Geotechnical Laboratory

 

The Geotechnical Laboratory is used to study the material properties of soil and the interactions between soil and structural elements such as steel, concrete, geosynthetics, or timber that are used for bridge foundations and retaining wall systems. Testing is also performed to calibrate numerical models for finite element modeling.

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 applicability and to identify opportunities for improvement. In addition, instrumentation is installed in the field  to monitor and evaluate performance of bridges, pavements, and slopes.

Indoor Laboratory

Figure 1. Large-Scale Direct Shear Device.

The indoor facility is capable of conducting basic index tests for characterizing soil and aggregate materials for both research studies and production projects. Unique capabilities include a 12-inch direct shear device, a 6-inch diameter triaxial unit, and a 20-kip universal testing machine. The laboratory also has a variety of fixtures and auxiliary equipment to conduct a variety of specialized tests to include the evaluation of innovative instrumentation for geotechnical applications.

Figure 2. Strength Testing of Geosynthetics.

Figure 3. Large Diameter Triaxial Device.

Figure 4. Frictional Connection Testing: Side View.

Figure 5. Frictional Connection Testing: Top-Down.

Figure 6. Calibration Reaction Assembly.

Figure 7. Evaluation of Pressure-Sensor Technology.

Figure 8. Standard Direct Shear Device.

Outdoor Laboratories: Test Pits

One of the outdoor laboratory facilities consists of two test pits that are 18 feet wide, 23 feet long, and 18 feet deep. The pits can be filled with various soil types for modeled shallow or deep foundation experiments and have also been used to conduct full-scale wall experiments and to test the tension capacity of ground anchors. The pits have reinforced concrete walls, sump pumps to control water-table levels, and anchorage systems to provide reaction loads for experiments.

The pits have a separate building to store the load-test equipment and a control room for the data-acquisition systems.

Figure 9. Mechanically Stabilized Earth (MSE) Shoring Wall Experiment

Figure 10. Helical Anchor Tensile Tests

Outdoor Laboratories: Full-Scale Test Sites

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. The following are a few examples of full-scale experiments in these locations to illustrate the capabilities of Turner-Fairbank Highway Research Center (TFHRC) to lead the advancement of the state of the art.

Figure 11. Geosynthetic Reinforced Soil (GRS) Test Pier

Figure 12. Prototype Geosynthetic Reinforced Soil -Integrated Bridge System (GRS-IBS)

Figure 13. Long-Term Performance of GRS Test Piers

Outdoor Laboratories: Strong Floor

The Geotechnical Laboratory has an outdoor strong floor that is also available for the construction and testing of full-scale geotechnical features on a rigid concrete platform. The spacing of the anchorage locations is 3 feet by 3 feet, each with a 300 kip capacity—similar to the Structures Laboratory—for the capability of a variety of load fixtures and arrangements.

Figure 14. Outdoor Strong Floor

Figure 15. National Cooperative Highway Research Program (NCHRP) 12-59 Experiment on the Strong Floor

Field Instrumentation

Figure 1. Long-Term Performance of GRS Abutments with Various Geometries on the Outdoor Strong Floor.

The geotechnical laboratory also calibrates many different types of typical and advanced geotechnical instrumentation and develops data acquisition systems for installation in the field. Recent installations have included pressure cells, strain gauges, tactile pressure sensors, in-place inclinometers, and survey targets. Various projects, including evaluation of bridge abutments and monitoring of pavement and slope conditions, are currently underway.

Figure 2. Pressure cell installation in Sheffield, MA.

 

Figure 3. Installation of automated MEMS-based accelerometer sensors and piezometers in Denali National Park, AK.

 

Figure 4. Solar powered remote data acquisition system in St. Lawrence, NY.