Assimilation of soft rock anisotropy into a non-linear constitutive framework supported by X-ray CT characterization

Complex geological formations have long posed significant challenges in geotechnical engineering, primarily due to their inherent anisotropy and the complex response of surrounding rock masses to excavation. In this study, the highly anisotropic ground surrounding the tunnel is modelled as a non-linear elastic medium during the loading phase, aiming to provide a realistic engineering representation of ground behaviour under excavation using the Hardening Soil Model (HSM) within both 2D and 3D finite element analyses (FEA). The tunnel’s surrounding ground was characterized through X-ray tomography to identify its microstructural features, and the HSM input parameters were defined based on laboratory test results. Numerical simulations revealed that vertical displacements differed by less than 3.5% between the 2D and 3D models, despite the additional constraints of the 3D configuration. Furthermore, monitoring data showed a high degree of correlation with numerical predictions, achieving accuracies of 98% and 94.83% in 2D and 3D analyses, respectively. These findings contribute to narrowing the existing gap in geotechnical engineering practice by offering a reproducible approach for analysing complex geological conditions.