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Rainfall has been considered as the major cause of the slope failure. The mechanism leading to slope failures included the infiltration process, surface runoff, volumetric water content and pore-water pressure of the soil. This paper describes a study in which simulated rainfall events were used with 2-dimensional soil column to study the response of unsaturated soil behavior based on different slope angle. The 2-dimensional soil column is used in order to demonstrate the mechanism of the slope failure. These unsaturated soil were tested with four different slope (15°, 25°, 35° and 45°) and subjected to three different rainfall intensities (maximum, mean and minimum). The following key results were obtained: (1) the stability of unsaturated soil decrease as the rainwater infiltrates into the soil. Soil that initially in unsaturated state will start to reach saturated state when rainwater seeps into the soil. Infiltration of rainwater will reduce the matric suction in the soil. Matric suction acts in controlling soil shear strength. Reduction in matric suction affects the decrease in effective normal stress, which in turn diminishes the available shear strength to a point where equilibrium can no longer be sustained in the slope. (2) The infiltration rate of rainwater decreases while surface runoff increase when the soil nearly achieve saturated state. These situations cause the soil erosion and lead to slope failure. (3) The steepness of the soil is not a major factor but also contribute to slope failures. For steep slopes, rainwater that fall on the soil surface will become surface runoff within a short time compare to the water that infiltrate into the soil. While for gentle slopes, water that becomes surface runoff will move slowly and these increase the water that infiltrate into the soil. [ABSTRACT FROM AUTHOR]

The paper describes and analysis loess substrate collapsing under embankment as a result of flooding. The threat of huge settlements is wide spread on large loess deposits areas especially in south part of Asia. The popular in Russian Federation and common used method developed by authors is the compaction of substrate by soil columns. It is used in a variant covered with geosynthetic as barrier and reinforcement under an embankment. Authors present results of numerical calculations in direct numerical deterministic approach. Origins of work are based on experiences from field installations of soil columns in dry or semi-dry areas which are touched by periodical high watering. The investigated task was solved in axisymmetric finite element method. Collapse effects into Drucker-Prager were described by cap compression limitation for poroelastic material into plastic standard cone. The one directional steadystate flow was attached as an analytical and the profile of under-pressure allowed water infiltration in the soil above the groundwater table. A results from both methods were connected by python's algorithm modifying soil characteristic. [ABSTRACT FROM AUTHOR]

The article discusses research which examined the dynamic soil compaction at different degree of saturation by numerical approach. Topics discussed include the presence of a non-wetting and a wetting phase, large deformations during dynamic compaction and the governing equations obtained based on the overall momentum balance of the mixture.

The article discusses research which examined the influence of wetting and drying on matric suction and moisture content of unsaturated compacted cohesive soils. Topics discussed include the increase in water content upon wetting resulting to significant matric suction reduction and the matric suction as a parameter to evaluate the effects of wetting and drying compacted soils.

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Expansive clay in semiarid area behaves features of typical unsaturated soil, which is sensitive to climate and moisture, appears multi-fissures, deterioration of mechanical performances with the change of moisture. Consequently, to ensure the rational design of foundation treatment, and safe operation, research on moisture migration mechanism of expansive clays is of great significance. Herein, test models of mixed water migration and vaporous water migration were presented to investigate the mechanism. Series of tests, in which the moisture content in left soil column was same as 24%, and in right soil column was 0%, 6%, 12% and 18% respectively, were conducted under constant temperature. It is concluded that the moisture content changed with increase of migration time in both migration models, and the migration behaves nonlinear when the initial water content increase up to 6% for mixed water migration model and 12% for vaporous water migration model. But the migration characteristic of mixed water and vaporous water were different. The initial 30 days the change of moisture water was larger in mixed migration model, however in vaporous water migration model within 60 to 90 days was larger. These results will provide a basis for reveal evolution mechanism of engineering behaviors of unsaturated expansive clays. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to provide a numerical solution for simultaneous heat and mass transfer within frozen soil surrounding building foundations. The soil freezing characteristic curve and therefore the ice content are obtained by combining a generalised form of the Clapeyron equation with the soil water retention curve (SWRC) and the thermodynamical equilibrium. The mass conservation is derived by considering the phase change and the water flux due to infiltration. Also, the heat conservation is derived considering phase change, conduction and convection of heat. This results in a system of coupled and highly non-linear differential equations. The numerical method used to solve the system of partial differential equations is based on a Galerkin finite element method with adaptive mesh refinement and dynamic time step control. The developed solution is validated by comparison with experimental data obtained from literature. An application is then presented to demonstrate the heat and mass transfer as a result of heat dissipation of a foundation. The distribution of temperature and ice water content are discussed and it is shown that in spring months (March, April and May), despite the temperature above 0°C at the ground surface, a frost zone still exists within the foundation soil. In the cold period, a high rate of heat transfer between the ground and the upper part of the basement wall causes a sudden change in temperature. Also, during the cold period, it is observed that the heat loss from basement walls is several times higher than the heat loss from the floor slab. [ABSTRACT FROM AUTHOR]

The article presents a study which analyzed the stability of unsaturated infinite slope under rainfall-induced infiltration condition, considering the suction stress. It discusses the Soil-Water Characteristic Curve (SWCC), hydraulic conductivity function (HCF), and suction stress characteristic curve (SSCC). To analyze the stability of unsaturated infinite slop under infiltration condition due to rainfall, the variation of matric suction and volumetric water content should be considered.

A model for water retention in pores representative of unsaturated granular media is described. Retention behavior in an idealized angular pore is upscaled to the bulk scale using a statistical framework for pore size distribution that independently accounts for partially filled pores in the form of liquid bridges and completely filled pores in the form of saturated pockets. This distinction allows the water retention curve to be modeled over the complete range of saturation (pendular, funicular, and capillary regimes). Material properties including surface area, porosity, and grain size distribution are used to constrain the model calculations. Development and characteristics of the model are described; model predictions are compared with experimental measurements for unsaturated sand. [ABSTRACT FROM AUTHOR]