Experimental and numerical study of cemented clays

Abstract

This thesis deals with the numerical and experimental investigations of Savar area clays of Dhaka city .Three critical state soil models were used to numerically simulate the drained and undrained stress-stress response under triaxial condition of Savar area clays, with and without cementation. The models used were the Modified Cam Clay (MCC) model, Modified Modified Cam Clay (MMCC) model which incorporates cementation strength and the Extended MMCC model or EMMCC model incorporating cementation breakdown effects. The numerical study provides an 111- depth understanding of the strengths and limitations of eli tical state models to simulate the stress-strain behaviour of Savar area clays, with and without cementation, and in drained and undrained condition. In particular, it was observed that the MCC model could simulate the effect of cementation on clays. However, the MMCC model which explicitly incorporated the effect of tensile strength in the MCC model, significantly improved the predictions expected for the effect of cementation on clays. Finally, it was shown with the EMMCC model, that cementation breakdo\\~l effects could also be incorporated in the MCC model and simulated with this model. Such analysis may be necessary in particular situations or cases of soil behaviour. Finally, experimental model-scale footing and pile tests were carried out in a consolidation mold containing Savar area clays, with and without cementation. The experimental data clearly indicated that cementation of clays significantly increases the bearing capacity mobilised by footings resting on such soils. The results of the tests were numerically simulated using elasto-plastie finite clement analysis and the Modified Cam Clay model. The experimental data was subsequently compared with numerical predictions. The comparison of the results of finite element analysis for footings resting on cemented and uneemented Savar area clays, with experimental data showed that, using the MCC model for such analysis could predict the effect of cementation of clays on footing behaviour. Finally, the strengths and limitations of the MCC model in predicting the load-displacement response of model-scale footings and piles resting on Savar area clays, with and without cementation, were critically evaluated.