Some geotechnical properties of residual mica schist derived subgrade and fill materials in the Ilesha area, Nigeria

Abstract

Fine grained micaceous soils are known to be relatively difficult to densify by compaction, and they may pose subsequent stability problems to pavement structures constructed over them if appropriate caution is not exercised during the construction period. The texture, consistency. compaction and CBR characteristics of the mica schist derived lateritic soils in the Ilesha area were studied for a critical evaluation of the long term performance of soils which have been used as borrow materials in the construction of stretches of the Ife-Akure highway. X-ray diffraction studies confirm that the main clay mineral present is kaolinite, but it is associated with various amounts of illite, montmorillonite and chlorite. Densification by compaction was observed to be relatively inhibited when the maximum dry density values are compared with those of other lateritic soils occurring in the same locality. Soaked CBR values are low, ranging from 6% to 14% only. Textural considerations disqualify the soils as borrow material, but surprisingly, the consistency limit values make them tolerable.