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Unsaturated Soil Mechanics
20 May 2004-
TL;DR: Unsaturated Soil Mechanics as mentioned in this paper provides a comprehensive introduction to the fundamental principles of unsaturated soil mechanics and provides extensive sample problems with an accompanying solutions manual, and brings together the rapid advances in research in unsaturated soil mechanics in one focused volume.
Abstract: DESCRIPTION Unsaturated Soil Mechanics is the first book to provide a comprehensive introduction to the fundamental principles of unsaturated soil mechanics. * Offers extensive sample problems with an accompanying solutions manual. * Brings together the rapid advances in research in unsaturated soil mechanics in one focused volume. * Covers advances in effective stress and suction and hydraulic conductivity measurement.
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TL;DR: In this paper, the suction stress characteristic curve (SSCC) for unsaturated soil is presented, and the experimental evidence shows that both Mohr-Coulomb failure and critical state failure can be well represented by the SSCC concept.
Abstract: The concept of the suction stress characteristic curve (SSCC) for unsaturated soil is presented. Particle-scale equilibrium analyses are employed to distinguish three types of interparticle forces: (1) active forces transmitted through the soil grains; (2) active forces at or near interparticle contacts; and (3) passive, or counterbalancing, forces at or near interparticle contacts. It is proposed that the second type of force, which includes physicochemical forces, cementation forces, surface tension forces, and the force arising from negative pore-water pressure, may be conceptually combined into a macroscopic stress called suction stress. Suction stress characteristically depends on degree of saturation, water content, or matric suction through the SSCC, thus paralleling well-established concepts of the soil–water characteristic curve and hydraulic conductivity function for unsaturated soils. The existence and behavior of the SSCC are experimentally validated by considering unsaturated shear strength data for a variety of soil types in the literature. Its characteristic nature and a methodology for its determination are demonstrated. The experimental evidence shows that both Mohr–Coulomb failure and critical state failure can be well represented by the SSCC concept. The SSCC provides a potentially simple and practical way to describe the state of stress in unsaturated soil.
715 citations
Additional excerpts
...Lu and Likos 2004 , for example, presented a theory for directly applying the suction stress concept to calculate lateral earth pressure....
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...Capillary interparticle force is marked by high variability as a function of particle size and water content, as well as the potential capacity for producing very strong attractive stresses Santamarina et al. 2001; Lu and Likos 2004 ....
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TL;DR: In this paper, microbially induced calcite precipitation (MICP) has been used for soil stabilization in geotechnical engineering applications, such as liquefiable sand deposits, slope stabilization, and subgrade reinforcement.
Abstract: A newly emerging microbiological soil stabilization method, known as microbially induced calcite precipitation (MICP), has been tested for geotechnical engineering applications. MICP is a promising technique that utilizes the metabolic pathways of bacteria to form calcite precipitation throughout the soil matrix, leading to an increase in soil strength and stiffness. This paper investigates the geotechnical properties of sand bio-cemented under different degrees of saturation. A series of laboratory experiments was conducted, including sieve analysis, permeability, unconfined compressive strength, consolidated undrained triaxial, and durability tests. The results indicate that higher soil strength can be obtained at similar CaCO3 content when the treatment is performed under a low degree of saturation. The experimental results are further explained with a mathematical model, which shows that the crystallization efficiency, i.e., actual volume of crystals forming at the contact point where they contribute the most to strength, can be calculated from the degree of saturation and grain size. Fine sand samples exhibited higher cohesion, but lower friction angle than coarse sand samples with similar CaCO3 content. The results also confirm the potential of MICP as a viable alternative technique for soil improvement in many geotechnical engineering applications, including liquefiable sand deposits, slope stabilization, and subgrade reinforcement. The freeze-thaw and acid rain resistance of MICP-treated sand has also been tested.
492 citations
TL;DR: In this article, the authors present a review of the mechanical properties of wet granular media, with particular emphasis on the effect of cohesion and open problems that might motivate future studies in this exciting but mostly unexplored field.
Abstract: Most studies on granular physics have focused on dry granular media, with no liquids between the grains. However, in geology and many real world applications (e.g. food processing, pharmaceuticals, ceramics, civil engineering, construction, and many industrial applications), liquid is present between the grains. This produces inter-grain cohesion and drastically modifies the mechanical properties of the granular media (e.g. the surface angle can be larger than 90 degrees). Here we present a review of the mechanical properties of wet granular media, with particular emphasis on the effect of cohesion. We also list several open problems that might motivate future studies in this exciting but mostly unexplored field.
439 citations
Cites background or methods from "Unsaturated Soil Mechanics"
...Relatively low suction can be measured or controlled by using tensiometers and the axis-translation technique [28]....
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...Adapted from [28]....
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...The tool to measure the suction by using the HAE disk is called a tensiometer, which is composed of a cup made of a HAE ceramic and a sensor to measure the liquid pressure, connected by a tube filled with liquid (water) [28]....
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...[28]....
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...material is given by ∆P = Pa − Pl [28]....
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TL;DR: In this article, a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions is presented. But the authors do not consider the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil.
Abstract: [1] We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework.
342 citations
TL;DR: In this paper, the relative importance of soil properties, rainfall intensity, initial water table location and slope geometry in inducing instability of a homogenous soil slope under different rainfall was investigated through a series of parametric studies.
Abstract: Rainfall-induced slope failure is a common geotechnical problem in the tropics where residual soils are abundant. Although the significance of rainwater infiltration in causing landslides is widely recognized, there have been different conclusions as to the relative roles of antecedent rainfall to landslides. The relative importance of soil properties, rainfall intensity, initial water table location and slope geometry in inducing instability of a homogenous soil slope under different rainfall was investigated through a series of parametric studies. Soil properties and rainfall intensity were found to be the primary factors controlling the instability of slopes due to rainfall, while the initial water table location and slope geometry only played a secondary role. The results from the parametric studies also indicated that for a given rainfall duration, there was a threshold rainfall intensity which would produce the global minimum factor of safety. Attempts have also been made to relate the findings from this study to those observed in the field by other researchers. Results of this parametric study clearly indicated that the significance of antecedent rainfall depends on soil permeability.
281 citations