The engineering properties of soils and tailings often exhibit significant anisotropy._x000D_
One area where this has been well documents is undrained shear strength._x000D_
Materials sheared in directions close to the principal stress direction in situ, i.e. triaxial compression, typically exhibit higher undrained strengths than those sheared in other directions such as simple shear._x000D_
Importantly, along the most common critical failure surfaces relevant to tailings stability, whether primarily through tailings or a critical foundation layer, saturated materials are generally much closer to the simple shear loading direction than triaxial compression._x000D_
Therefore, testing undrained shear strength of tailings or foundation soils in triaxial compression is likely to result in overestimation of the relevant strengths for design._x000D_
Although these issues have repeatedly documented in the geotechnical literature for over three decades, they are not appreciated sufficiently across our industry._x000D_
In an attempt to address and highlight these issues, a review is carried out of historical reference to the importance of simple shear loading._x000D_
Attention is then drawn to the techniques applied in three recent post-failure investigations, where simple shear testing was applied._x000D_
Finally, some relevant laboratory test results from a recent project in which the author was involved are outlined.CITATION:Reid, D, 2018. Importance of the simple shear loading direction to the stability of tailings storage facilities, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 274-284 (The Australasian Institute of Mining and Metallurgy: Melbourne).