| With the fast growth of China’s economy,the construction pace of high-speed rail network(HSRN)continues to accelerate.Furthermore,the "Four Vertical and Four Horizontal" HSRN has been formed,and the "Eight Vertical and Eight Horizontal" HSRN is being shaped by increasing its density.The HSRN has spanned from the early simple single-line structure composed of high-speed rail(HSR)stations to the complex multi-level network structure composed of HSR stations,HSR lines and HSR organizations.With the expansion of the HSRN’s scale,its coverage area has gradually increased,which plays an increasingly prominent role in social and economic development.Hence,ensuring the security of the HSRN is significant,which has become an important part of the national security strategy.But unfortunately,extreme disasters have occurred frequently in China in recent years with the rapid intensification of global warming.As a result,the types and numbers of disasters suffered by the HSRN have also increased sharply,which may cause extremely serious consequences and even bring huge losses to the country and society.In particular,due to the complex and dynamic relation among HSR stations,HSR lines and HSR organizations,the impact of disasters on HSRN may go beyond a single station,line,or even organization,and spread among them,leading to seriously secondary and derivative disaster consequences.Additionally,HSR stations,HSR lines and HSR organizations are located in different levels of HSRN,and the losses and impacts caused by their failures are not the same,which makes the response to HSR disasters more difficult and complex.Therefore,how to ensure and improve the security level of HSRN from a multi-level perspective has become an important challenge and problem faced by relevant administrations.Analyzing and recognizing the vulnerability of HSRN and finely managing its vulnerability from a multi-level perspective to effectively reduce its vulnerability have become a necessary prerequisite and an important approach to improving the capability of disaster prevention and reduction of HSRN and ensuring its safe operation.This dissertation focuses on the issues of modeling and describing of dynamic HSRN at multi levels and assessing method suitable for the vulnerability of the multi-level HSRN under considering its multilayered and dynamic characteristics,which takes the vulnerability assessment as the main line and starts from the formation mechanism of HSRN vulnerability.The main contents of this dissertation are as follows:(1)Dynamic model construction of HSRN from a multi-level perspective.The internal cause of the vulnerability of HSRN is the sensitivity of its own structure and function to hazards.Therefore,clarifying the structure and function of HSRN is the basis for assessing its vulnerability.Based on this,the dynamic model of HSRN from different levels of perspectives is developed under considering the multi-level structure and the dynamic function of its attributes.Firstly,the components of HSRN are clarified from piont-line-plane level,so as to analyze the relations between the comopents at different levels.Secondly,the theories and methods of complex network and super network are applied to hierarchically describe the relations between the components of HSRN at different levels from the spatio-temporal dimension,based on the routes of train operations within HSRN.Thirdly,based on the spatiotemporal relations between the components,the dynamic network models at the station level,at the line level,and at the organization level are constructed respectively.Finally,the HSRN in Chinese mainland is taken as a case to verify the validity of the proposed model.(2)Performance assessment method for multi-level HSRN.The performance of HSRN is taken as the indicator of its vulnerability measurement,so the construction of the performance assessment method is the premise of the vuvulnerability assessment of HSRN.Firstly,the commonality of functional characteristics of HSRN at different levels is analyezed and described from the perspective of the services it provides based on the functional characteristics of multi-level HSRN.Secondly,generalized trip cost and passenger flow are selected as the assessment indicators of the performance of HSRN at different levels based on the commonality of its functional characteristics.Thirdly,a novel method for assessing the performance of HSRN at different levels is proposed by referring to the accessibility theory and considering the two dimensions of network structure and function comprehensively.Finally,taking the HSRN in Chinese mainland as a case,combined with the relevant operation data and statistic data,the performance of China’s HSRN at different levels is evaluated,and its differences at different leves are compaered and analyzed.(3)Vulnerability assessment method for multi-level HSRN.Hazards are taken as the external triggers for the vulnerability of HSRN.Based on the relations between hazards and network failure,the assessment method for the vulnerability of HSRN is proposed according to its performance loss.Firstly,the complexity of the hazards China’s HSRN suffers is empirically revealed on the basis of the historical data,and the hazards are described from the spatiotemporal dimension.Futhermore,the complexity of the failure and performance loss of HSRN is revealed by considering the hazards.Secondly,the failure states of components in HSRN at different levels are divided and described,and then their failure modes and failure propagation between them are aslo investigated.Thirdly,combined with the relations between hazards and components failure and based on the commonality of the consequences caused by hazards,the components failure within HSRN at different levels is modeled by taking the compontents and their failure status as the core.Then,a method for assessing the vulnerability of HSRN at different levels is proposed on the basis of its performance loss degree.Finally,the vulnerability of China’s HSRN at different levels is simulated and analyzed by combining the typical disaster cases and their commonalities,especially July 20 Heavy rainstorm in Zhengzhou,Super Typhoon Lekima,and 2008 snow disaster in China,which verifies the validity of the proposed method.(4)Critical components identification and vulnerability regionalization of HSRN for vulnerability management.The main purpose of aassessing the vulnerability of HSRN is to understand and recognize the distribution of its vulnerability on the whole,so as to improve the safe operation level of HSRN through effective management of its vulnerability.Therefore,combined with the realistic demands of the vulnerability management of China’s HSRN,the application research is conducted from two aspects of critical components identification and vulnerability regionalization.Firstly,the definition of critical components and the significance of identifying critical components are illustrated,and then the identification method of critical components is developed based on enumeration model.Secondly,the method for regionalizing the vulnerability of HSRN is proposed based on the spatial regionalization theory.Finally,the critical components and vulnerability regionalization map of China’s HSRN at the station level,line level and organization level are presented respectively.Furthermore,the corresponding vulnerability management insights and suggestions are illustrated.In summary,the research results of this dissertation not only enrich the modeling methods of infrastructure network systems,but also extend the theory and method of the vulnerability assessment of infrastructure network systems and its application.The obtained findings can provide decision-making assistance for the rational layout of operation and maintenance resources,optimal develpoment of operation and maintenance strategies,and delicacy management of HSRN vulnerability. |
