Effects of Regrading on Properties of Coastal Plain Sands

Abstract

Silica sand, known to be physically, structurally and chemically stable is an important component of Coastal Plain Sands (CPS), a problem soil in Southern Nigeria. The CPS lateritic soil was stabilized with silica sand passing 0.425mm sieve, and the stabilized soil was subjected to Atterberg Limits, compaction and soaked/unsoaked California Bearing Ratio (CBR) tests. All tests were carried out according to BS 1377:1990. The results show that the plasticity characteristics (LL, PL, SL and PI) decreased, the maximum dry density increased, while the optimum moisture content reduced with sand content. The effects in these instances are most prominent at about 10% sand content. Peak soaked/unsoaked CBR of the sand stabilized soil were recorded at about 15% sand content. Sand was found to curtail the destabilizing action of water on CPS. The observed behaviour of the sand stabilized CPS soil has been explained through Engineering Geological principles and concepts. It is concluded that addition of 10% 15% sand is optimum and cost effective in stabilizing CPS, and that the stabilized soil has a great potential in addressing the problem of road stability on CPS terrain.