Study On Tunneling Parameters Of Mud Water Shield Tunnel With Sand And Limestone Composite Strata

With the high development of the urban rail transit nowadays,as the most commonly used in the subway construction,shield tunneling has obvious economic and efficiency.Although technology of shield tunneling develop rapidly,the stratum is diverse and complex,especially in Pearl River Delta like Guangzhou.There are lots of composite stratum in Guangzhou,and the upper-soft and lower-hard composite stratum is also a source of risk in shield tunneling.To ensure the security of excavation of shield tunnel in such stratum and ensure shield machine can be adapted to this stratum,the shield type selection and the arrangement of the cutters must be considered adequately.Meanwhile,to prevent the ground collapse accident cause the tunneling parameters unsuitable controlling,the tunneling parameters must be considered reasonably.After referring extensive literature and based on the project of urban subway tunneling engineering of Xiaoping station to Shijin station of Guangzhou Metro line 8,the excavation of shield tunneling in sand-and-limestone stratum is considered in this paper.The main research contents are as follow:(1)According to the engineering project,the applicability of shield machine selection principle is studied for sand-and-limestone composite stratum.And according to the cutting tool’s data,the applicability of the cutting tool layout principle for evaluating the cutting tool is studied.(2)According to the type selection of shied machine,the slurry pressure and shield trust under uniform stratum are analyzed,and they are compared with the measured data.Finally,mathematical model for the slurry pressure and shield trust under composite stratum are gave.(3)Collecting and comparing the tunneling parameters under uniform stratum and composite stratum of this project,so that to analyze the regular of the parameters under composite stratum.Fitting the relationship of the tunneling parameters which are difficult to analyze.And giving the mathematical model of them to provide the basis for the parameter control.(4)Based on the project,used the finite element software of Midas GTS NX to simulate the process of tunnel shield.And verifying the correctness of the model.Then,on the basis of this model,using orthogonal test to design the test conditions and analyzing the effect and significant of ground subsidence by the slurry pressure,shield trust and grouting pressure.Moreover,basic on the results of the orthogonal test,and quoting the driving speed so that to optimizing the tunneling parameters further.Then guaranteeing the safety and efficiency of the follow-up construction.