Abstract Design and engineering facilities are often constructed in complex geological mixtures or fragmented rocks such as mélanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentines. These types of geological materials are generally chaotic and mechanically and/or spatially heterogeneous rock masses, which are composed of relatively strong rock inclusions, surrounded by weaker matrix, and may be considered as bimrocks (block-in-matrix-rocks; Medley, 1994). The preparation of standard and representative cores from these types of rock masses for conventional laboratory experiments is almost impossible. In the literature, there are a few attempts to overcome this difficulty by developing empirical approaches based on case histories and laboratory studies on bimrocks. However, despite these attempts, there is no widely accepted empirical approach in the rock mechanics community. In this study, some conceptual equations, which are open to improvement, were generated by considering literature findings to predict strength of unwelded bimrocks.