Model experiment of rock blasting with single borehole and double free-surface

Abstract

In order to improve the quality of laneways and tunnel excavation by drilling and blasting and by making effective use of explosive energy, a model experiment of rock blasting with a single borehole and a double free-surface was performed with the objective of studying the effect of parameters such as charge structure, free-surface and rock compressive strength on rock blasting. The model experiments indicate that: 1) the smaller the rock compressive strength and density, the more distinctive the cavity expanding action by blasting; 2) the powder factor in an air-decoupling charge structure is larger than that in a coupling charge structure, i.e., the explosive energy in an air-decoupling charge structure transferred to the rocks is less than that in a coupling charge structure; 3) a free-surface improves the utilizations of explosive energy; 4) an air-decoupling charge structure helps to maintain the integrity and stability of wall rock in controlled perimeter blasting, such as in roadways and tunnel excavation by drilling and blasting.