Underground large scale test facility for rocks : Geophys Res Lett, V8, N7, July 1981, P709–710

This brief note discusses two advantages of locating the facility for testing rock specimens of large dimensions in an underground space. Such an environment can be made to contribute part of the enormous axial load and stiffness requirements needed to get complete stress-strain behavior. The f . '-.1 high pressure vessel may also be located below the floor level since the '· lateral confinement afforded by the rock mass may help to reduce the thickness of the vessel. Introduction A large scale test facility for geological materials~ particularly rocks serves as a via media between the conventional small scale testing and the in-situ testing. Small scale tests suffer from lack of clear cut approach for translating the data to actual rock ·behavior, while in the in-situ tests, the boundary conditions are not always clearly defined. It may also be difficult to eliminate some of the parameters inherent in an in-situ environment which could complicate data interpretation. Tests on large sized samples of rock may help to bridge the gap between these two extreme forms of testing. Tests on 1 arge sized specimens of rock to failure demand very high devi atoric loads, on the order of hundreds of megaNewtons. Also, most of the brittle rocks tend to fail in an explosive manner, if tested in loading system with comparatively low axial stiffness. Confining pressures of the order of 200MPa may require very special mechanical design requirements. ~This brings in a number of questions regarding the structural requirements of the loading frame and the pressure vessel as well as maintenance and safety of the facility and the personnel.