Theoretical and Laboratory Study of Deep-Based Structures. Volume II. Model Tests and Analyses of Mighty Epic Structures

摘要

Laboratory tests were performed on 5/8-inch- (16mm) diameter scale models of cylindrical structures fielded in Mighty Epic. The model structures were tested in 4-inch- (0.1-m) diameter specimens of SRI RMG 2C2, a tuff simulant. Results from these tests show that (1) structures are damaged less during dynamic loading than during static loading, (2) if yielding occurs in the free field, tunnel closure is not greatly influenced by structure strength, and (3) structures can effectively resist deformation under repeated loading. Theoretical analyses were performed for axisymmetric loading of a deep-based structure in SRI RMG 2C2. Results show that (1) the analyses can predict tunnel closures measured in the isotropic loading laboratory tests, (2) theoretical tunnel closures under plane strain loading (radical pressure at infinity and axial strains identically zero) and isotropic loading (hydrostatic pressure at infinity) differ only slightly, but (3) tunnel closure and rock stress field under end-on loading differ substantially from closure and stress under isotropic loading; thus substantial theoretical extrapolation of rock response is needed to predict tunnel closures in the field during end-on loading using isotropic loading laboratory data, even though both loading types produce symmetric tunnel response. (Author)