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Snowmelt erosion is an important way of soil loss in Chinese Mollisol region. However, little is known about the effects of seepage flow and soil thaw depth on hillslope snowmelt runoff erosion. An indoor simulated experiment was conducted to analyze the impacts of seepage flow and soil thaw depth on hillslope snowmelt erosion. There were two snowmelt flow rates (1 and 4 L·min -1 ), two soil thaw depths (5 and 10 cm), and two near-surface hydrological conditions (with and without seepage flow). The results showed that hillslope runoff depth and soil erosion amount in the treatment with seepage flow were 1.1 to 1.2 times and 1.3 to 1.9 times of those in the treatment without seepage flow, respectively. Under two snowmelt flow rates, when soil thaw depth increased from 5 cm to 10 cm, hillslope runoff depth and soil erosion amount increased by 10.0% to 13.5% and 15.4% to 37.1% in the treatment without seepage flow, respectively. In the treatment with seepage flow, when soil thaw depth shifted from 5 cm to 10 cm, hillslope runoff depth increased by 6.5% to 8.5%, and soil erosion amount remained stable. Moreover, hillslope rill development was comprehensively influenced by seepage flow, soil thaw depth, and snowmelt flow rate, with rill erosion amount occupying more than 72% of hillslope snowmelt erosion amount. Compared with the treatment without seepage flow, flow velocity and shear stress under the treatment with seepage flow increased by 20.3% to 23.2% and 37.0% to 51.3%, respectively; but Darcy-Weisbach friction coefficient reduced by 9.0% to 21.4%, which caused an increase of hillslope snowmelt erosion. In addition, seepage flow enhanced rill development, which caused rill erosion amount to increase by 43.6% to 69.9% compared with the treatment without seepage flow, and it further resulted in the increase of hillslope snowmelt erosion amount. The main reason for soil thaw depth enhancing hillslope snowmelt erosion amount under the treatment without seepage flow was that both sloping runoff erosivity and erodible materials increased with increasing soil thaw depth. Furthermore, soil thaw depth had a significant impact on hillslope rill morphology development under the treatment with seepage flow. Rill widening process was dominated when soil thaw depth was 5 cm, whereas rill incision process was dominant when soil thaw depth was 10 cm. This study could improve the understanding of hillslope snowmelt erosion mechanism in Chinese Mollisol region and provide theoretical guidance for the development of water erosion model.

• A moisture-heat coupling model for artificial ground freezing was proposed. • The model was to quantify the temperature field under various seepage conditions. • The predicted results were in agreement with the monitored results. • An increase in seepage velocity increases the time for freezing curtain formation. Artificial ground freezing (AGF) is a reliable technique for ground improvement to address adverse geotechnical engineering conditions. The formation of a freezing curtain during the AGF process is crucial as it serves to control groundwater flow and enhances the strength of the soil. However, groundwater flow has a considerable influence on the formation of the freezing curtain because it provides a continuous source of heat. Thus, to investigate the influence of water flow on the freezing process during AGF, a moisture–heat coupling model was proposed considering ice/water phase transition to quantify the temperature distribution in soil during the freezing process. The proposed numerical model was further validated using thorough laboratory tests under various seepage flow conditions. Finally, a numerical simulation of AGF was conducted for the end well of the Harbin metro station in China. Five representative monitoring points on the end well were selected and continuously monitored for 30 days to predict the formation of a freezing curtain. It was observed that the temperature results obtained using the proposed model are consistent with actual field monitoring data. [ABSTRACT FROM AUTHOR]

Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface of silty sand seabeds, i.e., the phenomenon called wave-induced soil erosion. This is thought to be due to the seepage flow caused by the pore-pressure accumulation within the seabed. In this paper, a kind of three-phase soil model (soil skeleton, pore fluid, and fluidized soil particles) is established to simulate the process of wave-induced soil erosion. In the simulations, the analytical solution for wave-induced pore-pressure accumulation was used, and Darcy flow law, mass conservation, and generation equations were coupled. Then, the time characteristics of wave-induced soil erosion in the seabed were studied, especially for the effects of wave height, wave period, and critical concentration of fluidized particles. It can be concluded that the most significant soil erosion under wave actions appears at the shallow seabed. With the increases of wave height and critical concentration of fluidized particles, the soil erosion rate and erosion degree increase obviously, and there exists a particular wave period that will lead to the most severe and the fastest rate of soil erosion in the seabed. [ABSTRACT FROM AUTHOR]