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Research: Testing Reinforcement Materials

Modular block face of test wallBaton Rouge, Louisiana: The Louisiana Transportation Research Center recently conducted a year-long test of a reinforced-soil embankment built on a soft-clay foundation. The researchers wanted to evaluate the performance of several types of reinforcement materials and to learn how the embankment would deform with settlement of the foundation soil.

Settlement Plates and GeogridThe embankment is 6 meters high, 47 meters long, and 8 meters wide, with a vertical facing of modular blocks. Tensar UX 1600 geogrid, shown in the photograph at left, was installed to improve the load-carrying capacity of the weak base soil. Other types of reinforcement grids were installed behind the facing, extending 4 meters into the embankment. The back of the embankment was completed with a 1:1 slope.

Location of InstrumentsThe drawing at right shows the locations of the instrumentation used to monitor deformation of the embankment. Most settlement was expected near its face. Two horizontal inclinometers were installed, one along the length of the face and the other across the the embankment. The horizontal inclinometers, which provided high-resolution settlement profiles, were complemented by a number of settlement plates and by optical survey targets located on the facing. Lateral deformations were monitored by eleven vertical inclinometers and by survey targets on the facing.

Settlement plot from Horizontal InclinometerMonitoring began at the beginning of construction and continued through the year. The horizontal inclinometer measurements (left) compared well with the settlement plate data (below) and the survey targets. The plots shown here span the first six months of project. The largest settlements occurred about 1.5 meters from the facing, as expected. Lateral displacements at the facing varied from 12 to 50 mm. At the end of the year, the largest settlement was 355 mm (14 inches).

Settlement measured by settlement platesThanks to Dr Khalid Farrag, PE and the Louisiana Transportation Research Center for contributing this story. Dr Farrag is the research coordinator for the LTRC's Geosynthetics Engineering Research Laboratory. The LTRC was created to conduct research to improve transportation systems in Louisiana. Its projects are largely funded by the US Federal Highway Administration.

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