Improving rockfall monitoring with distributed acoustic sensing: The role of operational parameters

Understanding the factors influencing distributed acoustic sensing (DAS) signal response is essential for advancing rockfall monitoring technologies. This study presents a comprehensive field experiment investigating the impact of gauge lengths, installation methods, and fiber-optic cable packaging structures on DAS signals from simulated rockfall impacts. A deployed fiber-optic array with varied cables and installation conditions recorded signals across four-gauge lengths, three installation methods, and four cable types, evaluated using sensitivity and fidelity metrics. Key findings confirm that while increased gauge length boosts sensitivity, it detrimentally reduces fidelity; consequently, a 2-m gauge length is recommended for high-frequency rockfall seismic signals. Well-coupled direct burial significantly enhances signal sensitivity and fidelity, whereas poorly coupled methods (cased conduit, ground deployment) introduce “weak coupling noise” and pseudo waveforms. Fiber-optic cable properties—diameter, Young’s modulus, and internal structural contacts—also critically affect signal quality. Balancing signal performance with operational practicality, a high-strength, lightweight fiber-optic cable with favorable DAS characteristics is recommended for mountainous rockfall monitoring. These findings provide crucial insights and practical guidelines for optimizing the design and deployment of DAS-based rockfall monitoring systems in challenging terrains.