Bearing capacity and settlement behavior of unsaturated soils from model footing tests

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Title: Bearing capacity and settlement behavior of unsaturated soils from model footing tests
Authors: Sun, Rui
Date: 2010
Abstract: A series of model footing tests were conducted to determine the bearing capacity and settlement behaviour of four different soils of which the first two were coarse-grained soils (Le. Filtration sand and Quarry sand) and the remainder two were fine-grained soils (i.e. Sil-co-sil 106 and Mil-u-sil 30) using four different sizes of model footings (Le. 20 mm x 20 mm, 37 mm x 37 mm, 41.75 mm in diameter, and 50 mm x 50 mm) over a suction range of 0 to 8 kPa. This range of matric suction 0 to 8 kPa extends over the boundary effect, transition and residual stages (Vanapalli et al. 1999) for the two coarse-grained soils (Le. Filtration sand and Quarry sand). A soil container which is 300 mm in diameter and 700 mm in height has been used in the experiment. The targeted matric suction values in the soils were achieved by controlling the level of water table in the soil container and confirmed using Tensiometers installed in the soil at different depths. The experimental results demonstrated that: 1) The variation of bearing capacity of coarse-grained soils (Le. Filtration sand and Quarry sand) with respect to matric suction was nonlinear in nature. The bearing capacity increases up to the residual suction value and then decreases with further increase in matric suction values. The trends for settlement are however opposite; the settlement decreases up to residual suction value and gradually start increasing along with an increase in the matric suction. 2) For the unsaturated fine-grained soils (Le. Sil-co-sil 106 and Min-u-sil 30), bearing capacity increases and settlement decreases as the matric suction increases because the suction range (Le. 0 to 8 kPa) is in the boundary effect zone. In other words, the suction range in the boundary effect zone is lower than the air-entry value (i.e. saturation zone). More detailed discussions are offered with respect to the bearing capacity and settlement behaviour of unsaturated soils including the influence of footing size on the bearing capacity and settlement results. In addition, these test results were used to verify the semi-empirical models proposed by Vanapalli and Mohamed (2007) and Oh et al. (2009) for predicting the bearing capacity and settlement behaviour of unsaturated soils, respectively.
URL: http://hdl.handle.net/10393/28533
http://dx.doi.org/10.20381/ruor-12588
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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