Dynamic back-calculation of the collapse of the Saint-Maximilien mining field during mining on rock salt in Varangéville (1873)

The mining field within the 11th seam was developed in a room-and-pillar method with squared pillars of 6 m × 6 m and a mined height of 5.5 m. Drift width were 8 m in SW-NE-direction and 9 m in the perpendicular direction. A 29 m × 40 m shaft safety pillar was left in the center of this mining field (Fig. 1). The extraction ratio was 82%. Mining operation was realized by pre-cuttings with waterjets followed by blasting. The water dissolves slots from the rock salt which leads to better blasting conditions. Otherwise, the water causes weathering of the underlying marl layers.