Calculation of proper burden

The trial and error method and engineers’ experiences are used for drilling pattern design in most open pit mines. The burden parameter is one of the most important and critical variables of blast pattern design in open pit mines so that other blasting variables are associated with it. The purpose of this research is to formulate the burden parameter for the Chadormalu iron ore mine and generalize the obtained equation to other open pit mines in Iran. At first, the used burden parameter in main pit in Chadormalu iron ore is compared with the existing empirical relations. In this regard, a new relation has been obtained based on data from other open pit mines in Iran. The base of this equation is modification of the Konya relation and consideration for bench height. The result- ing equation has been used in designing and optimizing the southern mass in Chadormalu iron ore mine, which has a different bench height with respect to the northern one. The results include reduction in excavation costs, backbreak, number of boulders in muck pile (respectively 27%, 56% and 67%), elimination of toe problems and increase in excavation rate (36%) in comparison to the primary pattern

Blasting pattern design is the first step in the open pit mining cycle. The minimum distance between the free face and the axis of the blasthole is called burden that is the most important and critical variable in blast designing of open pit mines [1]. The thickness of burden depends on other blasting factors and its variance has great effects on blasting consequences. The effects of this factor are considerable. If the thickness of burden is too little, flyrock and air blast are increased, the rock becomes much more fragmented, a lot of noise is created, and a significant part of the explosive energy is wasted. If the thickness of burden is excessive