Using Dynamic Cone Penetrometer Tester to Determine CBR and Bearing Pressures of Subsurface Soils in Parts of Owerri, Southeastern Nigeria

Abstract

Using dynamic cone penetrometer tester (DCPT) to determine the CBR and bearing pressure of subsurface soils in parts of Owerri, southeastern Nigeria were investigated in this study. Six (6) DCPT were measured to the depth of 6 m. The data obtained from field DCP test was plotted on the graph of penetration resistance (mm/blow) versus penetration depth (m); which revealed the soil profile of three layers with different penetration consistencies and resistances. The highest PR (mm/blow) recorded was 11.4 mm/blow and the lowest is 55.5 mm/blow.  The layers encountered during the measurement ranges from loose, medium and dense soils, where the average thicknesses of loose layers ranges from 0.1 to 0.5 m, medium layers 0.5 to 3.0 m and dense layers 3.0 to 6 m. The average CBR values recorded at interval of 1m to 6 m depths are as follows: 5%, 8%, 12%, 15%, 16% and 16%. Accordingly, the averages bearing pressures calculated were 104.8 KN/m2, 165.5 KN/m2, 231.9 KN/m2, 283.3 KN/m2, 291.5 KN/m2 and 301.1 KN/m2. It shows significant increase in strength with depths.