Countermeasures for Surface Settlement in Constructing Shallow Overburden Urban Tunnels Penetrated through Active Fault

摘要

Recently in Japan, there are increasing number of cases where tunnels are excavated in urban areas through use of a mountain tunnelling method. Under the circumstances, it is required that appropriate Countermeasures against ground subsidence be taken and that lining as well as tunnel support that suit the specific load conditions be constructed. However, their design method has not yet been satisfactorily established. The late application of various Countermeasures to the excavation of the same tunnel has enabled us to compare their results in terms of the topography, ground conditions, and construction conditions. As a result, desirable design approach to the lining and tunnel support of the shallow overburden urban tunnels has considerably been elucidated, in connection with employment of side drift, long steel pipe fore-piling method, and such as Countermeasures against ground subsidence.