This study delves into the utilization of an innovative numerical modelling approach to investigate the impact of reinforcing pillars on their strength and stability. Existing case studies in the literature have demonstrated that various methods such as tendon installation, pillar strapping, and the application of shotcrete or thin spray-on liners are commonly employed for pillar reinforcement. However, there is a notable absence of a well-defined methodology for selecting the appropriate support type or determining the necessary support capacity. Consequently, despite the implementation of substantial support measures, certain mines continue to experience pillar collapses. The impact of pillar confinement on a mine wide scale can be analysed thanks to a limit equilibrium model, that was built into a displacement discontinuity boundary element program. The model that incorporates confinement along the pillar's perimeter to replicate how the support interacts with a failing pillar. As part of this study the effects of confining a pillar were analysed and are shown to accurately predict that increased confinement results in a reduced extent of pillar failure.

A comprehensive geotechnical investigation program including geophysical well logging was implemented at an iron ore deposit in Uzbekistan, which targeted at gaining parameters for resource/reserve estimation and mine planning. The deposit represents an asymmetric, approximately ellipsoidal elongated body of about 4.5 by 1.8 km in size. The ore body of vanadiferous titano-magnetite-rich clinopyroxenite is surrounded by metasedimentary strata that form a north plunging synclinal structure, and crop out at three sides of the deposit. Evaluation of the obtained geotechnical data revealed that the project site is generally characterized by significantly varying rock mass conditions. Host rocks are inhomogeneous, foliated and the mechanical properties are directional. The different strata of the surrounding metasediments show high diversity of rock mass properties. For the evaluation of the pit slope stability, kinematic as well as deterministic and probabilistic analyses and a sensitivity analysis were made. In addition to the investigation of potential block failures along discontinuities in the benches, numerical modelling was conducted for the overall pit slopes to evaluate final pit wall stability in the design sectors and assist the mine planning and optimization. It was found that the maximum possible final pit wall angles depend less on the conditions of the ore body rock mass, but essentially on the metasedimentary rocks and dip at the syncline outlines. In contrast, a much steeper overall slope angle that can reach up to the maximum single bench angle would be possible in the north, if leaving a safety pillar of stronger pyroxenite in the slope wall to prevent sliding in the thick Alluvial cover sediments. Based on the findings the mining plan was developed, which included as main tasks the selection of the most suitable mining concept, a pit optimization analysis, mine layout design, mine sequencing, long-term production scheduling, and mine equipment selection.

Early determination of jumbo drill performance is crucial for selecting appropriate mining and civil engineering equipment. Quick and simple laboratory tests are needed for accurate predic-tions of on-site drilling rates. The Sievers’ J-miniature drill test represents thrust and rotation in a rotary-percussive drilling process. Continuous monitoring of drill penetration in these tests provides valuable information on penetration rate–time plots. In our study on sandstones and limestones from an Asturias mining site, miniature drill tests reveal two distinct periods in pen-etration–time curves: an initial period with a peak attributed to drill bit adjustment and a subse-quent stable period, offering a realistic representation of material drillability. Comparing labor-atory test results with jumbo drill performance in the same lithologies opens a new possibility to predict jumbo drill performance.

Úcar's criterion establishes a correlation between the principal stress axes during failure and the compressive uniaxial strength as well as the tensile strength of the rock. Consequently, it can be employed in the "prediction mode" during the initial stages of a project to determine the parameters for the resistance equations using simple compression and tensile tests (such as Direct Tensile or Brazilian tests), yielding a reliable estimate (with a confidence level of over XX%). As the project progresses to more advanced stages, it is generally recommended to conduct triaxial tests on specific rock units. In such cases, Úcar's criterion demonstrates a remarkably accurate fit. This study explores both aspects of Úcar's criterion, utilizing literary and experimental triaxial test datasets (over one hundred independent data sets, covering a wide variety of rock types) to evaluate the level of data fitting achieved. Furthermore, a similar analysis is conducted using the Hoek-Brown criterion, allowing for a comparative assessment of the performance of both criteria. From the analysis of the results it can be seen that the Úcar's criterion, used to predict the rock behaviour (i.e. with uniaxial tests and stresses), compares favourably even with the use of the H-B equations in adjustment mode (i.e. with triaxial tests).

This research studied the size effect and anisotropy of shale strength under polyaxial compressive stress conditions through laboratory experiments. Firstly, this research designed an in-house polyaxial compression test setup, which included a uniaxial compression test machine, biaxial platens, and confining devices. Secondly, this research prepared cubic shale specimens at the sizes of 25.4, 50.8, and 76.2 mm and orientations of 0, 45, and 90°. At last, this research conducted the uniaxial, biaxial, and triaxial compression tests on these specimens. The test results shows that the strength presents a decreasing trend as size increased irrespective of specimen orientation and stress condition. The anisotropic behavior of strength is unaffected by specimen size, but it varies as the stress condition changed. This transition is due to the second principal stress, which has a noticeable effect on the failure mode of shale and leads to the change of strength anisotropy.

Permeability around faults varies locally due to the existence of damage zone and clayey fault cores that experienced deformation and fracturing. Therefore, proper assessment of local changes in permeability around fault is recognized as an important research area for geoengineering applications such as radioactive waste disposal and carbon sequestration and storage. We developed a simple permeability testing device to measure the distribution of hydraulic conductivity around faults. The key advantage of this equipment is its porta-bility and simplicity, allowing on-site measurements. First, we used this equipment to measure the hydraulic conductivity on the standard rock samples and compared the results with data obtained from conventional laboratory hydraulic conductivity tests. Thereafter, we applied this approach to rocks containing faults to study the characteristics of hydraulic conductivity around faults.