Proposed a New and Practical Equation for Examine a Coarse Grain Friction Angle by Utlized the Results of SPT

Soil friction angle is one of the basic parameters in determining the shear strength of coarse-grained soils, which is often determined in the laboratory by spending a time and cost, and the use of field experiments has solved this problem. In this regard, Standard Penetration Test (SPT) is one of the most practical field tests that is commonly used in granular soils. In recent years many researches are proposed that present the correlation SPT and shear wave velocity, undrain shear strength and friction angle. Many correlations between SPT and soil friction angle are proposed but most equation with SPT numbers greater than 35 predict the right answers. The correlation between SPT results and soil bearing capacity has been studied and reported by various researchers.  In additional, some correlation between SPT and Soil friction angle have been proposed that each of those evaluated the material of specific area. In this paper new practical equation is proposed that presents an acceptable result in all SPT numbers. With use of this equation, the results can be predicted more accurately.