Journal of Cold Regions Engineering

Applying prewet deicers to roads during adverse winter weather is a cost-effective strategy to improve transportation safety and mobility. Prewet deicers have a small amount of liquid product applied to solid salt or salt/sand that speeds up ice melting and reduces deicer bounce-and-scatter loss. This study first presents the results of an in-depth survey of the Pacific Northwest on prewetting practices and then presents laboratory tests that quantified the ice melting, frictional behavior, and variation in snow–pavement bond strength of salt prewetted with various liquid deicers and at various rates. An ice melting test is a broadly accepted method to gauge the basic performance of deicers in a laboratory. More sophisticated laboratory tests on asphalt pavement samples with realistic snow and representative trafficking motion and forces were conducted. The laboratory tests confirmed that the prewetting liquid-to-solid application rate in the range of 33–67 L/t (8–16 gal./t) is reasonable for increasing the speed and total ice melting capacity (IMC) of solid salt. Furthermore, prewetting significantly reduced snow–pavement bond strength but did not increase friction more than dry salt.

This paper describes an application for microbial induced calcite precipitation (MICP) on the cementation of shale soils for ground reinforcement in cold regions. The micro and macrostructures of the cemented body were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) imaging techniques. The results showed that MICP can cement shale particles effectively with a significant amount of generated calcites on the surfaces of particles. Cementation tests for shale soils with various size distributions indicated that shale allows easy deposition of calcium carbonate (CaCO₃) crystals with high bond strength. The optimal particle size distribution to achieve high strength should include particles with good grading in all size ranges. To investigate the damage characteristics of the cemented body in response to freeze–thaw weathering processes, tests were carried out on samples with four different water contents. The apparent damage characteristics of the cemented body and the development of pores and fissures due to freeze–thaw weathering were studied in detail. The results showed that the freeze–thaw failure of the cemented body was a physical process occurring when the frost heave force exceeded the bond strength created by MICP. When the number of freeze–thaw cycles exceeded a certain threshold, large areas of damage were formed, leading to significant spalling on the surface of the cemented body. More severe spalling damage was observed for cases with higher water content and more numbers of freeze–thaw weathering cycles. The T₂ spectrum curves of the cemented body showed that the development of small to medium size pores was dominant for the cemented body with low water content and for high water content, the continuous expansion of large size pores was dominant. In addition, this feature was consistent with the observations from magnetic resonance imaging (MRI) images.

To study how the coupling between acid–base pollution and freeze–thaw cycles (FTCs) affects the shear-strength properties of recompacted loess, soil specimens are subjected to direct shear tests after FTCs. The experimental results indicate that of the cohesion and internal friction angle of polluted soil, the former is much more likely to be affected by FTCs. The cohesion deteriorates significantly with more FTCs, and this is the main reason for the change in soil strength, i.e., the acid–base pollution acts to increase the soil strength, but the FTCs act to reduce it. The strength indexes of soil specimens with different concentrations of chemical solution after FTCs are also different. The order of the coupling effect on the soil strength is secondary pollution > primary pollution > no pollution. The composition of the soil specimens differs with the order in which the chemical solutions are added, thereby leading to differences in the apparent and strength characteristics of the soil after FTCs. It is concluded that consideration must be given to the impact of the change in soil strength properties after secondary pollution in seasonal frozen areas.

Full-scale thawing experiments, performed on three types of homogenous, initially frozen soils, were carried out during late winter 2011 and repeated in 2012. An auxiliary heat source (hydronic heating) was employed to initiate and expedite the thawing process. The corresponding phase change, soil temperature increase, and variations in bound and unbound water content were monitored during the experiments. The resulting thermal response have been published in an earlier paper by the authors. In the current paper, the remaining results are presented. This includes spatial and temporal soil moisture variations and resulting thaw rates. Results from both experiments show similar trends. Generally, frost-susceptible soils, such as silty sand, contain more water and thaw slower relative to coarser soils, such as gravelly sand. Very porous soils (uniform gravel) with low water content thaw comparatively slower. Thaw rates compiled from soil moisture records correspond well with similar based on soil temperature. The degree of water redistribution and migration is higher in silty sand compared with coarser soils. These processes are more prominent in the uppermost layer for all soils examined.

Wellhead subsidence is one of the most severe engineering disasters during drilling operations in cold regions. Based on the characteristics of thaw-induced settlement of frozen soil, a thermal–fluid–soil coupling numerical model was developed in this study to analyze the probability of settlement at wellbores drilled in the cold sea areas of polar regions. The results show that the thawing of frozen soil due to the heat transfer from hot fluid flowing in the casing to the frozen soil layer is an important reason for the instability of the wellhead. The wellhead subsidence is due not only to an overall formation settlement that results from the thawing of large areas of frozen soil but also to the collapse of the formation surrounding the wellhead due to the accumulation of plastic deformation. The thickness of frozen soil depends on the seafloor temperature, but the thickness of frozen soil and the seafloor temperature exert contrary influences on the stability of the wellhead. A thicker frozen soil layer requires a lower seafloor temperature, leading to higher instability. However, a lower temperature is favorable for the stability of the wellhead. The wellhead stability is a result of the comprehensive interaction of these two factors. Improvement in the heat-insulating property of the casing is an effective method for maintaining the stability of the wellhead. When the thermal conductivity of the casing is lower than 0.1 W · (m°C), the stability time of the wellhead is feasible for the duration of general drilling operations. These research findings provide a theoretical basis for maintaining wellhead stability during drilling operations in cold regions.

During summer 2017, two parallel trenches were excavated in the Sagavanirktok River (located in northern Alaska, United States) to acquire construction material for roadwork on the Dalton Highway nearby. A study to estimate the time it would take for the trenches to fill with the upstream sediment was needed. In undertaking this study, we used three bed sediment transport equations for gravel-bed rivers available in the Sedimentation and River Hydraulics—Two-Dimensional model, with three hydrograph input scenarios: (1) normal cumulative volumetric flow; (2) maximum discharge; and (3) maximum cumulative volumetric flow. These scenarios, coupled with the three sediment transport equations, produced a total of nine simulations. Scenario 1 predicted a time to refill of 1–3.75 years based on the sediment transport equations used. Scenarios 2 and 3 predicted shorter times to refill. All three sediment transport equations predicted that sustained high flows are capable of refilling the trenches in 1 year. This is the first time that calculations have been made to estimate the refilling time of an extraction site on the Sagavanirktok River. These calculations could expedite the permitting process, eliminating the need for a new extraction site by returning to a site that has refilled with sediment. An indirect benefit of these calculations is that they provide information for fisheries biologists working in northern regions.