A substantial amount of experimental evidence suggests that the critical state envelope for ballast is nonlinear, especially at low confining pressure. To study the implications of this nonlinearity and the associated role of particle breakage, monotonically loaded drained triaxial tests were conducted using a large-scale cylindrical triaxial apparatus. A nonlinear critical state envelope is determined in the q-p= and -lnp= planes. Mathematical expressions for critical state stress ratio and specific volume are proposed to incorporate the evolution of particle breakage during monotonic shearing. In this paper, an elastoplastic constitutive model based on the critical state soil mechanics framework is presented to capture the salient aspects of stress-strain behaviour and degradation of ballast. Constitutive parameters were conveniently determined from large-scale laboratory tests. The model is able to predict the monotonic shear behaviour of ballast corroborating with the laboratory measurements. The proposed model is further validated using experimental results available from past independent studies.
Disciplines
Engineering | Science and Technology Studies
Publication DetailsIndraratna, B., Sun, Q. & Nimbalkar, S. (2015). Observed and predicted behaviour of rail ballast under monotonic loading capturing particle breakage. Canadian Geotechnical Journal, 52 (1) Abstract: A substantial amount of experimental evidence suggests that the critical state envelope for ballast is non-linear, especially at low confining pressure. In order to study the implications of this non-linearity and the associated role of particle breakage, monotonically loaded drained triaxial tests were conducted using the large-scale cylindrical triaxial apparatus. A non-linear critical state envelope is determined in the q-p' and -lnp' planes.Mathematical expressions for critical state stress ratio and specific volume are proposed to incorporate the evolution of particle breakage during monotonic shearing. In this paper, an elasto-plastic constitutive model based on the critical state soil mechanics framework is presented to capture the salient aspects of stress-strain behaviour and degradation of ballast.Constitutive parameters were conveniently determined from large-scale laboratory tests. The model is able to predict the monotonic shear behaviour of ballast corroborating with the laboratory measurements. The proposed model is further validated using experimental results available from past independent studies.