An Advanced Displacement-Confinement Method for Design of Mechanized Shield Tunnels in Soft Ground

Abstract

This paper presents the Advanced Displacement-Confinement Method (ADCM), a semi-analytical framework for the design of mechanized shield tunnels in soft ground. The method bridges the gap between empirical design methods and full three-dimensional numerical analyses by providing a transparent, mechanistically informed workflow. ADCM integrates two new modules: the SHIELD model, which projects face and grout pressures onto the tunnel cross-section to define a circumferential distribution of applied loads and a confinement ratio index; and the RINGS model, which describes ground convergence using a Mohr-Coulomb shear-hardening constitutive model which does not require an iterative solver. Together with conventional structural lining design models and empirical settlement transfer functions, these components allow direct evaluation of the relationships between TBM operation, ground response, lining loads, and surface settlements. The method is computationally efficient, requires only standard input parameters, and produces results consistent with case histories from soft ground shield tunnelling projects. Its scope is limited to short-term behaviour under closed-face conditions, but within this range ADCM offers a practical and reliable design tool that supports both preliminary assessments and parametric studies as well as accurate real-time back-analysis.