| The safe and stable operation of the road transportation system is of great significance to national security and economic and social development.In order to cope with the impact of frequent disasters in an extreme environment,it is necessary to improve the resilience of the road transportation system,so as to maintain a high level of service in an adverse environment or quickly resume normal operation after damage.This dissertation focuses on the long-term performance dynamics of the road transportation system resulted from frequent damages and recovery process in an extreme environment,identifies the key bottlenecks of road network capacity,and puts forward some efficient resilience optimization measures.The specific research contents are as follows:(1)The distinctions between extreme-environment resilience and non-extreme environment resilience.At present,most of the existing researches in road network resilience are designed for the non-extreme environment.Under an extreme environment,the road network facilities are facing a more severe test of survivability and sustainability.It is necessary to analyze the functional dynamics of road network facilities under the impact of multi-hazard,high-intensity,and high-frequency disasters.This dissertation combs the existing literature of infrastructure resilience research,presents the key characteristics of road network resilience under an extreme environment,and establishes the overall framework for the following analysis.(2)The failure risk of the road network in an extreme environment.This dissertation points out the extreme-environment chracteristics of the road network,including the disaster characteristics and disaster causing factors.On the one hand,the probabilistic seismic hazard analysis method is introduced to analyze the seismic failure risk of the road network by earthquake disaster scenario generation,site movement characteristics analysis,and facility fragility evaluation.On the other hand,the mountain disaster hazards are analyzed according to the environmental risk factors,and the disaster resistance of the roadway facilities is evaluated based on the facility parameters,such as the structural types,traffic capacity,etc.The damage states of roadway facilities are predicted using the load-resistance interference method.(3)The simulation of the long-term operation and recovery process of the road network in an extreme environment.Based on the failure risk of the road network,this dissertation uses the Monte Carlo simulation method to predict the occurrence location,time,and recovery time of various kinds of disaster events.The simulation model of emergency repair and recovery for the failed road links is then established.According to the disaster situation,the repair sequences of failed road links are determined by the availability of recovery resources and the importance of each road link.Finally,a traffic assignment model is established to study the traffic flow distribution of the damaged road network based on the principle of user equilibrium.Its purpose is to evaluate the social functionality of the damaged road network.(4)Resilience analysis and optimization strategy for the road network.Based on the service level of road network during the long-term operation in an extreme environment,this dissertation puts forward the evaluation indexes for the transportation capacity resilience of a road network from the perspective of mobility,accessibility,and casualties.It deeply taps into the resilience optimization potential of the transportation system,points out the key points for post-disaster transportation service support,studies the applicability of kinds of resilience optimization measures,and develops a resilience optimization model to strengthen the transport capacity of the road network under an extreme environment during the future long-term operation.Combining the above methods,including failure risk analysis,emergency repair,and traffic assignment simulation,a resilience analysis framework for road network under an extreme environment is formulated.The proposed framework is applied to the SichuanTibet road network,and the resilience optimization strategy is presented by comparing the network capacity in perfect operation with that in damaged states.It helps to identify the weak bottleneck of the road transportation system by studying the resilience of the road transportation system in an extreme environment and provides information basis for decision-makers to strengthen the guarantee capacity for traffic functionality of road network. |
