COMPACTIVE EFFORT

The lateritic soils show a great variation in their properties as per their geological parent, weathering and mineralogical structure resulting in natural variation even in the relatively small geographical regions. Such variability presents serious difficulties to the engineers in determining their behaviour as well as designing the necessary compaction specifications. This study was intended to examine the impacts of different compactive efforts on lateritic soil engineering properties and to see how best they can be utilized in a civil work activity, using Oluku Borrow Pit and Blocks of Flats Gully Site in Benin City as the case study. Two samples of bulk laterite soil samples were collected at the two sites, dried in the air, ground and sent to the lab. The preliminary index tests such as particle size distribution, Atterberg limits, natural moisture content and specific gravity were conducted in order to classify the soils. Standard Proctor, West African Standard (WAS) and Modified Proctor methodologywere used to conduct compaction tests to measure the Maximum Dry Density (MDD) and Optimum Moisture Content (OMC). To determine the strength properties of the compacted soils, California Bearing Ratio (CBR) tests were later conducted in the soaked and unsovid states.The findings indicated that the maximum dry densities and the optimum moisture contents of both soils were increased by the increase in the compactive effort. Using the West African Standard compactive effort, optimum moisture content in the form of the West African Standard was a maximum of 10 per cent, with a maximum of 2.08 Mg/m3 dry density. The Oluku Borrow Pit soil, which had a lower content of fines (about 4.95-5.53% less the 0.075 mm sieve at shallow depths), presented a better performance with unsoaked CBR ranging between 28% at the shallow depths of compaction under the Modified Proctor compaction, whereas the soaked CBR was between 4-6%. Conversely, the Gully Site soil, which contains more fines (30 to 44 percent passing 0.075 mm sieve) registered lower unsoaked values of CBR of 2 to 4 percent and soaked values below 1 percent, which means that it is highly sensitive to moisture.