Structure and Calibration of Constitutive Equations for Granular Soils

• Published in: Studia geotechnica et mechanica Vol. 36; no. 4; pp. 35 - 46
• Main Authors: Sawicki, Andrzej, Sławińska, Justyna, Mierczyński, Jacek
• Format: Journal Article
• Language: English
• Published: Wrocław De Gruyter Open 28.02.2015; De Gruyter Brill Sp. z o.o., Paradigm Publishing Services; Sciendo
• Subjects: constitutive equations; granular soil; pre-failure deformations; triaxial conditions
• ISSN: 0137-6365; 2083-831X; 2083-831X
• DOI: 10.2478/sgem-2014-0034

The form of incremental constitutive equations for granular soils is discussed for the triaxial configuration. The classical elasto-plastic approach and the semi-empirical model are discussed on the basis of constitutive relations determined directly from experimental data. First, the general structure of elasto-plastic constitutive equations is presented. Then, the structure of semiempirical constitutive equations is described, and a method of calibrating the model is presented. This calibration method is based on a single experiment, performed in the triaxial apparatus, which also involves a partial verification of the model, on an atypical stress path. The model is shown to give reasonable predictions. An important feature of the semi-empirical incremental model is the definition of loading and unloading, which is different from that assumed in elasto-plasticity. This definition distinguishes between spherical and deviatoric loading/unloading. The definition of deviatoric loading/unloading has been subject to some criticism. It was therefore discussed and clarified in this paper on the basis of the experiment presented.