An Estimated Correlation between California Bearing Ratio (CBR) with some Soil Parameters of Gypseous Silty Sandy Soils


California Bearing Ratio (CBR) value represents the main soil characteristic factor for paving design of flexible pavements & paving of airport sites. It should be used to determine subgrade modulus of crust soil layer, by using certain correlations. It is a very important engineering parameter for soil condition for design of subgrade of flexible roads. CBR values of soil may be affected by other parameters, like maximum dry density (MDD) & optimum moisture content (OMC), soil types, (coarse material of gravel and sand content), etc. for un-soaked condition of samples. Evaluation of CBR in direct test is a time waste process. This case study was conducted to find out the relationship between CBR values with MDD, OMC, standard penetration test (SPT) and coarse material content of some soil samples collected from the investigated project during 2011 with approximate area about (30) Km2, with Latitude (32.319810o -32.412226o) and Longitude (44.144141o - 44.243775o). A statistical method was used for estimating the relationship between the CBR and MDD, OMC, standard penetration test (SPT) and coarse material content of the soil desiring to obtain a relationship and a formula combining the previous two variables. A reasonable relationship represented by first degree formula was obtained. On the other hand, the time and efforts will be minimized in estimation of CBR instead of the used processing to determine the soil parameter.