## 4 Conclusions  
The analysis of wear levels was performed on the basis of data from 41 copper ore receiving bins installed in 15 retention bunkers. The results confirm previous observations which suggest that the character of the failures and the degradation processes are largely influenced by the bunker operating conditions and by the varying lithology of the transported material (copper ore). The varying physical and mechanical properties of copper ore and the varying parameters of its flow cause the pressures exerted on the hopper walls to vary, and this may be identified as the most significant reason behind the intensive abrasive wear.  
Varying parameters of the transported ore and the specific character of the mining operation do not allow the identification of the influence of the grain size, moisture content, and lithology on the process and on the degree of wear on the elements of the receiving bin. Calculations can only be made with the use of quantitative measures related to average parameters of copper ore. Such measures of failure rates for receiving bins in retention  
Figure 15: Mass indicator values for the elements A, B, C of the analyzed bunkers.  
bunkers may include a number-based failure indicator and the indicator per unit mass of the transported copper ore.  
The analysis of the failures demonstrated that the element most prone to wear and tear is the lining in the bottom of the feeder trough, designated in Figure 2 with symbol A. This element is subject to loads from the falling lumps of ore, while the trough reciprocates simultaneously. The cyclically reversing direction of motion is the obvious reason behind the accelerated wear on this element. Other elements prone to wear include the vertical sealings designated with symbol B, which operate in a zone affected by great speed differences. The movement of ore along the side walls of the hopper at an increasing pressure is caused by the narrowing of the space inside and results in accelerated wear on the lining, i.e., the element C. The failure rate of the elements A, B, and C allows a conclusion that accelerated abrasive wear occurs in areas where relative speed differences are observed in combination with pressure or impact-related loads. Recommendations include the use of appropriate materials, with properties and geometries which would ensure not only increased durability but also similar wear rates of individual elements.  
Based on the number of the observed failures, the design of the receiving bin was demonstrated not to be optimal for the transferring of the increased loads resulting from the current output potential of the mine, and the amount of the transported ore over a unit of time significantly affects the frequency of service works. The identified types of damage, along with the failure rates, indicate directions for the required modernization efforts. The obtained results may be used to verify simulation models. Further stages of this research include using the FEM and DEM tools in order to develop a model simulating the flow of ore through the bunker. The final result of the research will comprise a set of complex design guidelines for new solutions based on local operating conditions.  
Conceptualization, R.K. and M.S.; methodology, R.K., N.S., and M.S.; formal analysis, N.S. and M.S.; investigation, N.S. and M.S.; resources, M.S.; data curation, N.S. and M.S.; writing--original draft preparation, N.S. and M.S.; writing--review and editing, N.S. and R.K.; visualization, N.S.; supervision, R.K.; project administration, R.K.; funding acquisition, R.K. All authors have read and agreed to the published version of the manuscript.  
This research was co-funded with the research subsidy of the Polish Ministry of Science and Higher Education granted for 2021.  
Not applicable.  
Restrictions apply to the availability of these data. Data was obtained from the mining company.  
The authors declare no conflict of interest.