DEVELOPMENT OF FRACTURE NETWORKS BY SHEAR: EXPERIMENTAL RESULTS.

The growth of networks of shear fractures is explored in experiments with samples of wet clay subjected to plane strain deformation in a rigid apparatus. The individual fractures grow longer by three mechanisms: in-plane propagation, off-plane propagation and coalescence. The calculated length parameters in the experiments as well as in three field cases discussed, suggest that the fundamental parameters in fracture analysis are the normalized cumulative length and the length of the shortest fracture measured.