Is soft rock also non-abrasive rock? An evaluation from lab testing campaigns

Soft rocks are traditionally regarded in terms of low uniaxial compressive strength (UCS <25 MPa). However, other geomechanical and geological properties such as mineralogical composition, and microstructure should be considered when characterizing the properties of soft rocks. The term soft rocks includes a broad variety of rocks coming from various geological origins. Fabric and state of weathering control inherent anisotropic properties of strength and abrasivity of the various rock types. In this study, a suite of rocks from different geologic settings in the Austrian Alps and surrounding countries is analyzed to evaluate connections between the UCS, CERCHAR Abrasivity Index (CAI), and mineralogical composition (equivalent quartz content - FEQu) with emphasis on soft rocks. It is shown, that in order to assess the properties of soft rocks more accurately, the classification scheme can be expanded beyond the simple UCS approach by including mineralogical information and abrasivity values. This holistic approach more adequately captures the breadth of soft rock properties and allows a differentiated distinction of soft rocks in terms of strength and hardness.