Resilience Assessment And Enhancement Of Regional Road Networks Against Debris Flow Hazards

As an important part of national critical infrastructure,road networks are the backbone to support the development of economic and people's daily life.However,due to the fact that road networks are widely distributed in different natural geographical units,road networks are subject to different types of natural disasters,such as earthquake,flood and debris flow.Among these disasters,debris flow is the major threat to road networks,and empirical studies indicate that the frequency and magnitude of debris flows shows an increasing trend.How to improve road networks resilience and mitigate the adverse consequences of debris flow has attracted great attention of governments and researches in the world.However,most existing studies focused on the modeling and simulation of debris flow hazards and vulnerability analysis of road networks against debris flow hazards,while only few studied road networks resilience against debris flow hazards.This thesis proposes a comprehensive framework to study the regional road networks resilience against debris flow hazards.This framework includes road networks modeling,road fragility assessment,accessibility assessment,resilience assessment and design of resilience improvement decision.For the fragility assessment,a data-driven debris flow method is used to simulate the debris flow hazards,and the fragility of the road section is generated by combining the fragility curve.For the accessibility assessment,the average shortest travel time between cities is chosen as the accessibility metric.For the design of resilience improvement decision,this thesis considered engineering resilience enhancement approach(such as slope reinforcement)and complementary resilience enhancement approach(such as integrated with railway and aviation system).Based on this framework,this thesis selects the road networks in southwest China for example analysis.For engineering resilience enhancement approach,when the budget is sufficient,the road networks resilience can be improved as 41.62%;when the budget is limited,the road networks resilience can be improved as 27.73% by selecting 32 road sections for slope reinforcement.For complementary resilience enhancement approach,the integrated of the existing railway networks and aviation networks make the road networks resilience increase as 30.34%.For the big cities such as Chengdu and Kunming,even if the road networks are damaged by 90%,the shortest travel time between them will not change.For the small cities such as Meishan and Anshun,when the road networks are damaged by 60%,the connection between the cities is already vanished.If a train line which crossed 8 cities is added between Chengdu and Tibet,the road network resilience can be improved as 1.05%.The framework and case study of this thesis provide theoretical support for the decision-making of pre-disaster prevention and post disaster recovery of regional road networks against debris flow.In addition,this framework can be applied to the resilience study for other natural hazards(such as flooding,landslide)or other transportation systems(such as bus system,metro system).