Theory 19/Rock Mechanics
Brittle-to-Ductile Is a Pressure Ratio
The claim
The brittle-to-ductile transition in rock is set by the ratio of pore pressure to confining pressure rather than by depth.
01The mechanism
Effective stress controls whether microcracks can propagate; when pore pressure approaches confinement, effective stress is too low to sustain brittle failure.
02Predictions
- P1Transition should track the pressure ratio.
- P2Depth alone should mispredict across pore-pressure regimes.
03Refutation
Transition tracking depth would remove the pressure ratio.