Extracting and copper production on a large scale generates large volumes of postflotation mine tailings. The scale of operation and development of tailings storage facilities (TSFs) forces the use of innovative solutions enabling safe storage now and in the future. Any changes to the operation require multi-directional monitoring of the impact of these changes on storage safety. The ongoing exploitation will be ensured by expansion of the TSF and a change in tailings storage technology. This approach will preclude the need for changes to the new location, such as changes of land use, and will minimise the volume of mine waste. The paper presents the results of pilot studies carried out to implement the change in postflotation tailings storage technology at Żelazny Most TSF (Poland) in the future. The aim of the paper was settlements prediction of tailings and comparison of deformations with observed settlements. Settlements prediction of tailings was made on the basis of the results of the DMT (Marchetti Dilatometer Test), recommended for the prediction of natural soil settlement. Depending on the analysed zone of the TSF, settlements ranged from a few centimetres to over 1.5 m. Despite the difference shown, the results of DMT and geodetic measurements indicate a convergent trend of settlement.