关键词: 浅埋富水全强风化花岗岩, 公路隧道, 瞬变电磁仪, 超前探测

Abstract: The Mabiejiao Tunnel in the Jinghai Expressway project has the characteristics of shallow burying, unsymmetric pressure, rich groundwater, and extremely soft rock mass.  The exposed geomaterials during the tunnel excavation consist of silty clay and completely weathered granite saprolite with individual less weathered sphere boulders. The stability of the surrounding rock is poor and small disturbance in the tunnel excavation could easily induce the liquefaction of the surrounding rock mass. Construction related geo-hazards, such as, rushing of mud and groundwater at the excavation surface and at the bottom of supported surface, rock collapse at the crest of arch and side walls, are frequently occurred. This paper presents a case history of applying the transient electromagnetic method to collect groundwater information at the supporting area and the ground surface in the Mabeijiao Hunnel of Jinghai Expressway. The collected data could be used in providing advanced hazard prediction and providing design and construction guidance of the shallow buried highway tunnel excavation in saturated completely weathered granite saprolite soils. The collected data could also minimize the impact of adverse factors on the tunnel excavations. 

Key words: aturated completely weathered granite, shallow buried highway tunnels, transient electromagnetic device, advanced detection