Study On The Tunneling Parameters Of Shield Tunneling In Upper-soft And Lower-hard Composite Ground

Shield method has been more widely used in the subway tunnel construction. The control of the tunneling parameters plays a vital role in the process of shield construction. At present, the research of the shield tunneling parameters is more concentrated in the shield construction under uniform stratum conditions, but the research of the tunneling parameters on the upper-soft and lower-hard stratum conditions is relatively lagging in the shield construction. The upper-soft and lower-hard composite stratum conditions construction is a common type of special geological conditions in the shield tunnel construction, and in the condition of tunnel construction on the upper-soft and lower-hard stratum conditions many different degrees of surface collapse phenomenon appeared in the domestic and foreign. Therefore, it is necessary to make predictions for reasonable selection of the shield tunneling parameters on the upper-soft and lower-hard stratum conditions, to analyze the change of the tunneling parameters and the influence of surface subsidence, and to study the intrinsic relationship of the tunneling parameters, furthermore, to ensure the safety of the shield construction process on the upper-soft and lower-hard composite stratum conditions and improve the efficiency of shield tunneling.On the basis of referring to many extensive literature, and take the shield zone of the Shenzhen metro line station5from the People-administer Station to Five River Station as the engineering background, shield construction tunneling parameters were studied and analyzed on the upper-soft and lower-hard composite stratum conditions. The main work is as follows:(1) The composition of the shield construction cutter torque and shield thrust under uniform stratum conditions were analyzed and made part of the calculation method. On this basis, the composition of the shield construction cutter torque and shield thrust on the upper-soft and lower-hard stratum conditions were analyzed and made part of the calculation method.(2) According to engineering practice, the FLAC3D three-dimensional finite difference software is used to simulate the surface subsidence and the surrounding rock deformation in the same tunneling parameters (soil pressure, grouting pressure, the grouting volume, etc.) in the shield construction. Soil pressure as the way of the vertical force was applied to the excavation of the surface in the simulation; Grouting pressure and grouting volume were simulated in the form of grouting effect. It was analyzed that the effects of tunneling parameters change of the surface subsidence and the surrounding rock deformation according to the results of numerical simulation.(3) By statistical analysis of the actual collection of tunneling parameters in the shield construction process on the typical upper-soft and lower-hard composite stratum conditions in the shield zone, obtained the scope of application of the tunneling parameters in the shield construction on the upper-soft and lower-hard composite stratum conditions. And the correlation between various tunneling parameters was analyzed, meanwhile verify the relevance of the similarities and differences between the validation of tunneling parameters on the upper-soft and lower-hard composite stratum conditions and under uniform stratum conditions in the shield construction. Finally, the reasons why different were analyzed.