Abstract
In unstable soils, a special erosion process termed suffusion can occur under the effect of relatively low hydraulic gradient. The critical hydraulic gradient of an unstable soil is smaller than in stable soils, which is described by a reduction factor α. According to a theory of Skempton and Brogan (1994) [1], this reduction factor is related to the stress conditions in the soil. In an unstable soil, the average stresses acting in the fine portion are believed to be smaller than the average stresses in the coarse portion. It is assumed that the stress ratio and the reduction factor for the hydraulic gradient are almost equal. In order to prove this theory, laboratory tests and discrete element modelings are carried out. Models of stable and unstable soils are established, and the stresses inside the sample are analysed. It is found that indeed in unstable soils the coarse grains are subject to larger stresses. The stress ratios in stable soils are almost unity, whereas in unstable soils smaller stress ratios, which are dependent on the soil composition and on the relative density of the soil, are obtained. A comparison between the results of erosion tests and numerical modeling shows that the stress ratios and the reduction factors are strongly related, as assumed by Skempton and Brogan (1994) [1].
Highlights
For the subsoil below pavements, dams or dikes, the stability against erosion with regard to seepage forces in-How to cite this paper: Ahlinhan, M.F., Wouya, E.K., Tankpinou, Y.K., Koube, M.B. and Adjovi, C.E. (2016) Experimental and Numerical Investigation of Stress Condition in Unstable Soil
There is a slight influence of relative density on the reduction factor
Experimental tests presented in the paper in hand show that the critical hydraulic gradient for upward seepage flow is dependent on the instability index of the soil and to a minor extent on its relative density
Summary
For the subsoil below pavements, dams or dikes, the stability against erosion with regard to seepage forces in-How to cite this paper: Ahlinhan, M.F., Wouya, E.K., Tankpinou, Y.K., Koube, M.B. and Adjovi, C.E. (2016) Experimental and Numerical Investigation of Stress Condition in Unstable Soil. For the subsoil below pavements, dams or dikes, the stability against erosion with regard to seepage forces in-. (2016) Experimental and Numerical Investigation of Stress Condition in Unstable Soil. It is of particular importance to identify and assess unstable soils, because here at relatively small hydraulic gradients, a special erosion process termed “suffusion” can occur. As result of the process, the fine fraction of the soil is washed out through the pores between the coarse-grained soil fraction. This increases the soil permeability and can lead to large civil works settlements or to the failure
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