Department Events

Events

  • Nov
    15

    SEGIM Seminar Series: Bazalel Haimson

    McCormick - Civil and Environmental Engineering

    11:00 AM A230, Technological Institute

    EVENT DETAILS

    ROCK DEFORMATION AND FAILURE UNDER TRUE TRIAXIAL STRESS CONDITIONS

    Triaxial testing aims at providing realistic simulations of rock properties in situ. In conventional triaxial testing a rock cylinder is subjected, typically, to a preset lateral confining pressure and a rising axial stress, until failure occurs; the corresponding principal strains in the test sample are simultaneously recorded. This configuration, however, replicates only the special cases of principal stress condition in which 2 = 3, or 2 = 1. Crustal stress measurements have repeatedly shown that in situ principal stresses are generally unequal (1 ≠ 2 ≠ 3). True triaxial tests, in which three unequal principal stresses are applied to cuboidal rock samples, provide a more realistic simulation of the in situ stress regime. The rock mechanics group at the University of Wisconsin has conducted a multi-year research of true triaxial testing. A loading system was fabricated, which enables the application of three independent and mutually orthogonal loads. The apparatus was used to carry out extensive series of true triaxial experiments in two crystalline rocks (Westerly granite and KTB amphibolite) and two porous sandstones (Coconino and Bentheim).

    The tests revealed that the intermediate principal stress (2) plays a critical role in the stress-strain behavior, failure level, failure mode, and failure-plane attitude. For a preset 3, 1 at failure is not a constant, as indicated by conventional triaxial tests, but rises with 2 magnitude, and in crystalline rocks it can reach levels 50% or more higher than when 2 = 3. Moreover, failure-plane dip direction is not random, as in conventional triaxial tests, but aligned with 3. In addition, failure plane angle is not a material constant, since it also varies with 2 magnitude. In the sandstones tested the 2 effect is less pronounced. It is also evident that the higher the porosity the lower the effect of 2. Over the same σ3 range applied, the σ2-dependence of failure mode in the higher porosity (24%) Bentheim is different from that in Coconino (porosity 17%). Both sandstones failed dilatantly at low σ3 magnitudes, along steeply inclined failure planes striking in the 2 direction. However, at high σ3 (100-120 MPa), Bentheim sandstone failed by developing shear-enhanced compaction bands, inclined less than 450. At σ3 = 150 MPa failure occurred in the form of pure compaction bands normal to 1 direction. Compaction bands were not observed in the Coconino. Microscopic observations via SEM indicate that tensile microcracking is dominant in dilatant failure (under low σ3), while pervasive grain crushing and pore collapse inside compaction bands are observed at high σ3.

    Bezalel C. Haimson is Emeritus Professor, Department of Materials Science and Engineering, and Geological Engineering Program, University of Wisconsin-Madison. He received his PhD degree (Rock Mechanics) in 1968 from University of Minnesota, under the supervision of Professor Charles Fairhurst. He has been at University of Wisconsin since 1969, after an 18 months stint as senior research engineer at Halliburton Oil Service Company.

    His research interests are the state of stress in the Earth's crust and its measurement; mechanical behavior and brittle fracture of rock subjected to true triaxial stresses; borehole stability and breakouts; compaction bands in quartz-rich sandstones; and cyclic fatigue in rock.

    Dr. Haimson is a Fellow of the American Rock Mechanics Association (ARMA). He has received the 2006 American Rock Mechanics Association Award for Research in Rock Mechanics, the 2000 U.S. National Committee for Rock Mechanics Applied Research Award, the 1997 Society of Mining, Metallurgy and Exploration (SME) Rock Mechanics Award for the development of hydraulic fracturing as an engineering method of in situ stress measurement, the 1975 American Society for Testing and Materials (ASTM) Award for contributions to rocks and soils mechanics, and the 1970 U.S. National Committee on Rock Mechanics Research Award in recognition of the development of the hydraulic fracturing stress measurement method. He is the author/coauthor of three books on rock mechanics and of over 200 professional papers.

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    TIME Wednesday, November 15, 2017 at 11:00 AM - 12:00 PM

    LOCATION A230, Technological Institute    map it

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    CONTACT Tierney Acott    tierney-acott@northwestern.edu EMAIL

    CALENDAR McCormick - Civil and Environmental Engineering

  • Nov
    29

    Special Seminar: Lori Graham-Brady

    McCormick - Civil and Environmental Engineering

    2:00 PM A230, Technological Institute

    EVENT DETAILS

    TIME Wednesday, November 29, 2017 at 2:00 PM - 3:00 PM

    LOCATION A230, Technological Institute    map it

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    CONTACT Tierney Acott    tierney-acott@northwestern.edu EMAIL

    CALENDAR McCormick - Civil and Environmental Engineering

  • Dec
    1

    EES Seminar Series: Jason He

    McCormick - Civil and Environmental Engineering

    2:00 PM A230, Technological Institute

    EVENT DETAILS

    TIME Friday, December 1, 2017 at 2:00 PM - 3:00 PM

    LOCATION A230, Technological Institute    map it

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    CONTACT Tierney Acott    tierney-acott@northwestern.edu EMAIL

    CALENDAR McCormick - Civil and Environmental Engineering

  • Dec
    6

    SEGIM Seminar Series: Francesco Lanza di Scalea

    McCormick - Civil and Environmental Engineering

    11:00 AM A230, Technological Institute

    EVENT DETAILS

    TIME Wednesday, December 6, 2017 at 11:00 AM - 12:00 PM

    LOCATION A230, Technological Institute    map it

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    CONTACT Tierney Acott    tierney-acott@northwestern.edu EMAIL

    CALENDAR McCormick - Civil and Environmental Engineering

  • Dec
    9

    Northwestern Engineering PhD Hooding and Master's Recognition Ceremony

    McCormick School of Engineering and Applied Science

    10:30 AM Ryan Family Auditorium, Technological Institute

    EVENT DETAILS

    TIME Saturday, December 9, 2017 at 10:30 AM - 12:00 PM

    LOCATION Ryan Family Auditorium, Technological Institute    map it

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    CONTACT Paula Straaton    p-straaton@northwestern.edu EMAIL

    CALENDAR McCormick School of Engineering and Applied Science

  • Dec
    11

    SEGIM Seminar Series: Zdenek Bittnar

    McCormick - Civil and Environmental Engineering

    2:00 PM A230, Technological Institute

    EVENT DETAILS

    TIME Monday, December 11, 2017 at 2:00 PM - 3:00 PM

    LOCATION A230, Technological Institute    map it

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    CONTACT Tierney Acott    tierney-acott@northwestern.edu EMAIL

    CALENDAR McCormick - Civil and Environmental Engineering