Attack of Fortified Places. Including Siege-works, Mining, and Demolitions. / Prepared for the use of the Cadets of the United States Military Academy

by James Mercur

For ordinary earth and gunpowder, when L. L. R. is measured in feet, eqs. (6) and (7) become, respectively:

For an overcharged mine,

C = (1/10)[l + (7/8)(r - l)]3 (6´)

For an undercharged mine,

C = (1/10)[l - (7/8)(l - r)]3 (7´)

8. Giving to l the same value in equations (4), (6), and (7), we have

C´ = C((7/8)[r/l] + (1/8))3, (8)

In which C = charge for common mine with L. L. R. and crater radius = l. C´ = charge for over or undercharged mine with L. L. R. = l and crater radius r. Equations (6), (7), and (8) having been deduced from the relations existing between C, l, and r for mines varying from common mines up to those in which r = 3l may safely be used for overcharged mines up to this limit.[9] In their applications to undercharged mines they become uncertain when r = (½)l; and when r = (⅜)l the computed charge generally produces a camouflet.

These computed charges are:

for r = (½)l, C´ = 0.1779C; for r = (⅜)l, C´ = O.1636C.