An amount of explosives, whether it be cylindrical, spherical, etc in
configuration, with a hollow cavity in one face or end is known as a
hollow or shaped charge. When this charge is initiated, a focussing of
explosive energy will occur within this cavity. This focussing, or
concentration of detonation products creates an intense localised force
greater than just the simple detonation of a conventional explosive,
(without a hollow cavity). If this hollow cavity explosive is directed
against a target material this concentrated force is capable of creating a
deeper penetration than the same amount of explosive without the hollow
cavity. If a metallic liner material is used in the hollow cavity, upon
detonation of the explosive this liner will form into a high velocity
penetrating jet. Depending on the explosive type and the liner material's
configuration the jet tip can travel up to 10 km/s. Linear shaped charges were developed using the abovementioned
shaped charge concept but instead of being formed about an axis, they are
elongated and constructed along the principal axis. Therefore instead of
creating a narrow circular penetration jet, it forms a thicker planar cutting
jet ideal for linear cutting purposes. Using Linear Shaped Charges (LSC) for pre-splitting is expected to
result in more accurate directional fracture propagation, while minimising
lateral micro fractures in the surrounding rock mass which is required to
remain undamaged.