Primary tunnel lining with PP FRS and rigid bolts

Steel fibre reinforced shotcrete has been extensively used in tunnels for underground support for better rock quality, and in combination with bolts for poorer rock quality. In this paper are presented results of the laboratory research and field tests to investigate the possibility of using the polypropylene (PP) fibres instead of steel ones. The laboratory research included testing the properties of different sorts and shapes of PP fibres, bond properties (pull-out tests) of PP fibres from different concrete mixes and standard bending test of concrete prisms. With obtained data the computer analyses were conducted, for different stages of construction, by means of FLAC computer program, which included the interaction of primary layer and reinforced rock. For the sake of comparison test fields on the site were executed with steel and PP fibers and steel reinforcing meshes. The bearing capacities of shotcrete with PP fibers, tested in situ with hydraulic jacks, were of the same order as for shotcrete with steel fibers or reinforcing meshes.