Quantification of rock mass condition based on fracture frequency using unmanned aerial vehicle survey for slope stability assessment

Abstract

The rapid urbanization and economic development of the country forced the people to expand economic activities to the hilly terrains. This causes the need for the stability assessment of the slopes to mitigate economic losses, damage to property, environmental degradation, and severe injuries or fatalities. In general, kinematic and limit equilibrium analysis (LEM) techniques are in practice for the stability assessment of the rock slopes. These techniques are well established in identifying the type of failure along the rock slope and calculating the factor of safety (FOS). The primary limitations of these techniques are that it ignores the rock mass condition, and sometimes a highly fractured rock mass is represented as stable with no risk of failure. In this paper, integrated geological mapping, Schmidt hammer rebound survey, and unmanned aerial vehicle (UAV) survey were carried out to assess the stability of the slope using LEM and kinematic analysis. Besides this, the paper also aimed to quantify rock mass conditions based on fracture frequency. The kinematic analysis reveals that the rock slope is safe from the risk of planar failure and direct toppling. In comparison, 213 (3.31%) intersections were identified as critical for wedge failure. The FOS obtained for the potential wedge using limit equilibrium analysis confirmed that the rock slope is stable. In contrast, the fracture frequency assessment of the rock slope reflects that 56% of the total slope area is moderate to highly fractured. This is alarming from a safety point of view. The integrated UAV, geological mapping, and Schmidt hammer approach used in this study is mooted as an expeditious and inexpensive slope stability assessment technique.