| Due to the specific geologic and hydrographic properties of the sandy surrounding rock at Xiang'an end of the eastern passage of Xiamen Subway Tunnel, such as coarse sand granules, large quantities of water in the sand bed as well as its high permeability, the construction face is vulnerable to collapse and water burst after excavation which pose great difficult for tunnel constructions.Firstly, this thesis makes detailed observation on the damage process of the face in every sub-grade surrounding rock of the sandy tunnel in model tests and works out the characteristics of the position, form, temporal relationship and spatial relationship of the damages.The thesis further classifies face damages into three modes: unsupported-section damage mode,face damage mode, unsupported plus face damage mode. The thesis also does an analysis of the influences on the face damage by rock's physical and mechanical properties, buried depth ratio, drilling footage, inerface between soft rocks and hard rocks.Based on the model test studies, this thesis reveals that the excavation of the sandy surrounding rock is extremely dangerious.It recommends a series of measures for the tunnel construction: the ground water level should be lowered; water in the sand layer should be drained; special construction method should be adopted: reducing the excavation area of the face and the length of drilling footage,and simultaneously increasing pretreatment and support for the face and the drilling footage after excavation.Finally, from the data obtained from the monitoring of the construction site this thesis analyses the tunnel stability after excavation and the influence of the construction dangers on the tunnel, and draws conclusion that the tunnel design and construction technologies on the whole meet the consturction needs, and ensures the construction scurity.But there is security risk in some part.It needs some modifications on the construction parameters.
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