25 March 2026 - 26 March 2026
Following the tragic collapse of the Coalbrook Colliery in 1960, Salamon and Munro published their well-known equation for pillar strength in 1967. This equation became the statutory basis for coal pillar design and was later adapted for use in hard-rock mines. In the years that followed, further collapses occurred, fortunately without loss of life and the statistical database of collapsed pillars used by Salamon and Munro continued to grow. There are now 85 documented collapse cases, compared to the 27 available in the 1960s. It also became apparent that not all coal has the same strength. The Vaal Basin, for instance, is notorious for its weak coal. Additional methods of statistical analysis were subsequently developed.