Study On Safety Evaluation Method Of Tunnel Supporting Structure Based On Characteristics Of Cracked Concrete

In reinforced concrete structures, concrete cracking is inevitable phenomenon, the majority of reinforced concrete structures are working with cracks. Similarly, in the secondary tunnel lining of reinforced concrete will also cracks, especially in the tunnel variation cracks will greatly increase the possibility. In the existing code, the cracks are considered for their impact on the durability of the structure, without taking into account the relationship between crack and secondary lining security. Through theoretical analysis, the method through the cracks to evaluate lining security is discussed, and then by the value simulation checking, the corresponding criterion is put forward. Finally, the rationality of the method has been validated in this paper by the method of moment curvature of the initial support to supplement safety check calculation. The main research results are as follows:1. Through theoretical analysis, the causes and types of cracks are discussed, and the calculation method of crack width code is analyzed and the crack width calculation method is derived based on numerical analysis, and the establishment of reinforced concrete cracks numerical model is carried out and the parameters of various types of units in the crack model are determined. Finally the basic assumptions and propose evaluation method of lining safety based on the cracks are put forward.2. Based on the classification of all kinds of tunnel defects, the reasons for each type of tunnel defects is analyzed, a series of tunnel defects of conditions are setted out. With an engineering example, through large-scale finite element analysis software ANSYS to calculate various types conditions, crack distribution of various types of working conditions are analyzed, the maximum width of cracks and safety factor of the most disadvantaged sections are calculated, the relationship between width of cracks and safety factor are found, the ultimate crack width based security analysis is determined. Finally the type of lining defects can be determined form the distribution of cracks, and whether the lining is safe or not can be determined according to the maximum width of cracks.3. Based on moment curvature calculation method being explored, and the calculation algorithm moment curvature by a programming language is presented and the relationship between curvature and moment of the lining is obtained. Then, the moment curvature relationship of material parameters is inputted to the finite element analysis software ADINA, and the results of the moment curvature lining and the general elastic lining are analysed, and finally the conclusion that moment curvature beam is more reliable to simulate secondary lining is put forward.