Geohazard Challenges Facing Major Oil And Gas Pipelines In East And North Africa
Depending on the circumstances, the design of any major oil or gas pipeline against geohazards may be a very demanding task, especially in areas with extreme terrains. The term "geohazards" may include landslides, soil erosion, karst phenomena and river migration. Nevertheless, in areas characterized by moderate or high seismicity the design of a buried or an above-ground pipeline may be a more challenging task since both safety and serviceability are directly related to the earthquake-related geohazards and the seismic vulnerability of the pipeline under consideration. The current paper is involved with the areas of East and North Africa where many oil and gas fields have recently been discovered, a fact that will certainly lead to the construction of many major oil and gas pipelines in the near future. The seismicity of the regions is known to be high and the geomorphology varying. After a short description of the tectonics, the geomorphology and the geology of the two areas, particular emphasis is given on the geohazards and mainly on the earthquake-related geohazards of the areas. Apart from the strong ground motion (i.e. acceleration and velocity levels) which is regarded as a key parameter of the design, the paper describes various potential phenomena of geotechnical earthquake engineering, such as active faults, soil-liquefaction phenomena (i.e. buoyancy, settlements or lateral spreading), and earthquake-triggered slope instabilities. Therefore, since the proposed oil and gas pipelines cannot avoid all the problematic areas, their final design should include (a) quantitative assessment of all geohazards and earthquake-related geohazards, (b) realistic soil-pipe interaction analyses, and (c) optimum design of various geotechnical and/or structural mitigation measures.