Influence of faulting on a mine shaft—a case study: part I—Background and instrumentation

The impact of geological structures on the stability of underground infrastructures is well recognised. Moreover, the influence of major geological structures such as faults, becomes critical when the stability of underground infrastructures which are essential for mine production, are threatened. The X41 shaft is the man and supply shaft at the Copper Mine, at Mount Isa, Australia. Here, there has been observed evidence of degradation manifested by the development of cracks in the shaft concrete lining since the early nineties. In addition, the shaft steel structure is being deformed and needs regular and meticulous maintenance. The shaft degradation has been attributed to the presence of two major geological structures, the W41 and W42 faults, which intersect the shaft in two distinct locations.This paper presents a case study whereby the causes of shaft degradation were examined. The influence of faulting and mining sequence on the stability of the main mine shaft were investigated by means of field investigations and numerical modelling. This paper concentrates on the field investigation performed as part I of this project. It provides a review of work done prior to this study and exposes the past field monitoring practices and those that were implemented to characterise the observed displacement in the X41 shaft.