With reference to Problems 1 and 2, suppose the pillars are 45 45 ft and that

Question:

With reference to Problems 1 and 2, suppose the pillars are 45 × 45 ft and that a size effect exists such that Cp = C1 (0.78 + 0.22 Wp/Hp). If the mining height changes from 30 to 120 ft, as a sill between two ore horizons is removed, what is the resulting pillar safety factor, all other parameters remaining the same? What is the pillar safety factor if the size effect is neglected?