The excavation of a large open pit may be viewed as the artificial production of a slope comparable with the slope of a natural, mountain side. Consequently, examination of the topography and shape of natural slopes in similar materials in the vicinity will assist the engineer, to understand the slope behavior in the pit.
The geology of the materials in the pit should be studied as thoroughly as possible. The general stratigraphy, including dipping and folding of the strata, faults, joint patterns and gouge materials on the joints should be recorded as a continuing operation, starting with the first examination of the ore body.
The aim should be to discover patterns in the occurrence and orientation of these phenomena which will enable the engineers to anticipate the behavior of controlling geological structures behind the working, slopes of the pit.
The degree of homogeneity of the geological materials is of great importance. The presence of weak strata, seams, or gouge in harder materials will often be the controlling factors in stability.
Natural slopes frequently reflect these features. The engineer should try as far as possible to arrange his operations to work with, instead of against, nature. It should be the continuing aim of the pit engineers to find simple criteria, such as indices of drilling speed or the relative ease of digging, for recognizing such weak conditions in the natural soil or rock. The value of these continuing studies, as an integral part of the mining operation, cannot be over-emphasized.
