves, tides, earthquakes, etc.At present, in China, stability researches of submarine slope lack of systematic research which consider the processes of slope destroying, the internal stress and deformation, the size of destroyed slope, the assessment and prediction of stability. There is few quantitative calculation can be applied to practical work. The internal relation of stress and deformation is a vital factor to the systematic research.In this paper, the study area is in parts of KenDong area in the Yellow River estuary. It collects and processes the basic geological data and field survey data, including water depth data, geological drilling data, engineering geological drilling data, sub-bottom profiles data, hydrodynamic in-situ observation data, etc. By the qualitative analysis of engineering geological conditions, field survey data and results of previous studies, it summarizes the destroying process and influencing factors. It calculates the internal stress and deformation, stability factors in an extreme condition of 50-year strong north wind.The results show that in the study area, there are many slopes destroyed in an extreme condition of 50-year strong north wind, but the scale of them are small, the length range from 3～21 m, affecting depth range from 0.4～4.5 m.The soil has low degree of consolidation, high poriness, low strength and small permeability. The stratigraphic texture in the modern Yellow River Delta is complex and specific. The foreslope is steep in this area. Earthquakes, waves and tides can influence the stability of submarine slope. Therefore, the study area’s slopes destroying are mainly caused by the combined action of soil properties, the stratigraphic texture, topography and dynamic factors.Slope instability in the study area is from rotating to sliding. According to the analysis of stress and deformation, with the displacement and stress increases, the slope destroys from rotating to sliding. Finally, it slides along the slope.In this paper, it obtains the quantitative or semi-quantitative relations between the influencing factors and the minimal slope stability factor. In the study area, the quantitative relation between the minimal slope stability factor and water depth (3-9 m) is negatively correlated, the quantitative relation between the minimal slope stability factor and slope gradient (0～2°) is also negatively correlated, it also summarized the mathematical expressions. This paper also obtains the semi-quantitative relation between the minimal slope stability factor and waves, the semi-quantitative relations between the minimal slope stability factor and soil mechanical parameters. These relations are useful for preliminarily identifying potential destroyed slope.In this paper, it tries to combine the method of finite element and limiting equilibrium to calculate the stability factor. There are a small number of researches use the method of combining the two method in the submarine analysis of the submarine delta in the Yellow River estuary. The results of estimating the stability of submarine slope which use the method used in this paper can be referenced in practice or follow-up study.