Quantification of Rock Joint Roughness Using Terrestrial Laser Scanning

Abstract

Rock joint roughness characterization is often an important aspect of rock engineering projects. Various methods have been developed to describe the topography of the joint surface, for example Joint Roughness Coefficient (JRC) correlation charts or disc-clinometer measurements. The goal of this research is to evaluate the accuracy, precision and limits of Terrestrial Laser Scanning (TLS) for making remote measurements of large-scale rock joints. In order to find the most appropriate roughness parameterization method for TLS data and to analyse the capability of TLS for roughness estimation, experiments were made with a 20 × 30 cm joint sample. The sample was scanned with TLS and compared to reference measurements made with the Advanced TOpometric Sensor (ATOS) system. Analysis of two roughness parameterization methods, virtual compass and disc-clinometer, and angular threshold method, showed that the latter is less sensitive to noise. Comparative studies of ATOS and TLS roughness parameters indicate that the TLS can adequately quantify surface irregularities with a wavelength greater than 5 mm from a distance of 10 m.

Range Versus Surface Denoising of Terrestrial Laser Scanning Data for Rock Discontinuity Roughness Estimation

“…The Grasselli parameter is highly sensitive to TLS noise. Fractal representations of surface features have also been found to be sensitive to noise (Khoshelham et al 2011), as well as roughness values obtained through virtual compass and disc-clinometer measurements (Bitenc et al 2015c). Further research is warranted to assess the relative sensitivity of alternate roughness parameters to TLS noise.…”

“…The empirical roughness parameter developed by Grasselli (2001), hereafter referred to as the Grasselli parameter (G), has been adopted in this research, since it quantifies the direction dependence of roughness, is applicable to rock surfaces, and is least sensitive to data noise (Bitenc et al 2015c). The Grasselli parameter is based on an angular threshold concept and was initially developed to identify potential contact areas during direct shear testing of artificial tensile rock fractures.…”

Potential and Limitations of Terrestrial Laser Scanning for Discontinuity Roughness Estimation

“…The empirical roughness parameter developed by Grasselli (2001), hereafter referred to as the Grasselli parameter, has been adopted in this research, since it quantifies the direction dependence of roughness, is applicable to rock surfaces presented in 2.5D, and is least sensitive to data noise (Bitenc et al, 2015c). It was calculated for 72 analysis directions (γ i , i=1…72).…”

Evaluation of Wavelet Denoising Methods for Small-Scale Joint Roughness Estimation Using Terrestrial Laser Scanning

“…1D wavelet denoising resulted in more realistic estimates of the roughness; however the fractal parameters, which were used to describe the roughness, were found to be too sensitive to noise. Therefore, in our previous study (Bitenc, 2015) different methods were tested considering noise sensitivity. The angular threshold method, hereafter referred to as the Grasselli parameter after Grasselli (2001), appeared to be least sensitive to measurement random errors.…”