Investigation on the tail brush induced loads upon segmental lining of a shield tunnel with small overburden

Abstract

Damage to the tunnel segmental lining induced by the construction loads has become an important issue in recent years. To investigate the influence of tail brush induced loads on linings during construction, in-situ monitoring was carried out to measure the pressure on the lining of a large cross-river shield tunnel with a small overburden in silty sandy ground in China. Time history of pressure distribution on the lining during tunnel construction was obtained using PAD type earth pressure gauges. Distribution of bending moments and axial forces and related crack width of segments were also examined. The in-situ monitoring results showed that the pressure induced by tail brush (steel plate brush and wire brush) had an important influence on the segments while the shield machine was passing through. Moreover, results from laboratory tests carried out on steel plate brush and wire brush to investigate the extent of loading, revealed that the load by the steel plate brush was more significant than that by the wire brush. Based on the data analysis and field observation, it can be concluded that the non-uniform distribution of pressure induced by steel plate brush might have caused cracking and water leakages in the segments, which can provide valuable references for damage prevention from construction loads in practice.