Search results for "unsaturated soil"
showing 10 items of 13 documents
Shear Strength of a Compacted Scaly Clay from Suction-Controlled Triaxial Tests
2012
The paper presents the results of an experimental research aimed at investigating the shear strength characteristics of an unsaturated compacted scaly clay. Shear strength was investigated by suction-controlled triaxial compression tests on dynamically compacted samples. Collected results point out that suction effects on stiffness and shear strength can be very different for suction values applied lower or greater than air entry value (AEV), corresponding to the material void ratio.
Modelling landslides in unsaturated slopes subjected to rainfall infiltration using material point method
2016
This paper presents a dynamic fully coupled formulation for saturated and unsaturated soils that undergo large deformations based on material point method. Governing equations are applied to porous material while considering it as a continuum in which the pores of the solid skeleton are filled with water and air. The accuracy of the developed method is tested with available experimental and numerical results. The developed method has been applied to investigate the failure and post-failure behaviour of rapid landslides in unsaturated slopes subjected to rainfall infiltration using two different bedrock geometries that lie below the top soil. The models show different failure and post-failur…
Life cycle environmental assessment of retaining walls in unsaturated soils
2022
Abstract Retaining structures above groundwater level support soils that are usually in a state of partial saturation and subject to the actions of atmospheric agents. The current design approach considers the possible extremes of soil conditions – either totally dry or totally saturated – but it neglects matric suction’s contribution to soil shear strength. This work aims to describe how unsaturated-soil mechanics of can positively influence the sustainability of retaining structures through a holistic, multidisciplinary, geotechnical, and environmental analysis. The geotechnical analysis allows to estimate the lateral earth pressure of a geostructure in both unsaturated and extreme soil c…
Shear strength of a compacted scaly clay in variable saturation conditions
2015
Scaly clays are stiff and highly fissured clays often used as construction materials. This paper presents the results of triaxial compression tests carried out on saturated and unsaturated samples of a compacted scaly clay. Complementary investigation on the microstructural features and their evolution with the amount of water stored into the material are also presented in order to shed light on the evolution of the micro- and macroporosity with suction. The water retention behaviour of the compacted scaly clay is also addressed. The results from the controlled suction triaxial tests are used to discuss the applicability of a single-shear strength criterion to compacted double-structured cl…
Coupled hydro-mechanical analysis of compacted bentonite behaviour during hydration
2021
Abstract This study analyses the response of compacted bentonites upon hydration based on a coupled hydro-mechanical elasto-plastic framework. As an alternative to multi-porosity interpretation, the framework was selected based on the experimental evidence of adsorbed water behaviour in bentonites and the volumetric response at saturated states, apparently independent of its initial state. Based on these premises, a water retention model was formulated using an explicit distinction between adsorbed water and free water, enabling the postulation of the water properties and behaviour depending on its state. In order to effectively account for the transition between unsaturated to saturated st…
Investigation into water retention behaviour of deformable soils
2013
The paper presents an experimental and modelling approach for the soil-water retention behaviour of two deformable soils. The objective is to investigate the physical mechanisms that govern the soil-water retention properties and to propose a constitutive framework for the soil-water retention curve accounting for the initial state of compaction and deformability of soils. A granular soil and a clayey soil were subjected to drying over a wide range of suctions so that the residual state of saturation could be attained. Different initial densities were tested for each material. The soil-water retention curves (SWRCs) obtained are synthesized and compared in terms of water content, void rati…
Hydro-mechanical behaviour of a sandy silt from a river embankment
2020
The paper presents the results of an experimental campaign aimed at characterizing the hydro-mechanical behaviour of a sandy silt from a river embankment. Due to continuous river level fluctuations and changing climatic and environmental conditions, flood embankment materials experience frequent variations in degree of saturation and suction values. Such variations strongly impact the earthwork performance both in terms of seepage and stability conditions. For these reasons, a detailed characterization of the material behaviour in unsaturated conditions was carried out. Experiments were designed in order to highlight the response of the involved soil in terms of changes in matric suction an…
Modeling Round Robin Test: An Uncoupled Approach
2014
Abstract The solution of the modeling test presented in the paper is based on an uncoupled hydro-mechanical approach. Firstly, the controlled infiltration process is modeled by a finite element transient groundwater seepage software. Afterwards, calculated pore water pressures at successive instants are used for the slope stability analysis. Time evolution of the slope stability is analysed by using the infinite slope model, according to the classical limit equilibrium method.
The use of soil water retention curve models in analyzing slope stability in differently structured soils
2017
Abstract This study analyzes whether and at what rate the parameterization of the Soil Water Retention Curve (SWRC) affects the analysis of shallow slope stability for differently structured unsaturated soils. Advanced empirical or physically-based equations of SWRCs have been proposed in literature to describe soil systems characterized by the so-called bimodal porous domain. In unsaturated soils, SWRC affects the stability assessment in two ways. It influences the resistance properties in terms of shear strengths, which depend on the soil water suction; and it affects the hydrological process modeling (e.g. infiltration) directly influencing soil moisture patterns and indirectly influenci…
Yielding of a quartz sand from saturated to dry state
2020
The paper presents the results of an experimental work where we analyse the behaviour of an unsaturated quartz sand in a wide range of degree of saturation (from saturated to dry state). The possibility of anticipating the hydro-mechanical behaviour of the soils when they approach the dry state is fundamental in many areas. An extensive experimental program, including controlled-suction and constant water content oedometric tests, was carried out to deeply analyse the water retention behaviour and the relationship between the yield stress and suction (Loading-Collapse curve). All elasto-plastic models provide a monotonically increase of the yield stress with suction. This assumption implies…