Full-scale in-situ experiments on mass-damper-enhanced guiding flexible rockfall barriers for rockfall mitigation

Mitigating rockfall hazards on high and steep slopes remains a longstanding challenge in engineering geology. Guiding flexible rockfall barriers (GFRBs) are widely used to reduce risks to infrastructure and settlements, but conventional systems may provide insufficient out-of-plane restraint during high-energy impacts, limiting trajectory control and energy attenuation. This study integrates mass dampers (MDs) into GFRBs and evaluates their protective performance through full-scale in-situ impact tests on a stepped rock slope. UAV-based stereovision and high-frequency tension measurements were used to quantify block kinematics and barrier responses for blocks of different masses under unprotected (UP), conventional protection (CP) and three MD-enhanced configurations. The results showed that MD position strongly influenced the observed system response. MD-enhanced configurations promoted a transition from airborne projectile motion to slope-following sliding and rolling. Across the single-run protected cases, lower mass damper protection (LMDP) showed the most favourable observed response, yielding a descriptive mean system-level energy dissipation ratio of 96.1%, compared with 73.5–86.3% for CP and 33.7–47.2% for UP. Upper and middle MD configurations produced a descriptive mean increase of 4.8 percentage points relative to the corresponding mass-matched CP cases when lower run-out space was constrained. Rope-tension responses were consistent with strengthened lower-boundary restraint, broader load transfer and prolonged block–net–slope interaction. These site-specific findings identify MD position and local topography as coupled design considerations, supporting lower-boundary restraint where downslope run-out space is limited and selective use of upper or middle MDs under suitable terrain conditions.