Analysis of Directional Evolution of Tunneling-Induced Ground Settlement in Spatially Variable Soils with Rotated Anisotropy

This study investigates how rotated anisotropic spatial variability controls the magnitude, dispersion, asymmetry, and peak location of tunneling-induced ground settlement. A non-intrusive random finite element framework was developed by coupling rotated anisotropic random fields with a two-dimensional Mohr–Coulomb elastoplastic tunnel model. The framework uses the autocorrelation-distance ratio dh/dv and principal-direction angle beta to describe soil directional structure, and 400 Monte Carlo realizations were performed for each case. The numerical model was first compared with monitoring data from the Shenzhen Mawan Subsea Tunnel. Parametric analyses then quantified the effects of spatial variability in elastic modulus E, cohesion c, and friction angle phi, followed by an assessment of the independent and coupled effects of dh/dv and beta. Increasing E-cov from 0.1 to 0.5 raised the mean maximum settlement from approximately 12.1 to 14.4 mm and produced the largest response dispersion among the tested parameters. Increasing dh/dv widened the mean settlement trough from approximately 25 to 47 m. The peak-offset probability increased from 45.3% at beta = 0 degrees to 76.7% near beta = 100 degrees and reached 82% for the coupled case beta = 90 degrees and dh/dv = 12. These results show that rotated anisotropy can leave the ensemble-mean trough nearly symmetric while substantially increasing realization-level peak migration and uncertainty. A multi-index assessment combining maximum settlement, trough width, slope index, and peak-offset probability is therefore more informative than maximum settlement alone. The conclusions describe comparative probabilistic trends within the adopted model and parameter ranges rather than exact site-specific predictions.