Evaluating the strength and deformability of sandstones

Abstract The mineralogy, texture and wave velocity characteristics of a range of sandstones were studied to aid the understanding and prediction of geotechnical properties. From a consideration of volumetric strain variations it is apparent that the weaker rocks display a behaviour markedly different from the stronger rocks. In the weaker rocks, the elastic range is limited to very low stress levels. The sensitivity of the strength and volumetric strain to sample moisture content has also been evaluated and shown to be an important variable in rock deformability behaviour; a decrease in moisture content tends to suppress the onset of dilatancy and microcracking, leading to an increase in peak strength. Microscopic characteristics, in particular in the areas of grain contact and cementation, were successfully used to explain the strength and deformability behaviour of a wide range of sandstones. Practical index parameters for assessing the strength and deformability of sandstones are outlined. Characterization by S waves shows potential as a complement to the index tests of saturated moisture content and point load for weak and strong sandstones respectively.