The Moinho (windmill) complex sulphid orebody has got structural conditions of being exploited by methods of great production capacity. This paper is a summary of all the mining practice at Pirites Alentejanas: the mine planning, the rock mechanics and production use modern tools and technics, the teamwork and the integration of the different areas make a rational exploration possible, with positive results when compared with other similar operations.
Le gisement du Moinho (moulin a vent) de sulfures complexes a des conditions structurales pour être explote par des metodes de grand capacite de production. Cette comunication est urn sommaire de toute la practique miniere developpe par Pirites Alentejanas: la planification miniere, mecanique des roches et production utilize des moyens et techniques modernes. Le travail d'equipe et l'integration des differents departements, rende possible une explotation racional, optimizee, avec des resultats positives et competitives, comparables a ceux la d'autres mines similaires.
Das lager der Moinho (Windmuehle), aus vielfaltigen sulfid, hat strukturelle Möglichkeiten mit methoden aus grober produktion sfahigkeit erforscht zu werden. Diese mitteilung ist eine zusammen fas sung bergwerksdurchfuehrung von Pirites Alentejanas: die bergwerksplannung, gesteinsmechanik und produktion gebrauchen moderne werkfenge und techmiken, die gemeinschafsarbeit und die integration der verschiedenen bereiche verursachen einer rationale bewirtschafunfmit positiven und ergebnisser, wenn mit anderen, gleicharhigen bewirhcheltungen verglichen.
Pirites Alentejanas is a mining company that has been exploiting since a very long time different sulphide orebodies of copper, lead and zinc, such as: S. João, Algares, Feitais orebodies (nowadays Moinho and Gaviao in the future). All the orebodies are located in the Iberian Pyritic belt of Portugal and constitute a reserve of more than 170MT. The production of Mina do Moinho is nowadays of 1.2MT and probably it is going to be increased soon to 1.6MT. During three decades the Cut-and-Fill was the mining method used in Aljustrel. Through its evolution were achieved big stopes (130m × 30m), that induced us to think about methods of greater productivity. The Moinho orebody has got structural conditions to be explored by such methods, because it is a mineralized subvertical (70°) mass (500 × 60 metres), with very good geomechanics caracteristics. The SubLevel Stoping was thought as a first project, to increase the capacity of the mines in the late seventies and its final conception, took in account the technological evolution available at the end of the 80s. The lay-out must consider the expected cut off grade, the required number of stapes, the introduction of technologies and equipment of high productivity, usually related to surface mine exploitations, and a high performance in each operation. The easiest way to concentrate the means is to work with high geometrical scale operations, i.e., large drilling and blasting patterns, great capacity of mucking and transport. These operations must be efficaciously planned, performed and controlled. If this trinomial is fullfilled in each operational mine stage, the whole work will also be efficacious. The result performances and mine costs obtained up to now allow us assert to that the exploitation of Mina do Moinho in Aljustrel is a success of the Portuguese Mining Engineering. The actual stapes dimensioning took in account the previous experience of the old stapes of cut-fill.
The stope preparation was made so that the three chambers of each level should coincide in the same vertical plane. Blasthole drilling is approximately 30m downwards and parallel.(Fig. 2). The technology chosen was the downhole hammer with a working pressure of 18 bars.