Impact of Multivariate Cross-Correlation between Soil Parameters on Maximum Longitudinal Deformation of an Operating Tunnel Induced by Ground Surface Surcharge

Existing tunnels are inevitably disturbed by adjacent engineering projects, with ground surface surcharge accounting for the largest proportion. Meanwhile, the influence of spatial variability of soil parameters on tunnel deformation cannot be ignored, especially for the cross-correlation when a multivariate random field is modeled. Unfortunately, studies about the coupled effect of multivariate cross-correlated random fields and surcharge on longitudinal deformation of tunnels in three-dimensional (3D) space are quite scarce. Thus, this study firstly investigated the coupled impact of the multivariate cross-correlation of soil parameters and ground surface surcharge on the maximum longitudinal deformation of an existing tunnel in 3D space by using the random FEM (RFEM) combining the parallel technology integrated within ABAQUS. The Young's modulus, Poisson's ratio, and friction angle were discretized and highlighted by isotropic cross-correlated random fields. The results showed that the surcharge has quite a significant impact on the deformation of an operating tunnel especially in spatially variable soil. The calculation result obtained by random variable theory (RVT) was smaller than that of random field theory (RFT) because the former ignored the structural characteristics of soil parameters. Conventional single-parameter random fields (SRF) and multivariate independent random fields (IRF) may overestimate the tunnel deformation compared with multivariate cross-correlation random fields (CRF). Further parameter studies found that a larger cross-correlation coefficient between soil parameters will result in a smaller tunnel deformation in the CRF model.