Intensive economic development is associated with an increasing demand for raw materials, including minerals. An illustrative example of this issue is the development of the copper industry. A significant problem arising from the scale of copper production is the management of an ever-growing amount of post-flotation tailings. This necessitates the need to ensure the continuity of safe storage. This study presents the results of studies on the behavior of deposits in the Żelazny Most Tailings Storage Facility (Poland). The primary objective of this study was to estimate the settlements of tailings under variable deposition conditions. The results were assessed using two methods: indirect and direct; this was based on cone penetration test (CPTU) results. The results were verified using Modified Cam Clay (MCC) modeling. Depending on the type of test, settlements ranged from several dozen centimeters to over three meters. Despite the observed differences, the results of both CPTU methods indicate a convergent trend in tailings behavior. Conversely, the results estimated using the direct method and numerical modeling demonstrate a high level of agreement.