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.