چكيده به لاتين
Evaluating of the structural use of steel fibers as a substitute for steel reinforcing bars in precast segments of tunnels excavated by tunnel boring machine (TBM) - that due to the significant cost and time savings as well as greater durability, resulting in growing demand in the context of its use as a structural reinforcement - is the main purpose of this study.
In this study, firstly after reviewing the structural design principles of segmental lining of tunnels, the problems of the conventional reinforcement of segments has been investigated. Then, as a supplementary alternative and even replacement, the basis for fiber concrete structural design has been provided. After that - considering the thesis theme that is an applied research – the application of this new material in structural design has been evaluated using case study methodology. In this regard, a reinforced concrete segmental tunnel (under construction) has been analyzed by FEA software ANSYS and re-designed using the steel fiber concrete and finally, two alternatives (conventionally reinforced concrete and steel fibre concrete) have been compared.
Based on the results of this case study - that considering the geological conditions and diameter of the tunnel, is a challenging choice for fiber concrete usage - reinforcement of segmental tunnel with steel fiber concrete tunnel segment is possible. It is noteworthy that the tunnel passes through poor rock formations and also the structure is one of the tunnels diameters of the top. In order to strengthen the segment against non-uniform support conditions mostly (under advancing jacks), ladder reinforcement has been considered merely at peripheral joints. As a result, in a project that its geotechnical conditions are not ideal, with provision of a hybrid structural solution (combination of fibre concrete with local rebar reinforcement) - in addition to saving time and labor - the technical advantages of fiber such as high toughness, impact and cracking resistance could be used. The striking point in this study is response evaluation of non-uniformity segment support under loading of thrust jack pressure that has been studied in particular.
Keywords: Tunnel Boring Machine (TBM), Segment, Fibre concrete, Bursting stress, Hybrid
