This type of blasting is virtually benching on a large scale. The depth and
burden of the holes are much greater, and in consequence, the hole diameter
must also be increased to ensure sufficient concentration of the explosive
charge. Wellhole blasting is used in limestones esp. if the beds are horizontal
and well-defined. It is not often used in highly abrasive igneous rocks because
of the cost of drilling. Fraenkel
Source:
Dictionary of Mining, Mineral, and Related Terms
