Research On Water Inflow Control And Construction Problems Of Forked Tunnel In Water-enriched Region

Due to the advantages of improving line-type and suitable for special topography condition,forked tunnel is widely used,including baziling tunnel in shanghai to chengdu west expressway、jiaozhou bay subsea tunnel、wanshishan tunnel in xiamen and shenzhen subway.In china,plentiful experience has been accumulated in the construction process of forked tunnel no matter in western alpine canyon or subway station、underground interchange and urban expressway connecting line.However,problems such as simplex construction methods、powerful support on the whole while relative weakness at local placemass cracks appearing in lining which lead to leakage exists generally.At present,chinese traffic construction career has bright prospect.Researches on construction methods of multi-arch tunnel help those proposed to construct avoid the problems above and lead to multi-arch tunnels playing great roles in traffic construction career.For tunnels in water-enriched area,grouting circle can reduce the permeability coefficient of grouting circle、improve the stability of surrounding rocks and plug water effectively.Consequencely,as an important waterproof and drainage measure in the process of tunnel construction in water-enriched area,the research on the plugging water effect and economic rationality of groutig has great value.Relying on the shenzhen east transit expressway connecting line project,study on reasonable permeability coefficient of grouting circle was carried out through indoor model test,which proposed permeability coefficient suitable for the project.On the basis of the result,bifurcate position of tunnel in guduiling region was chosed to conducting numerical calculation under fluid-structure interaction condition in order to obtaining reasonable construction method used in large section area、multi-arch area and neighborhood tunnels and appropriate excavation sequence.Therefore,main contents and results are as follows:(1)With the self-designed equipment and analogous material prepared according to the similarity principle,indoor experiment about reasonable permeability coefficient of grouting circle was conducted.Through testing water inflow effected by grouting circle,reasonable permeability coefficient of grouting circle was obtained under economic rationality.(2)Based on the theory of fluid-structure interaction,bifurcate position of tunnel in guduiling region was chosed to conducting numerical calculation including both side drift method and three-step method used in large section area、three-drift method and non-central excavation method used in multi-arch area、benching tunnelling method and CD method used in neighborhood tunnels.Through analyzing the result from the point of displacement、stress、porewater pressure,reasonable construction method used in large section area、multi-arch area and neighborhood tunnels was obtained(3)3D-model based on bifurcate position of tunnel was established.Under different excavation sequence,monitoring sections in large section area、multi-arch area and neighborhood tunnels were set in the excavation process of the model in order to acquiring the surrounding rock changes of displacement、stress、porewater pressure and plastic zone.As a result,better excavation sequence was acquired in the comparison of different excavation sequence.