Slip propagation along frictional discontinuities

Slip initiation and propagation along non-homogeneous frictional surfaces are investigated by loading specimens of gypsum in biaxial compression. The specimens used in the tests are composed of two individual blocks with perfectly mated contact surfaces. The contact surfaces have on their upper half a frictional strength smaller than on their lower half. This creates a “weak” surface on the upper half and a “strong” surface on the lower half....