Controlling blast energy parameters to ensure intensive open-pit rock fragmentation

Abstract

Controlling blast action, in order to increase its energy efficiency in a production blasthole is quite an important issue. This is because it enables the formation of broken rock mass with preset coarseness parameters. Increasing the blast pressure and the time of the blast impact on a rock mass is traditionally recommended as one of the ways to improve the blast action on the rock mass, thus reducing the oversize yield in open pits. One device which enables this approach to a certain extent is a turbulator. The turbulator is fabricated of aluminum plate twisted in a helical fashion around its longitudinal axis. It is mounted in a production blasthole according to a specially designed scheme. The methodology developed to study the stress and strain state of a rock mass when using a turbulator in a blasthole explosive charge allows the size of radial fracture zone and the radius of rock fragmentation to be defined. A method was developed to initiate blasthole charges in a pit blasting block. It includes drilling blastholes, filling them with explosive, installing downhole blasting caps, and blasting using non-electric initiation system. A blasting block is divided into two equal parts (sections), which in turn contain three series of blastholes for short-delay blasting. Blasthole charges are initiated simultaneously in the two parts of the block based on a trapezoidal blasting pattern, thus ensuring meeting detonation waves. In the first series, instantaneous blasting of blastholes located on both ends of the blasting block and forming a trapezoid (in plan view) is carried out. Then after 42 ms, the second series of blastholes (also forming a trapezoid) is detonated. After another 42 ms, the remaining blastholes are detanoated along the perimeter of the blast block in the third series. Implementation of this design with the effect of turbo-blasting for rock fragmentations by blasthole charges at the Kalmakyr deposit of JSC “Almalyk Mining and Metallurgical Complex” has led to the reduction of consumption of explosives, volume of drilling, secondary fragmentation costs, and increased productivity of excavators and mining safety.