Relative Proliferation of Gullies on Three Geological Sediments: The Influence of Soil Consistency Limits and Shear Strength

Abstract

This study was carried out to evaluate the influence of soil consistency limits and shear strength on the relative proliferation of gullies on three geological sediments, namely: the Upper Coal Measures (UCM), the Ajalli Sandstones (AS), and the Lower Coal Measures (LCM), which has been ranked as AS > UCM > LCM. Soil samples were collected from a depth range of 60-90 cm of sampling pits dug at a selected location on each of these texturally homogenous and unique formations. These were analysed for consistency limits and shear strength using standard methods and procedures. Results showed that the plasticity index (PI) of the UCM (PI UCM) was 24.49%; PI AS , 5.89%; and PI LCM , 44.85%. The shear strength (S) of the UCM (S UCM) was 314.74 KN/m 2 ; S AS , 196.23 KN/m 2 ; and S LCM , 321.72 KN/m 2. The results of the study show that rankings of the respective contributions of these two geotechnical properties to the vulnerability of the sediments to gully (soil) erosion follow the same order of proliferation of gullies on the plateau landscape: AS > UCM > LCM. Hence, consistency limits and shear strength parameters partly influence and explain the relative proliferation of gullies on the three formations. Further studies are required to determine other soil factors of gully erosion in the area in order to evolve appropriate management strategies for these sediments.