A laboratory investigation into the effect of confinement on the dynamic cone penetration index of a lateritic soil for field compaction verification

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The compaction quality control process may be simplified by introducing the Dynamic Cone Penetrometer (DCP) as a compaction verification tool. To use the DCP for this purpose requires a field calibration exercise. The calibration parameters κ, and λ and the magnitudes of the dynamic cone penetration index (DPI) are known to be influenced by many factors including soil type, density and moisture content. Due to the sensitivity of these parameters to the soil factors, a new calibration test has to be performed whenever there is a change in the material source. However, in-situ calibration test is tedious and time consuming and tend to decrease the attractiveness of compaction verification using DCP. To overcome this challenge, in-mould DCP is proposed. However, the influence of confinement provided by compaction moulds needs to be examined and quantified in order that the laboratory determined parameters may be used in the field. This research investigated the influence of horizontal confinement provided by the in-mould DCP on the DPI of a lateritic soil. The lateritic soil were compacted at the optimum water content using the modified AASHTO in seven moulds of nominal diameters of 100mm, 150mm, 200mm, 300mm, 400mm, 500mm and 600mm. For each mould, three levels of compaction ranging from 80% to 100% were performed. This was followed by conducting the in-mould DCP test with a DCP equipment of hammer mass 8kg in accordance with ASTM D 6951-03. From the study, it was found out that, for a given mould diameter, the DPI (mm/blow) reduced with increasing dry density. The effect of confinement was observed to increase as the mould diameters increases but from 500mm, the effect of confinement was insignificant. For the 500mm diameter mould the effect of confinement increases the DPI value in the CBR mould by 2.2. A relationship was developed between level of laboratory compaction and DPI that may be used for field compaction verification.
A thesis submitted to the Department of Civil Engineering, College of Engineering in partial fulfillment of the requirements for the award of the degree of Master of Science.