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

Fracture Mechanics

What distinguishes the rock mechanics field from other fields such as soil mechanics is the presence of discontinuities in the rock mass. The behavior of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities, or fractures, within the rock. Such fractures are found at any scale, from few microns to tens of kilometers.

The research involves experimental and numerical investigation of fracture initiation and coalescence of pre-existing discontinuities in the rock, and the experimental determination of the geophysical signature of damage. The focus is on mixed mode loading (I-II-III) of discontinuities both open and closed.

Experiments in the laboratory are conducted on natural rocks and on rock-model materials to investigate cracking.
Cracks in uniaxial compression. Pre-existing fracture at 45°
  • Bobet, A., and Einstein, H.H. (1996). Fracture Coalescence in Rock Material under Uniaxial and Biaxial Loading. Proceedings of the 2nd North American Rock Mechanics Symposium: NARMS'96, Montreal, pp. 1603-1609.

  • Bobet, A. and Einstein, H.H. (1998). Fracture Coalescence In Rock-Type Materials Under Uniaxial And Biaxial Compression. International Journal of Rock Mechanics and Mining Sciences, Vol. 35, No. 7, pp. 863-889.

  • Bobet, A. and Einstein, H.H. (1998). Numerical Modeling of Fracture Coalescence in Rock Materials. International Journal of Fracture, Vol. 92, No. 3, pp. 221-252.

  • Vasarhelyi B. and Bobet, A. (2000). Modeling of Crack Coalescence in Uniaxial Compression. Rock Mechanics and Rock Engineering, Vol. 33, No. 2, pp. 119-139.

  • Bobet, A. (2000). The Initiation of Secondary Cracks in Compression. Engineering Fracture Mechanics, Vol. 66, No. 2, pp. 187-219.

  • Sagong, M. and Bobet, A. (2000). Coalescence of Multiple Flaws in Uniaxial Compression. Proceedings of the North American Rock Mechanics Symposium: Pacific Rocks 2000, pp. 1203-1210.

  • Bobet, A. (2001). Influence of the Loading Apparatus on the Stresses within Biaxial Specimens. Geotechnical Testing Journal, Vol. 24, No. 3, pp. 256-272.

  • Bobet, A. (2001). Numerical solution of initiation of tensile and shear cracks. Proceedings of the 38th U.S. Rock Mechanics Symposium, pp.731-738.

  • Sagong, M. and Bobet, A. (2002). Coalescence of Multiple Flaws in a Rock-model Material in Uniaxial Compression. International Journal of Rock Mechanics and Mining Sciences, Vol. 39, No. 2, pp. 229-241.

  • Sagong, M. and Bobet, A. (2003). Micro-fractographic Characterization of Tensile and Shear Cracks. Proceedings of the Soil and Rock America 2003 Symposium, pp. 937-944.

  • Bobet, A. and Einstein, H.H. (2004). Crack Coalescence in Brittle Material - An Overview of current Knowledge. EUROCK Conference, Salzburg, Austria, pp. 475-478.

  • 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.

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

  • 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 pages.

  • Park, C.H. and Bobet, A. (2007). Crack initiation and propagation from frictional fractures. Proceedings of the 1st Canada-US Rock Mechanics Symposium, pp. 557-564.

  • Park, C.H. and Bobet, A. (2008). Numerical modeling of fracturing in a rock model material with pre-existing flaws. Proceedings of the 42nd US Rock Mechanics Symposium and 2nd U.S.-Canada Rock Mechanics Symposium, Paper No. ARMA 08-134, 9 pp.

  • Park, C.H. and Bobet, A. (2009). Crack coalescence in specimens with open and closed flaws: a comparison. International Journal of Rock Mechanics and Mining Sciences, Vol. 46, pp.819-829.

  • Park, C.H. and Bobet, A. (2010). Crack initiation, propagation and coalescence from frictional flaws in unixial compression. Engineering Fracture Mechanics, Vol. 77, pp. 2727-2748.

  • Bobet, A., Pyrak-Nolte, L., Choi, M.-K., and Hedayat, A. (2011). Mechanical and Geophysical Characterization of damage in Anisotropic Rock. Proceeding of the NSF CMMI Grantees. Atlanta, January 4-7.

  • Hedayat, A., Bobet, A., and Pyrak-Nolte, L.J. (2012). Monitoring slip initiation and propagation along frictional interfaces with seismic wave transmission. Proceedings of the 46th US Rock Mechanics/Geomechanics Symposium, Chicago IL. CD-ROM.

  • 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.

  • Hedayat, A., Pyrak-Nolte, L.J., and Bobet, A. (2013). Multi-modal monitoring of slip along frictional discontinuities. 47th US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, USA, 23-26 June 2013, paper 13-298.

  • Choi, M.K., Pyrak-Nolte, L.J., and Bobet, A. (2013). Relationship between Shear and Normal Stiffness in a Fracture Subjected to Mixed-Mode Loading. 47th US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, USA, 23-26 June 2013, Paper 13-405.

  • Hedayat, A., Pyrak-Nolte, L.J. and Bobet, A. (2014). Geophysical Investigation of Shear Failure along Cohesive-Frictional Rock Discontinuities. 48th US Rock Mechanics / Geomechanics Symposium held in Minneapolis, MN, USA, 1-4 June 2014, Paper 14-143.

  • Hedayat, A., Pyrak-Nolte, L. and Bobet, A. (2014). Detection and Quantification of Slip along Non-uniform Frictional Discontinuities using Digital Image Correlation. ASTM Geotechnical Testing Journal, Vol. 35, No. 5, doi: 10.1520/GTJ20130141.

  • Hedayat, A., Pyrak-Nolte, L. and Bobet, A. (2014). Multi-modal monitoring of slip along frictional discontinuities. Rock Mechanics and Rock Engineering, Vol. 47, No. 5, pp. 1575-1587. Invited paper.

  • Choi, M.-K., Pyrak-Nolte, L.J., and Bobet, A. (2014). The Effect of Surface Roughness and Mixed-mode Loading on the Stiffness Ratio kx/ky for Fractures. Geophysics, Vol. 79, No. 5, pp. D319-D331, doi: 10.1190/GEO2013-0438.1.

  • Hedayat, A., Pyrak-Nolte, L.J. and Bobet, A. (2014). Seismic Precursors to the Shear Failure of Rock Discontinuities. Geophysical Research Letters, DOI: 10.1002/2014GL060848.

  • Modiriasari, A., Bobet, A., and Pyrak-Nolte, L.J. (2015). Monitoring of Mechanically-Induced Damage in Rock using Transmission and Reflection Waves. 49th US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, USA, 28 June-1 July, Paper 15-245.

  • Bobet, A. and Yu, H. (2015). Stress Field Near the Tip of a Crack in a Poroelastic Transversely Anisotropic Saturated Rock. Engineering Fracture Mechanics, Vol. 141, pp. 1-18.

  • Modiriasari, A., Bobet, A., and Pyrak-Nolte, L.J. (2016). Monitoring Rock Damage caused by Cyclic Loading using Seismic wave Transmission and Reflection. 50th US Rock Mechanics / Geomechanics Symposium held in Huoston, TX, USA, 26-29 June, Paper 16-569.

  • Modiriasari, A., Bobet, A. and Pyrak-Nolte, L.J. (2017). Active Seismic Monitoring of Crack Initiation, Propagation, and Coalescence in Rock. Rock Mechanics and Rock Engineering, Vol. 50, No. 9, pp. 2311-2325, https://doi.org/10.1007/s00603-017-1235-x.

  • De Melo Moura, D. and Bobet, A. (2017). Crack Coalescence in Rock-Model Materials through a Frictional Interface. 51st US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, USA, 25-28 June, Paper 17-504.

  • Modiriasari, A., Bobet, A. and Pyrak-Nolte, L.J. (2017). Use of Seismic Wave Conversions (S-to-P wave) to Monitor Shear Crack Growth. 51st US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, USA, 25-28 June, Paper 17-411.

  • Jiang, L., Modiriasari, A., Bobet, A. and Laura J Pyrak-Nolte, L.J. (2017). P-S & S-P Elastic Wave Conversions from Linear Arrays of Oriented Microcracks. Abstract No. H13A-1343 presented at Fall Meeting AGU (American Geophysical Union), New Orleans, LA,11-15 December.

  • Modiriasari, A., Jiang, L., Yoon, H. Bobet, A. and Laura J Pyrak-Nolte, L.J. (2017). Effect of Layering on Cracking Initiation and Propagation under Uniaxial Compression. Abstract No. H13A-1344 presented at Fall Meeting AGU (American Geophysical Union), New Orleans, LA,11-15 December.

  • Bobet, A., Modiriasari, A., and Laura J Pyrak-Nolte, L.J. (2017). Detection and monitoring of shear crack growth using S- P conversion of seismic waves. Abstract No. MR42A-07 presented at Fall Meeting AGU (American Geophysical Union), New Orleans, LA,11-15 December.

  • Modiriasari, A. and Bobet, A. (2018). Deteccion de Fracturas por Metodos Geofisicos. 19 Convencion Cientifica de Ingenieria y Arquitectura, La Habana, Cuba, 26-30 November, 2018, paper 4CIIC-30.

  • Modiriasari, A., Pyrak-Nolte, L.J. and Bobet, A. (2018). Emergent Wave Conversion as a Precursor to Shear Crack Initiation. Geophysical Research Letters, Vol. 45, pp. 9516-9522. DOI: 10.1029/2018GL078622.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2019). Unconfined Compressive Strength of Additive Manufactured Layered Rocks with Oriented Texture. 20th International Conference on Finite Elements in Fluids, Chicago, IL, accepted.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2019). Monitoring Fracture Formation in Additively Manufactured Anisotropic Rocks. 9th International Conference on Acoustic Emission and 61th Acoustic Emission Working Group Meeting 2019, Chicago, IL, accepted.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2019). Effect of Mineral Orientation on Roughness and Toughness of Mode I Fractures. 53rd US Rock Mechanics / Geomechanics Symposium held in New York, NY, USA, 23-26 June, Paper 19-483, accepted.

  • 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.

  • De Melo Moura, D. and Bobet, A. (2019). Influence of Flaw Geometry on Crack Coalescence across an Interface in a Rock Model Material. 53rd US Rock Mechanics / Geomechanics Symposium held in New York, NY, USA, 23-26 June, Paper 19-388, accepted.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2019). Mixed-Mode Fracture Propagation in Layered Printed Rocks with Oriented Texture. American Geophysical Union, 9-13 December, 2019, San Francisco, CA.

  • Bobet, A., Morris, J.P., Yoon, H. and Pyrak-Nolte, L. (2019). Damage Mechanics Challenge: Simulation of Failure Load and Crack Geometry. American Geophysical Union, 9-13 December, 2019, San Francisco, CA.

  • Pyrak-Nolte, L., Jiang, L., Modiriasari, A., Yoon, H. and Bobet, A. and (2019). Translating the Micro-scale to the Macro-Scale: Signatures of Fracture Evolution. ISRM 14th International Congress of Rock Mechanics, Iguassu Falls, Brazil, September 13-18, 2019. Keynote paper.

  • De Melo Moura, D. and Bobet, A. (2019). Cracking across a Smooth Interface in a Rock-Model Material. ISRM 14th International Congress of Rock Mechanics, Iguassu Falls, Brazil, September 13-18, 2019. Accepted.

  • Pyrak-Nolte, L.J., Jiang, L., Mitchell, Ch., Xu, Z., Cao, H., Yoon, S., Kang, P.K., Rimsza, J.M., Trageser, J.E., Bobet, A. and Yoon, H. (2020). Rock-Fluid Interactions: Fracture Formation and Fluid Distributions. American Geophysical Union, accepted.

  • 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.

  • Yoon, H., Williams, M., Jiang, L., Bobet, A. and Pyrak-Nolte, L. (2020). Geomechanical Characterization of Gypsum-based 3D Printer Materials. GSA 2020 Connects Online, The Geological Society of America (GSA), 1-17 December, 2020.

  • Modiriasari, A., Bobet, A. and Pyrak-Nolte, L.J. (2020). Seismic Wave Conversion Caused by Shear Crack Initiation and Growth. Rock Mechanics and Rock Engineering, Vol. 53, pp. 2805-2818. https://doi.org/10.1007/s00603-020-02079-2.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2020). 3D Printed Rock: Mineral Fabric as a Hidden Variable in Fracture Formation. Scientific Reports, Vol. 10, No. 2260, 9 pp., https://doi.org/10.1038/s41598-020-58793-y.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2021). Fracture Formation in Layered Synthetic Rocks with Oriented Mineral fabric under Mixed Mode I and II Loading Conditions. 55th US Rock Mechanics / Geomechanics Symposium. Paper ARMA 2021-1767. Accepted.

  • El Fil, H., Pyrak-Nolte, L.J. and Bobet, A. (2021). Transmitted, Reflected and Converted Modes of Seismic Precursors to Shear Failure of Rock Discontinuities. 55th US Rock Mechanics / Geomechanics Symposium. Paper ARMA 2021-1436. Accepted.

  • Han, K., Pyrak-Nolte, L.J. and Bobet, A. (2021). Experimental Investigation of Rock Saturation Determination. 55th US Rock Mechanics / Geomechanics Symposium. Paper ARMA 2021-1766. Accepted.

  • Wang, Ch., Jiang, L., Bobet, A. and Pyrak-Nolte, L. (2021). Modeling Tensile Fracture in Layered Rocks with Oriented Mineral Texture. 55th US Rock Mechanics / Geomechanics Symposium. Paper ARMA 2021-2043. Accepted.

  • Jiang, L., Yoon, H., Bobet, A. and Pyrak-Nolte, L. (2021). Induced Fracture Geometry in Layered Media under Mixed Mode I and III Loading Conditions. American Geophysical Union, 13-17 December, 2021.

  • Han, K., Pyrak-Nolte, L.J. and Bobet, A. (2022). Geophysical Response of Saturated Rock Joints during Shear. 56th US Rock Mechanics / Geomechanics Symposium. Paper ARMA 2022-995. Accepted.

  • De Melo Moura, D. and Bobet, A. (2022). Crack Interaction with a frictional interface in a rock-model material: An experimental investigation. Rock Mechanics and Rock Engineering, accepted.