Study On Construction Method Of Biaoshuiyan Tunnel Of Xiang Li Expressway

Biaoshui Yan tunnel is the one of the key control projects of Xiangli Expressway,It's the largest underground Interchange tunnel in mountain areas at present in China.Especially the shallow buried soft rock tunnel with SC-1 type section(K76+235~YK76+290 and YK75+322~YK75+427)and the largest excavation span of super large section tunnel of SE type section(ZK75+990~ZK76+060),the most complex structure of double-arch tunnel without middle–wall.The shallow buried weak surrounding rock section contains weak soft weathered with strong weathered fractured slateand and other unfavorable geology,the middle's maximum excavation span is 28.96 m of the super large section tunnel,the vault is flat.During construction,it is easy to cause the relaxation and instability of the surrounding rock and the collapse of the vault.The most complex structure of double-arch tunnel without middle–wall,it is greatly influenced by bias pressure,It is easy to cause cracking of primary support structure in construction.Therefore,in order to ensure the safety of the tunnel construction,it is necessary to study the construction method.This is the breakthrough point of article,the construction methods of the soft rock section,the super large section and the double-arch tunnel without middle–wall are studied emphatically.The main contents are as follows:1,The criteria for determining shallow tunnel and super large section tunnel,the construction mechanics characteristics of three special tunnels,the calculation method and research status of surrounding rock pressure of tunnels are briefly described.2,According to the topographic and geological conditions of the shallow buried soft rock tunnel,in order to control the settlement and deformation caused by the excavation of the tunnel,the method of precast concrete short pile reinforce the ahead of the core soil is proposed,the single short pile length and the excavation footage is keep equal,so that recycling;for reinforcement the excavation face of tunnel's core soil,the glass fiber anchor and the precast concrete short pile reinforcement methods are used,through numerical simulation,the reinforcement effect is analyzed from convergent deformation,extrusion deformation of tunnel excavation face,pre-convergent deformation point of view.3,For the shallow buried soft rock tunnel,the construction process is simulated,include method of double side wall heading method,one side wall heading method,two step retaining core soil excavation method,ADECO-RS method,ADECO-RS combined with two step excavation method,the influence of different construction methods on the stress and deformation of tunnel surrounding rock and primary lining is analyzed,through the stress and deformation characteristics,the reasonable construction method of this section of the tunnel is determined.4,For super large section tunnel,using the finite difference method to simulate these construction process such as double side wall heading method,one side wall heading method,two step retaining core soil excavation method,ADECO-RS method;the stress characteristics and deformation laws of surrounding rock and initial lining are analyzed,and the most suitable construction method for super large section tunnel is compared and analyzed.5,With regard to the double-arch tunnel without middle–wall,using the finite difference method to simulate the construction process,the force characteristics and deformation rules of tunnel surrounding rock and primary support,the construction characteristics of the tunnel are compared through the construction process.6,In the course of the tunnel construction,the surrounding rock pressure,the vault and the surface settlement are monitored in the field,and the monitoring results and numerical simulation are compared and analyzed.