CORRELATION BETWEEN UNCONFINED COMPRESSIVE STRENGTH AND INDEX PROPERTIES OF SOILS: A CASE STUDY IN SARBO TOWN, JIMMA ZONE

Abstract

Correlations are important to estimate the engineering properties of soils, particularly for projects where there is a financial limitation, a lack of test equipment, or limited time. Although correlations are commonly used in the preliminary stage of any project, it is reasonable to assign a unique strength to soils for their respective physical properties. Therefore, this study aims to establish a correlation between unconfined compressive strength and index properties of soils. In this work, undisturbed and disturbed soil samples were collected from fourteen test pits at 1.0 m and 2.0 m depths and from four test pits at a depth of 1.5m for a total of thirty two sample specimens using purposive sampling techniques. Forthe test procedures, American Society for Testing and Material (ASTM) standards and Indian Standard Methods of Test for Soils (IS) were used. To develop the correlational models for this study, Statistical Package for Social Science (SPSS-25), Microsoft Excel-2016, and Origin-Pro 8.5 softwares were used. The objective of this study is modelling of Unconfined compressive strength with index properties in the study area. Based on both single and multiple linear regression analysis a unique correlation is obtained by combining Unconfined compressive strength (UCS) with soil index properties for the study area. From the laboratory test results, the soil type of study area was fine-grained with high plasticity silty soil (MH) and clayey soil (A-7-5) according to the soil classification systems of USCS and AASHTO respectively with medium-stiff to stiff unconfined compressive strength consistency. Accordingly, the best Model is obtained from single linear regression (SLR) analysis and given by 𝐶𝑆 = 385.334 − 3.697 ∗ 𝐿𝐿with R 2=0.871, p-value =0.000 < 0.05nfor fine grained cohesive soils of the study area