Small strain stiffness of unsaturated soil - Laboratory determination and numerical simulation (in Czech)
Abstract
Moduli of soils at small strains represent important input parameters in geotechnical numerical modelling. The presented triaxial testing deals with the shear modulus of a reconstituted unsaturated fine-grained soil, and its decay with the strain level.
The maximum shear modulus G0 was measured using bender elements at isotropic net stress, and its decay curve by submersible LVDTs at short continuous drained shear loading probes at different suction and net stress levels. An increase of G0 was observed first on increasing the net stress, and secondly on wetting.
The tested soil did not exhibit the usual plateau of constant elastic value of G0 at very small strains, the stiffness decay started at the strains below the conventional threshold strain of 0.001%. The laboratory data were used in calibrating an advanced constitutive model for unsaturated soils, and its capability to simulate the unconventional behaviour was demonstrated.