| As the relatively low strength of loess, large soan loess tunnel with large deformation after the excavation. Together with large sPan loess tunnel'soeciaty of span large and flat shape, construction of the difficulty is self-evident. Currently, experience of in the design and construction is not mature, Therefore,it is necessary to study the large soan loess tunnel. In this paper, combined the Dunliang tunnel,the stress and the displacement of the large span loess tunnel portal'surrounding rock and the supporting Struetures are studied by theories analysis, field measurement andnumerical simulation, and the data of monitoring measures are analysedand feedbacked.The main researh is as follows:1. The field monitoring was against on five class surrounding rock of portal. Monitoring the results of the scene reveals the double sidewall drift method construction in settlement laws, the right hole of sedimentation value is greater than the left hole,and all more than led hole. The excavation of the led hole has a great effect for side of the hole of convergent defonrmation.2. Strengthening the foundation of the tunnel effect is analyzed, The result showed that the steel pipe grouting reinforcement effectively controlled the deformation of tunnel, enhance the loess'inherent ability to support, and the steel pipe reinforcement technology for simple, safe, fast, etc.it is a very effective reinforment measure of surrounding rock in the soft rock tunnel.3. Uses the MIDAS/GTS analysis software, has carried on the computation to the tunnel entrance section construction process, the computed result and the scene monitor data's software analysis result has carried on the contrast confirmation.According to the above research results,the DunLiang tunnel uses the supporting structural style which may well control deformation, and guarantee supporting structure stability. The research resultswill have the guide and the reference value to the next similar tunnel design and construction.
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