A project in shale will have an average bench height of $21$ ft$.$ ANFO specific

gravity $0\mathrm{.}90,$ will be the explosive used on the project. Dolomite, specific gravity $1\mathrm{.}3,$ will be

the primer explosive used. The dolomite comes in $10-$in$.$long $1-$in$.$diameter sticks. The

contractor$$s equipment can easily drill $3-$in$.$diameter holes. It is assumed that single rows

of no more than $10$ holes will be detonated instantaneously. The holes will be lined. The

thickness of the lining material is in$.$ To ease the fieldwork all design dimensions should be

in integer numbers $($ft$).$ Calculate an appropriate burden distance for the blast design.

Local regulations require a minimum scaled distance factor, Ds $=50.$

a$.$ Determine the burden distance and spacing of the blast holes for instantaneous detonation.

b$.$ What is the largest total weight of explosives that can be simultaneously detonated based on the

vibration$/$safety distance criteria $($equation $12\mathrm{.}128$th edition, $13\mathrm{.}129$th edition$)$