Fuzzy Risk-Based Maintenance Strategy with Safety Considerations for the Mining Industry

Enterprises today are increasingly seeking maintenance management strategies to ensure that their machines run faultlessly. This problem is particularly relevant in the mining sector, due to the demanding working conditions of underground mines and machines and equipment-operating regimes. Therefore, in this article, the authors proposed a new approach to mining machinery maintenance management, based on the concept of risk-based maintenance (RBM) and taking into account safety issues. The proposed method includes five levels of analysis, of which the first level focuses on hazard analysis, while the next three are connected with a risk evaluation. The final level relates to determining the RBM recommendations. The recommendations are defined in relation to the three main improvement areas: maintenance, safety, and resource availability/allocation. The proposed approach is based on the use of fuzzy logic. To present the possibilities of implementing our method, a case study covering the operation of selected mining machinery in a selected Polish underground mine is presented. In the case of mining machinery, fourteen adverse-event scenarios were identified and investigated; general recommendations were also given. The authors have also indicated further directions of research work to optimize system maintenance strategies, based on the concept of risk-based maintenance. Additionally, the discussion about the implementation possibilities of the approach developed herein is provided.

Sublevel stoping with applying artificial hardening stowing pillars for extraction of veins in complicated geotechnical conditions

In the process of underground mining of deep levels rock pressure can appear in any form, creating a serious threat to the lives of miners, disrupting the normal course of mining works and reducing the efficiency of mining production. The solution of the problem of rock pressure control becomes very urgent for underground mines developing vein deposits at a depth of more than 250 m. The aim of the study is the development and justification of mining methods to provide safe and efficient mining of deposits in complicated mining and mechanical conditions. In this paper, the factors of redistribution and dangerous concentration of stresses in the mined ore mass were identified, the methods of rock mass management in complicated geotechnical conditions were studied, and their advantages and disadvantages were revealed. It was determined that the sublevel stoping with the combined use of existing methods of rock pressure control and applying selfpropelled mining machinery is currently one of the most promising method finding widening application scope. In the context of Zarmitan gold ore zone the options of technological schemes of the sublevel stoping method were considered, providing for a combination of different methods of rock pressure control, allowing to minimize the disadvantages of one method through using the advantages of other ones. We proposed sublevel stoping options with artificial polygonal pillars and with artificial columnar pillars, which allowed to reduce ore losses in inter-stope pillars, arch pillars, and secondary dilution. In addition, artificial pillars, taking compressive/tensile stresses, prevent their concentration and create safe conditions for extraction at adjacent and underlying levels.

Fatigue lifetime correction of structural joints of opencast mining machinery

Opencast mining machinery represents a group of large-scale individually manufactured technical objects operated with long-life requests. Since their manufacturers are obliged to provide product that will reach declared time of life, fatigue strength and durability conditions have to be taken into account for superstructures to meet the requirements. The paper highlights main problems occurring while assessing fatigue lifetime during design. Firstly, the short survey of current state of the art regarding the approach to this problem is presented. Secondly, the most important reasons of unsatisfactory accuracy of the assessments are discussed. As a main objective of the study, the authors introduce the unique method of continuous fatigue lifetime correction for the welded superstructures during the machine lifecycle, as a remedy for this group of machinery. Furthermore, results and experience from adapting the approach in real object are presented, including fatigue lifetime correction due to the real intensity of loading acquired from a bucket-wheel excavator during its longlasting operation. It is expected that proposed procedure can help to improve credibility of fatigue lifetime assessment of heavy earthmoving machinery