Study of core disking phenomenon on compact conical-ended borehole overcoring technique; A Case study for measurement in borehole with inflow at Toki Granite

Sato, Toshinori  ; Tanno, Takeo; Hikima, Ryoichi; Sanada, Hiroyuki; Kato, Harumi*

Japan Atomic Energy Agency has been conducting stress measurements by overcoring method, to aiming establish a firm scientific basis for safe geological disposal. Core disking is observed where rock stress measurements are performed by compact conical-ended borehole overcoring technique in the depth of 300 m from the surface at the Mizunami Underground Research Laboratory. In this report, failure initiation of core disking is discussed.