Valls-Marquez, Monica (2009)
Ph.D. thesis, University of Birmingham.
Accurate prediction of soil behaviour around tunnel excavations is vital for the assessment of its effects on existing infrastructures and services, both underground and surface, and evaluation of risks to enable safe designs. This thesis evaluates the capabilities of four constitutive models in reproducing the intrinsic experimental behaviour of stiff clay when subjected to tunnelling-induced stress paths. Relevant stress paths have been determined from 2D and 3D finite element analysis using PLAXIS. Reconstituted Speswhite Kaolin clay specimens have been prepared from slurry, their properties investigated in detail, and tested using state-of-the-art stress path equipment and on-sample instrumentation. The soil model testing software SM2D has been used to compare the models’ predictions to the experimental measurements. The results have shown that there are yet many limitations in terms of accurately simulating the response of overconsolidated clay when subjected to extension, essential in tunnelling problems. Also the only model considered that has features to account for small-strain behaviour has been found to be too crude in its current state to be applied to complex geotechnical problems without further reflection. Some suggestions for improvement have been given. The results presented should help in making a more informed selection of models for design purposes.
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