Numerical modelling of a NATM tunnel construction in London clay

Abstract

AB5TRACf: The finite element program CRItical State Program (CRISP) has bcen used to model the New Austrian Tunnelling Method (NAT:V1) in London Clay. The non-linear behaviour of the London Clay was p1odelled by a Strain Dependent ~(odjfied Cam Clay (SDMCq mooel and the tunnel lining was modelled bv col\Stant and time-dependent elastic models. 111e col\Struction process was modelled in two and three Jimel\Siol\S by removing soil elements in sequence. 111e tunnel lining was either assumed wished.in-place or introduced after the excavation of each panel. The results obtained from plane strain and three Jirnel\Sional analyses are compared to assess the importance of arching of soil ahead of tunnel face.