SENSITIVITY OF AMBIENT RESONANCE MONITORING TO ROCK SLOPE KINEMATICS: TRACKING THE COEVOLUTION OF INSTABILITY DAMAGE AND NATURAL FREQUENCIES USING DISTINCT-ELEMENT MODELING

Spectral analysis of in-situ ambient vibration measurements can reveal changes to unstable rock masses during slope failure, and are becoming increasingly utilized in slope stability monitoring in support of hazard mitigation. The dependency of a rock slope’s natural frequencies on mass and stiffness implies that internal or boundary condition changes that affect one or both of these properties are detectable through continuous or repeated frequency measurements. However, the impact of slope kinematics on frequency changes, and the expected form and sensitivity of frequency evolution associated with progressive failure are not well understood and need clarification before this technique can be used in practical scenarios. Since rock slope failures occur infrequently, numerical modeling is necessary to study the anticipated responses from in-situ monitoring. We use Itasca’s Universal Distinct Element Code (UDEC) to evaluate the sensitivity and evolution of rock slope resonance properties for different kinematic failure modes, including planar sliding, flexural toppling, and slab toppling. The outputs of our study aim to improve understanding of failure scenarios that are well-suited for in-situ ambient resonance monitoring, and support future experiments designed to explore the form and sensitivity of the frequency response for site-specific cases.