When designing a blast, engineers must consider a variety of factors governing how the blast will proceed, including the burden and spacing. Burden usually refers to the distance between the first row of blast holes and the free face; it can also refer to the distance between the rows of drilled holes. Spacing is the distance between the individual holes within any row.

Surface mining blasting practices have been standardized substantially since the rise of ammonium-nitrate-based explosives and blasting agents. In any blast, particular patterns governed by rock type, soil density, grade, and other factors must are generally followed in order to achieve desired effects. Correct burden and spacing, as well as proper charge density, hole depth and diameter, and timing ensure a blasts’ effectiveness and safety.

Figure: Burden and spacing are two of the basic geometric properties of blast design.