Multi-stage plug for creating air chambers in blast holes in underground mining

Abstract

The present invention relates to a multi-stage plug for creating air chambers in blast holes used in underground mining, tunneling, civil engineering, and demolition. The invention comprises two or more interconnectable modules, each incorporating conical plugs selected from finned helix plugs, plugs with wavy folds, and plugs with zigzag folds. The modules are joined by rigid spacer bars or tubes that allow for progressive adjustment of the air chamber length according to the blast design. The plugs are made of resilient plastic material that elastically reduces its diameter during insertion into the blast hole and subsequently creates a harpoon-like locking mechanism against the inner wall of the hole. This mechanism simultaneously forms the air chamber and retains the explosive within the blast hole, particularly in vertical or oblique overhead blast holes.