Tag Archives: FHWA

Calibration of Resistance Factors for Drilled Shafts -A report from the LADOTD

Note: Okay – I’ll admit – I also do a blog for the Geo-Institute Deep Foundations Committee.  as such, there are often things that I feel should be posted at both – to get the widest possible audience! So, if you have already been over there, this post will look very familiar.  It is much easier to reuse a post written by yourself. – Robert

With the adoption of LRFD design methods by the American Association of State Highway and Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), and most state Departments of Transportation,  the big question in the geotechnical world is “What resistance factor should we use for __________?”.  AASHTO LRFD Bridge Design Specifications provide a lot of guidance, but many in the industry are working to calibrate resistance factors to regional or local design methods and soil conditions. Various universities and state DOTs, with assistance from FHWA, National Highway Institute (NHI), and the Transportation Research Board (TRB) are conducting research projects to provide some answers to the big question (there is never just one answer in geotechnical engineering!).

Randy Post over at GeoPrac.net recently blogged about a newly released report from The Louisiana Transportation Research Center and the Louisiana Department of Transportation and Development (LADOTD) on their investigation for calibrating resistance factors for the design of axially loaded drilled shafts.  From the report abstract:

As a continuing effort to implement the LRFD design methodology for deep foundations in Louisiana, this report will present the reliability-based analyses for the calibration of the resistance factor for LRFD design of axially loaded drilled shafts using Brown et al. method (2010 FHWA design method). Twenty-six drilled shaft tests collected from previous research (LTRC Final Report 449) and eight new drilled shaft tests were selected for statistical reliability analysis; the predictions of total, side, and tip resistance versus settlement behavior of drilled shafts were established from soil borings using both 1999 FHWA design method (O’Neill and Reese method) and 2010 FHWA design method (Brown et al. method). The measured drilled shaft axial nominal resistance was determined from either the Osterberg cell (O-cell) test or the conventional top-down static load test.

You can download a PDF of the report here.

FHWA Research Project: Post-Grouted Drilled Shafts


(Note from Robert: I used material from the team proposal and the article referenced below for this post, with the authors’ permission. Also, DBA is a significant participant in the project and we hope to provide updates as things move along.)

The Federal Highway Administration (FHWA) has partnered with the ADSC: The International Association of Foundation Drilling (ADSC-IAFD) on a comprehensive research project on post-grouted (also called base grouted or tip grouted) drilled shafts. The FHWA and the deep foundations industry are very interested in the proper application and implementation of post-grouting for drilled shafts. The potential benefits of post-grouting have been demonstrated, and the industry has attempted to capitalize on these benefits in numerous ways. Some of these attempts have been successful while others have not, which has led to confusion and even misapplication of post-grouting technology within the industry.

The project will include an extensive synthesis of existing practice and literature, evaluation of theoretical concepts, full-scale field testing, and comprehensive analysis of the field testing to develop design methods. Each phase of work will have a set of deliverables that will go through a rigorous review process. The project is anticipated to be completed sometime in 2014.

The four main objectives of the research program are:

  1. Bound the application of the post-grouting technology for the current state-of-knowledge;
  2. Quantify the improvement mechanism(s) for the post-grouting of drilled shafts;
  3. Develop design methodology(ies) for appropriate applications of post-grouting; and,
  4. Provide method(s) for verification.

To accomplish these objectives, a highly qualified and experienced team of practitioners and researchers has been assembled to execute this project. This team includes industry representatives from construction, design, and academia that can bring a variety of perspectives to the project as well as respond to input from the many stakeholders within the geotechnical and transportation design and construction communities that routinely implement this technology.

Dr. Antonio Marinucci, MBA, P.E., of ADSC-IAFD will serve as Project Manager for the project and will be responsible for coordination and oversight of all project activities. Dr. J. Erik Loehr, PE, of the University of Missouri will serve as Principal Investigator (PI) with overall technical responsibility for the project including technical planning, data collection, synthesis, interpretation, and document production. Three Co-Principal Investigators (Co-PIs) will collaborate with Dr. Loehr to address the technical aspects of the project: Dr. Marinucci of ADSC-IAFD; Dr. Dan Brown, P.E., D.GE of Dan Brown and Associates, PC; and Dr. Jesús Gómez, P.E., D.GE of Schnabel Engineering Consultants, Inc.

An Advisory Panel will be utilized to provide additional objective technical insight regarding planning and execution of the project and development of the project deliverables, as well as unique expertise regarding specific aspects of the proposed work. The Advisory Panel will include:

Mr. Tom Armour, P.E., D.GE of DBM Contractors, Inc.

Dr. Donald Bruce, CEng, D.GE of Geosystems, LP

Mr. Allen Cadden, P.E., D.GE of Schnabel Engineering Consultants, Inc.

Dr. Steven Dapp, P.E. of Dan Brown and Associates, PC

Mr. Michael Muchard of Applied Foundation Testing

Dr. Miguel Pando, PEng of the University of North Carolina at Charlotte.

To provide objective review and evaluation of project plans and deliverables at key stages of the project, a formal Peer Review Panel will be formed composed of representatives from throughout the drilled shaft industry. The peer review process will be coordinated through the drilled shaft technical committees of each of the major stakeholder organizations in the U.S.: the ADSC-IAFD Drilled Shaft Committee; the ASCE/Geo-Institute (ASCE/GI) Deep Foundations Committee; the Deep Foundations Institute (DFI) Drilled Shaft Committee; and the Transportation Research Board (TRB) Committee on Foundations of Bridges and Other Structures.

The final component of the project team will be the ADSC-IAFD Contractor Members, Associate Members, and Technical Affiliates that will provide substantial in-kind contributions to meet the needs of the proposed experimental programs. Likely in-kind contributions from ADSC members will include provision of testing sites and facilities, construction equipment, materials, testing apparatus, as well as services necessary to complete the proposed project.

The configuration of this team consisting of the PIs, the Advisory Panel and the Peer Review Panel will provide a thorough review process as well as “checks-and-balances” against any perceived or realized personal biases regarding the use of post-grouting with drilled shafts. It is believed that the recommendations resulting from this effort will reflect a consensus on the application, design and construction of base-grouted drilled shafts that will be accepted by the industry at-large. This should result in consistent application of this technique by the industry.

For a detailed description of the project, see the article linked below from May 2012 issue of Foundation Drilling magazine, available from the ADSC-IAFD. In the article, Dr. Marinucci provides the first in a series of updates that will be published reporting the progress of the research through the various phases of the project. We’ll provide posts here as new reports are released, as well as posts of all the action when field work gets started!

ADSC-FHWA Research Project: Evaluation and Guidance Development for Post-Grouted Drilled Shafts for Highways

New FHWA Drilled Shaft Manual is Done!

FHWA GEC 10 DrilledShaftsAlthough I have known for several weeks that the manual was finished (I work for one of the authors, after all!), I was waiting for the FHWA to post the link for the new manual before posting this…and now it is here!   My friend, Randy Post, has an outside review (meaning not connected to one of the authors!) over at his blog Geoprac.net.  Not only did he get “the scoop” on me, but he covers some of the highlights of the “what’s new” with the new, fully revised manual.   The biggest change is completely re-writing the design sections to follow LRFD as well as to update the methods for calculating soil and rock resistance.  As Randy also notes, the manual has been given a Geotechnical Engineering Circular (GEC) designation: GEC 10.  Make sure and go read his review, as well as check out the other things on his blog (disclosure by Robert: I am an occasional contributor there).

The manual’s authors are three of the country’s top experts in drilled shaft design and construction: our own Dan A. Brown, Ph.D, P.E. , John P. Turner, Ph.D, P.E. of the University of Wyoming, and Raymond J. Castelli, P.E. of Parsons Brinckerhoff.   As with any major FHWA publication such as this, there was significant industry involvement in the review process through various technical committees and individuals from ADSC, DFI, and Geo-Institute.  A note from Dan:

The completion of this manual is a great relief and satisfaction.  Many thanks to John Turner’s hard work and also for Ray Castelli’s diligent work to review and make us better.  Special thanks to PB Project Manager Jeremy Hung and our FHWA sponsor Silas Nichols for their dedicated efforts to help get this done, and to all of you who contributed.

Dan and John have been using the material in the NHI course this fiscal year, having done some pilot courses the previous year.  Some NHI courses, including the Drilled Shaft course, can be hosted by non-government groups.  There are also some public seats available occasionally at DOT hosted courses.  The NHI catalog page for this course is here.

Download Drilled Shafts:Construction Procedures and LRFD Design Methods, 2010.

Also linked on our Publications page.

Update (7/12/10): For those that prefer the feel of a printed volume in their hands, the ADSC: The International Association of Foundation Drilling will be the distributor of the printed volume of the manual through their Technical Library.  It will be available soon, according to ADSC.  We’ll post about it as soon as it is available.

Update 2 (8/19/10): The printed manual is now available.