International Workshop in “Geoenvironment and 99 Geotechnics”, September 2005, Milos island, Greece Developing Fuzzy Inference Systems (FIS) for the evaluation of multiple- layer lignite deposits M. Galetakis and A. Vasiliou Department of Mineral Resources Engineering, Technical University of Crete, Greece Ch. Roumpos and F. Pavloudakis Public Power Corporation of Greece ABSTRACT The difficulties that rise during the evaluation of multiple-layer lignite deposits come from the deposit structure (alternating lignite layers with intercalated material of varying thickness), as well as from the limitations of the applied selec- tive mining. Thin layers of lignite and interbed- ded waste layers are grouped under specified assumptions regarding thickness and ash con- tent, to form the exploitable blocks. However, in practice the decision for excavating a block is made under subjective constraints of different importance or by using uncertain data. Ad- vances in Fuzzy Inference Systems (FIS) have provided a new approach to the evaluation of multiple-layer lignite deposits. FIS have the ability to handle imprecise or incomplete or lin- guistically ambiguous information and to incor- porate them into decision-making processes. In the developed FIS (Mamdani type) new linguis- tic variables, concerning with working condi- tions, operators’ experience and production were involved. The FIS was used for the estima- tion of quality characteristics and reserves of the exploitable lignite produced from Southern Field mine, Ptolemais (Greece). 1. INTRODUCTION For the exploitation of multi-seam lignite depos- its such as those encountered in the Ptolemais - Amynteon basin, in the area of Western Mace- donia, the continuous surface mining method is used. Large-scale equipment (high capacity bucket wheel excavators, conveyor belts and stackers) is selected to achieve high output rate with low cost per tone of mined lignite. Nowa- days the Western Macedonia Lignite Centre (WMLC) has six large scale open pit mines, which handle 300 Mm 3 of material and produce 57.5 Mt of lignite. The lignite deposits under exploitation cover an area of 160 Km 2 including 4,000 Mt of proven geological reserves and 2,000 Mt of exploitable reserves under the cur- rent economical and technological criteria. It is estimated that the lignite of the Ptolemais- Amynteon basin is sufficient to supply the exist- ing power plants for another 35 years. In 2004 lignite production from WMLC contributed 56.5 % to the total energy production in Greece. The extreme splitting of lignite seams, which are separated by non-lignite layers, called part- ings, makes the selective mining a necessity (Fig. 1). The implementation of selective min- ing procedures as well as discontinuous and/or combined mining methods differentiates the mining technology at the WMLC from the re- spective technology applied in similar opencast lignite mines. The lignite supplied by opencast mines must correspond to the quality require- ments of power stations shown in Table 1. Figure 1: Typical multiple layer lignite deposit.