A Conceptual Approach for Preliminary Rock Slope Design in Remote Mountainous Terrain

ABSTRACT: In recent years, researchers and geotechnical engineers have combined different methods to improve the accuracy and reliability of rock slope designs. Rock slope stability designs are crucial for both mining and civil engineering projects. The Q-slope and Slope Mass Rating (SMR) systems are widely used empirical methods that are based on the rock mass classification system for assessing stable slope design angles. The representative stereonet plot is initially used when an exposure of fractured rock is available to perform a kinematic analysis during preliminary design. Geophysical methods are commonly used to determine the bedrock depth and strength of rock masses. The Q-slope method evaluates the stability of rock slopes based on the geological conditions and engineering properties of the rock mass, while the SMR method considers the slope geometry and the influence of discontinuities orientation on the slope stability and recommend suitable support systems. Both the Q-slope and SMR methods require rigorous field investigations for the collection of rock mass data. The limit equilibrium method (LEM) is widely used to determine the factor of safety (FOS) of a slope, which normally requires comprehensive geotechnical investigations. However, sometimes it is challenging or impossible to obtain comprehensive intrusive investigation data in remote areas due to the difficulty in site access (e.g., no access road in mountainous terrain). Limited geological mapping and surface geophysical surveys are more feasible methods for gathering geotechnical design parameters for remote sites. Therefore, it is important to adopt alternative design methods for rock slope stability assessment during the preliminary design phase.. A conceptual approach is suggested in this paper that combines Q-slope and SMR with LEM for preliminary rock slope designs under the commonly faced engineering challenge when there is limited geological mapping, surficial geophysical surveys, and borehole investigation data. The kinematic analysis and geophysical data are usually used to develop the design basis for the conceptual layers in the stability section. A design flow chart is developed that may be used in the stability assessment. It is proposed that this approach is more suitable during the pre-feasibility or feasibility design, and that it provides more useful guidance as input to the detailed engineering design and construction stages.