A Fractal Approach to Predicting Interface Shear Behaviour

Modelling of the shear behaviour of discontinuities, such as those inherent in rock masses, or those that exist between structures and geomaterials in general is extremely complex. The behaviour of the discontinuity or the interface is often critical to the behaviour of the whole system, and yet the interface behaviour is often poorly understood, and therefore poorly modelled. The particular interface problem with which the authors have been concerned is the shear response of the shafts of piles drilled into weak rock. As with interface shear problems in general, the roughness of the interface is critical. This paper describes a simple fractal-based approach to understanding and quantifying roughness, which has been incorporated into a rational method for evaluation of pile shaft resistance. A case study using this approach is included.