Characterizing Slope Stability of Colluvial Soils in Ohio Using LiDAR Data

Abstract

Instability of colluvial slopes is a recurring problem along highways throughout Ohio, USA. Colluvial soils in Ohio are typically derived from shale and claystones, which are prevalent in the southern region of the state. The objective of this study was to investigate the differences in engineering properties of colluvial soils in relation to bedrock, and to evaluate the use of Light Detection And Ranging (LiDAR)-based imagery in differentiating between the types of slope failure that occur in shale-derived versus claystone-derived colluvial soils in Ohio. Fourteen colluvial slopes located along highways and affected by slope movement were sampled in central and southern Ohio. The engineering properties determined to date include slake durability indices of bedrock units and natural water content, grain size distribution, and Atterberg limits of soil samples. Additional laboratory tests will include hydrometer analysis, direct shear tests of rock-to-rock and rock-to-soil contacts and x-ray diffraction analysis on clay fractions of bedrock samples. LiDAR data were used to generate digital elevation models and hillshade maps with contours for identifying different types of slope failure affecting shale-derived versus claystone-derived soils. Preliminary laboratory results indicate that claystones are less durable than shales and, generally, claystone-derived colluvial soils have higher plasticity index values than shale-derived soils. Initial evaluation of LiDAR effectiveness indicates that LiDAR imagery may be useful in differentiating between rotational slides common in claystone-derived soils and translational slides common in shale-derived soils.