EXPERIMENTAL INVESTIGATION OF STEEL FIBERS’ EFFECT ON THE IMPROVEMENT OF MECHANICAL PROPERTIES OF CONCRETE SEGMENTAL LINING IN MECHANIZED TUNNELING

The lining system, used in tunnel boring machines, is made of precast concrete segments. use steel fibers this kind support system can not only decrease production time and costs but also improve compressive, tensile as well flexural behaviors. A study has been carried out to examine the mechanical properties segments Tabriz metro line-2 project using three types fibers: 3D, 4D, 5D. Various experiments were investigated monitor workability Steel Fiber Reinforced Concrete (SFRC) under various loads. results confirmed an improvement specimens’ because these fibers. 5D, 3D provided greatest effect on strength fiber-reinforced concrete, respectively. 28-day tensile, strengths specimens are incremented by 13%, 68%, 154%, In addition, conducting tests orientation fibers, placing perpendicular load compressive almost 18%.