Rock profile roughness parameters appropriateness for joint surface geometrical characterization
Pedro Alameda-Hernández1; Rachid El Hamdouni2; Clemente Irigaray2; José Chacón2
1 Universidade Federal de Ouro Preto (UFOP); 2 Universidad de Granada
Resumo
Roughness influences considerably rock joints shear strength, and, consequently, rock mass stability, especially regarding slopes. However, the most common rock mass classification systems, as well as other analysis methods, introduce rock joint roughness by subjective personal estimation. This subjective personal bias can be avoided by applying roughness parameters calculated through mathematical algorithms to digitized profiles or surfaces. However, a correct rock joint roughness parametrization has not been achieved yet because of the geometrical complexity of these natural surfaces. This work shows the behaviour of the most common roughness profile parameters in different rock joints. The appropriateness of these parameters is tested and, consequently, several recommendations are offered for choosing the most appropriate one according to the rock type and the profile digitalization method. The parameters chosen were the roughness profile index (Rp), the first derivative root mean (Z2) and the fractal dimension (D) calculated through the divider method. For comparison among these three parameters the Joint Roughness Coefficient (JRC) was calculated from each one of them applying the most accepted equations proposed in the technical literature. Two physical digitalization procedures, by means of stylus profilometers, were applied; one of them is to be applied in field and the other in laboratory; they permitted spatial sampling intervals of 0.8 and 0.0625 mm respectively. The rock samples chosen for this work belong to different rock types with different joint roughness morphologies: stepped and undulated, smooth and rough. For achieving this wide range of roughness morphologies, the experimental work has been performed with different lithologies; a quartzite showing a stepped profile, a micaceous schist with a smooth but positively stepped profile, a calcareous schist similar to the micaceous but not so explicitly smooth and stepped, a dolomitic marble, smoother and more undulated than the others, a
Palavras-chave: rock roughness; rock slope stability; data acquisition; stylus profilometer