Shallow tunnel construction with irregular surface topography using cross diaphragm method

This paper presents the analysis of site monitoring results from a high-speed railway tunnel excavated in shallowly buried soft ground with irregular surface topography using the cross diaphragm method. The surface and subsurface settlements, the normal pressures between surrounding ground and primary lining and between primary and secondary linings were systematically monitored at three tunnel cross sections. The specific surface settlement characteristics associated with tunnelling under irregular surface topography conditions in comparison to those under horizontal surface conditions are illustrated. The “rebound” phenomenon of a relative settlement curve from the intermediate anchor to the top of the access tube is observed, which can be introduced to determine the stability of a tunnel project during construction. The normal pressures measured between the soft ground and the primary lining show close agreement with the theoretical analysis results. The normal pressures measured between the primary lining and the secondary lining should be used before the influences of cell installation effects and other related factors have been considered. But the pressure measurements can still provide valuable information of a tunnel project.