Effect of a peat layer on the ground thermal regime along the Hudson Bay Railway

ABSTRACT: The progression of climate change since the late 20th century has led to permafrost thaw and has significantly impacted infrastructure systems in polar and semi-polar regions. Consequently, there is a need to forecast the expected impact and find optimal and practical adaptation strategies. The Hudson Bay Railway (HBR), located in Northern Manitoba, is experiencing impact to the operations and serviceability due to permafrost degradation. Climate change has brought an increase in air temperature and a decrease in freeze-back. This phenomenon leads to changes in the ground thermal regime that increases the active layer thickness and permafrost degradation. Improved knowledge on the thermal mechanism of permafrost thaw and key parameters governing it is required. In thermal modeling of a soil medium, several parameters, including material thermal properties, are able to change the thermal response of the system. All these parameters can be affected by the soil type and texture. The presence of a peat layer on top of permafrost-affected soils can alter the thermal behavior of the system due to peat’s high water content. In this study, finite element thermal modeling using ABAQUS software is employed to evaluate the effect of peat layer thickness on permafrost thermal response. According to the results, as the peat layer overlying the permafrost thickens, the active layer thickness (ALT) increases due to the high water content and thermal conductivity of saturated peat in the HBR region. However, beyond a peak peat thickness, no further increase in ALT is observed. The findings contribute to a broader understanding of the peat layer's role in the thermal stability of the ground in the HBR area.