scholarly journals Water retention behaviour of compacted and reconstituted scaly clays

2020 ◽  
Vol 195 ◽  
pp. 03026
Author(s):  
Marco Rosone ◽  
Alessio Ferrari
Keyword(s):  
Water Retention ◽  
Void Ratio ◽  
Dew Point ◽  
The Other ◽  
Compacted Clay ◽  
Water Retention Properties ◽  
Scaly Clay ◽  
High Suction ◽  
Water Retention Behaviour

The paper presents the results of an experimental research devoted to investigate the response to suction variations of a scaly clay in compacted and reconstituted conditions. Different experimental techniques (axis translation, vapour equilibrium, dew point psychrometer suction measurements) were combined in order to explore the water retention properties in a wide suction range (0 ÷ 110 MPa). Experimental results allowed to define the water retention domains for a constant reference void ratio, highlighting the significant role of the microstructure on the response of the investigated clays. In particular, the collected results showed that in the low-medium suction range, the peculiar microstructural features give to the reconstituted clay a better retention capability than the compacted clay. However, the increasing suction induces a significative volumetric shrinkage on the saturated reconstituted clay, especially when the latter is initially normally consolidated. On the other hand, quite similar retention properties were recognized in the high suction range.

Water Retention Properties of a Compacted Clayey Silt Including Void Ratio Dependency and Microstructural Features

2012 ◽  
pp. 153-158
Author(s):  
Rodrigo Gómez ◽  
Enrique Romero ◽  
Gabriele Della Vecchia ◽  
Cristina Jommi ◽  
Josep Suriol ◽  
...  
Keyword(s):  
Water Retention ◽  
Void Ratio ◽  
Clayey Silt ◽  
Water Retention Properties

Hydraulic conductivity of bentonite-sand mixtures

2000 ◽  
Vol 37 (2) ◽  
pp. 406-413 ◽  
Author(s):  
P V Sivapullaiah ◽  
A Sridharan ◽  
V K Stalin
Keyword(s):  
Hydraulic Conductivity ◽  
Water Retention ◽  
Void Ratio ◽  
Clay Content ◽  
Liquid Limit ◽  
Natural Soils ◽  
Waste Containment ◽  
Clay Liner

The use of bentonite alone or amended with natural soils for construction of liners for water-retention and waste-containment facilities is very common. The importance of bentonite content in reducing the hydraulic conductivity of liners is well recognised. The study illustrates the role of the size of the coarser fraction in controlling the hydraulic conductivity of the clay liner. It has been shown that at low bentonite contents the hydraulic conductivity of the liner varies depending on the size of the coarser fraction apart from clay content. At a given clay content, the hydraulic conductivity increases with an increase in the size of the coarser fraction. But when the clay content is more than that which can be accommodated within the voids of the coarser fractions, the hydraulic conductivity is controlled primarily by clay content alone. Four different methods of predicting hydraulic conductivity of the liners are presented. Using two constants, related to the liquid limit, the hydraulic conductivity can be predicted at any void ratio.Key words: clays, hydraulic conductivity, liquid limit, liners, void ratio.

scholarly journals Investigation into water retention behaviour of deformable soils

2013 ◽  
Vol 50 (2) ◽  
pp. 200-208 ◽  
Author(s):  
Simon Salager ◽  
Mathieu Nuth ◽  
Alessio Ferrari ◽  
Lyesse Laloui
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Void Ratio ◽  
Degree Of Saturation ◽  
Retention Data ◽  
Soil Water Retention ◽  
Retention Behaviour ◽  
Wide Range ◽  
Water Retention Behaviour

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 ratio, and degree of saturation, and are expressed as a function of the total suction. The studies enable assessment of the effect of the past and present soil deformation on the shape of the curves. The void ratio exerts a clear influence on the air-entry value, revealing that the breakthrough of air into the pores of the soil is more arduous in denser states. In the plane of water content versus suction, the experimental results highlight the fact that from a certain value of suction, the retention curves corresponding to different densities of the same soil are convergent. The observed features of behaviour are conceptualized into a modelling framework expressing the evolution of the degree of saturation as a function of suction. The proposed retention model makes use of the theory of elastoplasticity and can thus be generalized into a hysteretic model applicable to drying–wetting cycles. The calibration of the model requires the experimental retention data for two initial void ratios. The prediction of tests for further ranges of void ratios proves to be accurate, which supports the adequacy of formulated concepts.

scholarly journals Preliminary investigation on the water retention behaviour of cement bentonite mixtures

2020 ◽  
Vol 195 ◽  
pp. 03032 ◽  
Author(s):  
Paolo Trischitta ◽  
Renato Maria Cosentini ◽  
Gabriele Della Vecchia ◽  
Gianluigi Sanetti ◽  
Guido Musso
Keyword(s):  
Water Content ◽  
Water Retention ◽  
Preliminary Investigation ◽  
Retention Behaviour ◽  
Laboratory Characterization ◽  
Wetting Fluids ◽  
Slurry Wall ◽  
Slurry Walls ◽  
High Suction ◽  
Water Retention Behaviour

Cement bentonite mixtures are often used to build slurry walls for the containment of both aqueous and non aqueous pollutants, due to their quite low hydraulic conductivity and relatively high ductility and strength. Although their hydro-mechanical behaviour in saturated conditions has been studied in the past, a part of the slurry wall is expected to rest above the groundwater level. The hydraulic characterization in unsaturated conditions is then particularly relevant to evaluate the performance of the barrier, especially when it is aimed at containing non aqueous pollutant liquids which are lighter than water (LNAPL). These non wetting fluids rest above the water table and their penetration is possible just if the barrier is unsaturated. This paper presents some preliminary results of a laboratory characterization of the water retention behaviour of three different cement bentonite mixtures. The mixtures, prepared at cement – bentonite mass ratios ranging from 4:1 to 6:1, were immersed in water and cured for 28 days. Their water retention behaviour was then determined along drying and wetting paths through different techniques, namely axis translation, filter paper and vapour equilibrium. In the high suction range, the water content – suction relationship was found to be independent of cement-bentonite ratio. In the low suction range, the water content at a given suction was found to decrease for increasing cement bentonite ratios.

scholarly journals Humidity interaction of lichens under astrobiological aspects: the impact of UVC exposure on their water retention properties

2015 ◽  
Vol 14 (3) ◽  
pp. 445-456 ◽  
Author(s):  
J. Jänchen ◽  
J. Meeßen ◽  
T.H. Herzog ◽  
M. Feist ◽  
R. de la Torre ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Thermal Analysis ◽  
Low Temperature ◽  
Water Retention ◽  
The Other ◽  
Dry Conditions ◽  
Buellia Frigida ◽  
Water Retention Properties ◽  
The Impact ◽  
Hydration And Dehydration

AbstractWe quantitatively studied the hydration and dehydration behaviour of the three astrobiological model lichens Xanthoria elegans, Buellia frigida and Circinaria gyrosa by thermoanalysis and gravimetric isotherm measurements under close-to-Martian environmental conditions in terms of low temperature and low pressure. Additionally, the impact of UVC exposure on the isolated symbionts of B. frigida and X. elegans was studied by thermoanalysis and mass spectrometry as well as by gravimetric isotherm measurements. The thermal analysis revealed whewellite as a component of C. gyrosa which was not found in B. frigida and X. elegans. Neither the water retention nor the thermal behaviour of symbionts changed when irradiated with UVC under dry conditions. On the other hand, UVC irradiation of the wet mycobiont of B. frigida had a distinct impact on the hydration/dehydration ability which was not observed for the mycobiont of X. elegans. Possibly the melanin of B. frigida's mycobiont, that is not present in X. elegans, or a specifically damaged acetamido group of the chitin of B. frigida may be the sources of additional UVC-induced sorption sites for water associated with the UVC exposure.

Effect of Bentonite on the Performance of the Limestone Manufactured-Sand Mortar

2013 ◽  
Vol 357-360 ◽  
pp. 1374-1378 ◽  
Author(s):  
Chun Hui Yu ◽  
Gu Hua Li ◽  
Jin Liang Gao ◽  
Bo Lan ◽  
Qun Wei ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Water Demand ◽  
Water Retention ◽  
Manufactured Sand ◽  
Mortar Strength ◽  
Water Retention Properties

In order to improve workability of manufactured-sand mortar, limestone manufactured-sand mortar mixed with bentonite, and discussed the role of different dosage of bentonite that had played on mortar fluidity, consistency, layered degree ,mortar compressive and flexural strength. The results show that, mortar water demand increases, fluidity, consistency, stratification decreases with increasing bentonite dosage. Bentonite can be good to improve the water retention properties of the mortar. Doped bentonite mortar strength improved, when doped with 0.9%, mortar has best water retention, flexural, compressive strength also reached maximum.

scholarly journals A water retention model for compacted clays subjected to salinization and desalinization processes

2020 ◽  
Vol 195 ◽  
pp. 02011
Author(s):  
Giulia Scelsi ◽  
Gabriele Della Vecchia ◽  
Guido Musso
Keyword(s):  
Water Retention ◽  
Double Porosity ◽  
Matric Suction ◽  
Clay Liners ◽  
Retention Model ◽  
Environmental Actions ◽  
The One ◽  
Wetting Process ◽  
Water Retention Properties

Environmental actions are known to induce relevant effects on the fabric of compacted active clays, which are successfully described by adopting a double porosity framework. In particular, the role of aggregate deformation has been recognized as fundamental to interpret the water retention behavior and the transport properties. These aspects are particularly relevant in the context of clay liners, being the material cast in place in unsaturated conditions and subjected to wetting process by pore fluids characterized by a chemical composition that is different from the one of compaction. Experimental data evidence that the water retention properties of active clays evolve as a function of pore water chemistry, since for a given matric suction the mass of stored water changes with water salinity. In this paper, a double porosity water retention model is proposed, capable of reproducing the variation of matric suction with water content accounting for the salinity of pore fluid. The role of salinity changes is accounted for by a suitable evolution law for aggregate deformation, which in turn affects the inter-aggregate porosity and thus the storage properties of the material.

scholarly journals Water retention and characteristic curves representing tropical clay soils from Africa

2020 ◽  
Vol 195 ◽  
pp. 01019
Author(s):  
K.M.A. Alhaj ◽  
G. Biscontin ◽  
M.Z.E.B Elshafie ◽  
A.S. Osman
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Void Ratio ◽  
Energy Levels ◽  
Dew Point ◽  
Degree Of Saturation ◽  
Measuring Instruments ◽  
High Plasticity ◽  
Soil Water Retention ◽  
Initial Void Ratio

Soil water retention curves (SWRCs) form an essential component of frameworks coupling the hydromechanical behaviour of unsaturated soils. The curves describe how suction changes with variables such as degree of saturation, void ratio and volumetric/gravimetric water content. SWRCs can be determined from incrementally drying initially saturated reconstituted samples to a final residual state, thus developing the primary drying curve (PDC). The primary wetting curve (PWC) is established from subsequent incremental wetting from residual state and is hysteretic compared with the PDC. SWRCs for reconstituted, high-plasticity, tropical clays from Africa (Sudan, Tanzania and South Africa) will be produced using suction measuring instruments, a tensiometer, filter paper and a dew point potentiometer. The development of SWRCs under various subsequent cycles of drying will be presented and discussed along with details concerning volumetric changes and cracking during drying. In order to investigate the uniqueness of the PDC and PWC and the effect of initial void ratio, SWRCs will be determined for samples formed by reconstituted from slurry under different applied energy levels.

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