R. Meyer J. Köhler A. Homburg Explosives

Permissibles; Permitted Explosives
Fig. 20. Slotted mortar.
The slot does not extend over the whole length of the borehole and
does not begin at the mouth of the hole.
A specially dangerous condition can arise when several shots are fired
in one round by means of electric delay detonators. A preceding shot
may then break the coal of another hole or even cut off the whole
burden of the charge in question so that it is partly or completely
exposed. This condition is simulated in the angle-mortar test.
Fig. 21. Angle shot mortar.
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A steel cylinder of 230 mm (9 in.) diameter and 2 m (~1/2ft) in length
with a right-angled groove is positioned in the gas chamber of a testing
gallery against an impact steel plate at given distances and different
impact angles, as shown in Fig. 21. Trains of several cartridges or of
the full length of 2 m are placed in the groove of the angle and fired
into the methane-air mixture.