Scanline sampling techniques for rock engineering surveys: Insights from intrinsic geologic variability and uncertainty

Abstract

Discontinuity surveys are based on collecting rock data from fieldwork and are an essential component of rock-mass quality estimation in rock engineering. Strength, deformability and permeability characteristics of a rock-mass are strongly influenced by its discontinuities. Scanline surveys are a reliably technique in which a line is drawn over an outcropped rock surface and all the discontinuities intersecting it are measured and described. The discontinuity geometry for a rock-mass is characterised by the number of discontinuity sets, mean density and the distributions for location, orientation, size and spacing/fracture intercept. Rock site investigation deals with several key elements that need to be addressed, namely the information required to characterise the rock system and the intrinsic uncertainty associated with this information. This way, quantifying the information content of the on-site measurements and creation a database is vital to be used for decision making processes and risk assessment on rock engineering design projects. In addition, a clear geology framework plays a key-role to support the investigation of all rock engineering projects. Nevertheless, the intrinsic variability of geological, petrophysical and geotechnical properties must be quantified for reliability-based design and to decrease the geological uncertainty. All geologists and engineers’ practitioners must have the aim to contribute to the correct study of the ground behaviour of soil and rock, their applications in sustainable design with nature and environment and to satisfy the society’s needs.