Soil Characterization Based on Physical and Mechanical Properties of Pliocene-Pleistocene Geology in Bukidnon Philippines

Abstract

Soil characterization is important since it gives an idea of the state of soil in the field. Moreover, Philippine geology map shows a vast area of Pliocene-Pleistocene classification, where until now no up to limited study presented the soil characteristics of this type of geology. These soil characteristics are essential for engineering purposes like design, land development, slope stability, disaster risk mitigation, stabilization, and other relevant utilization. In addition, it identifies if the soil in the site is problematic like being expansive or collapsible. In this study, the soil from thirty sampling locations in the two barangays of Kibawe, Bukidnon with Pliocene-Pleistocene geology is characterized based on their physical and mechanical properties. The results showed that the soil in this geology is classified as fine-grained soil with other locations as gap-graded. The plasticity index (PI) varies from 14.11-71.28%, which indicates medium to very high plasticity. The liquidity index (LI) of the soil varies from 0.12 to 0.96 which means that the soils at their in-situ water content are in the plastic state of intermediate strength and can be deformed like a plastic material. Based on USCS, there are four soil types CH, MH, CL and ML while based on AASHTO soil classification system it belongs to A-7-5 and A-7-6 groups with moderate and high plasticity, respectively. Majority of the soils under this geology are highly expansive and have a high tendency to swell. On the other hand, it has 25 locations that are non-collapsible soil and only 5 are collapsible. In terms of cohesion-PI relationship, it shows that the cohesion value increases with the increasing value of PI. However, the friction angle for CL and ML decreases with increasing PI; while the friction angle for CH and MH increases with increasing PI. While some laboratory tests are expensive, these results may help estimate the soil properties and shear strength from other locations with the same geology.