ABSTRACT
The paper presents the strategy followed in modelling the injection of cement mixes, aimed at the improvement of the mechanical characteristics of the in situ granular soil before the excavation of a shallow tunnel. The effect of the injections is simulated by applying inelastic strains to the region where soil improvement occurs. The way in which this is accomplished has a remarkable influence on the prediction of induced heave. It is shown that a convenient way for modelling the grout injections is that of applying anelastic strains and improving soil characteristics in regions having the shape of a bulb, created in correspondence of the valves of the injection tubes. Either uniform mix diffusion or localization in flat lenses ('claquage') can be modelled by varying the aspect ratio of the bulb. A comparison between calculated and measured soil movements in an actual case is finally presented. It is shown that good agreement is achieved by assuming that uniform diffusion occurs in depth while 'claquage' lenses are formed at shallow depth.
