• Prof. Pinnaduwa H.S.W. Kulatilake
  • Prof. Pinnaduwa H.S.W. Kulatilake
  • University of Arizona, USA
  • Title: Required Data and Computational Techniques to Investigate Deformation and Stability of Rock Masses in Underground and Surface Mine Excavations in Three Dimensions
  • Abstract:
    Deformation and stability of rock masses in underground and surface mine excavations depend on the following factors: 1. Lithological system that exists in the rock mass; 2. Major discontinuity geometry system (large scale features) of the rock mass; 3. Minor discontinuity geometry pattern (small scale features) that exist in each lithology; 4. Intact rock and rock mass physical and mechanical properties of each lithological unit of the rock mass; 5. Mechanical properties of the discontinuities of the rock mass; 6. In-situ stress system of the rock mass; 7. Applied boundary conditions to the rock mass; 8. Water conditions in the rock mass if applicable and 9. Dynamic loading conditions which may be applicable to the rock mass due to blasting and earthquakes. Usually the lithological system and the major discontinuity pattern that exist in the rock mass are very complex. Currently available sophisticated, powerful three-dimensional (3-D) stress analyses software do not have the capability of modeling such complexity. Therefore, the lithological system and the major discontinuity network should be modeled separately before importing them to 3-D stress analyses software to perform 3-D discontinuum stress analyses. Examples of such modeling through previously conducted case studies will be covered in the presentation. Sampling of minor discontinuity geometry data either through manual or remote fracture mapping techniques is subject to sampling biases. In addition, minor discontinuity geometrical parameters exhibit high variability. Therefore, sampling bias corrections need to be applied using geometrical probability techniques before inferring probability distributions for each of the minor discontinuity geometry parameter using probability and statistical techniques. It is important to note that such procedures are not available in the 3-D stress analyses software available at present. Therefore, modeling of discontinuity minor discontinuity geometry parameters need to be performed separately before importing the results of them to 3-D stress analyses software. Examples of such modeling through previously conducted case studies will be covered in the presentation. Rock mass mechanical properties exhibit anisotropic scale dependent properties. The procedures that are used to estimate rock mass mechanical properties using rock mass classification systems do not have the capability of capturing the anisotropic scale dependent properties. Please note that rock mass classification system indices such as RMR, Q and GSI are scalars. On the other hand, both the rock mass strength and deformability change with the direction. Therefore, they are tensors. This presentation will cover estimation of rock mass strength and deformability parameters incorporating intact rock properties and minor discontinuity geometry and capturing the scale effects and anisotropy through a previously conducted case study. In most numerical modeling studies very little attention is paid in estimating the discontinuity mechanical properties comprehensively either through laboratory or field tests. This presentation will cover procedures to estimate all the needed mechanical properties of discontinuities to perform 3-D discontinuum stress analyses. Variability and uncertainty of estimated mechanical properties for rock masses and discontinuities are unavoidable. Therefore, sensitivity or probabilistic analyses should be performed to evaluate the effect of the said material parameter variability and uncertainty. Because a large number of material parameters are used in performing the 3-D stress analyses, the number of combinations of stress analyses that need to be performed will be large. This leads to very high computational time. This presentation will cover how to reduce the total number of combinations and thus the computational time using the statistical experimental design techniques. The complicated lithological system and the discontinuity network that exist in the rock mass play a major role on the in-situ stress system. This will be shown through case studies in the presentation. Then one can ask the question “Can we use the measured in-situ stress system in the field in performing 3-D numerical stress analysis”. This aspect will be discussed in the presentation. Numerical stress analyses results depend on the boundary conditions applied to the numerical model. This will be shown through case studies in the presentation. In addition, use of appropriate boundary conditions in 3-D numerical modeling will be discussed in the presentation. All the aforementioned, clearly indicate the uncertainty we run into in predicting the deformation and stability around underground excavations in 3-D. This means it is necessary to compare the numerical predictions with measured field deformations and stresses. Such comparisons will be shown in the presentation using previously conducted case studies.
  • Biography:
    Dr. Pinnaduwa H.S.W. Kulatilake is a Professor of Geotechnical Engineering and Director of Rock Mass Modeling and Computational Rock Mechanics Laboratories at the University of Arizona. He is a registered Professional Civil Engineer in California. He received his B.Sc. (in 1976) in Civil Engineering from the University of Sri Lanka, Peradeniya, MS (in 1978) in Soil Engineering from the Asian Institute of Technology, Bangkok, Thailand and Ph.D. (in 1981) in Civil Engineering (with geotechnics emphasis) from the Ohio State University, USA. He has over 35 years of experience in rock mechanics & rock engineering associated with mining, civil and petroleum engineering, and applications of probabilistic and numerical methods to geo-engineering. He has written over 200 papers and is a member of several technical committees. He has delivered 25 keynote lectures and over 40 other invited lectures throughout the world on topics related to rock fracture network modeling, probabilistic geotechnics, mechanical and hydraulic properties of joints, rock slope stability and mechanical and hydraulic behavior of rock masses. He has been a research paper reviewer for 20 technical Journals and an editorial board member for Int. Jour. of Rock Mechanics & Mining Sciences, Int. Jour. of Geotechnical and Geological Engineering, Int. Jour. of Advances in Geological and Geophysical Engineering, Coal Science and Technology and Journal of Mining & Science-Turkey. He has taught short courses on stochastic fracture network modeling, rock slope stability analysis, Block theory, and rock joint roughness and aperture in 18 countries covering all 6 continents. He has served over 20 years either as the primary or the sole examiner for the geological engineering professional exam conducted by the Arizona State Board of Technical Registration. He was a Visiting Professor at the Royal Institute of Technology and Lulea University of Technology in Sweden as part of his sabbatical leave. Also, he was a Visiting Research Fellow at the Norwegian Geotechnical Institute, for another part of his sabbatical leave. Due to the contributions he made on teaching, research, consulting and service activities, he was elected to the Fellow Rank of the American Society of Civil Engineers at the relatively young age of 45. In 2002, he received Distinguished Alumnus Award from the College of Engineering, Ohio State University and Outstanding Asian American Faculty Award from the University of Arizona in recognition of his achievements and contributions made to the advancement of his profession. In December 2005, Eurasian National University, Kazakhstan conferred him “Honorary Professorship”. In August 2007, he organized and ran a successful International Conference on Soil & Rock Engineering in Sri Lanka. In January 2009, he organized and ran a high quality International Conference on Rock Joints and Jointed Rock Masses in Tucson, Arizona. He was the guest editor for two special issues published in the Jour. of Geotechnical and Geological Engineering. He received “Kwang-Hua Visiting Professorship” for 2009-2010 from the College of Engineering, Tongji University, China. He is a Recipient of “Guest Professorship” from Wuhan University, China for 2010-2013. Recently he received an award in the amount of 515,000 RMB (US$ 81,320) from the Chinese Academy of Sciences to spend a sabbatical in China as a Senior Visiting Professor. However, he was not able to accept it because of high level of research in US. In October 2013, he received a Peter Cundall Award for a paper submitted to 3rd Flac-Dem Symposium which was held in China.
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Conference:
October 23-25, 2015
Paper or Abstract Submission Due:
July 8, 2015  >> September 9, 2015
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Early Bird Registration due for Audience: July 15, 2015
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