Hydro-mechanical response of a fractured granitic rock mass to excavation of a test pit — the Kamaishi Mine experiment in Japan

A thermo-hydro-mechanical experiment was conducted in a fractured granitic rock mass at the Kamaishi Mine in Japan. The experiment consists of the excavation of a cylindrical test pit on the floor of an experimental drift. The test pit was then filled with bentonite with an embedded heater. During the excavation of the test pit, the hydro-mechanical response of the surrounding rock was monitored. This paper presents the efforts of four research teams to numerically simulate the hydro-mechanical response of the rock mass during excavation. While the total inflow rate to the test pit, the flow distribution on the pit walls and the displacements in the rock mass away from the pit could be reasonably predicted, the pore pressure in individual boreholes, and the expansion behaviour of the pit were less successfully simulated. The reasons for these discrepancies are discussed in the paper.