For marble underground excavation it is important to develop a collection of procedures, rules and models in order to collect information to build a database, making it usable and available to all users so that they can make decisions. The information must be based on technical and economic criteria, during the lifetime of the excavation and after the close down of the mining activities. The case study presented using this methodology is a marble underground extraction, localized in the region of Estremoz/Borba/Vila Viçosa, Portugal.
The Estremoz/Borba/Vila Viçosa marble region has a number of characteristics that creates difficulties on a long/medium underground quarry planning. In small areas inside a quarry, several parameters change, sometimes apparently without rules. For example, even if mechanical characteristics are quite constants, with very small variations, the highly fracture density (that leads to a large quantity of different dimensions and forms of blocks) and the changes in colours both in matrix and veins are very frequent, being very difficult to get large stocks of marble with the same mechanical/commercial/aesthetic characteristics. As well known, the price of marble blocks is made accordingly to its geometry, size and especially its colours and colours shape, along with other factors. Basically this is a problem that almost every company that deals with Estremoz/Borba/Vila Vicosa marble has to face. This paper presents one methodology that tries to help this specific Portuguese marble industry with their problems in marble extraction. It is very important to implement an interactive information system for zoning rock masses, to map parameters, like extraction recovery, in actual and in future mining excavations areas. Creation of potential risk maps for evaluation of mechanical or structural instabilities, changes in block dimension and colours, are situations that define the economical risk of marble mining exploitations. The system will inform about potential risk (in a geotechnical and commercial sense); organize monitoring actions and make statistical analysis. This information is fundamental for the decision support system, helping engineering planning, using technical and economical criteria. In underground marble quarrying this type of control is new. Even in surface quarrying the systematic technical-economical control is not yet a common tool. The success of any dimension stone company in Estremoz/Borba/Vila Vicosa cannot be based in simple standard mining planning actions. The decisions have to consider not only structural and mechanical parameters but also commercial factors that market dependent; different clients need certain quantities and specifics types of marble in different times; which are not always available.
For the success of the management procedures of marble underground excavations it is essential to standardize the data monitoring collection and subsequent results treatment procedures during not only the mining activities and also afterwards. In this way, the system could not be affected, even if the teamwork is changed, once the decisions should be based on clear, objective criteria and procedures. These are the reasons that make so important workers technical formation actions and the establishment of monitoring procedures manuals.