Field Performance of a Highway Slope Made of Expansive Yazoo Clay in Mississippi: Fid-Bau Portal

Field Performance of a Highway Slope Made of Expansive Yazoo Clay in Mississippi

Khan / Nobahar, M. / Ivoke, J.

Rainfall-induced slope failure is a common problem in areas with slopes constructed on high plasticity clay soil. Slope failures are frequent in highway embankments and levees on expansive Yazoo clay in Mississippi, which causes significant maintenance problems and requires millions of state and federal dollars to fix it. During the rainfall, water infiltrates through the slope, which saturates the slope and may reduce the matric suction of the soil. However, very limited studies have investigated the variation of moisture and matric suction variation at the field scale. The objective of the current study is to evaluate the performance of a highway slope made of Yazoo clay using field instrumentation. The slope located along Terry Road at the Interstate 20 Interchange in the southwest of Jackson, Mississippi, is considered as the reference slope. The site was investigated using CPT testing and test borings. Moisture and water potential sensors were installed at the crest and middle of the slope at 1.5 m (5 ft), 3 m (10 ft), and 5 m (15 ft) depth. Moreover, two slope inclinometers were installed in the middle of the slope to monitor if there is any potential movement due to the moisture variation. Based on the field monitoring data, volumetric moisture content variation ranged from 20% to 40%, with higher moisture content correlating with rainfall events. As moisture content increased, the matric suction of the slope reached its minimum value at a total of 2-in. rainfall. Due to the change in moisture variation, a 11.43 cm (4.5-in.) movement was observed from slope inclinometer data.