Search results for "Water retention"
showing 10 items of 56 documents
Appendix – Additional Measurements
2016
This appendix deals with the determination of different soil physical and hydraulic characteristics used in the analysis and/or interpretation of the infiltration experiments. The core method and the excavation method for measurement of soil bulk density are initially presented. Determination of soil water content by the thermo-gravimetric and the Time Domain Reflectometry methods is then illustrated. Subsequently, field measurement of soil water matric potential by tensiometers is discussed. Laboratory determination of the soil water retention curve by tensiometric and pressiometric techniques is also described. Finally, different methods to test water stability of soil aggregates are illu…
Determining hydraulic properties of a loam soil by alternative infiltrometer techniques
2015
Testing infiltrometer techniques to determine soil hydraulic properties is necessary for specific soils. For a loam soil, the water retention and hydraulic conductivity predicted by the BEST (Beerkan Estimation of Soil Transfer parameters) procedure of soil hydraulic characterization was compared with data collected by more standard laboratory and field techniques. Six infiltrometer techniques were also compared in terms of saturated soil hydraulic conductivity, Ks. BEST yielded water retention values statistically similar to those obtained in the laboratory and Ks values practically coinciding with those determined in the field with the pressure infiltrometer (PI). The unsaturated soil hyd…
DETERMINING THE SATURATED HYDRAULIC CONDUCTVITY OF A LOAM SOIL WITH DIFFERENT INFILTROMETER TECHNIQUES
2015
The saturated soil hydraulic conductivity, Ks, is one of the most important soil hydraulic properties since it controls many hydrological processes. This hydrodynamic parameter depends on soil texture and structure and it is very difficult to measure. Infiltrometer techniques are becoming very popular to determine Ks in the field but testing alternative approaches is necessary for specific soil types. For a loam soil, the estimated Ks values with six infiltrometer techniques were compared. The so-called BEST procedure of soil hydraulic characterization, the pressure infiltrometer (PI), single head experiments with both the tension infiltrometer (TI) and the mini disk infiltrometer (MDI), th…
Effect of biochar on the physical and structural properties of a sandy soil
2019
Abstract Biochar application to soil can be considered as a means to improve soil quality, thereby optimizing irrigation management and reducing irrigation needs, especially in dryland regions. This paper is aimed at investigating the effect of biochar (BC) on a desert sandy soil (Al Foah, United Arab Emirates) in terms of bulk density, porosity, water retention, plant available water (AWmax), aggregate stability (AS) and specific surface area (BET-SSA). BC was produced from forest biomass (Italy). Soil water retention was measured by the High Energy Moisture Characteristic (HEMC) and by pressure plate measurements, by using BC fractions equal to 0 (soil only), 0.014, 0.091, 0.23, 0.33 and …
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…
Water retention behaviour of compacted and reconstituted scaly clays
2020
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 mic…
Use of BEST Procedure to Assess Soil Physical Quality in the Baratz Lake Catchment (Sardinia, Italy)
2016
Conversion of Mediterranean maquis and/or natural forest into agro-pastoral lands is a cause of soil degradation in many Mediterranean areas. Indicators of soil physical quality (SPQ) quantitatively linked to soil hydraulic properties are a valuable tool to assess the effect of land use changes. In this investigation, the Beerkan Estimation of Soil Transfer parameters (BEST) procedure for soil hydraulic characterization was used to estimate SPQ indicators. Four areas of the Baratz Lake watershed, Sardinia, Italy, characterized by both typical natural vegetation (holm oak [ Quercus ilex L.] forest and high maquis) and degraded vegetation (grassland established after fire or clearing of the m…
Water retention behaviour and microstructural evolution of MX-80 bentonite during wetting and drying cycles
2014
MX-80 bentonite used in engineered barrier systems would be subjected to wetting and drying cycles. To assess the response of the material under such circumstances, a comprehensive experimental characterisation of the water retention behaviour of compacted MX-80 granular bentonite was performed in this study. A new methodology is proposed to investigate this behaviour under a constant volume condition for specimens prepared at different dry densities. The material was subjected to different hydraulic paths, including cyclic variations of the water content. As a result, an irreversible modification of the retention behaviour was observed when the material approached a fully saturated state …
Hydro-Mechanical Behaviour of a Sand-Bentonite Mixture for the Confinement of Nuclear Wastes
2019
The established concept for the protection of the biosphere from high-level nuclear wastes consists in the use of multi-barrier systems in deep geological repository, for which clayey geomaterials are key elements. Bentonite-based materials are selected as buffer and backfilling materials. Once in place, the barriers will be subjected to a series of severe loadings, including strong variations of suction (i.e. wetting and drying cycles). The paper presents selected results from a large ongoing research work to investigate the behaviour of bentonite-based materials in the context of nuclear waste disposal. In particular, the paper focuses on the response of a Sand/Bentonite mixture under dif…
Water retention characteristics of substrates containing biochar and compost as peat and perlite replacements for ornamental plant production
2021
In Italy peat and perlite are commonly used as growth substrates in ornamental plant nurseries. Requests for ecologically sustainable growth substrates have recently focused research on the study of new media. In this context, biochar and compost, by-products of other production chains, may play a relevant role. Four growth substrates were prepared by mixing (v/v) different porous matrices including a 2-mm sieved sandy loam soil namely: 50% peat and 50% perlite (PPr), 50% compost and 50% biochar (CB), 25% peat, 25% perlite, 25% compost and 25% biochar (PPrCB) and 25% peat, 25% compost and 50% mineral soil (PCM). Water retention curves of porous matrices and growth substrates were determined…