Fig. 4

Stress-strain relationships of all experiments, comparing samples exposed to \(\hbox {H}_2\)/brine and brine-only conditions, each tested under varying confining pressures (\(\hbox {C}_\textrm{p}\)). The shaded rectangle indicates the general region where cycling occurred across tests. The inset shows a representative experiment (YF12) and marks: A–the start of cyclic loading, B–the end of the last cycle, and C–the subsequent monotonic phase in which the deviatoric stress is increased to failure. Because cycle start and finish vary among tests, markers are shown only in the inset rather than on every curve.