Creep failure of natural gravelly soil and its simulation

In order to investigate creep failure behaviour of gravelly soils in the field, a series of triaxial compression tests was conducted on large-scale natural gravelly soil samples. The samples were retrieved by means of a new method using thick, water-soluble, polymer solutions from two tunnel excavation sites in Japan. Creep failure behaviour was evaluated by performing drained sustained loading at prescribed stress states during otherwise monotonic loading at a constant loading rate. Rate-dependent behaviour was also evaluated by stepwise changing vertical strain rate many times during otherwise monotonic loading at a constant strain rate. The observed viscous properties including creep failure behaviour were simulated by a non-linear three-component model taking into account the effects of particle characteristics on the viscous property parameters. The viscous property parameters evaluated for this simulation were compared with those of reconstituted granular materials obtained by previous studies. Shear moduli during the creep failure process, which were measured by the dynamic method, were also analysed.