Validity of approaches on stability assessment of toppling rock slope

Abstract

In addition to the kinematic analysis, slope stability assessment in terms of Factor of Safety (FOS) analysis is becoming increasingly important nowadays. The absence of a well-defined guideline for such analysis on toppling failure in Hong Kong implies that there is a need to explore the plausible ways to tackle this. As such, a study on the validation of approaches adopted in stability assessment on toppling rock slopes has been carried out, with an objective to explore the typical methods used in assessing toppling slope failure and confirm the reliability of the selected types of approaches to be applied in the actual slope condition.

This study first examines the toppling mechanism of general rock slopes as well as the existing approaches used for stability assessment of toppling rock slopes through literature review. With the development of the key fundamental knowledge of toppling failure analysis, in depth assessment on two selected approached, including Limit Equilibrium (LE) approach and Distinct Element Method (DEM), are undertaken through the use of a work example extracted from text book and a local case study. Data has been obtained from desk study on the reference text book as well as the available slope records and published geological map maintained by the Geotechnical Engineering Office (GEO) and Lands Department (LandsD), and these data are further verified by site inspection.

With the comparison between the results obtained from the LE approach and that from the numerical modelling by using computer software “UDEC”, the application of the LE approach is considered to be limited to slope with simple geometry, and hence its validity on assessing toppling slope failure in real case appears debateable. In addition, a parametric study is also conducted and verifies that the rock mass parameters are having a notably strong impact on the FOS calculation in UDEC. Way forward of this study is also discussed to provide a strategic plan for potential future assessment on this topic.