Figure G-34 shows a block of fine-grained limestone that was experimentally shortened by about 1% at room temperature. Four sets of fractures developed. Fractures of sets ‘‘a’’ and ‘‘b’’ are conjugate shear surfaces (the angular relationship between which can be measured directly on the diagram). Fractures of set ‘‘c’’ are extension fractures that formed during loading. Fractures of set ‘‘d’’ are extension fractures that formed during unloading when the orientation of σ₃ became vertical in the rock-squeezing apparatus. Determine the Coulomb coefficient m for this rock.

Figure G-34

Coulomb coefficient = Explanation 9 03