Civil Engineering and Architecture 11(4): 1835-1855, 2023 http://www.hrpub.org DOI: 10.13189/cea.2023.110414 Large Diameter Holes Presplitting Ahmed Hemed * , Latifa Ouadif 3GIE Laboratory, Mohammedia Engineering School, Mohammed V University in Rabat, Morocco Received February 10, 2023; Revised March 21, 2023; Accepted April 16, 2023 Cite This Paper in the Following Citation Styles (a): [1] Ahmed Hemed, Latifa Ouadif , "Large Diameter Holes Presplitting," Civil Engineering and Architecture, Vol. 11, No. 4, pp. 1835 - 1855, 2023. DOI: 10.13189/cea.2023.110414. (b): Ahmed Hemed, Latifa Ouadif (2023). Large Diameter Holes Presplitting. Civil Engineering and Architecture, 11(4), 1835 - 1855. DOI: 10.13189/cea.2023.110414. Copyright©2023 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Increasing the diameter of drill holes is an option to increase the tonnage in open-pit mines. This explains the appearance of unexpected disorders during drilling and blasting, the consequences of which classically take the form of both instability in the pit walls and collapses affecting the surface. Here, the phenomena observed are located between the slopes of the M'HAOUDATT pit. The disorders inherent in large-scale mining appear on the pit walls. The company operating the pit exploits the benches only with large diameter drills. The objective of this work is to find an optimal method to minimize the effects of the vibration of the blast on the pit of M'HAOUDATT in order to reward the absence of the Presplitting machines. Proposals to limit the effects of blasting were discussed in two aspects, such as reducing the tonnage of explosive in the holes or finding a way to reduce the diameter of the hole, which is considered inappropriate to create stable fronts. We conclude that it is preferable to play on the diameter of the hole and to concentrate on this direction in order to come up with a method to replace the absence of pre-splitting machines in the mine. The method of borehole diameter reduction is considered new for the pit operators. Therefore, it will not be effective in the test phases despite the relevant results after the front blasting. It is important to note the difficulties of replacing small drilling machines in open-pit mines. The implication is the efficiency of the method, the right way of execution and the training of the mine personnel. Keywords M'HAOUDATT, Open Pit, Slope Stability, Presplit, Drill, Blast, Explosive, ANFO 1. Introduction The determination of an optimal slope angle of an open pit, before its opening, is effectuated by taking into account geological and geotechnical parameters, necessary for the stability analysis [1]. The stability angles of the M'HAOUDATT pit are determined through an incomplete geotechnical model, due to the absence of a solid recognition method. Some parameters are therefore estimated. During the deepening of the pit, new information was collected [2]. The analysis of the stability of the slopes requires a detailed examination of the geological and geotechnical parameters of the rock mass. Indeed, these parameters influence the design of slopes, particularly in open pit mines [3, 4]. Slope stability is always influenced by the damage caused by blasting. This damage is evaluated by a damage factor [5]. The factor depends on the degree of perturbation to which a rock mass of variable geological strength index (GSI) is susceptible due to blast damage and stress relaxation caused by pit excavation [6, 7]. It describes the extent to which intact rock modulus is affected [8]. Such degradation of rock modulus and strength can result either from an increase in fracture frequency or from fracture expansion. Both phenomena can be caused by blasting [9].