STEEL FIBER REINFORCED CONCRETE (SFRC): THE USE OF SFRC IN PRECAST SEGMENT FOR TUNNELLING

摘要

The application and the use of steel fiber reinforced concrete (SFRC) in precast tunnel lining design is a growing trend due to its advantages in performance, durability and ease of manufacture compare to traditionally reinforced concrete. First we will give a brief state of the art concerning the use of SFRC for segmental lining. Then this paper will focus on a test program set up in order to simulate the precast tunnel segments subjected to local forces such as jack thrust during the installation process. For this type of industrial problem and for others involving SFRCs, the test to compare different SFRCs has to be carried out in compliance with an appropriate test specification. This paper describes the research program carried out with AFTES (French Tunnelling Association) and will explain through the test result the real behaviour of the different material (plain concrete, SFRC, rebars) under this critical load case. This test will enable the engineer to define a required level of performance for this type of loading in relation with project requirements. The test program showed the behavior of SFRC in this application and its efficiency compared to traditional reinforcement. Multiple cracking occurred resulting in plasticizing and damage,but never sudden dislocation and failure. The test type which appears the most interesting is the median off-centered impact load test which gives very similar results and shows remarkable ductility. In addition, this test is relatively easy to implement with test specimens easy to execute and handle.