The boulder, rock wall. bottom toe always appear in limestone mine mid deep bench blasting because of bedding, fault, joint and cave.
石灰石矿岩层较多，断层、节理裂隙和溶洞发育，爆破容易产生大块、岩墙和根底。
2
When the dip of bedding is less than the friction Angle of rock, the rock stratum will separate and some rock blocks in every rock stratum may slide along joint surface as a whole.