Abstract: A apparatus is provided for detecting deformation in solids in deep holes having a resilient vessel pre-stressed into a rock formation. The vessel is filled with fluid and is sealed except for an outlet tube of small diameter which extends all the way to, or close to, the surface. There the outlet tube terminates in an extensible bellows isolated from the atmosphere in an enclosed sealed vessel. The whole apparatus is completely filled with fluid. Any deformation of the vessel will cause fluid to be forced through the outlet tube and so cause the bellows to extend or contract. This motion can be monitored by any position-sensitive transducer such as a linear variable differential transformer or capacitance bridge. A second tube of the same length and size as the outlet tube is filled with the same fluid. This tube terminates at the bottom in close proximity to the resilient vessel. It also has a bellows and a displacement transducer at its upper end at the surface housed in an enclosed sealed vessel.

Abstract: A device for detecting deformations in solids includes a casing constructed and arranged to be insertable in a solid. The casing has walls defining a substantially closed container. The container has an inner dividing wall separating the container into an upper enclosed section and a lower enclosed section. A fluid substantially fills the lower enclosed section and is in fluid communication with the interior walls of the lower enclosed section. A first strain-sensing system is in fluid communication with the lower enclosed section of the container such that deformation of the walls causing pressure changes in the fluid are detected by the first strain-sensing system. A second strain-sensing system is disposed in the upper enclosed section. The upper enclosed section is at least partially filled with fluid. A valve fluidly couples the second strain-sensing system to the lower enclosed section.