Shallow multi-arch tunnel under unsymmetrical pressure has complex mechanical behavior to which further study is lacking at present. The existing design methods are thoughtless about the features of shallow and partial pressure. The phenomena of cracks, collapse or other diseases in tunnel lining structure are often seen during the construction or after the completion. Combining one tunnel example, this paper presented scientific feedback design method that suited for Shallow multi-arch tunnel under unsymmetrical pressure: made load back analysis with collected information during construction, then averaged the above load and field monitoring load to make forward analysis and internal force calculation, which was used as reference of reinforcement and sectional design for lining structure.
Tunnel and underground engineering projects have certain failure risks during construction and operation, including the risk of durability failure to which the study is not enough. In this paper, a whole set of research method for analysis, assessment and calculation on durability risk was proposed on the basis of identification to durability risk factors of large underground concrete structures. That is: this paper provided a method of reliability calculation by establishing failure mode and limit-state-equations according to reliability theory; then, classified and collated various risk factors by taking methods of analytic hierarchy process (AHP) and fault tree analysis (FTA); after that, the quantitative analysis of structural durability was done in accordance with Monte - Carlo (M-C) method. Finally, as an example, for the project of passage across the Yangtze River in Chongming, Shanghai, the above methods were applied to estimate the risk of durability failure of segment component. Effective measures and methods were presented and adopted to enhance the durability capacity of structure according to the results of analysis and assessment.
There will emerge cracks or damage due to the action of rock pressure or its own shortcomings and low strength for the lining structure in tunnel or underground engineering, especially at the places of excessive bending moment and tensile stress because of bias pressure where concrete will be pull apart for the deficiency of strength even to cause leakage and durability insufficient. Conventional maintenance and reinforce methods are time-consuming and laborious, and the effect is also not ideal. It is simple, timesaving and having a significant and lasting effect to use carbon fiber reinforcement method. This paper studied structure’s failure mechanism and on the basis of that the principle of fiber-plate reinforcement from the angle of structural plastic development, then studied the improvement of structure’s mechanical character and the change of design calculation method for single section of underground structure with carbon fiber plates by using the research method of plane-strain. At the same time, the typical model of integral failure for single section was analyzed and the calculation method and formulae of bearing capacity and reinforcing steel bars were deduced, which remedied the shortfall in the design specification for concrete structure. In the end, by comparing the calculation results of structure with fiber plates and that with not fiber plates based on engineering example, the conclusion that structure’s bearing capacity and capability of resistance to deformation had obvious improvement was obtained.
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