Abstract
The overloads of structures or embankments built on clayey soft ground are generally applied gradually, respecting a specific phasing. This phasing on construction allows the undrained shear strength of clay increasing over consolidation in order to avoid the risk of collapse during loading. In this work, the undrained shear strength of clay over the consolidation was estimated following SHANSEP method of which parameters proposed by eight researchers have been employed, as well as the slope stability analysis of embankments on soft soils during staged construction. Assessment of factor of safety for slope stability was conducted basing on the Bishop method. Additionally, the variations of undrained shear strength and factor of safety were presented. In order to validate the methods discussed in this study, slope stability analysis of five embankments constructed on clayey soft soils improved by the vertical drain technique in a high-speed railway construction project in Morocco was performed. For these embankments, field measurements about lateral displacement are presented. It was found that some of the adopted methods is in a good agreement with field measurements. Hence, generalization of these methods to many soft ground cases can be proposed.
Highlights
The vertical drain system is an effective method for accelerating soil consolidation
This study compares eight analytical methods, for estimation the undrained shear strength over consolidation, proposes a generalization to the case of five embankments on soft soils improved by vertical drains in Morocco
Comparison of undrained shear strength variations while consolidation is performed by combining the correlations presented in Table 1 to Equations 11 and 12, for normally consolidated and over consolidated soil respectively
Summary
The vertical drain system is an effective method for accelerating soil consolidation. Lawane et al (2018) have established correlations between shear strengths of disturbed samples and those of undisturbed samples of tropical soils of Burkina Faso using the Casagrande cell [19] Most of these methods have been developed for specific soil cases. In order allow a general solution for many cases of soft soils under staged construction; it is important to have a comparative discussion and results of numerical calculation on all existing methods. To achieve this objective, this study compares eight analytical methods, for estimation the undrained shear strength over consolidation, proposes a generalization to the case of five embankments on soft soils improved by vertical drains in Morocco
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