Abstract
Through this paper, a sampling methodology and a novel full automatic system adopting the continuous pressurization method which is capable of determining the Soil Water Characteristics Curve (SWCC) for both remoulded and undisturbed samples in a very short time were developed. The proposed system was validated by comparing the SWCCs of standard testing soils obtained using the developed system to the SWCCs obtained using a conventional method. Remoulded and undisturbed natural soil samples were tested, where the degree of disturbance influence on the obtained SWCC was discussed. In addition, the undisturbed samples containing moulds material influence on the obtained SWCC was investigated. It was found that remoulded samples do not properly represent the in-situ conditions with significant error that should be carefully considered when conducting analysis and proposing countermeasures against unsaturated soils related Geo-disasters. In addition, the material which the containing mould is made from has minor influence on the obtained SWCC which can be neglected. Finally, it can be concluded that the developed undisturbed soil water characteristics curve obtaining system is direct, rapid, reliable and simple. In addition, the proposed undisturbed sampling and testing methodology can be used to accurately evaluate the spatial variations of the SWCC regardless the heterogeneity of the soil profile.
Highlights
Earthquakes, typhoons and heavy rainfalls induced natural Geo-disasters occur at different locations causing serious damage to life and properties
It can be observed that the Soil Water Characteristics Curve (SWCC) obtained using the newly developed Continuous Pressurization Method (CPM) system is in well agreement with the SWCC obtained using the conventional method with precise accurate capturing of the Air Entry Value (AEV) and the residual suction value
In order to evaluate the boundary conditions influence considering the undisturbed samples being contained in steel moulds, while the remoulded samples being contained in acrylic moulds, standard Toyoura sand remoulded samples were prepared by compacting the soil directly into the steel mould used for undisturbed sampling, the steel mould was directly installed into the acrylic mould and the test was performed
Summary
Typhoons and heavy rainfalls induced natural Geo-disasters occur at different locations causing serious damage to life and properties. The water table and river water level rise causing increase in the pore water pressure resulting in total strength and stability loss through soil embankments which leads to failure. The proper determination of the hydrological and water retention properties of porous mediums is necessary for understanding the unsaturated soils behaviour. Among those properties, the Soil Water Characteristic Curve (SWCC) is a key index used for estimating many unsaturated soil relations such as the hydraulic conductivity function, water storage, shear strength and prediction of solute and contaminant transport [1, 2]. The existing laboratory techniques are limited due to the testing complexity, applicable only under the drying phase, discrete suction and water content measurements and prolonged testing time where depending on the amount of data points desired, testing may require at least several weeks or even
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