Soft Oedometer—A New Testing Device and Its Application for the Calibration of Hypoplastic Constitutive Laws
The problem addressed is how to obtain the material parameters of soils and other granular materials by means of a simple and fast laboratory test which fulfills the requirement of homogeneous specimen deformation. A new laboratory testing device called “soft oedometer,” characterized by an extensible lateral supporting ring, makes it possible to measure not only the vertical but also the lateral stress and strain of the specimen. The construction principles are presented as well as test results. The suggested evaluation of the latter makes it possible to determine the friction angle and all parameters entering hypoplastic constitutive equations without the need to achieve the limit state. In the present paper, the new apparatus is shown to make possible a particular test (oedometric test) which serves to fit a mathematical model called “hypoplastic constitutive law.” Using this model, other test types can be simulated realistically.