Geotechnical Aspects of Trans-Alaska Pipeline

Geotechnical design aspects of the 798-mile (1,285-km) trans-Alaska pipeline differ from those of more conventional pipelines in four respects: (1) The arctic climate and consequent presence of permafrost soils; (2) the remoteness of the project location; (3) design for seismic effects, and (4) specific environmental considerations. To accomodate these requirements, aboveground construction on structural vertical supports replaces the more conventional belowground construction for about half of the line. Use of belowground line is limited to areas that are stable under the applicable thawing and seismic conditions. It has been found necessary to consider quantitatively and design for the lateral and longitudinal support of the belowground restrained cross-country pipeline in bends and at the ends of belowground sections. The aboveground support bents consist of two vertical support members (VSM) and a cross beam. Several VSM types, including one that removes heat from the ground during freezing weather, were developed and design criteria for them generated.