This paper presents a methodology for determining the uniaxial and triaxial compressive strength of heterogeneous material composed of dacite (D) and altered dacite (AD). A zone of gradual transition from altered dacite to dacite was observed in the rock mass. The mechanical properties of the rock material in that zone were determined by laboratory tests of composite samples that consisted of rock material discs. However, the functional dependence on the strength parameter alteration of the rock material (UCS, intact UCS of the rock material, and m_i) with an increase in the participation of “weaker” rock material was determined based on the test results of uniaxial and triaxial compressive strength. The participation of altered dacite directly affects the mode and mechanism of failure during testing. Uniaxial compressive strength (σ_ci^UCS) and intact uniaxial compressive strength (σ_ci^TX) decrease exponentially with increased AD volumetric participation. The critical ratio at which the uniaxial compressive strength of the composite sample equals the strength of the uniform AD sample was at a percentage of 30% AD. Comparison of the obtained exponential equation with practical suggestions shows a good correspondence. The suggested methodology for determining heterogeneous rock mass strength parameters allows us to determine the influence of rock material heterogeneity on the values σ_ci^UCS, σ_ci^TX, and constant m_i. Obtained σ_ci^TX and constant m_i dependences define more reliable rock material strength parameter values, which can be used, along with rock mass classification systems, as a basis for assessing rock mass parameters. Therefore, it is possible to predict the strength parameters of the heterogeneous rock mass at the transition of hard (D) and weak rock (AD) based on all calculated strength parameters for different participation of AD.

The bucket-wheel dredge “Kovin I” for underwater coal mining with bucket-wheel type UCW-450 has been in operation for over 20 years. Based on analyzing the bucket-wheel dredger performance, productivity, maintenance costs, and reliability, a rational decision was made: to rehabilitate the most essential parts of the dredge, including the bucket wheel and the gearbox. However, the selection and construction of the excavator parts were performed on the ground of available laboratory data for digging resistance. The data itself was determined by the testing methodology that did not include the influence of surrounding water pressure at a certain depth of mining. According to the previous findings, it was necessary to develop a specific research and testing program that would involve appropriate laboratory testing of the geomechanical parameters. These were to represent the influence of hydrostatic water pressure on the working environment—coal. Nevertheless, geomechanical laboratory research tests were initially modified to provide reliable data of cutting resistance, especially in the water under different hydrostatic pressures, fully simulating the “in situ” working conditions of mining, i.e., cutting.

For the purpose of continuous production design in the deeper levels of underground mine JAMA Bor, at first the rock stability analysis of ore deposit 'Borska Reka' was performed before beginning of design the exploitation. Analysis was performed on the designed roadway model at the XVII level in ore deposit Borska Reka, with the scope of confirmation the relevance of data collected from previous research and studies. Analyses presented in this paper were performed by using software package Phase2, Rocscience Inc., which calculations are based on stress-strain condition analysis with finite element method to analyze behavior of rocks. It can be used for a wide range of engineering projects.

The mechanical behavior of the deposited clastic rocks can be observed and determined by analyzing the orthophoto images of unmanned aerial vehicles. Through the form of tension cracks on the front and body of the landslide, which is developed along the working slope of the landfill, the angle for the correction of the residual angle of internal friction can be determined. Calculations of slope stability should be performed with corrected values of the residual angle of internal friction, because it is a question of loose, saturated mica-dusty-sandy and weakly clayey materials. In this work, a series of cabinet experiments was conducted to determine the influence of crack shape on the strength parameters of deposited clastic materials. The results of the research indicate that the shape, length and frequency of mutually parallel cracks, created by the effect of eastern winds or Košava, associated with precipitation and vibrations can indicate the depth of the sliding plane and the angle of internal friction, as well as the overall fracture mechanism. Using statistical regression and optimization techniques, empirical relationships were derived to predict shear strength parameters as a function of crack geometry. The obtained results could contribute to a better understanding of the mechanical degradation of clastic rocks and provide a basis for an improved choice of parameters in the modeling of working slopes in landfills.

The uniaxial compressive strength (UCS) is one of the most important strength parameters for evaluating the mechanical behavior of rocks and is widely used as a fundamental input in rock mass characterization systems, empirical classifications, strength criteria, and various engineering design and calculation methods. Weak rocks, such as marls, exhibit a pronounced sensitivity to water content, which can significantly influence their strength and deformation characteristics. This paper investigates the correlation between water content and the reduction in UCS of marl samples. A series of laboratory tests were conducted on specimens with varying water contents. The results show a clear inverse relationship between water content and UCS, with strength decreasing progressively as water content increases. This reduction is attributed to the weakening of interparticle bonds, softening of the clay matrix, and increased pore water effects within the rock structure. The experimental data were analyzed to establish empirical relationships between water content and UCS reduction, providing a basis for predicting strength degradation under different environmental conditions. The findings highlight the critical role of water content in controlling the mechanical behavior of marls and emphasize the need to account for water content in geotechnical design and stability assessments in marl formations.

The Drmno opencast mine, located near the Danube and Mlava rivers, relies on the selection of an appropriate dewatering method. The stability of the final slopes of the mine is influenced by this choice. In this paper, the final slope stability of the Drmno opencast mine is analyzed using two characteristic profiles and three types of dewatering.