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In order to study the influence of different forms of defects on the stress of lining structure, through the model test, different forms of defects were simulated, and the changes of bending moment, axial force and safety factor at different parts of lining structure were analyzed. The results showed that the defects at the connection between the side wall and the inverted arch increased the bending moment and axial force at the middle of the lining arch waist and the inverted arch, and decreased the bending moment and axial force at the vault. According to the different forms of defects, the effects on different parts of the lining were different. When there were only concrete shrinkage defects or unconnected steel defects, the main influence parts of lining structure were haunch and side wall. When the two defects coexisted, the middle part of vault and inverted arch would also be greatly affected. The influence of concrete loose defects on the safety factor of lining structure was generally greater than that of unconnected defects of steel bars. The main influence areas were arch waist and side wall. When the two defects coexisted? the safety lector at the middle of arch waist and invert decreased obviously 3 which was 52.03% and 32.40% respectively. The effect of defects on the safety factor at the middle of the hance and inverted arch was greater than that at the vault and side wall. During construction? the quality of concrete pouring here should be strictly controlled to ensure the strength after forming, and the pouring thickness can be appropriately increased to make it have a higher safety reserve. [ABSTRACT FROM AUTHOR]

A lateral loading model box was used to carry out model tests under two cases: the tunnel was located in loess (case 1) and penetrated by potential sliding surface in loess (case 2). The stress characteristics of tunnel lining in the process of slope deformation were studied, and the laws of slope deformation, pressure change of tunnel surrounding rock and lining moment change were analyzed. Results showed that the surrounding rock near the slope side of the tunnel lining was easy to form a void zone under the two cases. The maximum width of the void zone was about 1 cm in case 1 and close to 2 cm in case 2. The void zone in case 2 was much larger than that in case 1, with a relative increase of 100%; Compared with case 1, the peak value of lining bending moment in case 2 increased significantly, with a relative increase of 159.33%, and the maximum increase was located in the area near the side arch foot of the slope. The slide of the potential sliding surface in the slope significantly increased the possibility of tunnel lining damage. [ABSTRACT FROM AUTHOR]