Engineers Australia

Tasmanian Rock Stress

P. B. Hills

Abstract

The first rock stress measurements undertaken in Tasmania formed part of an exhaustive and innovative study to create Tasmania’s first underground hydro-electric power station at Poatina in the central north of the State in 1960 (Endersbee and Hofto, 1963). Those were two-dimensional measurements undertaken using flatjacks. The first three-dimensional stress measurements in Tasmania were undertaken at the Dolphin Mine on King Island using CSIRO hollow inclusion (HI) Cells in 1975 (Worotnicki and Walton, 1976). Since then, the majority of stress measurements in Tasmania have been undertaken using HI Cells at mines and civil construction projects on the West Coast. However, innovation has remained a theme, and many techniques have been trialled for various reasons over the years, and these trials continue today.

The purpose of writing this paper is to collate the results of Tasmanian rock stress measurements and present them in a usable form for the majority of readers. A key requirement of the presentation was to be able to compile the results into a single data set. This was achieved by reprocessing all data to a common reference. Results are reported relative to true north. Where possible, results were reprocessed from the original measurement data. To the best of the authors’ knowledge, this paper documents all Tasmanian two- and three-dimensional virgin rock stress measurements, extant at the time of writing.

Not discussed in this paper, the World Stress Map includes a dozen or so stress observations derived from petroleum wells in the Bass Basin east of King Island. These represent the only records from within the Tasmanian jurisdiction included in the World Stress Map released by Heidbach el al. (2016).