[en] Trenching of the floor in the mine caused redistribution of the stresses around the mine openings. Since the pillars had already been loaded, no significant additional load was added to the pillars during floor excavation. From the data, it was evident that the general floor area of the excavation was structurally competent. The true pillar creep rate of 1 to 2 microinches per day would have allowed a larger trench cross section. The pillar skin showed no visible evidence of damage