ABSTRACT:

The impact of stress on the performance of underground excavations is well understood and widely accepted. A large database of direct in situ stress measurements now exists in Australia for both complexly folded and faulted hard rocks and flat lying sediments. The paper draws on databases gathered by the authors in the Yiligarn Craton region of western Australia, and in the Sydney and Bowen coal basins of eastern Australia. The density of the data in these areas is now sufficient to allow regional trends to be defined and used here to examine potential mechanisms that control stress regionally and with depth in widely different geological environments.

INTRODUCTION

The in-situ state of stress existing in a rock mass is widely recognised as being of major importance in the performance of excavations in rock. The inherent variability of stress fields associated with complex geological environments has meant that when information is required, the usual resort has been to sitespecific measurements. This situation is likely to continue, albeit that as the volume of rock stress data grows, the prospect of making a reasonable prediction of the stress field at a given location increases. Many of the Australian data sets that have become available in recent times tend to be concentrated within identifiable geological domains. This improves the potential for prediction within a domain, if not between domains. With the increasing density of data, it has become possible to place the results of stress measurements within the relevant geological framework. This paper explores the relationship between rock stress and the prevailing geological environment for some regions in Australia for which relatively dense and reliable data sets are available. The ability to make predictions of stress is discussed, as well as the nature of any common features between the regions.

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