A Low Cost Alternative Approach to Geological Discontinuity Roughness Quantification

Abstract

The surface roughness of geological discontinuities can be considered a key parameter in the evaluation of the stability of structures constructed within rock masses. Several different methodologies can be applied to determine this parameter and they vary in their complexity. The aim of this study is to correlate the peak friction angle (ϕp) of discontinuity planes of fresh bedrock with the Joint Roughness Coefficient, JRC. A simple low cost approach is presented based on the determination of JRC and the application of derived polynomial equations to determine the peak friction angle, ϕp from the surface roughness from geological discontinuities for the major lithologies found in Peninsula Malaysia. Eight thousand six hundred and seven tilt tests were conducted to obtain the correlations between peak friction angles with JRC of granite, schist, limestone, quartzite and sandstone. The respective polynomial equations are as follows: \n \n \nfor granite ϕp= −0.071 JRC2 + 3.56 JRC + 35.6° \n \n \nfor schist ϕp = −0.022 JRC2 + 3.21 JRC + 28.1° \n \n \nfor limestone ϕp= −0.0635 JRC2 + 3.95 JRC + 25.2° \n \n \nfor quartzite ϕp = −0.083 JRC2 + 4.17 JRC + 27.6° \n \n \nfor sandstone ϕp = 0.0424 JRC2 + 1.13 JRC + 29.2° \n \n \n \nFor all the derived polynomials, the coefficient of determination, R2 was greater than 0.9. The JRC can be determined as part of an engineering geological investigation and the respective polynomial applied to determine the peak friction angle, ϕp for the specific lithology.