An Improved Discrete Curvature Method For Disaster Vulnerability Analysis Of Urban Road Network

Urban road system is an important channel for the transportation of rescue workers and relief materials after disasters.It is necessary to maintain good traffic capacity after disasters.It is of practical significance to evaluate the traffic capacity of the road network during disasters and identify the vulnerable areas in the road network.Existing studies have shown that post-disaster network traffic capacity is related to network topology vulnerability,which can be measured by Ollivier-Ricci curvature(O-R curvature for short).Based on this,in view of the characteristics of the disaster damage of the urban road network,considering the influence of road section passage probability,the O-R curvature is transformed,and the method of evaluating the topological vulnerability of the road network by improving the O-R curvature is explored,and the model and analysis are carried out on the road network of 18 cities.The details are as follows:Firstly,the definition and calculation method of classical O-R curvature are introduced,and the negative correlation between O-R curvature and network topology vulnerability is illustrated.The method of urban road network modeling is given.The road network of Xingtai and Chengde is modeled and the O-R curvature is calculated.The characteristics of curvature distribution are analyzed.The maximum number of branch nodes is used to measure the network topology vulnerability.The results show that there is a negative correlation between O-R curvature and network topology vulnerability.Then,according to the characteristics of road network disaster damage,considering the influence of road section probability,the O-R curvature is improved.The improved O-R curvature of the road network in Xingtai and Chengde is calculated and compared with the classical O-R curvature.The difference of the distribution of the two curvature in the road network is analyzed,and the relationship between the improved O-R curvature of the road network and the disaster damage situation is compared.The results show that there is still a negative correlation between the improved O-R curvature and the road network topological vulnerability,and it is more consistent with the characteristics of road network disaster failure.Finally,the road network of 18 cities is modeled,the classic O-R curvature and the improved O-R curvature of the road network are calculated,and the curvature distribution characteristics of the regular,irregular and mixed road network are analyzed.The deterministic and random failure simulation of the road network was carried out,and the topological vulnerability of the road network was measured by the side failure rate,the number of branches,the maximum branch diameter and the maximum number of branch nodes,and the influence of the road network morphology on the O-R curvature and topological vulnerability was analyzed.The results show that,compared with the irregular network,the regular network has larger curvature mean,can better maintain the traffic capacity after disaster,and has less topological vulnerability.This study shows that the improved O-R curvature can take into account the characteristics of road network disasters and can better reflect the road network topology vulnerability.The results can provide reference for disaster prevention planning and design of urban roads.