Engineering Journal of Satbayev University

Dynamics of temperature-strength changes in the immediate roof and formation of the gasified cavity of an underground gasifier

P. Saik, V. Lozynskyi, M. Berdnyk, D. Klimov — Sat, 28 Feb 2026 00:00:00 +0000

This study aims to identify regularities in the evolution of the temperature field and the uniaxial compressive strength (UCS) of immediate roof rocks under the influence of chemical reaction zones along the combustion face. It also aims to determine how the goaf area forms and changes over time as a function of gasification duration, injection pressure of the blowing mixture, and coal seam thickness. The study was carried out using a laboratory UCG setup that reproduces combustion face advance and roof deformation. The temperature in the modelled immediate roof was recorded by sensors installed along the reaction channel. Siltstone samples taken from the immediate roof of seam n₇ⁿ at the Mezhyrichanska mine (SE “Lvivvuhillia”, Ukraine) were thermally treated and tested in uniaxial compression using a KL 200/CE-Tecnotest press. The goaf geometry was determined from roof-subsidence reference sensors, graphical reconstruction of contours at different time instants, and area calculation by the trapezoidal rule with consideration of producer-gas composition and concentration. At 0.55 m above the seam, temperature in the oxidizing zone (0-9 m) increased from approximately 323 to 550°C, reached about 573°C in the transition zone (9-11 m), and decreased to ~200°C in the reducing zone (11-30 m). UCS varied along the combustion face with a maximum near the transition zone and a subsequent decrease in the reducing zone. An exponential relationship was observed in the oxidizing zone, whereas a logarithmic relationship was observed in the reducing zone. The goaf area changed nonlinearly, predominantly exponentially, with gasification duration and seam thickness. It was also associated with the injection-pressure regime of the blowing mixture and roof-caving manifestations. The identified relationships can be used to predict goaf parameters and to assess roof stability when substantiating controlled UCG operating regimes.

Hydrogeological characteristics of the Alakol groundwater deposit for resort infrastructure development

Sat, 28 Feb 2026 00:00:00 +0000

The paper presents the results of a comprehensive geological and hydrogeological assessment of the Alakol groundwater deposit in the Alakol Depression, southeastern Kazakhstan. This deposit represents one of the principal groundwater sources for the rapidly developing resort infrastructure on the southern shore of Lake Alakol. It is therefore of considerable socio-economic importance for the region. The study examines the geomorphological setting of the area, the lithological composition and thickness of aquifer-bearing deposits, groundwater occurrence conditions, and the main factors governing groundwater recharge, flow, and discharge. The groundwater regime in both recharge and discharge zones is characterized, and the principal filtration flow directions and hydraulic relationships between groundwater and surface waters are identified. In addition, the paper evaluates the configuration of existing water intake facilities, groundwater abstraction rates, and the influence of pumping on the regional hydrogeological balance. Particular attention is paid to the rational use and protection of groundwater resources under conditions of increasing recreational pressure. The results may serve as a scientific basis for the further development of resort infrastructure and sustainable groundwater management in the southern coastal zone of Lake Alakol.

Numerical modelling of critical conditions for the onset of a limit state in the rock mass surrounding unfilled underground voids in iron ore deposits

M. Petlovanyi, K. Sai — Sat, 28 Feb 2026 00:00:00 +0000

The purpose of this study is to develop an approach for the quantitative assessment and prediction of rock mass condition surrounding unfilled underground voids, with a focus on a limit state associated with potential instability and ground surface collapse, using numerical modelling techniques. The investigation was carried out using finite element modelling of the stress-strain state of a stratified rock mass in the RS2 software package. To adequately reproduce the mechanical behaviour of fractured rocks of the Kryvyi Rih Iron Ore Basin, the stratified geological structure of the rock mass was incorporated into the model. The nonlinear Hoek-Brown failure criterion was applied, accounting for the Geological Strength Index (GSI). The existence of a transitional (near-failure) geomechanical state of the rock mass surrounding unfilled underground voids has been established. This state develops between stable and unstable conditions and is characterised by mechanical interaction between the void and the ground surface. A stable logarithmic relationship between the lower and upper bounds of the critical ratio H/L_c and the void depth has been identified, quantitatively reflecting the increase in rock mass resistance as the depth increases toward the limit state. An exponential relationship between the width of the ground surface subsidence trough and the parameter H/Lc has been identified, enabling the prediction of the extent of the potential collapse zone. An exponential relationship between the required strength of the cemented paste backfill and the H/L_c ratio has been established, defining the minimum bearing capacity of the backfill under near-failure conditions. For the first time, the existence of a distinct near-failure geomechanical regime of the rock mass surrounding unfilled underground voids has been quantitatively substantiated as an independent state preceding progressive ground surface collapse. The obtained relationships enable predicting the geomechanical condition of the rock mass above unfilled voids, determining the range of their critical geometric parameters, and timely identifying voids in a near-failure state. The developed approach can be applied in engineering practice to justify the parameters of cemented paste backfill from the surface to prevent sudden ground surface collapse.

Implementation of the 1992 Helsinki Convention in Transboundary Groundwater Management: A Comparative Analysis with the Case of the Shu Basin

Sat, 28 Feb 2026 00:00:00 +0000

In the context of increasing freshwater scarcity and climate change, effective transboundary water management, including groundwater resources, is particularly important. The 1992 Helsinki Convention provides an international legal basis for states to cooperate to protect and rationally use transboundary watercourses and aquifers. This article is aimed at a comparative analysis of the practice of implementing the provisions of the Convention in different regions of the world - Europe, Central Asia and Africa - with an emphasis on hydrogeological aspects. Particular attention is paid to the Shuya transboundary basin, located on the territory of Kazakhstan and Kyrgyzstan, as a case of partial implementation of international standards. Based on a systemic analysis of groundwater management, monitoring, and protection practices, recommendations are proposed to integrate the Convention's provisions into regional water policies and institutional mechanisms. The study aims to conduct a comparative analysis of the practice of applying the 1992 Helsinki Convention in various regions of the world, with an emphasis on transboundary groundwater, highlighting the problems and prospects of its implementation using the example of the Shuya basin. The study confirmed that the application of the 1992 Helsinki Convention varies significantly across geographical and political-institutional contexts.

A small-sized continuous reactor system for extracting nickel, cobalt and iron from stale tailings

Sat, 28 Feb 2026 00:00:00 +0000

The increasing accumulation of stale tailings from mining operations poses both environmental risks and opportunities for the recovery of valuable metals. This study focuses on the development, additive manufacturing, and experimental validation of a small-scale continuous reactor system for the extraction of nickel, cobalt, and iron from stale pyrite tailings at the Sokolovsko-Sarbaisky Mining and Processing Plant (Kazakhstan). The reactor system was fabricated using additive manufacturing (3D printing) with PET-G polymer, allowing for rapid prototyping, modular assembly, chemical resistance, and cost-effective production. The system comprises three sequentially connected reactors operating in continuous flow. Reagent and slurry feeding were conducted using peristaltic pumps, while a stepper-motor-driven mechanical stirrer ensured homogeneous mixing. Temperature was controlled by circulating a heat-transfer fluid through integrated heat-exchange channels, enabling stable operation over 20-120°C. Before leaching, stale tailings were subjected to oxidative roasting in a fluidized-bed furnace at 650-700°C for 1 hour, which facilitated the decomposition of sulfides into oxides. Subsequent leaching experiments were conducted with sulfuric acid concentrations ranging from 25 to 175 g/dm³, varying residence times, and controlled thermal conditions. Optimal parameters were established as 100 g/dm³ H₂SO₄, 100°C, and 120 minutes, resulting in recoveries of 93.01% for Ni and 91.49% for Co, with moderate Fe dissolution of 64.4%. The results confirm that the designed continuous reactor system provides reproducible hydrometallurgical performance, stable process control, and scalability potential. This approach highlights the combined advantages of continuous-flow chemistry and additive manufacturing in processing low-grade, environmentally challenging raw materials.

Research into the ternary-remelted alloy Ti-10V-2Fe-3Al structural and technological properties

A.T. Mamutova, T.А. Chepushtanova, B. Mishra — Sat, 28 Feb 2026 00:00:00 +0000

This paper presents the results of producing a triple-remelted Ti-10V-2Fe-3Al alloy. The results of SEM–EDS analysis of the alloy are reported, and the structure of the Ti-10-2-3 alloy along the height of an industrial electrode is determined. For the first time, results of a direct comparison between the morphology of the α/β phases and the local chemical composition in three characteristic zones of a 4.5 t electrode, “top”, “middle 1”, “middle 2”, and “bottom”, are obtained based on comprehensive SEM–EDS analysis. It is established that, with respect to the main alloying elements (Ti, Al, V), the ingot is fully chemically homogenized along its height, and the VAR (vacuum arc remelting) regime ensures an acceptable level of macrosegregation. It is shown that the concentrations of (Ti, Al, V), the principal alloying elements in Ti-10V-2Fe-3Al, do not change significantly between samples. SEM–EDS results indicate that the scatter in elemental concentrations is ≤1-1.5%, which is considered an indicator of high-quality VAR processing; this level of scatter implies minimal differences in elemental concentrations: Al variations are within ±0.5-1.0%, V variations are within ±0.5-1.0%, and Ti maintains a stable fraction of approximately ~83-86%. Morphological studies reveal that the α/β structure is formed uniformly, without pronounced columnar segregation. The results of the direct comparison of α/β-phase morphologies enabled the development of a quality-control methodology for electrodes based on SEM–EDS profiles.