Ejection crater

The ejection craterEJECTION CRATER (EN: explosion funnel, blasting cone; DE: Ausbruchtrichter; FR: cone d'arrachement; ES: cono de base; RU: воронка выброса) is the excavation, which is formed within the massif as the result of the destruction and displacement of the rock during the explosion. The major parameter of the ejection crater is the indicator of the action of the explosion:

n = r / W,

where "r" is the radius of the crater, in terms of the metres; "W" is the length of the line of the least resistance, in terms of the metres.

They distinguish the craters with the usual (n=1, r=W, the angle at the apex of the cone is 90 degrees), increased (n=1, r>W, the angle is more than 90 degrees), and decreased (n=1, r<W, the angle is less than 90 degrees) ejections. The volume of the ejection crater within the rocky rocks in case of the explosion of the single charge is determined according to the formula

v = n2W3.

In case of the "v" equal to 0.7, the observable crater on the horizontal exposed surface is not formed, and the action of the explosion is limited to the destruction and fragmentation of the medium. In this case, there is formed the destruction crater, the radius of which is determined according to the radius of the destruction zone on the exposed surface.

The parameters of the ejection crater are placed at the foundation for the calculation of the charges for the explosions for the ejection and fragmentation of the rocks. As the consequence of the local action of the explosion during the drilling-blasting works, the real shape of the crater differs from the calculated shape (see the Figure).

Within the strong rocks, the volume of the compaction zone near the charge is small, and the shape of the crater is similar to the theoretical shape (in case of the explosion of the concentrated charge, the shape is similar to the cone, while in case of the elongated charge, which is parallel to the horizontal surface, the shape is similar to the triangular prism). Within the non-rocky rocks and soft soils, the shape of the ejection crater is similar to the paraboloid or to the truncated cone.