Dr. Stokoe has been working in the areas of in situ seismic measurements, laboratory measurements of dynamic material properties, and dynamic soil-structure interaction for the past  35 years.  He was instrumental in developing the crosshole seismic method for in-situ shear wave velocity measurement to the method that has been adopted as the standard by the American Society for Testing and Materials (ASTM D4428M) and the method that is used by geotechnical engineering firms worldwide.  He has also developed a combined torsional shear/resonant column system which is now used by many universities and private firms in the U.S., Europe and Asia to evaluate dynamic material properties.

            In the last 30 years, Dr. Stokoe has conducted major research efforts in the areas of:  1. nondestructive testing (NDT) of pavements, runways and geotechnical systems, and 2. laboratory evaluation of soil and rock stiffnesses under cyclic and dynamic loading conditions.  He and his colleagues have developed the Spectral-Analysis-of-Surface-Waves (SASW) method for testing geotechnical and pavement systems and structural components.  Dr. Stokoe has conducted major studies using the SASW method to evaluate earth dams for the U.S. Bureau of Reclamation, the Icelandic government and Delft Geotechnical Laboratories and to evaluate debris slides for the U.S. Geological Survey and the Italian government.  He has also conducted comparison studies of the downhole seismic method with the SASW method for the U.S. Geological Survey and has performed extensive SASW investigations at the proposed high-level nuclear storage site at Yucca Mountain for the U.S Department of Energy.

            Dr. Stokoe has participated in numerous demonstration projects involving SASW testing of airport runways and taxiways  over the past 20 years.  Testing has been performed at McDill, Homestead, and Tyndell Air Force Bases.  Testing was also performed at the Cannon International Airport in Reno, Nevada and the Sonoma County Airport in Santa Rosa, California.  Over the past 10 years, Dr. Stokoe has applied the SASW method at John F. Kennedy Airport to evaluate changes beneath runways and taxiways due to micro-tunneling activities.

            As part of his activities in NDT of pavements, Dr. Stokoe and his colleagues have been actively involved in developing dynamic linear and nonlinear analyses for modeling and understanding falling weight deflectometer (FWD) measurements.  He and Dr. Roesset have presented and published papers at the Transportation Research Board Meeting in this area.  They have been successful in extracting the static pavement response from the dynamic FWD test as well as calculating the depth to bedrock from free vibrations of the pavement system in 120- to 180-ms long records.

            Over the past 10 years, Dr. Stokoe has been involved in the development of the Rolling Dynamic Deflectometer (RDD) with funding from Texas DOT and federal agencies.  The purpose of this device is to perform continuous profiles of pavement stiffness “on-the-fly.”  This deflectometer operates at speeds around 2 km/hr (about 1.2 mph) and presently represents a “one-of-a-kind” piece of equipment.  Most recently, the RDD has been used to profile runways at the Dallas-Fort Worth (DFW) Airport, the Portland Airport, the Seattle-Tacoma International Airport, the Atlanta International Airport and various highway pavement sections in Texas and Pennsylvania.

            The laboratory studies with which Dr. Stokoe has been involved can be divided into two groups.  The first group has dealt with the use of resonant column/torsional shear (RCTS) equipment to evaluate the nonlinear shear modulus and material damping of soils.  Most recently, Dr. Stokoe has completed three major laboratory studies in which nonlinear dynamic soil properties were being evaluated for:  1. the Savannah River site for the Westinghouse Corporation,  2. the Electric Power Research Institute, and 3.the ROSRINE (Resolution of Site Response Issures in the 1994 Northridge Earthquake) project.  These studies have been directed towards evaluating the response of soil sites during earthquake shaking.  These results were combined with other tests to develop a new nonlinear soil model (including frequency-dependent material damping).  Presently, dynamic rock properties are being evaluated with the RCTS equipment for the proposed Yucca Mountain High-Level Nuclear Waste site. 

            The second group of laboratory studies has dealt with axially loading specimens, either with transient pulses or continuous cycling for measurement of Young's resilient, constrained and shear moduli.  This work has been conducted with funding from the Air Force Office of Scientific Research, the United States National Science Foundation, the California DOT, and the Texas DOT.  Much of the recent work has been performed in conjunction with resilient modulus testing of subgrade soils.  Further, Dr. Stokoe has developed synthetic specimens which the SHRP project used in the evaluation of resilient modulus equipment.

      Dr. Stokoe is also actively involved in research dealing with ground motions associated with blasting, and exploration activities as well as construction and railroad operations.  His research activities also involve integrity investigations of deep foundations and structural components by wave propagation methods.  He has adapted the SASW method for testing concrete structural elements to evaluate damage and has been awarded Patent No. SN 071 462, 404 for In Situ Testing with Surface Seismic Waves of Materials Having Properties that Change with Time.

      Finally, Dr. Stokoe is the PI (along with co-PIs Prof. Rathje and Prof. Wilson) on a 4-year, $3 million NSF grant in the NEES (Network for Earthquake Engineering Simulation) program. This project will have a substantial impact on the geotechnical earthquake engineering community in the United States. The project involves the development of large-scale mobile field equipment for dynamic loading of geotechnical and structural systems. The equipment, which became operational in October 2004, presents field capabilities that never before existed and will be used in research, with the oversight of the University of Texas team, by universities and governmental researchers around the U.S. The equipment will be operated by the UT team over the next 10 years, with a yearly operating budget in excess of $700K from NSF.

George Goble, Ph.D.

George G. Goble Consulting Engineer, LLC