This paper presents the technological and structural design solution of a tunnel-shaped underpass constructed for the coal conveyor belt of a combined transport system, serving the Roof Exploitation Zone of the Gacko - Central Field open-pit coal mine. The underpass has a clear opening of 6.1 meters in width and 2.5 meters in height and is positioned at an azimuth of 140 degrees. It is integrated beneath a haul road intended for ultra-heavy-duty mining trucks, specifically BELAZ trucks with a payload capacity of 110 tonnes, used for overburden transport. The underpass is equipped with wing walls on all sides, to ensure structural stability and seamless integration with the surrounding terrain. The solution ensures uninterrupted operation of the conveyor system while maintaining the safety and functionality of the haul road for continuous mining operations.

The drive of the bucket-wheel on SRs1200 excavators is realized by a 400 kW electric motor and a multi-stage gearbox through which power and torque are transmitted from the drive motor to the bucket-wheel. The gearboxes used on these excavators are of a conventional extended design with parallel shafts and pairs of helical cylindrical gears, equipped with a main and an auxiliary drive. The main drive is used during bucket wheel operation, while the auxiliary drive is applied during overhaul activities and inspection. From the input shaft of the main drive to the output shaft, a four-stage gear transmission is formed. In previous designs, the gear on the output shaft was manufactured by casting, while the gearbox output shaft is hollow, allowing the bucket wheel shaft to be mounted through it. The objective of the research is the implementation of two different methods, one theoretical and one practical, for diagnosing the behavior and vibrations occurring in the drive group, with the aim of determining the most optimal approach to operation, maintenance, and necessary reconstruction of the gearbox. The basic diagnostic parameters are vibration values measured at characteristic locations throughout the drive group and its supporting structure. These measurements show good agreement with a mathematical 3D model developed using the Inventor software package, based on the finite element method, the theory of elasticity, and machine dynamics. Testing was performed prior to installation, followed by inspection after a certain number of operating hours, reconstruction of the gear teeth, and testing after reconstruction. A reduction in drive group vibrations of approximately 30% was achieved. The scientific contribution lies in the potential for future development of gearbox condition analysis models based on measured vibration parameters.

The Strmosten brown coal deposit, situated in the northern part of the Senje-Resavica Basin, has been the focus of long-term exploration to determine its reserves, quality, and geological framework. Investigations comprised field geological observations, drilling campaigns, underground workings, and laboratory analyses of collected samples. It was determined that the deposit includes multiple brown coal layers of variable quality developed within the Paleogene succession. Petrographic studies and huminite reflectance analysis reveal the presence of dull to semi-bright brown coals with an average huminite reflectance of 0.45%. The tectonic setting is complex, with pronounced fault structures affecting deposit continuity. Based on the processed data, assessments of on-balance and off-balance reserves, as well as potential mining conditions in the Rembas-Resavica Brown Coal Mine, were performed. The results provide a basis for further planning and economic evaluation of exploitation in the brown coal mine.

This paper presents the technological and structural solution for the reinforcement of the main load-bearing steel structure of the crusher facility at the Drmno open-pit coal mine near Kostolac. The structure in question is part of a coal crushing plant exposed to dynamic and static loads over extended periods of operation. In order to achieve the designed and required granulation of the crushed coal, the crushing plant was reconstructed. As part of this reconstruction, the existing belt feeders intended for feeding the jaw crushers were replaced with plate feeders. Due to the increased load on the structure, the steel structure was reinforced. The reinforcement was carried out using prefabricated HEB steel profiles with welded stiffeners, providing additional load-carrying capacity and improving overall structural stability. The adopted solution enabled continued safe operation of the facility. The paper also discusses the methodology of structural assessment, the installation process, and the effectiveness of the applied reinforcement system.

The process of coal crushing for the Kostolac "B" Thermal Power Plant is carried out at the "Drmno" crushing plant using two hammer crushers of Czechoslovak production (PSP Engineering a.s. Prerov), type KDV 1137, with a nominal capacity of 1350 t/h, an electric motor power of 1000 kW, and a rotational speed of n = 593 min⁻¹ (the circumferential-peripheral speed of the hammers is approximately 49 m/s). This type of crusher requires a specific feeding regime, meaning that the material must be delivered to a designated space between the impact rollers and the rotor. Additionally, the height from which the material falls into the crusher is limited to 2.2 times the rotor diameter. It is crucial that the feeding speed of the crusher remains below 2 m/s and that the material falls precisely into the designated crushing zone. This study examines the selection of the optimal variant for uniform crusher feeding to reduce the uneven wear of the hammers.

This paper examines the costs of mechanized transport used in the construction of exploratory underground corridors over a three-year period. During the execution of the works, data were collected on fuel consumption and spare parts required for the uninterrupted operation of the machinery. Based on the analysis of the collected data on machinery operation, direct dependencies were established between the monthly length of the constructed underground corridors and the operational costs of machinery operation and maintenance for material transport.