Risk Classification And Evaluation Of Railway Subgrade Engineering

In the field of railway construction, the risk management of bridge and tunnel engineering has made certain achievements. But for the subgrade engineering, risk management research starts late, and not widely applied. So aim at subgrade engineering, this dissertation analysis and research the two major works of subgrade engineering risk management:risk classification and risk evaluation.Risk classification is the premise and foundation of risk management. At present, the standard about risk classification in various industries is different Based on the analysis discussion of other industries and combining with the characteristics of subgrade engineering itself, this dissertation classify the risk of subgrade engineering to five category according to the source of risk:natural and environment risk, survey risk, design risk, construction risk and material risk. And this thesis demonstrates the feasibility of this kind of classification method from the principle of project risk classification. For a particular project risk events of subgrade engineering, we will identify the hazard factor from the five aspect, This dissertation analysis and research on fill subgrade, excavation subgrade, supporting structure of subgrade and special soil subgrade, and then summary the typical risk events of the various forms of subgrade and list the common hazard factors of each risk events. It can provide reference for specific subgrade engineering.Risk evaluation is the main work of the risk management. The risk of subgrade engineering is affected by multiple hazard factors that is random and fuzzy largely. Fuzzy comprehensive evaluation method can make a better evaluation result to such risks in the traditional risk evaluation methods. But we know the hazard factors of subgrade engineering have grey character besides random and fuzzy through research. Thus, this dissertation introducing the grey system theory to the subgrade engineering risk assessment, then proposes a fuzzy comprehensive evaluation method based on grey system theory. The overall process of this method is dividing the probability of risk factors into five evaluation class, so the probability of occurrence of hazard factors can be described by the grey class membership of the factors. At the same time, the importance of the hazard factors on the risk event can be described by the grey correlation degree. Then, we can evaluation the risk event through fuzzy comprehensive evaluation with the data of above two aspects above. This method considers the random, fuzzy and grey attribute of subgrade engineering and reduces the subjectivity of expert scoring meanwhile. So it is close to the engineering practice more.Finally, this thesis verifies the applicability of the subgrade engineering risk classification method and the feasibility of the fuzzy comprehensive evaluation method based on grey system theory through an engineering example about the settlement risk of soft soil subgrade. And put forward reasonable countermeasures according to the risk evaluation results.