Research On The Excavation Methods With Soft Surrounding Rock Tunnel Of Guanggan Expressway

It is inevitable to run into the soft rock whose overall strength is low and self-stability is poor when building a mountains tunnel due to the complicated geological conditions. Whether or not the tunnel could construct smoothly and safely when excavating in this geological condition, not only it affect by many factors,such as construction condition, surrounding rock condition, tunnel profile, buried depth, environmental condition etc,but also it depend on reasonable selection of construction method.If the selection of construction methods is undeserved, there would be seriously influence on the construction speed and cost. Meanwhile it would affect the construction safety, and even cause accidents which threatened the life safety of construction personnel and add unnecessary financial losses.The most important thing is the choice of the reasonable construction method in the soft rock tunnel construction process. Among the soft rock tunnel construction cases in the domestic can exemplify that, improper selection of construction methods cause numbers of disasters in process:large deformation,working face landslide.etc, such as south mountain pass tunnel on Zhengzhou-Xi’an Passenger Dedicated Line, ZhangJi old fort railway tunnel, Jinyun mountain tunnel on chengdu-chongqing express way, etc.Combined with traffic science and technology project in sichuan province—Key technology research of GuangGan highway construction and based on soft rock tunnel on GuangGan highway, this paper studyed adaptability of tunnel construction methods located in soft rock by using investigating into soft rock tunnel at home and abroad, monitoring at site, numerical simulating,laboratory model experimenting.etc. It propose reasonable construction method and circulation footage that provide reference for design and construction.The specific work reflected in the following:1. Combined with the sited monitoring data,we conduct preliminary evaluation of its adaptability by summarying construction methods the existing soft rock tunnel practice have used in domestic and overseas and making statistics on construction methods the soft tunnel used being built on GuangGan highway.2. Prototype Mount Dujia soft rock tunnel on GuangGan highway to make Analysis on stress and deformation of tunnel surrounding rock and shotcrete layer when tunnel excavation employ two-steps method, reserving core soil two-steps method, three-steps method, reserving core soil three-steps method.CD method,seven-steps.three-benching method respectively.Then we puts forward more reasonable construction methods.3. Select typical sections in Mount DuJia tunnel to analysis deformation of selected points arou-nd the hole rock which were measured in the process of various construction methods by ind-oor model experiments:using two-steps method,reserving core soil two-steps method.three-steps method,reserving core soil three-steps method.CD method to imitate respectively. It is for prov-iding reference for determination of reasonable construction methods.4. According to the monitoring data, integrated the analysis results of the numerical calculation and the model test to determine reasonable construction methods eventually.And then work out reasonable circulation footage by numerical simulation.