Abstracts:Ice gouging is one of the critical threats to the subsea pipelines crossing the Arctic and neighboring shallow waters. The burial of subsea pipelines is considered a viable solution to protect them against ice gouging attacks. The pipeline is usually buried below the deepest recorded ice gouges in that specific geographical location but is still threatened by subgouge soil deformation that is extended down the ice tip due to the shear resistance of the seabed soil. Determination of the subgouge soil deformations is a challenging design aspect that usually requires costly experimental and numerical studies to ensure the structural integrity of the buried pipeline against ice gouging. In this paper, an alternative and cost-effective methodology has been proposed using the group method of data handling (GMDH) to simulate the horizontal and vertical subgouge soil deformation profiles in the sandy seabed. Ten GMDH models (GMDH 1 to GMDH 10) were defined by using the governing input parameters comprising the soil depth ratio, the gouge depth ratio, the shear strength of seabed soil, the attack angle, the frontal berm height ratio, the horizontal and vertical loads, and the ice dynamics. The results from the best GMDH models were compared with the artificial neural network and empirical approaches, which showed a robust performance.

Abstracts:This manuscript presents and discusses the results of an experimental study on the deformation behavior, strength, and microstructural development of cemented paste backfill (CPB) with chloride-bearing antifreeze (calcium chloride, CaCl₂) in subzero environments. CPB samples with CaCl₂ at various concentrations (0, 5, 15, and 35 g/L) were cured at different subzero temperatures (−1, −6, and −12°C) that represent temperatures to which CPBs may be exposed in mines located in permafrost or cold regions. Unconfined compressive strength (UCS) tests were conducted after specific curing time (7, 28, 60, and 90 days). Moreover, microstructural analyses and monitoring experiments (for volumetric water content and matric suction) were performed. The results showed that the addition of calcium chloride antifreeze reduced the strength of CPB and had a significant impact on its stress–strain behavior and microstructural characteristics. Furthermore, it was also found that the strength of CPB decreased with an increase of calcium chloride concentration and subzero curing temperature. These findings provide important guidance for mine backfilling work of CPB with chloride-bearing antifreeze additives and productivity improvement in subzero environments.

Abstracts:Nowadays, chitosan biopolymer has received much research attention in geoenvironmental practices like soil erosion reduction, hydraulic conductivity, and heavy metal absorption in contaminated soil. Nevertheless, the effect of chitosan incorporation on freeze–thaw resistance of soft clays has not been evaluated comprehensively. In this research, different concentrations (2%, 4%, 6%, and 8%) of biocompatible chitosan, which is synthesized from the waste of shrimp shells, are utilized to investigate its potential in resistance of clay specimens subjected to 1, 2, 3, 6, 12, and 24 freezing and thawing cycles. The results demonstrate that the stress–strain behavior and compressive strengths of the specimens significantly depend on the amount of added chitosan solution. The unconfined compressive strength grows as the chitosan content increases from 2% to 6%. The 8% chitosan destroys the balance in the overall electrical neutrality of the mixture and does not make a noticeable influence in comparison to 6%. Moreover, the interparticle interactions are strongly linked to the curing time and moisture content of specimens, and chitosan solution can provide an extra interaction among clay particles in the early days. Increasing the curing time for the treated specimens leads to an increase in compressive strength while its efficiency remains constant over time. The durability index used to quantify the resistance of the treated specimens to freeze–thaw damage reveals that by three freezing and thawing cycles, the index reduces to 0.64 and 0.66 for samples in optimum and saturated water contents, respectively. This reduction will be negligible for higher cycles (e.g., 0.53 and 0.50 for 24 cycles). In addition, according to the analysis by scanning electron microscopy, the number of freezing and thawing cycles has a substantial influence on enlarging the voids and clay disintegration, which damages the stabilized soft clays.

Abstracts:The objective of this study is to evaluate the impacts of two commonly used temperature databases, Parameter-elevation Relationships on Independent Slopes Model (PRISM) and Topography Weather (TopoWx), on the quantity and distribution of snowmelt in the Missouri River Basin simulated by a new macroscale grid-based model for two representative flood and drought years. The model incorporates a unique LEGO-fashion framework to account for within-grid heterogeneity. The snowmelt simulations were compared with the SNOw Data Assimilation System (SNODAS) estimates, indicating that both data sets provided comparable snowmelt with the SNODAS data (R² > 0.91). Comparison of the modeling results revealed that both data sets provided comparable magnitude and distribution of the average monthly snowmelt. However, the average daily snowmelt varied up to 16.9% and the snowmelt variations were more pronounced in the areas with complex topography. The simulations suggested that even nuances in the snowmelt coverage led to significant changes in the simulated snowmelt quantity.

Abstracts:In recent years, permafrost warming has adversely affected the performance of infrastructure projects in northern Canada. The common construction practice in these permafrost-underlain areas is to use the pile foundation for building and infrastructure rather than using shallow foundations. Thus, the influence of warming permafrost on the loading capacity of pile foundations is critical for evaluating forthcoming changes under a warming climate. The present study was performed to assess the influence of temperature and loading rate on the adfreeze strength of piles in permafrost soil. A series of uniaxial compressive tests on wooden piles drilled into frozen soil were carried out at various temperatures, mimicking the conditions in warming permafrost. The results demonstrated that an increase in strain rate led to an increase in the adfreeze strength of piles. Moreover, the wooden piles exhibited peak adfreeze strength at a displacement of less than 2 mm for most temperature and deformation rate combinations. Interestingly, although the adfreeze strength of piles increased as temperatures cooled below −1°C, a transition phase between −3°C and −4.5°C was observed in which the adfreeze strength decreased. It could be noted that failure occurred in the wooden piles at temperatures colder than −5°C rather than frozen soil failure at these temperatures. These variations in the adfreeze strength were related to soil temperature, unfrozen water content, and the adhesive bonds at the interface between the frozen soil and pile.