15.4.4. Shear Strength of Pervious Soils In embankment sections of clean sand and gravel, the pore pressures develop primarily due to seepage flow. The changes in pore pressure on account of changes in the embankment volume are short-lived and can be neglected. Consequently, the effective stress method of stability analysis is used for sections of pervious sand and gravel. The strength characteristics of sand and gravel are determined by drained tests. Because of the limitations of the size of test equipment, it may not be possible to test gravels of larger size. The strength characteristics of such soil can safely be assumed as those obtained for finer fractions of the same soil (4).
