Global sensitivity analysis of influential parameters for excavation stability of metro tunnel

Abstract The application of a large-scale slurry-balance shield machine in super-large tunnel excavation (diameter >14 m) is much more difficult and risky than the common shield tunneling. The control of shield machine becomes a complex and difficult problem under frequently encountered unforeseen geological conditions. The operators of shield machine need to recognize the influential parameters for excavation stability, and then primarily adjust these influential parameters which can be controlled in shield machine tunneling. Aiming to find out the influential parameters for excavation stability, this study proposes a framework of global sensitivity analysis (GSA) by (i) employing three different meta-models namely polynomial chaos expansion (PCE), radial basis function (RBF), and support vector machine (SVM) methods to mimic the mapping relation between input and output parameters, and (ii) adopting three kinds of GSA methods namely Morris elementary effects, Sobol method, Expand Fourier amplitude sensitivity test (EFAST) algorithm to classify the parameters as important or unimportant (insensitive). The results show that the synchronous grouting pressure, advancing speed, and penetration are influential parameters to bubble chamber pressure, whereas the cutter rotation speed, cutter torque, penetration, and actual volume excavation are influential parameters to deviation angle. Here, we pay close attention to the most influential parameters that must be prioritized for parameter control, which can help the administrators optimize their management scheme of influential parameters during tunnel excavation. The follow-up research can focus on how to develop and explore additional particular details about the GSA method or some other data mining technologies for optimizing the management scheme of shield tunneling.