Study On Structure Health Assessment Of Large-scale Tunnels Under Complex Geological Conditions

With the rapid increase of construction scale and the extension of operation time of highway in China,the long-term operation safety of highway tunnels will be faced with more and more severe challenges.It is imperative to carry out long-term health monitoring and strengthen the research on health evaluation of tunnel structures.For large-scale tunnels under complex geological conditions,long-term health monitoring for each tunnel is not only expensive,but also difficult to construct,which is not practical.Therefore,it is of great significance to carry out long-term health monitoring for representative tunnels and to study structural health assessment methods suitable for large-scale tunnel group.Based on the large-scale tunnel group of Wen-Ma Expressway and Ya-Kang Expressway,the structural health evaluation of large-scale tunnel group under complex geological conditions is studied in this paper by means of data investigation,field test,data analysis,theoretical analysis and other research methods.The results of this paper are as follows:(1)Based on the investigation of the regional geological characteristics and construction characteristics of Wen-Ma and Ya-Kang Expressways,the regional characteristics of high-speed tunnels in Tibetan area are refined,the hazard sources of tunnels are identified,the selection principles of typical sections for health monitoring are put forward.Fifteen tunnel sections were selected as typical sections,and the corresponding monitoring projects are formulated.(2)Based on the field monitoring data,the safety factor of tunnel structure is calculated,the structural stress characteristics of typical tunnel sections of each hazard source are analyzed,and the structural safety of typical tunnel is evaluated.(3)In this paper,a long-term safety evaluation model of tunnel structure under complex geological conditions is established by using the theory of fuzzy comprehensive evaluation.The factors affecting the long-term safety of tunnel structure are analyzed in depth,and the two-level index system of the evaluation model is established;The four-level classification of the safety grade of tunnel structure and the safety classification benchmark of each influencing factor are formulated;The weight values of each factor are determined by AHP method;And the structural safety of health monitoring tunnel of Tibetan expressway is evaluated by this model.(4)According to the theory of fuzzy neural network,a structural health state deduction model of large-scale tunnel group under complex geological conditions is constructed.The deduction index are selected and the fuzzy rules of deduction index are formulated;The derivation of the large-scale tunnel group of the expressway in Tibet is divided.The model is used to realize the deduction of structure health status of the large-scale tunnel group in the Tibetan area,and the accuracy of the deduction is verified.