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Theoretical and Laboratory Study of Deep-Based Structures. Volume 2. Model Tests and Analyses of Mighty Epic Structures
Final rept. 1 Apr 1975-15 Jan 1979
SRI INTERNATIONAL MENLO PARK CA
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Laboratory tests were performed on 58-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.
APPROVED FOR PUBLIC RELEASE