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Some Techniques for analyzing downhole array data Ahmed Elgamal, Mourad Zeghal, J. Carl Stepp

International Workshop for Site Selection, Installation and Operation of Geotechnical Strong-Motion Arrays SEISMIC DOWNHOLE ARRAYS AND APPLICATIONS IN PRACTICE Ahmed Elgamal 1 , Zhaohui Yang 1 , and J. Carl Stepp 2 1 University of California at San Diego 2 COSMOS, Berkeley, California.

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Some Techniques for analyzing downhole array data Ahmed Elgamal, Mourad Zeghal, J. Carl Stepp

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  1. International Workshop for Site Selection, Installation and Operation of Geotechnical Strong-Motion Arrays SEISMIC DOWNHOLE ARRAYS AND APPLICATIONS IN PRACTICE Ahmed Elgamal1, Zhaohui Yang1, and J. Carl Stepp2 1 University of California at San Diego 2 COSMOS, Berkeley, California

  2. Some Techniques for analyzing downhole array data • Ahmed Elgamal, Mourad Zeghal, J. Carl Stepp • Shear Wave Propagation Velocity Using Cross Correlation Analysis • Resonant Site Characteristics through Cross Spectrum Analysis • Shear Stress-Strain History Identification • Local Shear Modulus and Damping Identification • Global Optimization of Site Dynamic Properties

  3. Shear Wave Propagation Velocity Using Cross Correlation Analysis

  4. Resonant Site Characteristics through Cross Spectrum Analysis Lotung LSST1 Array (Taiwan)

  5. Shear Stress-Strain History Identification Wildlife-refuge response during Superstition Hills earthquake

  6. Local Shear Modulus and Damping Identification Lotung LSST1 Array (Taiwan)

  7. Global Optimization of Site Dynamic Properties (Lotung LSST1 array)

  8. Literature Overview on Downhole Array Data Analysis Elgamal, A., Lai, T., Yang, Z. and He, L. (2001). "Dynamic Soil Properties, Seismic Downhole Arrays and Applications in Practice," State-of-the-art Paper, 4th Int. Conf. on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, S. Prakash (Ed.), San Diego, CA, March 26-31, 85 p.

  9. Challenging Issues … • Azimuthal Anisotropy. • Direct measurement of displacement (e.g., on sloping ground, during liquefaction).

  10. Hualien Downhole Array (Taiwan)

  11. Gunturi, V.R. and Elgamal, A. (1998). "Hualien Seismic Downhole Data Analysis," Engineering Geology, 50, 9-29.

  12. Direct measurement of displacement - GPS

  13. Blast-Induced Liquefaction Lateral Spreading Test Teerawut Juirnarongrit and Scott Ashford

  14. Aerial Photograph of Test Site Single Piles 9-Pile Group Flow Direction 4-Pile Group Teerawut Juirnarongrit and Scott Ashford

  15. Field GPS Unit Wireless Transceiver Equipment Enclosure GPS Antenna Teerawut Juirnarongrit and Scott Ashford

  16. Monitoring Center Unit Base Stations Teerawut Juirnarongrit and Scott Ashford

  17. Surface Movements Teerawut Juirnarongrit and Scott Ashford

  18. Direct measurement of displacement – Optical fiber sensor

  19. STRAIN, e Linear – Global Basis Functions Nonlinear – Arc Length Based Polynomial Basis Functions Mode Shape Basis Functions DISTRIBUTED DISPLACEMENTS Fiber Bragg Grating (FBG) - Based Measurement System(Overbey, L., Todd, M.D., Seaver, M., He, L., and Elgamal, A.) Distributed FBG Sensor Array Wavelength-Based Demultiplexing • Properties • Local, intrinsic (in-fiber) strain sensing • Insensitive to EM noise • Non-intrusive • Easy multiplexing • Sub-microstrain resolution • An Array was Mounted on a Beam and Inserted in Soil • Utilize bending of beam to capture soil motion • Models used to transform real-time distributed strain to displacement

  20. Max Displacement Results • Less than 2.5 in rms error for all methods in max displacement • Path forward: • Appropriate bonding/sealing agents • Flexible, embedded fiber design • boundary condition modeling changes • Method can be applied to experimental and field measurements • For more information – pick up a copy of a more detailed paper

  21. Thank You !

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