Use of decomposed granite soils as backfill for reinforced earth structures

Decomposed granite soils are widely distributed almost all over the nation. According to current practice, however, most of them are too fine to use as backfill for reinforced earth structures. In order to explore the possibility of using fine decomposed soils, a series of direct shear tests is performed. The tests shows that the interface friction angles between the soil containing different fines and rough surface reinforcements are not much different. The cohesion component between soils and rough surface reinforcements, which has been disregarded in current practice, exhibit in the interface to some extent. When those factors are involved in the design, the test results suggest a possibility of using much fine soils as the backfill.