Prediction of the life expectancy of organic covers

The present paper aims to predict the life expectancy of organic covers, un der various climatic conditions, when established over reactive sulphide wa stes. Prediction is enabled with the use of a computer program that analyze s and interprets experimental data derived from laboratory tests, regarding the application of an organic cover over reactive unoxidized arsenopyrite concentrate. The life expectancy of organic covers can be predicted by establishing thei r potential to prevent influx of air into the underlying reactive sulphide mass. Influx of air can be calculated by recording O-2 concentration in por e air, which is directly related to the moisture content (m) within rite or ganic material, The moisture content, in each area under study, depends mai nly on rainfall rate (w) and on organic material width (h). By correlating these two parameters, provided that the initial moisture content is known, the moisture content within the organic mass, as well as its monthly variat ions, can be accurately predicted over long periods of time. The methodology used for the prediction of the life expectancy was based on the study of the relationships, which are considered as critical for the e ffective operation of an organic cover, namely (a) monthly moisture content change vs, monthly rainfall rate and width of the organic cover and (b) O- 2 concentration vs. moisture content. Finally, two case studies examining the application of organic covers over reactive sulphide materials are presented and discussed. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.