Simple shear test for interfaces between core and filter soils in rock-fill dams

The mechanical behavior of the interface between core and filter soils plays an important role in the construction of rock-filled dams with a composite earth core as a permeability barrier. This paper describes the use of a laminar-ring simple shear apparatus that was developed to test interface properties, a device that uses stacked steel rings to contain the specimen. A series of interface tests between core and filter soils were conducted using the developed apparatus. During the test, the normal stress was kept constant, and the shear stress and the relative displacement were measured. Furthermore, the deformation features of specimen were measured using LVDTs placed at each of the laminar-rings. Test results show that the shear strength of the interface is controlled by the weaker of the two individual soils.