Study On The Mechanical Characteristics Of The Large Thickness Subway Tunnel On Remnant Collapse Of Loess After Immersion

The rail rapid transit of xian-lintong lies in 23.2m collapse loess,how to deal with such thick collapsible is the key problem for engineering technicians,because of less engineering experience.In addition,the collapsible of rail rapid transit is moderate or severe wet level.When the loess is collapse,the safety of subway tunnel is an ordeal.In order to solve the problems above,field watering test,centrifugal model test and FEM method were used to analyze the influence of different collapsible area to foundation and subway tunnel,the safety treating depth was predicted according different collapsible area,determined the relationship and rule of destruction level and treating depth,developed the rule of foundation treatment in thick collapsible loess area.First,the watering rule of collapsible loess area was studied,the collapsible type,the collapsible level and the collapsible depth of collapsible loess were determined,based on the watering field test,the infiltration pattern was analyzed.Second,based on the modified centrifuge,the foundation and tunnel destruction experiment was conducted systematic under the condition of watering collapsible loess,and the destruction form of foundation and tunnel structure was observed,the mechanical character of tunnel model under the condition of untreated loess foundation was analyzed,also the influence factors of destruction was analyzed.Third,take the resistance ability of composite foundation as the main line,combined the results of centrifuge test,based on the finite element soft,the numerical analysis was done based on the finite elemental soft,the stress of tunnel structure and foundation was analyzed.In the last,based on the real project of xian-lintong,the influence to the foundation under the condition of different treated depth loess was analyzed,the safety depth need to be treated was obtained,the relationship and rule of collapsible area and treated depth was obtained when the tunnel structure was destroyed,the collapsible loess foundation treatment principles of collapsible loess with big thickness was set,the treated thickness of collapsible loess and control standards of residual collapsible quantity were established.The research conclusions provide strong technical support and value for the subsequent similar projects.