Introducing a New Classification System for Estimating Non-cemented Alluvial Bimsoils Friction Angle

Due to heterogenous nature of bimsoils (complex mixture of rock blocks within a soil matrix), studying their behavior through conducting in situ and laboratory tests is really difficult. By developing methods for shear parameters estimation of bimsoils, engineers will be able to have insight about these parameters values without conducting expensive, difficult and sometimes impossible in situ tests. In this study a classification system for estimating friction angle of non-cemented bimsoils has been introduced. In these bimsoils, friction angle is mostly depended on shape and grading parameters of coarse grains. So, in this classification, rates have been allocated to circularity and roundness as shape parameters and uniformity coefficient of coarse-grained part of grading curve (Cuc) and fine gravel percent (FGP) as grading parameters. The rate allocation is based on results of large-scale direct shear tests on samples with different shape and grading properties. The results of verification have shown that this classification can be used for different non-cemented bimsoils in dry condition. Using this classification engineers will be able to have a comparative insight about different bimsoils friction angle simply through sieve analysis and determining circularity and roundness using image processing. The results of tests carried out in this study also have shown the remarkable effect of grains circularity on friction angle and lead to an insight about grains roundness effect on friction angle.