Abstract: As expressways extend into mountainous regions,a large number of high and steep slopes are formed through excavation.This has led to frequent geological disasters such as collapses,landslides,and debris flows,posing severe threats to highway safety.To enable dynamic early warning through multi-source monitoring of geological hazards on expressway slopes in the Western Guangdong mountainous areas and ensure safe highway operation,a warning indicator system is established.This system addresses the complex geological conditions and concentrated typhoon and rainstorms characteristic of the Western Guangdong mountainous areas,focusing on slope displacement,displacement rate,structural stress,and rainfall as monitoring parameters.Based on the deformation characteristics of weathered granite residual soil slopes,a four-level early warning system (blue,yellow,orange,and red) and corresponding thresholds are proposed.Integrating Beidou surface deformation monitoring,deep horizontal displacement monitoring,anchor cable stress monitoring,distributed optical fiber monitoring,and rainfall monitoring,an automated monitoring and early warning system for highway slopes is developed.Analysis of typical slope monitoring data reveales that during the monitoring period,the extreme values for displacement and rate from Beidou surface deformation monitoring are -99 mm and 7.40 mm/d,respectively.For deep horizontal displacement monitoring,the extreme values for displacement and rate are 55.386 mm and 3.83 mm/d,respectively.The single-day extreme rainfall is 458.1 mm.All these parameters reach the red warning level,and warnings are successfully issued.The implementation of corresponding measures preventes further slope deformation.This demonstrates that the developed system can timely reflect slope deformation characteristics and development stages,quickly and accurately identify potential geological hazards,achieve multi-level and multi-dimensional early warning for highways,and effectively improve the accuracy of slope geological disaster warnings.This system can serve as a valuable reference for geological disaster monitoring and early warning of highway slopes in China.

Key words: road engineering, early warning system, automated monitoring, slope disaster, warning threshold