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Geotechnical Facilities at TFHRC
The Geotechnical Laboratory at the TFHRC includes soil mechanics, soil behavior,
and foundations testing facilities. The primary functions of the laboratory are to
determine mechanical properties of ground materials and to evaluate soil-structure interaction
for bridge foundations and retaining walls. In addition, the laboratory can perform
rock mechanics, geophysical, and in-situ testing of various ground materials.
The GT laboratory facilities are capable of conducting all of the standard tests
for characterizing ground materials. In addition, model tests of piles, drilled shafts,
spread footings, and reinforced soil retaining systems can be conducted in large laboratory
tanks and test pits. Automatic pile drivers, an overhead crane, and load testing
reaction frames are available to conduct evaluations of load/settlement relationships
of instrumented foundation systems.
Indoor facility
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The indoor facility houses a below grade, 2-m cubical test pit, plus several
1.5-m-diameter by 1.5-m-deep steel tanks for testing smaller scale models in both sand
and clay. Loading is provided by a 16,250-kg reaction frame and a specially
designed jacking system that allows for the precise measurement of extremely small loads in
both compression and tension (extraction tests). An overhead, 5-ton capacity crane
is available for loading and unloading equipment and materials in the sunken pit and
test tanks. A small model automatic pile driver is also available to drive 250-mm- to
1-m-long model piles into sand or clay test tanks or pits. The driving weights can be varied
in small increments and adjustments can be made in the number of blows per minute.
Outdoor facility
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The GT outdoor facility consists of two, 7.0 x 5.5 x 6.0 m test pits
with concrete walls and drilled shafts anchored in bedrock for reaction loads up to
255,000 kg. The pits are filled with sand or clay to support either shallow or deep
foundation systems for the experimental test programs. In one corner of each pit is a sump
pump that is used to control the water level. The pits are served by a test control building
that houses the data acquisition system, the load testing equipment, and a larger model
pile driving rig that operates much the same as a prototype pile driver by
releasing heavy weights from a certain height to free fall and develop up to 2,000 ft-lbs of
driving energy (maximum 500-lb weight falling a maximum of 4 ft (1.3 m) to top of pile).
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Tour group at the GT outdoor
facility | Lateral statnamic load
test on a model pile group |
- A recent acquisition includes a 4 MN Statnamic device with a catch
mechanism, which was the first American-owned Statnamic device. The first
project was a series of load tests on model groups of piles at TFHRC . The
second project was a group load test of stone columns in cooperation with
the Hayward Baker Co. and the University of South Florida. The third project
was a series of lateral and vertical load tests on drilled shafts at the
Auburn University, NGES facility. A total of 10 axial and 4 vertical
Statnamic tests were performed at Auburn. The results will be compared with
static testing at the site.
- The GT outdoor facility also includes a mobile pile testing tractor and
trailer that was originally developed for the FHWA Demonstration Projects
Division under Demonstration Project No. 66 on Pile Foundations. At the
conclusion of the project, the trailer was transferred to the Geotechnical
Research Unit at TFHRC. The trailer includes a large, 1,000-ton (890-MN)
load frame with air compressor, generator, four 300-ton jacks, load cells,
LVDT's, and instrumentation readout devices. The reaction system must be
provided at the test site. The FHWA trailer comes with four high-strength
(A514) plates to provide connection between the load frame and the
anchorage system. Researchers from the GT laboratory perform comprehensive
load-testing studies on deep and shallow foundation systems to observe
performance and to obtain load settlement behavioral data for analytical
studies to improve foundation design procedures. Data are stored in
recently developed geotechnical data bases for future analysis by staff
using a number of new computer modeling techniques. The data bases will
provide a valuable standard against which new and existing design
procedures can be compared.
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Plate
load test |
Spread
footing load test |
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