Tha main objective of this work was to determine the range of temperature, pressure and damage conditions in the crust under which rocks will fracture in a brittle-elastic manner. In order to achieve that objective, we have designed and constructed an apparatus for the measurement of rock fracture properties at high temperatures and pressures, and performed a series of experiments to measure rock fracture and fluid transport properties.
We have designed and manufactured an environmental cell for the measurement of fracture mechanics parameters under high-temperature/high-pressure conditions. The design conditions are: (i) confining pressure up to 70MPa, (ii) temperature up to 450C, and (iii) water as the confining/pore fluid. Due to the highly corrosive nature water under these conditions, it was necessary to manufacture the cell and all its internal components from Hastalloy C (a high-strength nickel alloy developed by the US Navy). The cell, which has an outside diameter of 170 mm and an internal bore of 100 mm.
The cell is designed to take 60 mm diameter "short-rod" fracture mechanics specimens, manufactured to the standard ISRM geometry. Sample are heated by a fixed internal element, and are loaded to failure in tension by means of a small internal hydraulic actuator.