ABSTRACT:

Submarine landslide is a typical kind of geohazard on the continental shelf which may trigger impulsive waves and cause substantial damage to the safety of infrastructure such as underwater oil-pipelines and drilling platforms. The purpose of this study is to investigate the mechanism of two-dimensional low-angle submarine landslide resulted from the properties of the weak layer underneath the slope. It is indicated by some experimental and theoretical data that the disassociation of gas hydrates could directly increase pore water pressures, decrease effective stresses in the submarine slope, and reduce the friction coefficient between different soil layers of slope, in consequence the slope stability will be weakened. In this paper, a two-dimensional numerical simulation, incorporating upper-bound energy method is presented to improve the understanding of the failure mechanism of submarine gentle slope with low-angle. Based on the analysis, it is found that a very soft layer due to gas hydrate disassociation or low internal friction angle will pose a big threat to the slope stability. It is also found that the burial depth of the weak layer can influence the stability of the slope. Parametric study indicates that landslides may be triggered when the soft layer is liquefied and the shear strength tends to be very low.

INTRODUCTION

During recent years, the growing exploiting of nature resources on the continental shelf and the continuing need for coastal development have led to a better understanding of the causes and the inherent mechanisms of submarine landslides. However, unlike the analysis of subaerial landslide which has been done with an adequate knowledge of morphology and stratigraphy, some cases are unique to marine environment, i.e. role of gas charging, gas hydrate disassociation and wave action, which make it more difficult to understand and assess the submarine landslide (Locat and Lee, 2000).

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