Center for Drilled Shaft Engineering


Technical Advisory Council


John P. Turner, Ph.D, P.E., PG, D.GE

John Turner is a Senior Principal Engineer with Dan Brown and Associates and Professor Emeritus of Civil Engineering, University of Wyoming.  Dr. Turner has undergraduate degrees in geology and civil engineering, and received his Ph.D. in geotechnical engineering from Cornell University.  He joined Dan Brown and Associates in 2011 after 25 years in academia.  Dr. Turner is the author of NCHRP Synthesis 360, Rock-Socketed Shafts for Highway Structure Foundations (2006) and a co-author of the FHWA Drilled Shaft Manual (2010).  He is the author or co-author of over 100 additional publications on topics ranging from deep foundation case histories, analytical methods for foundation design, landslide stabilization, design and construction of geo-support systems for earth retention, and others.

Dr. Turner’s experience in drilled shaft engineering is extensive, beginning with his Ph.D. dissertation and carrying through to recent projects involving drilled shaft design and construction for major design-build projects involving long-span bridges.




Rudolph P. Frizzi, PE, GE, D.GE

Internationally Recognized Geotechnical Expert Mr. Frizzi’s geotechnical engineering and project management experience is extensive, with particular emphasis on: foundation design and construction in urban areas, and largescale land and waterfront public and private development projects throughout the United States and internationally. During his over 30 years in the industry, he has interacted on projects located in practically every continent world–wide, and has performed geotechnical investigations and designs, prepared plans and technical specifications, and observed field testing and construction as geotechnical “engineer of record” on countless projects.

Mr. Frizzi has obtained extensive field, office supervision, and project management experience including soil and rock sampling and insitu testing; monitoring pre, during, and postconstruction with stateoftheart geotechnical instrumentation; nondestructive testing; aqueous and subaqueous inspections and investigations; and heavy construction which has contributed to his practical approach to geotechnical problem solving.

Mr. Frizzi’s areas of expertise include: engineering shallow and deep foundation systems for supertall structures, stadia, and arenas; temporary and permanent lateral support systems in deep excavations; waterfront structures (levees, embankment dams, and related flood protection infrastructure); pipelines and tunneling; soft and hard rock treatment; surcharging of organic soils and loose sand; brownfield site redevelopment; earthwork; geotechnical instrumentation and vibration monitoring; construction dewatering; and forensic investigations. In addition to his “engineer of record” experience, Mr. Frizzi has provide expert geotechnical consultation and trial testimony on over 80 excavation and foundation litigation cases throughout the United States and internationally.



Scott Jacobs, P.E.




Ray Castelli

Ray Castelli has 40 years of experience in geotechnical engineering, including planning, analyses, design, and construction services for a broad range of major civil engineering projects including highways, bridges, tunnels and marine facilities. Mr. Castelli has a Bachelor of Engineering degree from The Cooper Union, and an MS degree from the University of Illinois at Urbana-­Champaign, and is a licensed professional engineer in ten states.  He is currently WSP | Parsons Brinckerhoff’s Technical Director for Geotechnical Engineering, and a Senior Vice President of the firm.

Mr. Castelli has provided geotechnical engineering services for major projects throughout the U.S. and overseas.  Some recent projects include the Ravenel Bridge over the Cooper River at Charleston, SC; the Audubon Bridge over the Mississippi River at St. Francisville, LA; the Paksey Bridge over the Ganges River in Bangladesh; the I-895 Bridge over the James River at Richmond, VA; the Kosciuszko Bridge in New York City, and the Gerald Desmond Bridge in Long Beach, CA.  Mr. Castelli is the author of more than 30 technical papers on geotechnical and foundation engineering topics, and is a co-author of FHWA manuals of practice for Subsurface Investigations (report No. FHWA-HI-97-021), Earth Retaining Structures (report No. FHWA-NHI-99-025); and Drilled Shafts: Construction Procedures and LRFD Design Methods (report No. FHWA-NHI-10-016).

Photo - Castelli

Vic Donald – Terracon

Erik Loehr – University of Missouri

Professor Loehr is the James C. Dowell Associate Professor in the Department of Civil Engineering at the University of Missouri (MU) and Senior Principal Engineer with Dan Brown and Associates.  He received his B.S., M.S., and Ph.D. degrees from The University of Texas at Austin.

Professor Loehr specializes in research and professional practice associated with complex soil-structure interaction problems and with development of innovative design and analysis methodologies that allow for practical implementation of reliability-based design, risk assessment, and asset management concepts.  He has conducted extensive research to evaluate use of structural elements for stabilization of earth slopes and the effects of moving soil on structural foundations.  He led a comprehensive research effort to develop new engineering guidelines for design of bridge foundations and earth slopes using LRFD for the Missouri Department of Transportation.  He served as Principal Investigator for a comprehensive project funded by FHWA to independently investigate performance of post-grouted drilled shafts and to develop best-practices and effective design guidance for this technique.  He is also currently leading development of FHWA’s Manual on Geotechnical Site Characterization (GEC-5).  Funding for his research has been provided by government agencies including the National Science Foundation, the Federal Highway Administration, the Department of Defense, and the Missouri Department of Transportation, and by private industry including the International Association of Foundation Drilling (ADSC), Nucor-Yamato Steel, and Trinity Products.

Dr. Loehr is also active in private practice and has consulted on notable private and government projects involving complex slope stability and deep foundation problems.  He actively participates in professional organizations including the ASCE Geo-Institute, the International Association of Foundation Drilling, the Deep Foundations Institute, and the Transportation Research Board.  He is currently Chair of the ASCE Geo-Institute’s Committee on Embankments, Dams, and Slopes and was Conference Chair for the 2013 ASCE Geo-Institute Annual Congress in San Diego.  He was the founding chairman of the Deep Foundations Institute (DFI) Committee on Deep Foundations for Landslides and Slope Stabilization and currently serves on the Board of Trustees for DFI. He has been an invited speaker at seminars and conferences both nationally and internationally and is a recipient of the ADSC Outstanding Service Award, NSF CAREER Award, the K.B. Woods Award from TRB, and the Missouri Innovative Researcher of the Year Award among other honors.  He is a registered Professional Engineer in the State of Missouri where he resides with his wife and four children.


Tom Armour, P.E., D. GE – DBM Contractors, Inc.

Tom Armour is the Past President of Donald B. Murphy Contractors, Inc. (DBM) in Federal Way, Washington, a nationally recognized design/build geotechnical specialty contractor.  He graduated from California State University at Sacramento (CSUS) in 1980 with a BSCE degree and continued with graduate studies in geotechnical engineering at CSUS and in business administration at National University.  Tom is Past President of the International Association of Foundation Drilling (ADSC) and has over 30 years of specialty geotechnical design and construction experience, including extensive work with drilled shafts.  He has received numerous awards from state and federal agencies and industry organizations for his work with innovative design and construction techniques.


Center for Drilled Shaft Engineering: 8445 Freeport Pkwy Suite 325 * Irving, Texas 75063 * 469-359-6000

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