Mineralogy and collapse behaviour of compacted lateritic soils from North-central Nigeria

Abstract

There is limited knowledge about the collapse behaviour of lateritic residual soils, particularly those from humid tropical climates like Nigeria. This work investigates the collapse potential (CP), at 200 kPa, of compacted lateritic soil specimens prepared from two lateritic soils of different mineralogy. The soils were compacted both at standard Proctor and modified Proctor energy levels. The soils consist mainly of silica, aluminium oxide and iron (iii) oxide. Both soils classify as silty sand (Unified Soil Classification System). However, sandstone derived lateritic soil from Gidansani (G sample) has lower liquid limit and plasticity index than the migmatite derived soil from Ilorin (R sample). CP varies from 5.3 % to 18.9 % for G soil and from 5.7 % to 16.6 % in the R specimens. This range of CP indicates that both G and R soils have moderately severe degrees of collapse. Specimens compacted dry of optimum exhibit a positive linear relationship with CP while specimens compacted wet of optimum exhibit reduced CP with increasing dry density. CP increased with moisture content and degree of saturation irrespective of the energy of compaction and soil type. Compaction at higher energy level reduces the tendency for large collapse.