01-09 P01 Water retention -Kannan & Singh SEAGS E-J 2019-03.pdf (original) (raw)
Related papers
Water retention characteristics of swelling clays in different compaction states
Geomechanics and Geoengineering, 2017
The soil water retention (SWR) characteristics of the clays play an important role in controlling their engineering behaviour, particularly, in the unsaturated state. Although, researchers have attempted to understand the water retention characteristics of the clays in their reconstituted or remoulded state, such studies are rare for the clays in their intact state. In this context, it becomes important to understand the influence of initial state of compaction, which would create different pore-and fabric-structure (viz., microstructure), on the water retention characteristics of the clays. With this in view, SWR behaviour was determined experimentally for the swelling clays (dried from different compaction states, viz., intact, reconstituted and remoulded) by employing Dewpoint Potentiameter (WP4C ). The changes in the pore-size distribution of the clays at different stages of drying cycle were also studied by employing the Mercury Intrusion Porosimetry. The study reveals that the SWR curves for the intact and reconstituted specimens of the clays converge beyond a certain stage of drying. Also, a critical analysis of changes in the pore structure of the swelling clay specimens, during drying, indicates that the progressively deforming pore structure play an important role in controlling its water retention characteristics to a great extent.
E3S Web of Conferences
The design of engineering structures is still a challenging task when considering unsaturated soil mechanics behaviour. The present paper focuses on analysing Soil Water Retention Curves (SWRC) for clayey soil samples collected from a purpose built experimental embankment. SWRC determination is crucial when analysing geotechnical parameters of the soil. During the measurements, soil samples were subjected to wetting and drying cycles using a stage procedure (where the process is carried out in stages to allow equalisation) and continuous processes. The methods used for obtaining the suction curves were high suction tensiometer, attached at the bottom of the sample, and pressure plates with suctions applied up to 800 kPa. The study compares laboratory methods on measuring suction for sandy clay samples. It proves that the wetting and drying history have an impact on the hydraulic behaviour of tested material. In order to give a wider picture of soil behaviour it also presents the outputs as a function of matric suction and volumetric and gravimetric water content, and degree of saturation.
Acta Geotechnica, 2017
The main objective of this paper is to examine how different engineering soils react to environmental variations and to provide correlations to characterize their behaviour under null external mechanical stress. Two French and two Algerian soils with liquid limits ranging from 36 to 112 were prepared under both slurry and Proctor compaction conditions, and then subjected to drying-wetting paths with suction controlled from several kPa to several hundreds of MPa. Experimental results are presented in five diagrams to show globally and simultaneously the shrinkage-swelling, saturation-desaturation and water retention characteristics. A reasonable consistency was observed between the oedometric and drying curves of slurry, confirming the equivalence between hydraulic loading (suction) and mechanical loading (consolidation stress) on the volume change behaviour of different soils. As an intrinsic parameter of soil nature, liquid limit was found to have a significant influence on the shrinkage limit, air-entry suction and compressibility of both slurry and compacted samples. For that reason, correlations between these characteristics and liquid limit were set up, providing a good basis for a first estimation of the drying-wetting curves. At the micro-scale, new experimental results were obtained: either on drying or wetting path, the micro-pores were almost unaffected, whereas, when matrix suction increased from 0.1 to 8 MPa, the volume of macro-pores decreased to quasi-closure. At last, the analogy between the compaction and drying-wetting curves, and the comparison of different methods to determine the water retention curve were addressed. Such analogies and comparisons contribute to a better understanding of the mechanisms of mechanical stress and suction.
A Retention Curve Prediction for Unsaturated Clay Soils
Springer Proceedings in Physics, 2007
In order to obtain the retention curve of unsaturated soil which is defined as the relationship between water content and suction, numerous laboratory tests have been done for many soils with different clay contents. The laboratory tests concern different types of soils; the swelling and not swelling clays (natural clay with high silt content and the bentonite clay). Two complementary experimental ways are conducted. The first which leads to measure suction is based on the filter paper method. The second with the dessicator allows to impose a high suction values.
Influence of water density on the water-retention curve of expansive clays
Géotechnique, 2012
There is increasing evidence from researchers on clay mineralogy that the density of water attached to clay minerals may be greater than 1·0 Mg/m3. This fact becomes especially evident in compacted highly expansive clays close to water saturation. This kind of material is being considered in the design of engineered barriers for radioactive waste disposal, because of its sealing and retention properties. From a geotechnical point of view, most of the analyses required to check the performance of the barrier are sensitive to the value considered for the water density. This is the case for the unsaturated flow calculations, which depend on the water-retention properties of the soil. This paper presents, first, a review of measurements performed at microscopic level. A description of the hydration process of expansive clay considering the micro and macrostructure is included. Then a method to obtain an average water density as a function of suction for sodium and calcium bentonites is ...
Comparison of Water Retention Curves for Clayey Soils Using Different Measurement Techniques
2006
Soil water retention curves were determined using four different techniques for suction measurement. Transistor psychrometer and non‐contact filter paper techniques were used for total suction determinations; pressure plates and in‐contact filter paper techniques were used for matric suction measurements. The soil water retention curves (WRC) were determined for bentonite, speswhite kaolin and a mixture of kaolin and sand (70 percent: 30 percent by mass). Specimens were prepared at their liquid limits and the WRC were ...
Compacted clay fills are generally placed at the optimum value of water content and, immediately after placement, they are unsaturated. Wetting might subsequently occur due, for example, to rainfall infiltration, which can cause volumetric deformation of the fill (either swell or collapse) with associated loss of shear strength and structural integrity. If swelling takes place under partially restrained deformation, due for example to the presence of a buried rigid structure or a retaining wall, additional stresses will develop in the soil and these can be detrimental to the stability walling elements and other building assets. Factors such as dry density, overburden pressure, compaction water content and type of clay are known to influence the development of stresses. This article investigates these factors by means of an advanced stress path testing program performed on four different clays with different mineralogy, index properties and geological histories.
Géotechnique, 65(2): 111–125 , 2015
Compacted clay fills are generally placed at the optimum value of water content and, immediately after placement, they are unsaturated. Wetting might subsequently occur due, for example, to rainfall infiltration, which can cause volumetric deformation of the fill (either swell or collapse) with associated loss of shear strength and structural integrity. If swelling takes place under partially restrained deformation, due for example to the presence of a buried rigid structure or a retaining wall, additional stresses will develop in the soil and these can be detrimental to the stability walling elements and other building assets. Factors such as dry density, overburden pressure, compaction water content and type of clay are known to influence the development of stresses. This article investigates these factors by means of an advanced stress path testing program performed on four different clays with different mineralogy, index properties and geological histories. Specimens of kaolin clay, London clay, Belfast clay and Ampthill clay were prepared at different initial states and subjected to “controlled” wetting whereby the suction was reduced gradually to zero under laterally restrained conditions (i.e. Ko conditions). The results have shown that the magnitude of the increase in horizontal stresses (and therefore the increase of Ko) is influenced by the overburden pressure, compaction water content, dry density at the time of compaction and mineralogy.
Water Retention and Compressibility of a Lime-Treated, High Plasticity Clay
Geotechnical and Geological Engineering, 2013
The paper presents a laboratory investigation, which quantified the beneficial effect of lime on the water retention, compressibility and overall volume changes of a high plasticity clay (London Clay). The study comprised oedometer testing (including suction controlled testing), shrinkage tests, and filter paper testing to determine the soil water retention curves of the drying soils. The latter tests showed that the shallowmixed lime-treated soils are likely to be partially saturated in situ depending on the environmental conditions; thus, unsaturated soil mechanics concepts are applicable for the description of their behaviour. The oedometer results quantified the marked decrease in the swelling and compressibility of the lime-treated soil compared to the untreated clay and the increase in the vertical effective yield stress (due to suction and cementation bonding). The lime enabled the soil to maintain a more open structure with respect to the untreated soil throughout the compression process, and appears to be the main factor influencing the compressibility of the unsaturated lime-treated soil (rather than suction) for the ranges of suction tested. Keywords Lime stabilisation Á London Clay Á Swelling Á Shrinkage Á Compressibility Á Moisture retention List of symbols e Void ratio G max Small-strain stiffness modulus G s Specific gravity m v Coefficient of volume compressibility m 1 s Coefficient of volume change of the soil skeleton with respect to net normal stress X. Zhang was formerly working at the Faculty of Engineering, Science and the Built Environment of London South Bank University, during the presented research.
International Journal of Geomechanics, 2019
This paper investigates the influence of lime stabilization of an expansive clay based on volumetric behavior and the soilwater characteristic curve (SWCC). The selected soil was a residual clay located in Victoria, Australia. Specimens treated with an optimum lime content (OLC) that was found to reduce swell potential were selected to investigate the SWCCs. Static compaction tests were conducted to establish the virgin compression surface. Hyprop (Meter Group, Pullman, Washington), filter paper, and the chilled mirror hygrometer were used to measure the SWCC at and below the surface at different net stress levels. To interpret the volumetric behavior of untreated and treated soil using the SWCC, swelling and collapse values were measured at various initial moisture contents and stress levels. The test results found that although the treated specimens were stabilized with lime at OLC, significant collapse and swelling potential were obtained when the lime-treated specimens were prepared at high suction value and wetted under low net stresses.