- Copyright © 2015, Environmental & Engineering Geoscience
Designing cut slopes along Ohio highways depends on local stratigraphy and slope stability problems. Based on stratigraphy and modes of failure, cut slopes in Ohio were divided into three types: 1) consisting of strong rock units (sandstones and limestones) that exhibit discontinuity-related failures; 2) consisting of weak rock units (shales, claystones, and mudstones) that exhibit raveling, gully erosion, and rotational sliding; and 3) consisting of interlayered strong and weak rock units where differential weathering causes undercutting-induced failures. Data regarding geological, geotechnical, and geometrical parameters were collected for 26 sites, representing the three types of slopes, and were used to perform: kinematic analysis, rockfall trajectory simulations, and global stability analysis. This paper focuses on the design of cut slopes in interlayered stratigraphy where differential weathering is the primary cause of slope instability. Based on stratigraphic variations, we categorized cut slopes in the interlayered units into four types: Type I - thick sandstone underlain by thick shale or claystone/mudstone; Type II - sandstone interlayered with shale or claystone/mudstone in nearly equal proportions; Type III -limestone interlayered with claystone/mudstone in nearly equal proportions; and Type IV - claystone/mudstone interlayered with minor, thin limestone layers. Based on stability analyses and rockfall simulations, we recommend cut slope designs for each stratigraphic sequence that consider slope angles for undercut units to reduce rockfall potential, slope angles for undercutting units that are close to naturally stable angles, benches to reduce undercutting and contain rockfalls, drainage to reduce erosion, and catchment ditches to contain rockfalls.