Fig. 6

Mohr–coulomb failure envelopes on shear stress (τ) versus normal stress (σ) plots for Treuchtlinger Marmor limestone. Legend is the same for all three panels. The pink area labelled R_MC indicates the uncertainty which was estimated based on the repeat experiments. a limestone with water, with a cohesion of 33 ± 5 MPa and a friction coefficient of 0.67 ± 0.07; b limestone with inhibitor 1 (3000 ppm), with a cohesion of 59 ± 10 MPa and a friction coefficient of 0.43 ± 0.11; c limestone with inhibitor 2 (3000 ppm), with a cohesion of 23 ± 3 and a friction coefficient of 1.01 ± 0.05