Optimierung der Exploration, Gewinnung und Materialcharakterisierung von Naturwerksteinen

Abstract

Since antiquity dimension stones have represented the embodiment of values like preciousness and longevity. The last several decades were characterised by a continuous growth in the use of dimension stones for building and ornamentation because of the diversity in the colors and structures. Due to the rapid development of the extraction and processing technologies for dimension stones, special requirements concerning the quality and dimensions of the extracted raw block material exist. Detailed geological investigations for characterising potential dimension stone deposits and the optimised utilisation of the resources have to be the aim when regarding both the economical as well as the ecological aspects. The first part of this research describes the methodological basics for optimising the quarrying and utilisation of dimension stones. Based on detailed studies of the discontinuity systems and its effect on the fragmentation of the rock masses, possibilities have been developed to adjust the excavation of the raw blocks to the prevailing geologic setting. Using theoretical and practical examples it could be demonstrated, that a fundamental geological investigation has to be carried out to increase the effectiveness of quarrying and processing of rock material, which also exerts a positive influence on the profitability of a deposit. Moreover, detailed knowledge of specific physical and technical properties is essential, since they control the behavior of the rock when being utilised for different applications, and are thus a contributing factor to the quality criteria of cut stone. Statistical analyses have been carried out on data collected from more than 2,300 rock varieties, where it was possible to define specific domains for most of the important parameters in the different lithologies. To evaluate the experimental data in a qualitative as well as quantitative way, statistical means have been developed and applied. The statistical methods are used for the prediction of the technical behaviour, which is based on parameters that can be determined in an easy and cost-effective way. The second part of this research applies the basic methods to two case studies concerning the assessment and evaluation of dimension stone deposits at different stages of exploration. Dimension stone deposits consisting of magmatic, metamorphic and sedimentary rocks in Argentina were studied in detail with respect to their depositional environment. The objective of the study is to create a general catalogue of commercial grades, whereby the assessments were mainly done by lithological, structural and geotechnical analyses. Investigations such as these are useful for the decision-making process and for the continuing development of a national dimension stone industry. For the rocks investigated the experimental data of the geotechnical properties are compared with the predictive values derived from the statistical analyses. Statistical approaches show that a preliminary estimate of the rock properties can be made, however specific structural elements have to be taken into consideration. In southern Tanzania, the second study deals with a dimension stone deposit, where the exemplary investigation and evaluation of a dolomite marble exposure is assessed within the framework of market-based criteria. The detailed studies of discontinuity system and rock properties at this location were combined to include more factors related to the quality of raw material and its variability in the deposit as well as to specific rock structure elements. The present work shows that detailed structural and lithological investigations based on geoscientific methods are essential in order to increase the effectiveness of exploration, extraction and utilisation of resource dimension stones.