Modelling Strains of Soft Soils

Deformations in soft soil are generally large due to the low stiffness. This behaviour requires a large deformation continuum approach. Here the focus will be on the strength of soft soils, especially peat. Peat is modelled with an elastic model with isotropic undrained shear strength. This study shows that elasticity and plasticity become entangled for soft materials. It is shown that classical solutions of plasticity theory do not apply for these materials, because the elastic component of the strains does not become negligible. And the small strain plasticity theory underestimates the strength of soft materials. The first part describes the simulations of a strip footing problem on soft soil. The second part describes a plate bearing test on peat in a large triaxial test apparatus and the numerical simulation of this experiment. The same simple model has been used to analyse this test. The simulation captures the essential features of the test i.e. the load curve and deformation pattern.