Correlation of Joint Roughness Coefficient (JRC) with Peak Friction Angles of Discontinuity Planes of Granites, Peninsular Malaysia

Surface roughness is an important parameter in the evaluation of the stability of structures excavated in rock masses as it controls the shear behaviour and the value of the peak friction angle of a discontinuity plane. Several approaches can be adopted for the determination of surface roughness of discontinuities. This paper presents a simple approach in the form of three (3) polynomial equations to correlate the peak friction angle (Φp) with the Joint Roughness Coefficient (JRC) for discontinuity planes in fresh, slightly weathered and moderately weathered granites. For fresh granite discontinuities, the polynomial equation is Φp1 = -0.071JRC^2 + 3.56JRC + 35.6. The polynomial equations for slightly and moderately weathered granite discontinuities are Φp2 = -0.087JRC^2 + 4.32JRC + 34.1 and Φp3 = -0.133JRC^2 + 5.08JRC + 29, respectively. These results offer an alternative method for the estimation of the Φp of the discontinuity planes by measuring the JRC values of the granite discontinuity planes in the field.