Back analysis of displacements for estimating spatial distribution of viscoelastic properties around an unlined rock cavern

A displacement back analysis algorithm is developed, considering the time-dependent effect of the rock mass. It can map spatially distributed the first elastic modulus (E-1), viscidity coefficient (eta(1)), and the second elastic modulus (E-2) of the Kelvin-Voigt viscoelastic constitutive model (VCM) and the Poynting-Thomson VCM in a rock mass by fusion of the observed displacement data from the excavation of an unlined rock cavern. The algorithm is tested and validated using numerical experiments with a synthetic heterogeneous rock mass. The results of the experiments show that this approach yields unbiased estimates of E-1, eta(1), and E-2 fields and quantifies their uncertainty. Further, the estimated fields closely predict shear strain distribution and displacements field in the example.