Studio tridimensionale del rivestimento di prima fase in spritz-beton di gallerie profonde

In this work the behaviour of shotcrete preliminary linings for tunnel construction has been analysed. This problem is quite complicated, due to the complexity of tunnel modelling and material nonlinearity. Few constitutive models able to describe the actual mechanical behaviour of the lining are available in technical literature. In most cases, material nonlinearity and the stress and strain distribution along the thickness of shotcrete lining are ignored and the design of lining thickness and reinforcement is frequently based on semi-empirical methods. In order to investigate the influence of reinforcement type on shotcrete behaviour, a series of NLFE analyses simulating the conventional procedure of tunnel excavation and lining have been carried out. The attention has been mainly focused on deep tunnels excavated in rock, considering different opening geometries and initial stress distributions. The local behaviour of shotcrete has been modelled through the PARC constitutive model, which is able to describe the behaviour up to failure both of ordinary and fibre reinforced concrete structures.