Research On Ability Of Drainage Cushion In Tunnel Composite Lining

With more and more problems of water seepage or gushing emergent,the drainability of drainage system in tunnel catches tunnel professors^'eyes.Empirical method is the main way to evaluate the capability of drainage system in design phase.Drainage cushion is the largest part of the drainage system,at present,the main materials used in the composite lining is geotextile.The research for the drainability or decompression through examination is the main theme of this thesis,and the main research outputs are as follows:?1?The fiber structure distribution of the cross section of synthetic staple fibers needling nonwoven geotextiles was observed by microstructure experiment,the result is used to optimize the theoretical calculating value of porosity of the cross section of the geotextile.The microstructure model of the cross section was established for a scientific computation.?2?According to point source inlet condition,a brand new test equipment was developed for the seepage experiment,and the drainage performance was tested.On the basis of experiment figures,the flow coefficient was proposed as a drainage performance parameter.According to the results,the flow coefficient of drainage mat is much larger than that of geotextile;the flow coefficient of 500 g/m² geotextile is significantly smaller than that of 300g/m² and 400 g/m² geotextile.?3?The hydraulic conductivity for the new test equipment was deduced according to fluid mechanics formula.The results show,the flow coefficient is greatly affected by the lateral pressure.When the lateral pressure is small,the flow coefficient of 500 g/m² geotextile is significantly smaller than that of 300 g/m² and 400 g/m² geotextile,but in a large lateral pressure,the flow coefficient of 500 g/m² geotextile is larger than that of 400 g/m² geotextile,and the gap is small.The result shows the anisotropy of geotextile drainage.?4?Through numerical simulation,the FLAC^3D is used for fluid-structure coupling calculation.Water pressure of the second lining in the condition of different drainage materials is compared,and results show the reduction of 400 g/m² geotextile is significantly smaller than other test specimens.So that,in the design phase of tunnel drainage system,the service environment should be fully considered,to choose suitable drainage material with multiple indicators.