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a b s t r a c tThe paper demonstrates the application of a hypoplastic model in class A predictions of a NATM tunnel in an urban environment. The tunnel, excavated in a stiff clay, is 14 m wide with 6 m to 21 m of overburden thickness. The constitutive model was calibrated using laboratory data (oedometric and triaxial tests) and the parameters were optimised using monitoring data from an exploratory drift. Based on the optimised data set, the future tunnel was simulated. After the tunnel excavation, it could be concluded that the model predicted correctly surface settlements, surface horizontal displacements, and the distribution of vertical displacements with depth. It overpredicted horizontal displacements in the vicinity of the tunnel.

SUMMARYTwo trial motorway embankments built on a landfill consisting of clayey lumps were monitored over the period of 3 and 5 years, respectively. The subsoil of the embankment was instrumented by hydrostatic levelling profiles, pore pressure transducers and depth reference points installed in boreholes. An advanced constitutive model for clays (hypoplastic model for clays with meta-stable structure) was used for numerical modelling of both case histories. Basic hypoplastic model for clays was calibrated using isotropic compression tests and triaxial compression tests on reconstituted clay. Three additional model parameters describing the effects of lumpy structure were calibrated using oedometer tests on specimens prepared from scaled-down lumpy material (material with smaller size of clay lumps). The performance of the model was evaluated by comparison with the results of the centrifuge model of self-weight consolidated landfill. Finally, the hypoplastic model was used for simulation of both trial embankments and the results were compared with in situ measurements. The degradation of the lumpy structure of the upper layer of the in situ landfill due to weathering was back analysed using monitoring data.

The shear modulus of cemented soils at very small strain (G 0 ) was studied. For artificially cemented clay, G 0 was found to be independent of the mean effective stress until the yield stress. After yield, a significant effect of structure degradation on G 0 was observed. The experimental data were interpreted by an equation, which relates G 0 of cemented soils to mean stress, apparent overconsolidation ratio and the state of structure (sensitivity). The equation was also found to represent G 0 of cemented sands.

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