Rock Breakage Explosions in mining make use of the pressures generated by the explosive gases and the mechanical behavior of rocks. Most notably is the fact that the horizontal/tensile strength of rock is significantly less than the vertical/compressive strength of rock. Going back to the image from the first page, as the explosion is triggered and propagates upward from the hole the gases generate enormous pressure against the sides of the hole resulting in the rock fracturing and the blast wave propagating outwards transferring energy from one rock molecule to the next. At a certain point the energy from the blast wave is not sufficient to break the rock anymore but the wave continues on through the rock mass in the form of vibrations. The confined explosive gases begin expanding into the fractures and cause displacement of the rock. The stemming at the top of the hole does not stop the blast wave but rather helps to confine the explosive gases and divert them to do work on the fractured sides of the hole thus moving the rock.