Research


The following is a concise overview of the research that the group is involved with. It is organized by topics, but of course there is a necessary overlap among topics. Credit must be given to the students, visitors, and faculty collaborators who have worked with us and have pushed the field forward.

Fracture Mechanics
Discontinuous Media
Autoadaptive Systems
Analytical and Numerical Models
Soil-Structure Interaction
Tunnels
Problem Soils
Extreme Events
Current Projects

Discontinuous Media

For most civil engineering materials, including rocks, fractures are closed or, if open, may close under compression. At some point during the loading process, closed fractures begin to slip and the shear strength may decrease from peak to residual. In other instances, frictional fractures have already slipped in the past along a certain area of the fracture, but slip can be activated in new areas as the load is increased (e.g. faulting). This constitutes an effective mechanism for fault and fracture activation and is the cause of progressive failure.

Slip initiation and propagation along non-homogeneous frictional surfaces are investigated by loading specimens in biaxial compression. The specimens used in the tests are composed of individual blocks with perfectly mated contact surfaces. The contact surfaces have on their upper half a frictional strength smaller than on their lower half.
This creates a “weak” surface on the upper half and a “strong” surface on the lower half. Slip starts on the weak area and, as the shear stress is increased, propagates towards the strong area. With further loading rupture occurs through the strong area as an unstable process that coincides with failure. The results show that the critical energy release rate GIIC is a good indicator of the rupture but, contrary to what has been assumed in the past, it is not a material property.
  • Bobet, A. (1999). Technical Note: Analytical Solutions for Toppling Failure. International Journal of Rock Mechanics and Mining Sciences, Vol. 36, pp. 971-980.

  • Mutlu O., Bobet A. (2004). Slip on Non-Homogeneous Discontinuities. Proceedings of the 6th North America Rock Mechanics Symposium (NARMS), Houston, Texas, June 2004, Paper No. 04-506, 9 pages.

  • Mutlu, O., and Bobet, A. (2005). Slip Initiation on Frictional Fractures. Engineering Fracture Mechanics Journal, Vol. 72, pp. 729-747.

  • Mutlu, O. and Bobet, A. (2005). A Fracture Mechanics Approach to Slip along Frictional Discontinuities. U.S. Rock Mechanics Symposium, paper 05-685, 10 pp.

  • Park, C.H. and Bobet, A. (2006). The Initiation of Slip on Frictional Fractures. 41st U.S. Rock Mechanics Symposium, Golden, CO, paper 06-923, 9 pp.

  • Mutlu, O. and Bobet, A. (2006). Slip Propagation along Frictional Discontinuities. International Journal of Rock Mechanics and Mining Sciences, Vol. 43, pp. 860-876.

  • Mutlu, O. and Bobet, A. (2008). The onset of slip on frictional discontinuities in brittle materials. Proceedings of the Symposium on Characterization and Behavior of Interfaces (CBI), D. Frost Editor. 2010 IOS Press, Amsterdam, The Netherlands, pp. 71-77.

  • Bobet, A., Fakhimi, A., Johnson, S., Morris, J., Tonon, F., and Yeung, M. (2009). Numerical Models in Discontinuous Media: A review of advances for rock mechanics applications. ASCE Journal of Geotechnical and Geoenvironmental Engineering,Vol. 135, No. 11, pp. 1547-1561.

  • Bobet, A. (2010). Numerical Models in Geomechanics. The Arabian Journal for Science and Engineering,Vol. 35, No. 1B, pp. 27-48. Invited paper.

  • Bobet, A., Einstein, H., Glaser, S., Laughton, Ch., Wang, J.S.Y., and Hladysz, Z.J. (2011). Engineering Research at the United States Deep Underground Science and Engineering Laboratory, in the Footprint of the Homestake Mine. Proceedings of SME.

  • Haimson, B., and Bobet, A. (2012). Introduction to Suggested Methods for Failure Criteria. Rock Mechanics and Rock Engineering, Vol. 45, pp. 973-974.

  • Alejano, L., and Bobet, A. (2012). ISRM suggested method: Drucker-Prager Criterion. Rock Mechanics and Rock Engineering, Vol. 45, pp. 995-999.

  • Choi, M.K., Pyrak-Nolte, L.J., and Bobet, A. (2012). Seismic Detection of Flow Paths in a Air-Filled Fracture under Stress. Proceedings of the 46th US Rock Mechanics/Geomechanics Symposium, Chicago IL. CD-ROM.

  • Lee, Y.K., Bobet, A. (2014). Instantaneous Friction angle and Cohesion of 2-D and 3-D Hoek-Brown Rock Failure Criteria in terms of stress invariants. Rock Mechanics and Rock Engineering, Vol. 47, pp. 371-385.

  • Bobet, A., Garcia Marin, V. (2014). A Stress and Displacement Discontinuity Element Method for Elastic Transversely Anisotropic Rock. International Journal of Numerical and Analytical Methods in Geomechanics, Vol. 38, pp. 1898-1922.

  • Tang, H.M., Huang, L., Bobet, A., EzEldin, M.A.M., Wang, L.Q., Wu, Y.P. and Hu, X.L. (2016). Identification and Mitigation of Error in the Terzaghi Bias Correction for Inhomogeneous Material Discontinuities. Strength of Materials, Vol. 48, No. 6, pp. 825-833.

  • Ma, J., Tang, H., Hu, X., Bobet, A., Zhang, M., Zhu, T., Song, Y., and Ez Eldin, M.A.M. (2016). Identification of Causal Factors for the Majiagou Landslide using Modern Data Mining Methods. Landslides, DOI:10.1007/s10346-016-0693-7.

  • Ma, J., Tang, H., Hu, X., Bobet, A., Yong, R., Ez Eldin, M.A.A. (2016). Model Testing of the Spatial-Temporal evolution of a Landslide Failure. Bulletin of Engineering Geology and the Environment, DOI: 10.1007/s10064-016-0884-4.

  • Borela, R., Bobet, A. and Ellett, K. (2016). Numerical Modeling of Desiccation and Tectonic Processes as Driving Mechanisms for Macro-Polygon Formation. The Geological Society of America, North-Central Section - 50th Annual Meeting (18,19 April 2016).

  • El Fil, H., Bobet, A., Pyrak-Nolte, L.J. (2019). Mechanical and Geophysical Monitoring of Slip Along Frictional Fractures. 53rd US Rock Mechanics / Geomechanics Symposium held in New York, NY, USA, 23-26 June, Paper 19-449, accepted.

  • Wang, X., Wu, W., Zhu, H., Zhang, H., Lin, J., Bobet, A. (2020). Improved friction force calculation with an augmented open-close iteration formulation in discontinuous deformation analysis. Computers and Geotechnics, Vol. 130, doi: https://doi.org/10.1016/j.compgeo.2020.103932.

  • Wang, Ch., Jiang, K., Bobet, A. and Pyrak-Nolte, L.J. (2020). Numerical Simulation of Rock Fracture Roughness due to Mineral Layering and Texture. American Geophysical Union, 1-17 December, 2020.

  • Kelam, A.A., Akgun, H., Bobet, A. and Kockar, M.K. (2021). Assessment of kinematic rock slope failures in Mudurnu Valley, Turkey. EUROCK, 2021. IOP Conf. Series: Earth and Environmental Science 833 (2021) 012061.

  • Wang, X., Wu, W., Zhu, H., Zhang, H., Lin, J.-S. and Bobet, A. (2021). A global direct search method for contact detection between arbitrarily shaped three-dimensional convex polyhedral blocks. Computers and Geotechnics, Vol. 150, https://doi.org/10.1016/j.compgeo.2022.104891.

  • Arslan Kelam, A., Akgun, H., Bobet, A. and Kerem Kockar, M. (2023). Engineering geological characterization and assessment of complex rock slope failures in Mudurnu, Türkiye. Natural Hazards. https://doi.org/10.1007/s11069-023-06331-0.

  • Arslan Kelam, A., Akgun, H., Bobet, A. and Kerem Kockar, M. (2024). Assessment of Complex Rock Slope Instabilities in Mudurnu, Türkiye, through Kinematic and Dynamic Analyses: A Case Study. Rock Mechanics and Rock Engineering, https://doi.org/10.1007/s00603-024-04271-0.