Study on ground suitability and construction countermeasures of metro shield in China

Abstract Because of unsuited shield type selection, equipment configuration and construction measures, lots of construction problems appeared like clogging, excessive settlement, spewing, abrasiveness, oversized grains and abnormal working parameters. Ground conditions and construction measures encountered in numerous metro projects across China are categorized in order to improve the selection of shields specific to complex ground conditions. Firstly, according to grain-size distribution, diversity of complex ground is classified as four types. Secondly, oriented by ground suitability problems, the four types are divided into eight sub-classes based on the critical geological parameters or conditions. In order to provide an overall view for planning of shield selection, the map of China consisting of metro cities is regionalized according to the above classification. In the end, construction countermeasures for each types are put forward including shield type selection, equipment configuration, soil conditioning and tunneling parameters. Conclusions drawn from the paper can improve current classification for shield tunneling and provide practically targeted references for engineers.