Rockfall kinematics and restitution coefficients via inertial navigation technology

Rockfall kinematic characteristics exhibit significant randomness and are influenced by factors such as rock mass properties, slope morphology, impact angle, and slope materials. Accurately determining the key parameters of rockfall movement is critical for understanding motion patterns and effectively preventing and controlling rockfall hazards. In this study, a monitoring system consisting of self-developed inertial navigation equipment, high-speed cameras, and an unmanned aerial vehicle was used to conduct onsite motion tests involving four differently shaped rock specimens on three types of slopes (bedrock, detritus, and clast bedding). The self-developed inertial navigation system integrated a high-dynamic-range accelerometer (±400 g) and a shock-resistant gyroscope (±4000°/s), capable of robustly collecting data during the test. The data collected from these tests were processed to extract key kinematic parameters such as velocity, trajectory, restitution coefficients, and friction coefficients. The test results demonstrated that the inertial navigation system accurately recorded the acceleration and angular velocity of the rocks during motion, with these measurements closely aligning with the field data. The normal and tangential restitution coefficients were found to be influenced primarily by the slope material and impact angle, with higher normal restitution coefficients observed for low-angle impacts. The normal restitution coefficients ranged from 0.35 to 0.86, whereas the tangential restitution coefficients ranged from 0.46 to 0.91, depending on the slope materials. Additionally, the sliding friction coefficient was calculated to be between 0.66 and 0.78, whereas the rolling friction coefficient for the slab-shaped specimen was determined to be 0.53. These findings provide valuable data for improving the accuracy of rockfall trajectory predictions and the design of protective structures.