Scheduling by Pushbacks: A historical review of optimization approaches for strategic open pit mine planning

Since the 1960s, the Scheduling by Pushbacks methodology has been the cornerstone of strategic open-pit mine planning, providing a structured way to balance operational feasibility with economic value. This paper offers the first comprehensive historical review of the methodology, with a focus on optimization methods, drawing on academic literature, industry conference proceedings, software manuals, doctoral theses, patent filings, and interviews with early developers. We highlight how early computational limitations gave rise to optimization-based heuristic approaches such as nested pit parameterization and cutoff grade optimization. We examine how these approaches were transformed into practical planning methods that flourished into a rich software industry, producing tools that remain widely adopted to this day. Finally, we trace how these methods have evolved to adopt modern integer programming approaches, enabling the solution of much larger and more detailed models, thereby increasing project value and reducing computation times. Our contribution is to bring these developments together in a review that shows how the various models and algorithms fit within a common framework and notation, highlights key methodological contributions, clarifies the range of approaches offered today in both academia and industry, and discusses current challenges, including producing mine plans that respect operational requirements such as minimum widths and ramp access, and integrating environmental constraints into scheduling.