Evaluation of correlation between internal friction angle and grains shape using laboratory tests and image technique of grains

Determination of geotechnical parameter in coarse grained alluvia is important subject in geotechnical study. The paper presented a method that can be used to determine the angle of friction with use from particle shape for coarse grained alluvia. In this paper from 9 location in Tehran alluvia prepared soil samples. The angle of friction was determined based on the results of a number of laboratory test (Classification, triaxial and direct shear tests). Then, images of the grains forming the samples were taken and compared with the chart presented by Krumbein and Sloss (1963). In this manner determined shape grains variable (Sphericity and Roundness). In order to 2520 grains were taken images with use by microscope and without microscope. A relationship between the angles of friction was determined with laboratory tests and shape grains variable is investigated and proposed. With increase of angularity and decrease roundness, angles of friction increases.