Mechanical properties of Michigan Basin's gypsum before and after saturation

Mohammadhossein Sadeghiamirshahidi, Michigan Technological University
Stanley Vitton, Michigan Technological University

©2019 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Publishers version of record:


The stability analysis of an abandoned underground gypsum mine requires the determination of the mine pillar's strength. This is especially important for flooded abandoned mines where the gypsum pillars become saturated and are subjected to dissolution after flooding. Further, mine pillars are subjected to blast vibrations that generate some level of macro- and micro-fracturing. Testing samples of gypsum must, therefore, simulate these conditions as close as possible. In this research, the strength of gypsum is investigated in an as-received saturated condition using uniaxial compressive strength (UCS), Brazilian tensile strength (BTS) and point load index (PLI) tests. The scale effect was investigated and new correlations were derived to describe the effect of sample size on both UCS and BTS under dry and saturated conditions. Effects of blasting on these parameters were observed and the importance of choosing the proper samples was discussed. Finally, correlations were derived for both compressive and tensile strengths under dry and saturated conditions from the PLI test results, which are commonly used as a simple substitute for the indirect determination of UCS and BTS.