Effect of overburden pressure and degree of saturation on compressibility characteristics
TL;DR: In this paper, the effect of the above parameters on compressibility characteristics of a clays was presented, where different steps undertaken for footing construction were simulated in the laboratory and different samples were prepared from oven-dry fraction passing 425 μm sieve.
Abstract: The settlement of a structure founded on clay comprises of immediate and consolidation settlements. In the case of clays, consolidation settlement is more than immediate settlement. The parameters influencing consolidation settlement of a normally loaded clay layer are degree of saturation (S%), void ratio (e) of soil prior to excavation, amount of overburden (σo) removed, amount of rebound and intensity of loading (σ) upon building superstructure. This paper presents the effect of the above parameters on compressibility characteristics of a clay. The different steps undertaken for footing construction were simulated in the laboratory. Remoulded clay samples were prepared from oven-dry fraction passing 425 μm sieve. The density of the samples was kept constant at 13 kN/m3. Degree of saturation was varied at 25%, 50%, 75% and 100%. The surcharge on the samples (overburden in the case of field clay layer) was varied as 25 kPa, 50 kPa and 100 kPa. Compressibility characteristics such as initial compression u...
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TL;DR: In this paper , a lignosulphonate (LS)-based composite admixture (CA) was used to cope with construction problems pertaining to expansive soils considering the hydromechanical properties.
18 citations
Dissertation•
07 Mar 2016
TL;DR: In this article, the effect of sample scale on fine-grained soil compressibility was investigated using the finite element software PLAXIS 2D and three different methods were used: Casagrande, Taylor's and Inflection methods.
Abstract: The need for an improved understanding of the influence of sample scale on the compressibility behaviour of fine-grained soils is crucial in many applications, such as roads, embankments and foundations. The effect of sample scale represents a challenge when obtaining engineering parameters in the laboratory compared to those obtained in the field. This research therefore aimed at contributing to existing knowledge through both experimental and numerical studies. The experimental study was completed via a series of consolidation tests on fully saturated fine-grained soil (i.e. kaolin clay) at various sample scales, which were subsequently explored analytically using the finite element software PLAXIS 2D. This type of clay was chosen as it is easily sourced and well known. A Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD) were employed in studying the micro-structure of the soil.
The Oedometer apparatus was used to obtain the combined effect of sample scale and initial moisture content on the compressibility parameters of kaolin clay. Compressibility parameters such as coefficient of consolidation (cv), compression index (cc) and coefficient of volume compressibility (mv) were also investigated in this study. Three different methods were used to obtain cv: Casagrande, Taylor’s and Inflection methods. The sample scales were divided into three categories: soil sample height, diameter and diameter to height (D/H) ratio scale. Particular attention was given to the D/H ratio effect on the compressibility parameters due to the frictionless boundary conditions, and sample diameter scale due to drainage path length.
Based on the experimental data, Taylor’s method was considered more reliable in deriving cv as compared to the Casagrande and Inflection methods, due to the end of primary consolidation (EOP) observed at all sample scales. It was also observed that on average, sample scale has an effect on cv with a correlation factor of 0.451 and that friction was reduced by 35%. The effect of sample scale on cc and mv was found to be insignificant. The investigation also showed a correlation factor between the initial moisture content and cv of 0.546 and, 0.162 and 0.026 for cc and mv respectively. The new proposed model developed in PLAXIS 2D was found to show no significant difference with the laboratory data except where the calculated coefficient of permeability was used. A new proposed model was developed in PLAXIS to further study the effect of sample diameter scale on the behaviour of fine-grained soils.
8 citations
Cites background from "Effect of overburden pressure and d..."
...…30 2-10: Variation in the compressibility parameters with change in degree of saturation as presented by Phanikumar and Amrutha (2014) ...................................................................................................
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...…29 2-9: Rate of initial compression at different degree of saturation (Sr) at a pressure of 25kPa (Phanikumar and Amrutha, 2014) .................................................................................................... 30 2-10:…...
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...%) or initial moisture content (w%), void ratio (e) and amount of overburden pressure (σpkPa) (Phanikumar and Amrutha, 2014)....
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01 Apr 2019
TL;DR: In this article, the effect of the soaking period of soil especially clay on its California Bearing Ratio (CBR) test value was studied and a precise reduction factor of the CBR in relation with soaking period was found.
Abstract: The quality of road pavement is affected mostly by the type of sub-grade which is acting as road foundation. The roads degradation is related to many factors especially the climatic conditions, the quality, and the thickness of the base materials. The thickness of this layer depends on its California Bearing Ratio (CBR) test value which by its turn is highly affected by the quantity of water infiltrated under the road after heavy rain. The capacity of the base material to drain out its water is predominant factor because any change in moisture content causes change in sub-grade strength. This paper studies the effect of the soaking period of soil especially clay on its CBR value. For this reason, we collected many clayey samples and on each soil, two groups of experiments were performed: main tests consisting of Proctor and CBR test from one side and from other side identification tests consisting of other tests such as Atterberg limits tests. Each soil sample was first subjected to Proctor test in order to find its optimum moisture content which will be used to perform the CBR test. Four CBR tests were performed on each soil with different soaking period. The first CBR was done without soaking the soil sample; the second one with two days soaking, the third one with four days soaking period and the last one was done under eight days soaking. By comparing the results of CBR tests performed with different soaking time, a more detailed understanding was given to the role of the water in reducing the CBR of soil. In fact, by extending the soaking period, the CBR was found to be reduced quickly the first two days and slower after. A precise reduction factor of the CBR in relation with soaking period was found at the end of this paper.
4 citations
Cites background from "Effect of overburden pressure and d..."
...HE water content of a fine grained soil as clay has a significant effect on its strength and on its compressibility characteristics [1]....
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Dissertation•
26 May 2019
1 citations
Cites background from "Effect of overburden pressure and d..."
...Phanikumar and Amrutha (2013) studied on effect of degree of saturation on consolidation settlement of a normally consolidated clay....
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Dissertation•
01 Jan 2018
TL;DR: In this paper, the authors explore disparate potential mechanisms of slope failure in a set of post-glacial landslides in northwest Yellowstone National Park, and quantify spatial relationships, topographic metrics, and relative age of eight landslides within the north entrance to the park, a system traversed by over 700,000 visitors every year.
Abstract: Landslides are ubiquitous to post-glacial landscapes worldwide. Withdrawal of glacier ice exposes over-steepened landscapes that may be unstable, and consequently susceptible to landsliding. Glacial debuttressing may directly destabilize slopes; however, seismicity and transitions to interglacial climates associated with greater effective moisture and subsequent degradation of permafrost may also play a role. Here, we explore disparate potential mechanisms of slope failure in a set of post-glacial landslides in northwest Yellowstone National Park. We quantify spatial relationships, topographic metrics, and relative age of eight landslides within the north entrance to the park, a system traversed by over 700,000 visitors every year. Analysis of high-resolution topography indicates increasing surface roughness of non-active landslides southward. These roughness values in ancient slides are roughly half those of the active Slide Lake Landslide, and suggest younging ages along the retreat path of the Yellowstone Ice Cap, consistent with glacial debutressing as the likely trigger for these slides. However, roughness values and their application for relative age dating are strongly confounded by topographic biases such as gullying, fluvial erosional contacts, and anthropogenic features (e.g., roads, structures). Once roughness biases are removed, we find roughness differences between landslides decrease, and do not support younging ages along the path of ice retreat. Thus, glacial debuttressing most likely only had a preparatory influence on slope failure, and was not the direct trigger. Analysis of subsurface soils at landslide toes indicate a >17 plasticity index, pointing to highly expansive clays that are sensitive to moisture addition. Stratigraphic relationships between post-glacial terraces and soil analyses suggest a late Pleistocene (~13 – 11.5 ka) timing for slide initiation, a period coincident with high available moisture. Stream power analysis indicates that Holocene incision of the Gardiner River is focused at a knickpoint locally coincident with the toe of the active Slide Lake Landslide, providing a mechanism for modern, local reactivation of the ancient slides. Together, our findings broadly show how quantifying the temporal and spatial patterns of landslides can be diagnostic of the controls on slope failure, and can be used to understand risk. They also highlight the importance of careful site calibrations and bias removals in roughness analysis.
1 citations
References
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Book•
01 Jan 1948
TL;DR: In this article, the authors present a survey of the properties of soils and their properties in terms of Hydraulics of Soils, Hydraulic and Mechanical Properties of Soil Exploration Hydraulic, Mechanical, and Hydraulic properties of soil.
Abstract: PHYSICAL PROPERTIES OF SOILS Index Properties of Soils Soil Exploration Hydraulic and Mechanical Properties of Soils THEORETICAL SOIL MECHANICS Hydraulics of Soils Plastic Equilibrium in Soils Settlement and Contact Pressure PROBLEMS OF DESIGN AND CONSTRUCTION Ground Improvement Earth Pressure and Stability of Slopes Foundations Settlement Due to Extraneous Causes Dams and Dam Foundations References Indexes
5,136 citations
01 Jan 1990
TL;DR: In this paper, a constitutive model for describing the stress-strain behavior of partially saturated soils is presented, formulated within the framework of hardening plasticity using two iodependent sets of stress variables: the excess of total stress over air pressure and the suction.
Abstract: The Paper presents a constitutive model for describing the stress-strain behaviour of partially saturated soils. The model is formulated within the framework of hardening plasticity using two iodependent sets of stress variables: the excess of total stress over air pressure and the suction. The mode1 is able to represent, in a consistent and unified manner, many of the fundamental features of the behaviour of partially saturated soils which had been treated separately by previously proposed models. On reaching saturation, the mode1 becomes a conventional critical state model. Because experimental evidence is still limited, the model has been kept as simple as possible in order to provide a basic framework from which extensions are possible. Tbe mode1 is intended for partially saturated soils which are slightly or moderately expansive. After formulating the model for isotropic and biaxial stress states, typical predictions are described and compared, in a qualitative way, with characteristic trends of the behaviour of partially saturated soils. Afterwards, the results of a number of suction-controlled laboratory tests on compacted kaolin and a sandy clay are used to evaluate the ability of the model to reproduce, quantitatively, observed behaviour. The agreement between observed and computed results is considered satisfactory and confirms the possibilities of reproducing the most important features of partially saturated soil behaviour using a simple general framework.
2,062 citations
"Effect of overburden pressure and d..." refers background in this paper
...Increased compressibility at higher degrees of saturation is possible due to changes in structure and fabric of clays and also due to collapse of clay structure occurring at higher water contents and higher degrees of saturation at a given loading (see Alonso et al. 1990)....
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TL;DR: In this paper, a constitutive model for describing the stress-strain behavior of partially saturated soils is presented, formulated within the framework of hardening plasticity using two independent sets of stress variables: the excess of total stress over air pressure and the suction.
Abstract: The Paper presents a constitutive model for describing the stress-strain behaviour of partially saturated soils. The model is formulated within the framework of hardening plasticity using two independent sets of stress variables: the excess of total stress over air pressure and the suction. The model is able to represent, in a consistent and unified manner, many of the fundamental features of the behaviour of partially saturated soils which had been treated separately by previously proposed models. On reaching saturation, the model becomes a conventional critical state model. Because experimental evidence is still limited, the model has been kept as simple as possible in order to provide a basic framework from which extensions are possible. The model is intended for partially saturated soils which are slightly or moderately expansive. After formulating the model for isotropic and triaxial stress states, typical predictions are described and compared, in a qualitative way, with characteristic trends of the...
2,041 citations
TL;DR: In this paper, a study of the micromechanical behavior of crushable soils is presented for a single grain loaded diametrically between flat platens, where data are presented for the tensile strengths of particles of different size and mineralogy.
Abstract: This paper presents a study of the micromechanical behaviour of crushable soils. For a single grain loaded diametrically between flat platens, data are presented for the tensile strengths of particles of different size and mineralogy. These data are shown to be consistent with Weibull statistics of brittle fracture. Triaxial tests on different soils of equal relative density show that the dilatational component of internal angle of friction reduces logarithmically with mean effective stress normalized by grain tensile strength. The tensile strength of grains is also shown to govern normal compression. For a sample of uniform grains under uniaxial compression, the yield stress is related to the average grain tensile strength. If particles fracture such that the smallest particles are in geometrically self-similar configurations under increasing geotoscopic stress, with a constant probability of fracture, a fractal geometry evolves with the successive fracture of the smallest grains, in agreement with the a...
708 citations
"Effect of overburden pressure and d..." refers background in this paper
...At low stress levels, compressibility of sands depends on initial density and at higher stress levels, yielding is observed (McDowell and Bolton 1998, Nakata et al. 2001)....
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