Experimental and numerical investigations of cracking onset time of Nkolomdom's (Cameroon) gneiss rock, during its breaking by a non-explosive expanding material

Abstract

In this paper, a non-explosive expansive material (NEEM) is used to fragment gneiss rock. The main objective is to evaluate the minimum cracking time (TOC) of this rock. For this, 45 rock blocks are selected and fragmented using the expansive cement blasting method. The minimum time for cracking to appear for each sample is studied. The multiple parameter linear regression method is used to establish a mathematical model of the minimum time for cracking to appear as a function of five parameters, namely the diameter of the borehole, the spacing between two holes, the ambient temperature, the temperature of the mixing water and the quantity of mixing water. The established model is then used to optimise this minimum cracking appearance time by the genetic algorithm method. The experimental result revealed a minimum time of 6 hours. A correlation coefficient of 0.804006634 is obtained with the established model. Optimisation by genetic algorithms (GA) revealed a minimum crack appearance time of 2 hours and 39 minutes.