Geotechnical Laboratory

The Geotechnical Laboratory is used to study the interactions between soil and structural elements made of steel, concrete, or timber that are used for bridge foundations and retaining wall systems.

The Geotechnical Laboratory consists of a standard indoor testing facility and several unique outdoor testing facilities. New materials and methods of design and construction are tested and evaluated in both indoor and outdoor environments to determine their acceptability and to identify opportunities for improvement.

Figure 1. Large Scale Shear Test Device.

Figure 2. Peformance test for Geosynthetic Reinforced Soil Composite.

The indoor facility is capable of conducting all of the standard tests for characterizing soil and aggregate materials for both production-type jobs and research studies. In addition, the indoor laboratory is capable of conducting specialty experiments related to soil-geosynthetic interaction and the evaluation of innovative instrumentation for geotechnology.

Figure 3. Evaluation of Pressure Sensing Technology.

Figure 4. Data Acquisition System Development.

Figure 5. Calabration Reaction Assembly.

One of the outdoor facilities consists of two 5.5-m by 5.6-m by 6.5-m test pits that can be filled with various soils to support either shallow- or deep-foundation systems of modest size. The pits have concrete walls, sump pumps to control water-table levels, and anchorage systems to provide reaction loads for experiments.

Figure 6. Outdoor Test Pit Facility.

The pits also are served by a test-control building that houses the data-acquisition systems and load-test equipment. The laboratory includes two additional outdoor test sites where full-scale bridge piers, abutments, and retaining wall structures were constructed for research and testing purposes. A newly built outdoor strong floor also is available for the construction and testing of full-scale geotechnical features on a rigid concrete platform capable of supporting a variety of load fixtures and arrangements.

Figure 7. Geosynthetic Reinforced Systems (GRS) Test Pier.

Figure 8. Outdoor Strong Floor

Background

During the 1970s, a series of Federal Highway Administration (FHWA) studies determined that various segments within the field of highway geotechnology needed significant improvement in design and construction applications. This was especially important considering that bridge foundations, retaining wall systems, cut and fill operations, embankments, and ground improvements account for more than 50 percent of the total cost of most highway construction projects. It was therefore imperative that accurate and rational guidelines be developed for geotechnical-related design and construction applications to ensure safe and efficient highway structures.  The following link is a summary report of past FHWA research activities in bridge foundations, ground improvement, and soil and rock behavior. 

http://www.fhwa.dot.gov/publications/research/infrastructure/geotechnical/98139/index.cfm

Other pertinent past research topics and activities of the geotechnical research team is the development of the deep foundation database, Automated Geotechnical Information and Design System (AGIDS), National Geotechnical Experimentation Sites (NGES), geotechnical risk and reliability, and in situ soil testing.

Most recently, a large focus of the geotechnical program has been to investigate Geosynthetic Reinforced Soil (GRS) for load-bearing applications and the use of GRS to build the Integrated Bridge Systems (IBS). Based on the research conducted at FHWA's Turner-Fairbank Highway Research Center (TFHRC), many inservice bridges were constructed. The proven performance of those bridges led to the selection of GRS-IBS technology for the Every Day Counts (EDC) initiative. The following link contains information about the GRS-IBS:

http://www.fhwa.dot.gov/everydaycounts/technology/grs_ibs/

Other current research includes characterizing aggregates, evaluating advanced geotechnical monitoring technologies, and deformation analysis of shallow foundations. Future work will continue to advance the state of the art in all facets of geotechnical engineering.

Figure 9. Protoype GRS-IBS at TFHRC