High Stress Flow Behaviour and Constitutive Modeling of Dry Granular Materials

• Author / Creator

  Mineneh, Abraham E.

• Landslides include various forms of geological mass movements such as falls, slides and flows under the force of gravity. Predictions of landslide kinematics and dynamics require knowledge of flow behaviour and mathematical modeling. Research into the flow behaviour of granular materials has revealed the existence of rate-dependent collisional behaviour at high shear rates and void ratios as well as rate-independent frictional behaviour at low shear rates and void ratios. However, the results of high stress shear experiments on small particles indicate that shear rate has no effect on flow behaviour. Following this finding, most geotechnical analyses of landslides have considered mainly frictional flow behaviour. Since the collisional behaviour of granular materials depends on particle inertia, both shear rate and particle mass (or particle density and diameter) are equally important in its occurrence. In this research, the relevance of rate-dependent collisional behaviour at high stress was re-investigated using simulation experiments on large size particles. The results indicate that rate-dependent flow behaviour is more likely to occur in rapid-flow landslides involving large particles, such as debris avalanches and rock avalanches. The critical state framework which captures the frictional behaviour was extended to capture rate-dependent collisional behaviour by adding shear rate as an additional state variable, based on the pioneering work of Campbell. The extended framework was used for flow classification, study of flow progress, and constitutive modeling. The effect of particle shape on granular flow behaviour and the extended critical state framework was reviewed using simulation experiments. Selected unified constitutive models proposed by Savage and Louge were evaluated using the extended critical state framework. In this research, new unified constitutive model is developed. The new model combines the frictional and collisional stress contributions using weighting functions called stress coefficients to determine the total stress. The stress coefficients are interdependent and are determined using empirical equations and detailed theoretical analyses. The new model is used to predict the extended critical state framework and implemented in the numerical model for inclined flows. The model performs well in capturing the extended framework and flow profiles of dense granular inclined flows on flat-frictional and rough bases.

• Subjects / Keywords

  • Critical state framework
  • Quasistatic flow regime
  • Avalanches
  • Constitutive Modeling
  • Intermediate flow regime
  • Discrete Element Method
  • Granular flow
  • Collisional flow regime

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3JH68

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.