Abstract
This paper describes a calibration procedure for the double structure constitutive model ICDSM (Imperial College Double Structure Model), developed for highly expansive clays, when the model is applied to MX-80 bentonite. Firstly, the model calibration process is discussed and organised in a number of hierarchical steps. These steps involve the estimation of the macrostructural parameters that can be derived from oedometer, isotropic and triaxial laboratory data. Estimation of the microstructural parameters is more challenging due to the limited knowledge of an expansive clay’s fabric and of the physico-chemical phenomena that control its evolution upon wetting. Nevertheless, this paper discusses the available sources of data and identifies the appropriate information that is needed to characterise the micro-structural behaviour of the bentonite. Finally, through the simulation of a swelling pressure test on a bentonite plug, the hydration of the material is studied as a hydro-mechanical coupled process. Particular attention is devoted to the evolution of the stress state of the sample, which is compared to the experimental measurements in order to demonstrate that the constitutive model accurately reproduces the expansive behaviour of MX-80 bentonite.
Highlights
The constitutive model ICDSM has been developed at Imperial College for the modelling of unsaturated, highly expansive clays ([1])
The numerical results obtained with the ICDSM are compared with the experimental data and the results given by the Imperial College Single Structure Model (ICSSM, [6])
The IC DSM has proven effective at reproducing the expansive behaviour of MX-80 bentonite during a radial swelling test
Summary
The constitutive model ICDSM has been developed at Imperial College for the modelling of unsaturated, highly expansive clays ([1]). The complexity of the model requires a hierarchical calibration process. As discussed in [2] for the Barcelona Expansive Model (BExM), the double structure should be accounted for in order to capture the expansive behaviour of compacted clays. In this paper a calibration process, specific to the IC DSM, is proposed for MX-80 bentonite. This process does not follow the same patterns suggested over the years for the Barcelona Basic Model (BBM, [3]), for example in [4]. The numerical results obtained with the ICDSM are compared with the experimental data and the results given by the Imperial College Single Structure Model (ICSSM, [6])
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