Performance of synthetic macrofibres in reinforced concrete for tunnel linings

The aim of this study was to evaluate the effect of synthetic macrofibres in tunnel concrete lining structures. Tunnel concrete linings must be able to resist flexure loads that occur in the ground and should be able to cope with the danger of cracking owing to their wide surface areas. Recent tunnel fires have raised concern because the collapse of the concrete lining structures can affect the safety of the tunnel. In this study, the effect of synthetic macrofibres was examined to improve the performance of the concrete lining in tunnels. By changing the fibre mixing ratio, it was found that a level above 0.5% was effective in controlling cracks. The effect of fibre mixing ratio on the flexural capability was also studied and it was found that the fibres were more effective than steel and that 2% mix was the best. The fire resistance of concrete containing synthetic macrofibres was studied and it was shown that the fibres prevented the concrete structures lining the tunnel from spalling.