Geophysics for Geotechnical Engineers

Geophysics for Geotechnical Engineers

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  GEOPHYSICS FOR GEOTECHNICAL ENGINEERS- BRIDGING THE GAP Ramanuja Chari Kannan PE FASCE CESWF-EC-D June 15, 2011 Atlanta, GA US Army Corps of Engineers BUILDING STRONG®
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  EVOLUTION OF GEOLOGY The earliest writing on Geology probably dates back to Theophrastus (372-287BC) who wrote a book on rocks called ‘Peri Lithion.” Abū Rayḥān al-Bīrūnī was perhaps the first person to document his observations about the earth and is credited with writing the first book on Geology. (A crater on the moon and the University in Tashkent are named after him). Will Durant in his History of Civilization recognized that al-Biruni worked on the hypothesis that the earth was a sphere, revolved around the sun and spun on it axis. The term “geology” was introduced by Jean-Andrè Deluc in 1778. William Smith (1769-1839) produced the first geological map of England and Ireland.
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  GEOLOGY TODAY Earth science  Geography Paleoclimatology Economic geology  Geological modeling Paleontology Mining geology  Geometallurgy Micropaleontology Palynology Petroleum geology  Geomicrobiology Petrology Engineering geology  Geomorphology Petro physics Environmental geology  Geomythology Plate tectonics Geoarchaeology  Geophysics Sedimentology Geochemistry  Glaciology Seismology Soil science Biogeochemistry  Historical geology Pedology (soil study) Isotope  Hydrogeology Speleology geochemistry  Meteorology Stratigraphy Geochronology  Mineralogy Biostratigraphy Geodetics  Oceanography Chronostratigraphy Lithostratigraphy  Marine geology Structural geology Volcanology
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  GEOTECHNICAL ENGINEERING The credit for understanding of the concept of soil as an engineering material should rightfully belong to Coulomb, who soon after his graduation in 1761 used his knowledge of mechanics to apply to pressure exerted by soils. Karl Terzaghi of course has been credited with not only coining the term soil mechanics, but also with realizing the importance of understanding geology in understanding soil physical properties. As the saying goes, the rest is history – of soil mechanics. No one is really sure when and why the term Geotechnical Engineering came to absorb soil mechanics, foundation design and anything else that has the word “soil” in it. Terzaghi’s wife Ruth, a geologist and his graduate student and Arthur Casagrande should be credited with connecting mechanics with the material.
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  MERGING GEOLOGY ANDGEOTECHNICAL ENGINEERING • Geology and Geotechnical Engineering merge in many areas – soil and rock physical properties, site characterization, mineralogy and foundation design. • While Geotechnical engineers have refined their laboratory testing, in-situ testing and design techniques, the amalgamation of geophysics and geotechnical engineering has not taken a significant role in the practice of geotechnical engineering. • Geophysical methods should be the primary investigative tool for geotechnical engineers.
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  GEOPHYSICAL METHODS METHOD MEASURED PARAMETER Ground Penetrating Radar (GPR) Dielectric Constant (indicate the top of rock surface) Electromagnetic Frequency and Electrical Conductivity (lateral variation in soil and rock; Time Domain (EFT) differentiate soil types including contaminated soils) Very Low Frequency (VLF) ER Electrical Resistivity (apparent resistivity) Electrical Resistivity / Capacitively Electrical Resistivity (stratification/spacial differentiation) Coupled Resistivity Spontaneous Potential (SP) Electrochemical and Streaming potential (Seepage) Seismic Refraction Seismic velocity, shear modulus (rock rippability) Seismic Reflection Seismic velocity (Stratigraphy) Surface Wave Analysis Seismic velocity, dispersion (S-wave/stratigarphy, karst features) Microgravity Density (bedrock/karst) Magnetic Potential Magnetic susceptibility (minerals, buried objects) Thermal Imagery Surface temperature (seepage, karst) Radio-metrics Natural Gamma Radiation (ores, fracture) Cross-hole tomography Subsurface profiling, stratigraphy (karst)
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  GEOPHYSICS FOR GEOTECHNICALENGINEERS • Policy Development • Recruitment and Training • Data management and analysis • Risk Assessment and Mitigation • Consultation and Technical Reviews • Quality Assurance • Periodic Inspection and Periodic Assessment Support
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  RMC’s PROGRAM • Develop1-, 5-, 10-, and 30-year infrastructure investment plans • Prioritize Issue Evaluations, Dam Safety Modification Reports, and Construction • Monitor progress and project management for dam safety projects • Support Senior Oversight Group and HQ efforts to manage funds and queues
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  HOW WE CANSUPPLEMENT RMC RMC’s CURRENT CONCERNS OUR RESPONSE AND POTENTIAL Dam Safety Regulation and Procedures SWF has involved RMC in our DSMS RMC’s need to define RMC Role role is evolving as we progress Geotechnical Issues dominate the SWF has one of the strongest staff support Portfolio and expertise in this area Risk Based Evaluation is needed SWF has the need to focus in this direction Organizational Improvement needed We have expertise gathered from CoS, Border Protection, Force Protection, LEED and Design experience Experienced Staff is Scarce We have surplus capacity from time to time and have a recruiting advantage Extensive outsourcing to A/E firms SWF has the potential to reduce A/E outsourcing Prioritizing and Implementation SWF is lower in priority as compared to NE and NW
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  A PLAN FORSWF’s RMC PROGRAM Within the first 30 days: Establish and staff the center Define roles and develop Position Descriptions Develop a 1-year and 5-year budget Establish program priorities Within the first 90 days: Internal Recruitment and assign responsibilities for the internal team Prioritize projects and develop schedules (primarily DSMS and LRP projects) Match national resources and develop talent pool Detailed budgets for DSMS and LRP and funding support
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  SWF’s RMC PROGRAMPLAN Within the first 1 year: Get project teams working on specific DSMS and LRP projects Assist the Levee CoP in developing LSMS methods Develop detailed 5-year design plan for DSMS and LSMS Develop Remedial action plans and construction plans Write contracts for remedial works – standardize if possible Within the first 5 years: Set up Inspection Plans based on risk evaluation Assist Dam and Levee CoPs to develop practice standards Document strategies from lessons learned Identify10-year and 60-year needs and needed infrastructure improvements.
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  THANK YOU