Quantification of the relative ability of rock to resist scour

The paper summarizes a methodology that can be used to quantify the relative ability of rock to resist scour. Rock’s relative ability to resist scour is a function of its intact material strength, block size, shear strength of discontinuities between blocks of rock, and the relative shape and orientation of the rock blocks. A geomechanical index that is known as the Erodibility Index is used to quantify the relative ability of rock to res ist scour, and is calculated as the product of four coefficients, each representing one of the four parameters. The orientation and shape of rock blocks are incorporated in one coefficient. A summary of the Erodibility Index Method that implements this measure of the Iekitive of rock to resist scour is presented in a companion paper to this volume ( Annandale 2002a )as is the approach to quantify scour extent ( Annandale 2002c ).