A geostatistical inverse approach to characterize the spatial distribution of deformability and shear strength of rock mass around an unlined rock cavern

A geostatistical back analysis is developed, which can map spatially distributed Young's modulus (E′), cohesion (c′), and internal friction angle (ϕ′) in a rock mass by fusion of the observed displacement data from the excavation of an unlined rock cavern. It is tested and validated using numerical experiments with a synthetic heterogeneous rock mass, created with field observed spatial variability. Results of the experiments show that this approach yields unbiased estimates of E′, c′, and ϕ′ fields and quantifies their uncertainty. Further, the estimated fields predict the plastic zone distribution and displacements of cavern periphery, which are nearly identical to those of the true field.