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|Federal Highway Administration > Publications > Public Roads > Vol. 57· No. 2 > National Geotechnical Experimentation Sites|
National Geotechnical Experimentation Sites
by Albert F. DiMillio and Geraldine C. Prince
The Federal Highway Administration's Geotechnical Research Program strives to develop practical, cost-effective technology for bridge foundations, retaining walls, and embankments.
A major focus of this program is the development of a designated system of national geotechnical experimentation sites (NGES) to improve our ability to find and evaluate new techniques for constructing safer and more economical highways and bridges. With this objective in mind, FHWA teamed up with the National Science Foundation to establish a system with a national management board and individual site managers. This article describes the system to accelerate geotechnical research to solve many serious, foundation-engineering problems and difficult, soil-support problems facing the highway community today.
During the last two decades, the geotechnical profession has witnessed major changes in the approach to site characterization and quantification of soil behavior. New in situ testing methods and improved field instrumentation provided valuable new tools to complement and/or create testing alternatives to laboratory procedures. These new techniques are leading to a better understanding of the static and dynamic properties of soils. Although the evolution of new techniques has been relatively rapid, duplication of effort and lack of cooperative work among the various research groups has made progress slower and more costly than might otherwise have been possible.
A lack of well-characterized, well-documented, reference sites has impeded the development and evaluation of new in situ testing methods. Such sites would allow ready comparison of new methods against known soil conditions and past testing programs. Unfortunately, in many cases, these previously studied sites are not available or are unknown to other researchers. As a result, the originators of a new method must perform their own extensive site investigation before reaching the initial objectives of the research. This increases the total project cost and wastes valuable time and effort.
Benefits from well-characterized and well-documented sites are not solely restricted to evaluation of new in situtesting methods. A prime objective of geotechnical engineering is to predict the performance of constructed facilities -- with or without soil and site improvement. The profession needs to evaluate its predictive capabilities by making comparisons with records of actual field performance. Thus, new geotechnical design and construction methods may be developed and tested at these sites, addressing not only the more conventional earthwork and design problems but also environmental problems such as hazardous waste containment.
To quantify ground response and ground failure potential, geotechnical earthquake engineers badly need sites that are well-characterized and permanently instrumented to record earthquakes. The development and verification of new tools to assess site-specific liquefaction potential, for example, require access to cohesionless soil sites where liquefaction has been observed during earthquakes and where soil characteristics are well documented. Instrumentation of such sites could provide field records for the solution of several important problems, including the quantification of pore pressure response and deformations that develop during liquefaction. Analogous sites in clay deposits are necessary to improve our understanding of how such deposits amplify detrimental earthquake motions.
In response to this recognized need, NSF awarded a grant in 1987 to the University of New Hampshire to evaluate the concept of establishing a designated national test site for geotechnical research activities. A steering committee was organized, and a workshop was planned to explore ways to facilitate the establishment of such a site. As a first step, the committee prepared a questionnaire on research interests and needs and sent it to more than 400 geotechnical engineers in universities; consulting firms; state and federal agencies; and drilling, testing, and equipment manufacturing firms. More than 200 responses were received, indicating a high degree of interest in having access to well-documented field sites. The respondents also suggested 81 different locations as potential sites.
Treasure Island Naval Station (Level 1)
Site I.D.: CATIFS
Location: San Francisco Bay, Calif.
Site Mgr:Mr. J. Richard Faris
Seismicity: Seismic zone: 4
Soil Types: Sand (Hydraulic Fill; 14.2 m), Med. Stiff Clay (15.2 m), M. Dense/Dense Sand (13 m), V. Stiff Clay (49.1 m)
Site Area: 0.2 ha (Fire Station #1) other locations possible
Depth to GWT: 1.5 m
Maximum Depth of Exploration: 104 m (bedrock at 91.5 m at test location)
Comments: Treasure Island is a 162 ha artificial island formed by hydraulic filling on a shoal adjacent to a large rock outcrop known as Yerba Buene Island in San Francisco Bay. The composition and consistency of the hydraulic fill varies across Treasure Island, but it is basically loose, fine to medium, silty sand with occasional clay zones. Seismologically, it is located roughly midway between the peninsula segment of the San Andreas Fault to the west and the northern segment of the Hayward Fault to the east. An earthquake of a magnitude at least 7.0 is predicted for one of these fault segments within the next 30 years, with an aggregate probability in excess of 50 percent.
The workshop participants met on September 26-28, 1988, at the University of New Hampshire. The 45 American and foreign geotechnical engineers were divided into five working groups prior to the workshop to start long distance deliberations on their assigned topics before the actual meeting. During the workshop, it became obvious that implementation of the workshop recommendations deserved special attention, and a sixth ad hoc working group was formed. The six working groups were:
The workshop included both plenary sessions, in which everyone could exchange ideas, and working group meetings to develop the reports of the different groups. A key note address opened the plenary sessios and focused the group on the objectives of the workshop. This was followed by six reports on experience with large geotechnical test sites in other countries -- Canada, France, Italy, Japan, Norway, and the United Kingdom.
These countries are far ahead of the United States in developing such sites, and the geotechnical profession in these countries has reaped multiple benefits from their use. The benefits include a strengthening of their position in the international geotechnical design and construction field.
The workshop participants agreed that identification and development of multiple-user sites in the United States would be most beneficial to geotechnical engineering. The survey of possible sites carried out prior to this meeting was potentially a valuable tool for experimenters in the field. Therefore, the participants recommended that it be developed into a catalog of potential sites that would identify other locations omitted from the original survey and summarize in a standardized format all available documentation for each site.
Assuming an evolutionary development of multiple-user experimentation sites, the working groups proposed a method for the eventual integration of available multiple-user sites into a U.S. system of geotechnical experimentation sites, suggested levels of data management for a corresponding nationwide data retrieval system, and recommended the minimum data base and physical requirements for sites intended to explore different problems.
Following the workshop, FHWA awarded a contract to the University of New Hampshire to develop a computerized central repository for all the data contained in the NGES catalog, plus any future data generated at the individual test sites. The cost of this project was shared by nine state departments of transportation -- Iowa, Louisiana, Massachusetts, Minnesota, Nebraska, New York, Texas, Washington, and Wisconsin.
A second workshop was sponsored by NSF and FHWA at Orlando, Fla., in October 1991 to initiate the implementation of the NGES as originally envisaged at the 1988 workshop. Participants at the Orlando workshop selected a small number of sites to form the core of the national system.
The group reduced the original 81 sites to a more manageable number of 40 sites. The 40 sites had reasonably good documentation of the soil conditions and previous experimentation results, a reasonable probability of continued access for at least five years, and a soil type of sufficient interest to geotechnical researchers. An initial screening prior to the workshop identified the nine most promising candidates for the designation of national geotechnical experimentation site.
The evaluators decided that none of the sites met all of the criteria for selection and recommended establishing a national system of multiple sites according to a hierarchy of graded levels that could fluctuate as conditions changed.
Texas A&M University and Treasure Island, Calif., the two sites which came closest to meeting all of the selection criteria, were named as Level I sites. Three sites -- located at the University of Houston, Northwestern University, and the University of Massachusetts -- were found to have some limitation that dropped them into Level II. The remaining four finalists were designated as Level III sites, and all others were grouped in Level IV. Each site will be reviewed periodically to determine if conditions warrant upgrading to a higher level. Loss of access or other negative circumstances may also result in downgrading a site.
Texas A&M University (Level 1)
Site I.D.: TXAMSAND & TXAMCLAY
Location: College Station, Texas
Owner: Texas A&M University
Site Mgr: Prof. Jean-Louis Briaud
Seismicity: Seismic zone: 0
Soil Types: Sand site -- (SP/SP-SM) uniform, medium dense, clean to silty (13.5 m) over clay shale (16.5 m).Clay site -- Highly plastic (CH), stiff (6.5 m; Clay I) to hard clay (5.7 m; Clay II) with high shrink-swell potential, over hard clay/clay shale (23 m).
Site Area: 3.2 ha
Depth to GWT: 6-7.3 m
Maximum Depth of Exploration: 30-35 m
Comments: Extensive in situ testing has been done at the sand site, as well as full-scale tests on an instrumented culvert, a ground-anchor wall, and several drilled shafts. The clay site has been used for a variety of tests on full-scale deep and shallow foundations, as well as for extensive in situ testing.
The Orlando workshop participants also founded a System Management Board to set policies for the use and operation of the sites and to ensure continuity, and they established positions for a system director and for individual site managers at each of the top five sites -- Levels I and II -- which form the central core of the system. A draft plan and suggested budget for managing the system and funding improvements to the core sites were prepared for submission to FHWA and NSF.
University of Massachusetts -- Amherst (Level II)
Site I.D.: MAUMASSA
Location: Amherst, Mass.
Owner: University of Massachusetts -- Amherst
Site Mgr: Prof. Alan J. Lutenegger
Seismicity: Seismic zone: 2A
Soil Types: Varved Clay - medium stiff to soft; CH, lightly overconsolidated. Upper 7.6 m are overconsolidated stiff crust. Estimated total thickness is 37 m.
Site Area: 1.2 ha
Depth to GWT: 0 to 2.5 m
Maximum Depth of Exploration: 24.5 m
Comments: The site is on a deep varved clay deposit (Connecticut Valley Varved Clay) on the University of Massachusetts, Amherst campus. A considerable body of data from field testing with a variety of tools is available, as well as a number of deep foundation tests and some laboratory data, including direct simple shear tests.
FHWA and NSF signed a system-support contract with the University of New Hampshire in 1992 to provide the overall management of the program and to operate and maintain the Central Data Repository. They awarded subcontracts to each of the five site owners and a part-time system director, Dr. Richard D. Woods of the University of Michigan. The board approved improvements to each site based on proposals submitted by the site managers. These improvements are currently underway.
The data base of the Central Data Repository includes graphs of representative profiles and typical plots of data for each site. Modem hookups provide remote access to individual test results and test data. This allows users to review the quality and numerical details of the results. An electronic bulletin board provides late-breaking news about various sites and programs available within the system.
Northwestern University (Level II)
Site I.D.: ILNWULAK
Location: Evanston, Ill.
Owner: Northwestern University
Site Mgr.: Prof. Richard J. Finno
Seismicity: Seismic zone: 1
Soil Types: Sand fill; SP, SP-SM, mostly dense to very dense, (7 m) over soft/medium clay; CL, (11.3 m) (Clay I) over stiff/very stiff clay (3.3 m) (Clay II)
Site Area: 0.2 ha
Depth to GWT: 3-4.6 m
Maximum Depth of Exploration: 24.4 m
Comments: This site was used for the pile prediction exercise carried out in conjunction with the 1989 ASCE Foundation Engineering Congress. Field and laboratory test data are available for the Sand Fill and Clay I, as well as results of pile and pier load tests .
The CDR is a user-friendly system shell with online computer search and data retrieval capabilities that enable geotechnical researchers to select the most appropriate site for their work. It can accommodate all essential information about each site such as generalized soil conditions, listing of all available test data, site logistics and limitations, published references, and other site information.
University of Houston (Level II)
Site l.D.: TXHOUSTO
The availability of national geotechnical experimentation sites that are already well-characterized and permanently instrumented will serve to accelerate innovative research on soil behavior and foundation engineering. Future research performed at these sites will be less individually oriented, with greater documentation maintained for the benefit of other investigators.
The initial tasks of identifying appropriate sites and setting up a management program have been completed. Funding to fully define the soil properties and site conditions for each designated site has been obtained under joint sponsorship of FHWA and NSF. Other sponsors will be recruited, and a schedule of user's fees will be considered. Knowledge of the site specifics will continue to be updated in the Central Data Repository as experiments are conducted at each site and data are accumulated.
Researchers and practitioners can exchange information and ideas through the NGES system to focus their thought processes into more definable channels because they will be comparing theories and testing procedures against the same reality. This, in turn, should lead to better communication of the effects of geotechnical phenomena to the geotechnical community, thereby reducing the misunderstandings, inconsistencies, empiricism, and untested theories that pervade geotechnical practice today.
NGES will foster more cooperation between public agencies, universities, and private sector groups -- something which has been missing from geotechnical engineering. In addition to providing a standardized base upon which to judge the results of new research, NGES will provide research sponsors like FHWA, NSF, and state highway agencies with more accountability than in the past because investigators will know that others can come to the same site and repeat the experiment.
In summary, development of well-characterized sites that are readily available to geotechnical engineering will encourage a variety of experimental activities which will lead to techniques for constructing safer and more economical structures. As an additional benefit, these improvements will make U.S. geotechnical design and construction firms more competitive in the international arena.
(1) Jean Benoit and Pedro de Alba. Designated Sites for Geotechnical Experimentation in the United States, Proceedings of the workshop at the University of New Hampshire, Durham, N.H., September 1988.
(2) Jean Benoit and Pedro de Alba. Selection and Management of National Geotechnical Experimentation Sites, Proceedings of the workshop at Orlando, Fla., October 1991.
(3) Jean Benoit and Pedro de Alba. Catalog of National Geotechnical Experimentation Sites, Report to the National Science Foundation and the Federal Highway Administration, April 1993.
Albert F. DiMillio is the geotechnology team leader in the Materials Division, Office of Engineering and Highway Operations Research and Development, at the Turner-Fairbank Highway Research Center in McLean, Va. He joined the Federal Highway Administration's Highway Engineer Training Program in 1967 after receiving a master's degree in geotechnical engineering from the University of Rhode Island. He served as an area engineer in the Indiana division office and as the regional geotechnical engineer in the Homewood, Ill., (Region 5) office before coming to the TFHRC in 1975 to run the Geotechnology Research Program. In 1991, he received the American Society of Civil Engineers' James Laurie Prize, given annually to an ASCE member who has made a significant contribution to the advancement of transportation engineering. He is registered as a licensed professional engineer in Indiana. DiMillio served on the original steering committee for the establishment of the national geotechnical experimentation sites, and he currently serves as co-chairman of the NGES System Management Board.
Geraldine C. Prince is a student at the Ecole Superieure de Commerce et d'Organisation in Paris, France. She was a summer intern at the Federal Highway Administration's Turner-Fairbank Highway Research Center in McLean, Va., from June to August 1993. During this time, she worked on the development of a marketing plan for the National Geotechnical
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