Evaluation Of Correlation Equations Of CBR Of Soils

Abstract

California Bearing Ratio (CBR) is extensively used parameter in design and construction of flexible pavements. Sub grade strength along the alignment of flexible pavements is required to be determined in terms of soaked CBR of soils. Also, CBR is used as design and quality control parameter of sub base and base layer materials. Considering significance of CBR determination and to cut down time delay in its determination, researchers have developed correlation equations for CBR of different soils in terms of easily determinable index and engineering properties. Correlation equations are developed in terms of single, two and multiple variables through linear and non linear regression analysis. The existing equations applicability to different soils require thorough evaluation of significant factors influencing CBR of soils and the number of influencing variables used in developing the equations. The present paper is aimed at evaluating the correlation equations for Clays and sandy soils from literature based on properties of 10 selected soil properties. The effectiveness of the correlation equations in more precise estimation of CBR is assessed in terms of number of variables used in the equations, selected variable(s) and method of regression analysis adopted.The study indicated that multiple variable linear regression equations with highest degree yielded better equations compared to non linear regression analysis. The study also revealed that the accuracy of CBR value increased with increase in degree of correlation equation.