Using RQD to estimate the deformation modulus of rock masses

Abstract

A comprehensive slope stability assessment of two sites, namely Site 1 and Site 2, has been conducted. An integrated Unmanned Aerial Vehicle Survey (UAV) and 2D Electrical Resistivity Tomography (2D ERT) survey at both sites were carried out. The rock mass quality using Rock Quality Designation (RQD) system was quantified, and discontinuity orientations were obtained from the UAV point cloud. The obtained discontinuity orientations were utilized to identify possible geometric failures such as planar, flexure and wedge. The 2D ERT survey at both sites was deployed to discern subsurface lithology. Based on the UAV survey, Site 1 slope was prone to flexure toppling and wedge failure. While few intersections at Site 2 were favourable for Wedge formations. 2D ERT survey reported four geological layers as water-saturated zone or clay layer (200–300 Ωm), highly fractured rock (400–700 Ωm), fractured rock (800–2200 Ωm) and fresh rock (>2200 Ωm) at both study sites. Combining the information of both techniques, the rock mass at Site 1 is moderately fractured to fresh rock. However, the top portion of Site 1 is highly fractured as compared to the lower portion. The rock quality at Site 2 is moderate to highly fractured rock mass. The integrated approach applied in this research study was proven expeditious, inexpensive and rapid for comprehensive slope stability assessment.