Stiffness of Toyoura Sand from Dilatometer Tests

Abstract

A series of dilatometer test profiles were carried out in a calibration chamber on Toyoura sand using a standard blade and a special research dilatometer. Pluviated sand samples were prepared using various combinations of boundary conditions, relative density, and stress history. The research dilatometer probe consists of a standard blade modified internally to allow monitoring of the complete pressure-displacement soil response during a test. Precise performance of small unload-reload cycles can also be performed to evaluate elastic deformation properties. The pressure-displacement response during the expansion tests clearly shows the influence of stress history and density. The stiffness of the Toyoura sand from both dilatometers were also compared to that measured in laboratory monotonic shear tests and to various empirical relationships. The results suggest that the moduli measured from the unload-reload cycles during the research dilatometer tests reflect the elastic properties of the soil and can be correlated to results from resonant column tests and monotonic torsional shear tests. Modulus values measured with the standard dilatometer are more representative of an elasto-plastic response.