Applicability of the multiple yield model for estimating the deformation of vertical rock walls during large-scale excavations

This paper describes the validity of the multiple yield model (MYM) based on a comparison between predictions by MYM analysis and in-situ measurements of two large-scale vertical excavations, about 30 m in depth and 100 m in width, for nuclear power plants. MYM is a finite element method for modeling the mechanical properties of intact rock and joint systems in rock mass. The method can analyze the non-linearity of deformation under loading and unloading stress paths. The analysis was conducted by determining the geometrical model of rock mass from test adit and borehole observations of discontinuities in conditions such as orientation, spacing, and persistence. The physical parameters of intact rock and discontinuities were determined by laboratory tests using sample specimens, taking the scale effect into account. The deformation mode and displacement value determined by the MYM analysis both corresponded well with in-situ measurements. We have confirmed that MYM can estimate the actual behavior of discontinuous rocks with adequate accuracy for practical application.

We have established a new analytical method for discontinuous rock.The method is a kind of FEM introducing the Multiple Yield Model. MYM can analyze non-linearity deformation property of joints and intact rocks. The validity was confirmed by real behavior of actual-large rock walls. The result shows adequate accuracy for practical problem.