INTRODUCTION
The Potash Corporation of Saskatchewan Mining Ltd. is the operator of four potash mines in Saskatchewan, Canada. These divisions mine the ore sylvinite, at horizons within the Prairie Evaporite formation. Fuzesy, (1982). The depth of the mining operations at all divisions is about 1000m below the surface. (Figure 1).
As part of the ongoing programme of research and development, it was desirable to evaluate the magnitude and direction of the fairfield stesses in the ore. The evaluation of data was of paramount importance in providing an input to the finite element analysis programme, which was to be used in the mine design problems, Mottahed et a1(1988). Serata obtained some values of the principal stresses using dilatometer type equipment in the Rocomville Division of P.C.S. Mining. Molavi(1987), but because of the propriety nature of the work and fewness of data, there was a need for a new approach to evaluation of these basic parameters.
This paper outlines the methodology adopted and discusses the data from the installation of six CSIRO Soft Hollow inclusion stressmeters, as manufactured by Rock Instruments Pty of Austrailia. The investigation had the clear objective of:
1. Determining the repeatability of the overcoring results.
2. Assessing the effect of creep on the overcoring results.
3. Determining the stress at selected sites.
The selected site was Room W36N 'B' at P.C.S. Mining Allan Division near Saskatoon, for the ease of access, availability of electrical power good ventilation, relative isolation from other workings. Two boreholes were drilled at the site, with hole No.1 on a bearing of 350° 29' 41" and dip of -5° 46' 06" and hole No.2 at a bearing and dip of 353° 40' 35" and -30° 07' 03" respectively. Figure 2.
