The wear of excavation tools is considered as one of the critical factors that affect the scheduling of shield tunnel construction. There is presently no effective countermeasure to prevent the occurrence of severe wear of excavation tools during tunnelling operations in complex geological formations. In addition, several problems are likely to occur, such as face instability and an unfavourable rate of tunnel advancement. The study reported in this paper analysed the various factors that affected the wear and performance of excavation tools during earth-pressure-balance machine tunnelling at the Ma-Lian section of the Guangzhou Metro line 9 in China. It was found that tunnelling in mixed ground conditions (the upper-soft and lower-hard stratum) led to severe wear of the cutter discs, resulting in additional costs and schedule delays. The values of the foam expansion ratio, concentration of foam agent and the foam injection ratio were measured at 20, 2.5%, and 40% respectively. Pre-grouting and effective soil conditioning were also found to be suitably used to prevent excessive wear of cutter discs and surface collapse incidents caused by face instability.
Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, Vol. 171, no. GE4 (2018), pp. 363-376
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Also see Discussion at https://doi.org/10.1680/jgeen.18.00129 and Corrigendum at https://doi.org/10.1680/jgeen.2018.171.6.562