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A platform for research: civil engineering, architecture and urbanism
Case Studies of Offshore Slope Stability
Submarine slides represent a significant threat for offshore infrastructure and for coastal communities. This paper presents four case studies where the stability of underwater slopes was investigated. In two cases, the slopes were near shore, whereas for the third and fourth cases, the slopes were in deepwater far from shore and at locations of large oil and gas exploitation projects. Two cases show the importance of integrating information from the geosciences to establish a realistic model of the slope and seabed. Submarine slides can be due to natural on-going processes or to human activities, or can be triggered by external processes such as earthquakes. Assessing a slope instability hazard requires information about the frequency of the sliding events and triggers, the soil conditions and the morphology of the area. Other than man-made activity causing underwater slides close to shore, earthquakes are probably the most common trigger of offshore slope instability. Three scenarios of earthquake-induced slope failure should be analyzed: 1) Failure occurring during the earthquake, where excess pore pressures generated by the cyclic stresses degrade the shear strength; 2) Post-earthquake failure due to increase in excess pore pressure caused by seepage from deeper layers; and 3) Post-earthquake failure due to creep and reduction of the shear strength. Soils with significant strain-softening are most susceptible to failure during earthquake shaking. The paper outlines a procedure for calculating the annual probability of earthquake-induced failure for a submarine clay slope. The main challenges for improved hazard and risk assessment are not only related to the probabilistic or risk analysis aspects of the offshore geohazards, but also to reducing the uncertainties in the parameters in the analysis.
Case Studies of Offshore Slope Stability
Submarine slides represent a significant threat for offshore infrastructure and for coastal communities. This paper presents four case studies where the stability of underwater slopes was investigated. In two cases, the slopes were near shore, whereas for the third and fourth cases, the slopes were in deepwater far from shore and at locations of large oil and gas exploitation projects. Two cases show the importance of integrating information from the geosciences to establish a realistic model of the slope and seabed. Submarine slides can be due to natural on-going processes or to human activities, or can be triggered by external processes such as earthquakes. Assessing a slope instability hazard requires information about the frequency of the sliding events and triggers, the soil conditions and the morphology of the area. Other than man-made activity causing underwater slides close to shore, earthquakes are probably the most common trigger of offshore slope instability. Three scenarios of earthquake-induced slope failure should be analyzed: 1) Failure occurring during the earthquake, where excess pore pressures generated by the cyclic stresses degrade the shear strength; 2) Post-earthquake failure due to increase in excess pore pressure caused by seepage from deeper layers; and 3) Post-earthquake failure due to creep and reduction of the shear strength. Soils with significant strain-softening are most susceptible to failure during earthquake shaking. The paper outlines a procedure for calculating the annual probability of earthquake-induced failure for a submarine clay slope. The main challenges for improved hazard and risk assessment are not only related to the probabilistic or risk analysis aspects of the offshore geohazards, but also to reducing the uncertainties in the parameters in the analysis.
Case Studies of Offshore Slope Stability
Lacasse, Suzanne (author) / Nadim, Farrokh (author) / Vanneste, Maarten (author) / L'Heureux, Jean-Sébastien (author) / Forsberg, Carl Fredrik (author) / Kvalstad, Tore J. (author)
Geo-Congress 2013 ; 2013 ; San Diego, California, United States
Geo-Congress 2013 ; 2369-2408
2013-02-25
Conference paper
Electronic Resource
English
Case Studies of Offshore Slope Stability
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