Room-and-Pillar Mining of Hard Rock the length the pillar area This leaves an opening every other of can be blasted. The pillars are the panel pillars shot two at a time using the same drilling pattern as previously mentioned. Once six pillars have been blasted and loaded out, the open stope is sealed at the end, and uncemented cycloned mill tailings are piped in to fill the void, thus eliminating any potential air blast. The pillar extraction sequence then begins again.