Most of the discontinuities and joints do not have smooth surfaces and they are covered with random distributed roughness. Finding the effective role of surface roughness on the behavior of discontinuities and on the shear strength of joints makes roughness measurement an important factor that has to be taken into account in geotechnical investigations. These information make the basis for realistic design of underground and surface projects such as tunnel, mines etc. Roughness has various features depending on the type of specimens, size and observation scale. In some cases, different methods of measurement return different results for the same specimen. Therefore, it is necessary to measure the roughness by an appropriate method and to represent it quantitatively in a mathematically adequate way. Quantifying the topography of rippled surface is the main challenge in roughness measurement. This quantifying method should return values which should be used in shear strength formulations for discontinuities. The first step is to measure the roughness topography by an appropriate tool and then their roughness must be quantified by a suitable method. There are different tools measuring the surface roughness. One of these tools is three-dimensional geometric system. Furthermore, several converters can be used amongst which the laser convert is one of them. In this paper, geometric methods used to measure roughness are reviewed. This is followed by a discussion on the various quantitative methods measuring roughness. The 3D laser instrument to record the roughness topography is further explained. Finally, a 2-D profile of a rock joint is scanned and interpreted before and after a shear test.

1.1 Rock mass

Properties of a rock mass are very well related to its joints hydraulic and mechanical properties which these discontinuities themselves are related to the morphology of the rock mass. Roughness as the most important factor of the morphology has a substantial role in the hydraulic and mechanical properties of discontinuities. Due to different results for different measuring methods and techniques for the same rock sample, measuring with precise equipments and quantifying with an appropriate method for the determination of shearing strength and hydraulic properties are essential.

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