The Transportation Research Board (TRB) has released a synthesis report prepared by Dan and Robert on large diameter piles: NCHRP Synthesis 478, Design and Load Testing of Large Diameter Open-Ended Driven Piles. The report is a summary of the state of practice with regard to Large Diameter Open-Ended Piles (LDOEPs) in the transportation industry. We conducted a survey of state DOTs as well as interviews with private practitioners to summarize current practices as well as recommend best practices with regard to the selection, design, installation, and testing of LDOEPs. Several state DOTs are using LDOEPs more regularly where large foundation loads may exist and/or the piles are subject to significant unsupported length due to scour, liquefaction, or very weak surficial soils. Marine construction conditions also favor the use of these piles, particularly where pile bents might be employed to eliminate footings.
You can download a PDF of the report or purchase a hard copy at the link below.
In the forward of the report, Andrew Lemer of TRB writes:
NCHRP Report 697: Design Guidelines for Increasing the Lateral Resistance of Highway- Bridge Pile Foundations by Improving Weak Soils presents design guidance for strengthening of soils to resist lateral forces on bridge pile foundations. Lateral loads may be produced by wave action, wind, seismic events, ship impact, or traffic. Strengthening of soil surrounding the upper portions of piles and pile groups—for example by compaction, replacement of native soil with granular material, or mixing of cement with soil—may be more cost-effective than driving additional piles and extending pile caps as ways to increase the bridge foundation’s capacity to resist lateral forces associated with these loads. This report presents computational methods for assessing soil-strengthening options using finite-element analysis of single piles and pile groups and a simplified approach employing commercially available software. The analysis methodology and design guidelines will be helpful to designers responsible for bridge foundations likely to be exposed to significant lateral loads.
NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects is a report on the current practices of allocating and managing geotechnical risk through the use (or lack of!) geotechnical information in transportation project bid documents. Even though design-build as a delivery process for projects has been around for a while now, the allocation of risk due to subsurface conditions is an issue still treated with a variety of approaches.
Those of us who have been in this industry for a while know that a thorough geotechnical investigation reduces both cost risk and construction/schedule risk. Design-build is an effective method for accelerating project construction and delivery; however, the acceleration of the schedule puts more pressure on the geotechnical design since “geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award.”
Because geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award, the design-builder’s geotechnical designers are under pressure to complete their work and enable foundation and other subsurface construction to commence. Successfully managing the geotechnical risk in a DB project is imperative to achieving the requisite level of quality in the finished product. The purpose of this synthesis is to benchmark the state of the practice regarding the use of geotechnical information in DB solicitation documents and contracts. The high level federal encouragement through EDC for state DOTs to accelerate project delivery by using DB elevates the need to manage geotechnical risk while expediting geotechnical design to a critical project success factor, and makes the results of this synthesis both timely and valuable.
As is the case with NCHRP synthesis reports, the authors conducted a literature review, conducted a survey of state DOTs and other agencies, and developed some conclusions that include effective practices for managing geotechnical risk.
The synthesis was based on a comprehensive literature review; a survey of U.S. DOTs, which received responses from 42 states (response rate = 84%); a content analysis of DB solicitation documents from 26 states; a content analysis of DB policy documents/guidelines from 12 state DOTs and 5 federal agencies; and interviews of 11 DB contractors whose markets encompass more than 30 states. The synthesis also furnishes three legal case studies (Colorado, Illinois, and Virginia) on cogent geotechnical issues and four geotechnical engineering case studies (Hawaii, Minnesota, Missouri, and Montana) that illustrate the methods transportation agencies use to deal with geotechnical issues on DB projects. Conclusions were drawn from the intersection of independent sources of information from the survey, case studies, and literature.
Some of the effective practices highlighted include the use of confidential Alternative Technical Concepts (ATC) during pre-bid, explicit differing site conditions (DSC) clauses that clearly quantify the design-build team’s risk and the threshold above which the DOT assumes the risk, the use of qualified personnel, and timely review schedules for geotechnical design items early in the project.
Our (DBA) experience in design-build has seen the range from effective practices to poor practices. This report provides a great summary of many of the effective practices we have found to be beneficial and that help reduce conflicts and delays. We can’t completely eliminate geotechnical risk, but it can be effectively and equitably managed.
TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 380: Guidelines for Geofoam Applications in Slope Stability Projects explores the use of expanded polystyrene-block geofoam for slope stabilization projects. For the purpose of the report, slope stabilization projects include new roadways as well as repair of existing roadways that have been damaged by slope instability or slope movement.
The research was performed by the Department of Civil Engineering at The University of Memphis (UoM). David Arellano, Associate Professor of Civil Engineering at UoM, was the Project Director. The other project investigators were Timothy D. Stark, Professor and Consulting Engineer, Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign; John S. Horvath, Consulting Engineer and Professor, Civil and Environmental Engineering Department at Manhattan College; and Dov Leshchinsky, President of ADAMA Engineering, Inc., and Professor, Department of Civil and Environmental Engineering at the University of Delaware.
This report presents the results of a study performed to develop a comprehensive document that provides both state-of-the-art knowledge and state-of-practice design guidance to facilitate the use of EPS-block geofoam for slope stabilization and repair. This report includes the following five primary research products: (1) summary of relevant engineering properties, (2) a comprehensive design guideline, (3) a material and construction standard, (4) economic data, and (5) a detailed numerical design example.
The project was initiated to develop comprehensive design guidelines for use of geofoam in slope stability applications. According to the Digest, geofoam use is becoming more widespread in the U.S., but the adoption of it as a routine roadway construction material has been slowed by lack of design guidelines.
Although EPS-block geofoam for road construction is an established technology and despite the more than 30 years of extensive and continuing worldwide use of EPS-block geofoam, it has been underutilized in U.S. practice because a comprehensive design guideline for its use as lightweight fill in roadway embankments has been unavailable. There was, therefore, a need in the United States to develop formal and detailed design documents for use of EPS-block geofoam in roadway applications.
Here is a blast from the past on pile groups: NCHRP Report 461 – Static and Dynamic Lateral Loading of Pile Groups. I had a request for this report recently, so I found it and figured we needed to post the links to it. Dan was the lead researcher on this report during his time at Auburn University, and had an all-star line up that included Dr. Mike O’Neill and Dr. Mike McVay, two of the heavy hitters in foundation engineering. The report introduction gives a good summary of the contents:
A key concern of bridge engineers is the design and performance of pile group foundations under lateral loading events,
such as ship or ice impacts and earthquakes. This report documents a research program in which the following were developed:
(1) a numerical model to simulate static and dynamic lateral loading of pile groups, including structural and soil hysteresis and energy dissipation through radiation; (2) an analytical soil model for nonlinear unit soil response against piles (i.e., p-y curves) for dynamic loading and simple factors (i.e., p-multipliers) to permit their use in modeling groups of piles; (3) experimental data obtained through static and dynamic testing of large-scale pile groups in various soil profiles; and (4) preliminary recommendations for expressions for p-y curves, damping factors, and p-multipliers for analysis of laterally loaded pile groups for design purposes. The report also describes experimental equipment for performing site-specific, static, and dynamic lateral load tests on pile groups.
Several full-scale field tests were conducted on pile groups of 6 to 12 piles, both bored and driven, in relatively soft cohesive and cohesionless soils. All of the groups were loaded laterally statically to relatively large deflections, and groups of instrumented pipe piles were also loaded dynamically to large deflections, equivalent to deflections that might be suffered in major ship impact and seismic events. Dynamic loading was provided by a series of impulses of increasing magnitude using a horizontally mounted Statnamic device.
For a relatively short (50 pages) report, there is a lot of information packed into it gleaned from a lot of full-scale field work.
TRB has released a new synthesis report covering scour of bridge foundations. Since this is an issue we are involved in on a lot of our big bridge projects, I felt it appropriate to share and help spread the word (Disclosure: I have not read the report yet – but plan to soon). ON large bridge projects we are often on the same team as Ayres Associates, Inc. , the firm of one of the three authors, Paul E. Clopper.
I found out about it from our friend Randy Post of Geoprac.net, so hat tip (h/t) to Randy:
TRB’s National Cooperative Highway Research Program (NCHRP) Report 717: Scour at Bridge Foundations on Rock presents a methodology for estimating the time rate of scour and the design scour depth for a bridge founded on rock. The report also includes design and construction guidelines for application of the methodology.
Check out Randy’s site – he does a great job keeping up with all sorts of things related to geo-engineering.
The Transportation Research Board of the National Academies has published a National Cooperative Highway Research Program synthesis report by Dan and Robert: NCHRP Synthesis 418–Developing Production Pile Driving Criteria From Test Pile Data. This synthesis provides a survey of the current practices used by transportation agencies to develop pile driving criteria, with special attention on the use of test pile data. The report covers issues related to developing driving criteria, the current practices used by the responding agencies, recommended useful practices that were identified, along with descriptions of the practical approach several agencies use to integrate a range of technologies to develop pile driving criteria under typical conditions. The information collected indicates that practices used by transportation agencies to develop pile driving criteria for production pile installation can be described as highly variable in terms of the level and sophistication of the testing performed.
Included in the report are:
Responses from a survey sent to all 50 state departments of transportation plus the District of Columbia and Puerto Rico (44 of the 52 agencies provided responses).
Interviews performed by telephone or in-person of nine of the responding agencies selected based on the written survey responses.
A comprehensive literature review on the range of practices included in test pile programs and their use in developing production pile driving criteria.
Discussions of the survey results.
Useful practices identified from the surveys.
Identification of research needs for this topic.
To purchase the print version of this report or get a PDF, follow this link to TRB. Click the “View This PDF” to get the PDF.
Please note that if you order the printed version, Appendices B and C (copies of the completed survey forms and interview notes) are available via download only.
Specialists in Deep Foundation Design, Construction, and Testing and Slope Stability Problems