Arctic Pipeline Engineering Toolbox

The proposed route of both the Mackenzie and Alaska Gas Pipelines from the Arctic down to southern markets in the United States and Canada has much of the northern section passing through terrain underlain by continuous and discontinuous permafrost. Infrastructure projects of this magnitude must ensure that lives, wildlife, the environment, and substantial investments are protected.

Understanding pipeline interaction with freezing ground and permafrost is of fundamental importance to companies charged with enhancing the safety, reliability, and productivity of energy pipeline infrastructure. In addition to these challenges, companies face increasingly stringent regulatory requirements for existing infrastructure and for the design and construction of future gas pipelines for Alaska and Canada’s Northwest Territories.

Buried pipelines are subjected to stresses imposed by the freezing process wherever spatial differences in frost heave exist. Variation in frost heave can be due to different soil properties and the differences in thermal transitions between perennially frozen soils (permafrost) and seasonally frozen soil. Differential frost heave combined with the resistance to deformation by either non-frost-susceptible soils or permafrost will result in bending stresses in pipelines.

To meet these challenges, Permafrost Environmental Consulting Inc. (PEC), a cold climate engineering company, developed a Database Library containing six databases comprising hundreds of data sets and a 14-volume engineering library. Pipelines in Permafrost and Freezing Ground addresses important information gaps identified by regulatory bodies and from industries worldwide experienced with pipelines in freezing ground and permafrost.

Compiled from data acquired during decades of field and laboratory research into the behaviour of full scale pipelines in permafrost and freezing ground, the databases and library help engineers and scientists understand soil strain and soil creep, frost heave and frost bulb growth, thaw consolidation that leads to pipeline relaxation, pressures in freezing soil and permafrost, and bending stresses in buried pipelines. It also provides information on the uplift resistance of pipelines, and of the hydraulic, thermal, and mechanical properties of freezing soil and permafrost.

By utilizing these Pipeline Research Council International’s endorsed databases, pipeline engineers are better able to develop, test, calibrate, and verify numerical models of frost heave, frost penetration, frost bulb growth, and the thermodynamic processes. The databases allow them to perform in-depth analysis of pipe-soil interaction in both freezing ground and permafrost, which will lead to better risk assessment capabilities for operating a high pressure gas pipeline in permafrost and soils exposed to seasonal freezing. In turn, pipeline companies are better equipped to ensure safe operation, meet regulatory requirements, and reduce long-term expenses.

Models developed using our Program Modules are used to Predict

• Soil strain and soil creep
• Frost heave and frost bulb growth
• Thaw consolidation and pipeline relaxation
• Pressure in freezing soils and permafrost-affected soils
• Bending stresses in buried pipelines
• Uplift resistance of pipelines in permafrost
• Hydrological properties of freezing soils and permafrost-affected soils

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