Mining Industry Journal

Numerical study on stability of retained roadway in non-pillar mining at Nam Mau coal mine

2026-01-07T07:44:43+07:00

By using numerical modelling method, the study aims to better understand the geomechanical behaviours of roof strata and stability of retained roadway in the non-pillar mining method at Nam Mau coal mine. The analysis of numerical model shows that when the face is far away from the retained roadway, the mining does not cause significant impact on roadway stability. When the face approaches the roadway, the vertical stress gradually increases around the roadway. The stress reaches a peak value when the face is from 10 to 20 m away and then rapidly decreases when the roadway complete falls within the stress relief zone of longwall. In combination with the insignificant concentration of horizontal stress, the surrounding stress condition induces the roadway to deform and fail when the face approaches roadway. The study finds that the roadway is significantly affected when the face is adjacent to it. The rock mass around roadway fails up to 25 m towards the unmined area. At the end of the upper panel mining, only immediate roof caves that form a caving line of less than 70 degrees to seam floor. The strong main roof does not cave but sag downwards, causing significant load on roadway. The results in this paper can serve as fundamental knowledge for efficient design of roof cutting techniques, contributing to reducing the cost of using non-pillar mining method into Vietnam coal industry.

Research on wall cutting using a mixed hydraulic-directed blasting method in mining technology without leaving protective pillars

2026-01-07T07:54:27+07:00

Controlling the rock mass's state to relieve mine pressure on the longitudinal haulage roadway in the longwall pressure zone is the most important and complex technological stage in the combination of support and maintenance solutions for reusing the longitudinal haulage roadway under non-pillar mining schemes. Directional roof-cutting blasting has been widely applied in China and the Russian Federation. Due to the the wide variability in physico-mechanical properties and structural characteristics of roof strata, it is difficult to form an ideal fracture surface (weakly connected surface) that allows the roof to cave and break as expected. In practice, combined methods are commonly employed: combining the method of concentrated blasting to cut the rock face with the method of blasting to break up the rock mass; combining the method of directional hydraulic blasting with the method of blasting to break up the rock mass. These approaches result in a very large volume of drilling and blasting work, especially in the case of mining thick seams according to the longwall mining scheme - lowering the roof to recover coal and the rock face is of a stable, non-collapsible type. Based on theoretical research and practical application of methods to weaken the rock mass, the authors propose a technology for roof cutting using a combined hydraulic-directional blasting method applied to the conditions of mining thick seams and some experimental results of the technology at the IV-9-17 longwall haulage roadway of Ha Long Coal Company.

Finite element and fictitious component methods for solving the poisson equation in a rectangular domain

2026-01-07T07:59:44+07:00

This study presents a novel hybrid numerical framework for solving the Poisson equation ∇²u = f in a unit square domain Ω, discretized into a uniform 14×14 coarse grid, with the computational domain encompassing a triangular subregion defined by vertices (0,0), (0,1), and (1,1). The methodology integrates the Finite Element Method (FEM) for triangulation—refining each grid cell into two linear triangular elements along a diagonal—with the Fictitious Component Method (FCM) to embed the irregular domain into a fictitious square, enhancing iterative efficiency. A stiffness matrix is assembled via FEM weak formulation, modified by FCM penalty terms, and solved using Richardson iteration with an optimal parameter ω ≈ 2/( + ), where and are extreme non-zero eigenvalues of the system matrix.

Numerical simulations across mesh refinements (3,249 to 201,601 nodes) demonstrate rapid convergence in 39 iterations to ||r|| < , achieving O(h²) accuracy ( < 0.00015) and linear time scaling (~1.2 ms/node). Compared to pure FEM, the hybrid reduces iterations by 54% and computation time by 40% on fine meshes, underscoring its novelty in preconditioning ill-conditioned systems for irregular geometries. This framework offers significant potential in geomechanics and mining engineering, enabling efficient modeling of stress-strain fields and rock deformation around tunnels, with broader applicability to nonlinear and 3D problems.

Mechanical performance of concrete incorporating fluidized catalytic cracking residue from the petrochemical industry as a supplementary cementitious material

2026-01-07T08:12:53+07:00

The increasing demand for sustainable construction materials has highlighted the need to reduce the environmental footprint of cement production. This study investigates the reuse of petrochemical residue fluidized catalytic cracking (RFCC) waste as a supplementary cementitious material (SCM) in concrete. RFCC was subjected to two activation methods: high-temperature treatment at 800, 1000, and 1200 °C, and mechanical grinding to enhance pozzolanic activity. Concrete mixtures were prepared with cement replacement levels ranging from 10% to 50% by mass. Fresh properties, including workability and setting time, and hardened mechanical properties such as compressive strength, flexural strength, and elastic modulus, were evaluated at 28 days. Results show that RFCC reduces slump and shortens the setting time of concrete mixtures. At 50% cement replacement, compressive and flexural strengths decreased by up to 45%. However, thermal activation at 1000–1200 °C significantly improved compressive and flexural strengths as well as elastic modulus by 10–20% compared to untreated RFCC. Ground RFCC showed lower early-age strength at 10% replacement but outperformed heat-treated RFCC at higher replacement levels (20–50%). The findings demonstrate that properly treated RFCC waste can replace up to 30% of cement without compromising mechanical performance, offering a viable route for cost reduction, carbon emission mitigation, and sustainable concrete production.

Experimental investigation on the effect of surface micro-texture on friction–wear characteristics and operational performance of swash plate axial piston pump

2026-01-07T08:20:21+07:00

In the context of the increasingly urgent demand for enhancing the operational efficiency and extending the service life of mechanical–hydraulic equipment, research into solutions that minimize friction- and wear-induced losses while improving lubrication performance in friction pairs operating under high load, high pressure, and high-speed conditions has become essential. Globally, the application of surface micro-texturing to friction pairs has emerged as a breakthrough in the field of tribology. Micro-textures such as micro-grooves, dimples, protrusions, and other specialized geometries have demonstrated a remarkable ability to improve lubrication effectiveness, reduce friction coefficients, and mitigate wear. These micro-texture designs have been successfully applied in several countries, including the United States, Austria, Turkey, Russia, and particularly China, achieving reductions in friction coefficient of up to 20%, extending component lifespan by 15%–35%, while also saving energy and lowering maintenance costs. This study presents an experimental investigation evaluating the practical effectiveness of micro-textures in improving the friction–wear performance and lubrication characteristics of a swash plate axial piston pump. The results contribute to clarifying the role of surface micro-texturing in reducing friction and wear, controlling lubrication regimes, and enhancing the overall efficiency of hydraulic equipment. The findings not only provide a scientific basis for applying micro-texture technology in hydraulic devices but also reveal its potential for deployment in mechanical and energy systems operating under harsh conditions, particularly in Vietnam’s mining and heavy industries.

Analysis of electron transport coefficients in gas mixtures for plasma discharge in emiconductor etching- Atrend in mining electrical equipment manufacturing

2026-01-07T08:27:22+07:00

This study presents the calculation and analysis of electron transport coefficients in gas mixtures composed of argon (Ar), molecular fluorine (F₂), and nitrogen (N₂), with a focus on their relevance to gas discharge applications. Using the BOLSIG+ Boltzmann solver and well-established electron collision cross-section data, key parameters such as mobility, diffusion coefficients, and ionization coefficients were evaluated across a range of reduced electric fields (E/N) and mixture ratios. These data serve as critical input for the modeling and optimization of low-temperature plasma discharges, particularly in applications such as reactive ion etching and thin film deposition using inductively coupled plasma systems.

Design of a vacuum contact pair for 660/1140 V switchgears used in underground mine power networks

2026-01-07T08:34:38+07:00

The vacuum contact pair located in interruption chamber (The vacuum contact pair) is the core component of switchgears used in mining power systems. The design and evaluation process of the vacuum contact pair are often influenced by empirical parameters. With the advancement of modern technology, the application of numerical simulation tools in vacuum contact pair design has significantly improved reliability and shortened the design time. This paper presents the analysis and design of a vacuum contact pair using the finite element method (FEM) implemented in ANSYS software. Experimental validation was conducted on a physical prototype to verify the theoretical results. The findings of this study provide a solid scientific basis for domestic manufacturers to develop and produce vacuum switchgears, contributing to the replacement of imported equipment for mining power systems.

Estimation of geological coal reserve by structure modeling for Vinacomin coal seams

2026-01-07T08:38:54+07:00

The structure of coal seams in Vietnam is quite complex with tectonic disturbances and inseam rock partings. Determining the geological structure, calculating reserves and especially the geological reserves of coal seams is a common but rather difficult task for mining engineers. The traditional method in Vietnam is linear interpolation and calculating reserves by parallel cross-sections. But now, with the support of computers, the modeling method is being widely applied, and moreover, it also helps to accurately describe the structure of the coal seam and eliminate the rockpartings located between the roofs and floors in the seams, which is very necessary for calculating coal reserves. At the same time, new criteria for coal reserves have also been introduced, such as T, T1, T2. This newly applied method of calculating coal reserves not only increases the accuracy, but also shortens the time and even increases the calculated coal volume compared to the traditional method, has many scientific and practical meanings, and can be effectively applied to geological and surveying works such as calculating geological reserves and calculating mining excavated volume.

The main content of the paper is to introduce the method of calculating reserves by combining structural modeling and thickness of coal seam. This method is applied to calculate all major coal seams in large open-pit mines of Vinacomin, but the typical case study presented in the paper is the case of Caoson and Hatu mines, using data from boreholes in Vinacomin's geological exploratory reports.

In order to have good results of reserve estimation, the article also introduces the creation of relational geological databases of coal deposits for mines. The modeling results demonstrate the effectiveness of these PC applied works, including establishment of coal seam structural maps such as elevation isolines of roof, floor and thickness of coal seams, as wel as tectonic zone planes. These modeling results can be served as the basis for mine design, mine planning, mine scheduling, mine optimization and economic efficiency calculation... on computers in a continuous and intergrated way.

Ứng dụng phương pháp giảm cường độ cắt trong nghiên cứu và xác định vùng biến dạng của mái dốc

2026-01-07T08:46:27+07:00

Quá trình thay đổi giá trị thông số cường độ chống cắt của đất tạo nên vùng biến dạng dẻo của mái dốc. Tại trạng thái sau biến dạng, vật liệu sẽ thay đổi và không còn ở trạng thái nguyên dạng như trước, các liên kết trong vật liệu bị phá vỡ và kết cấu bị phá hủy. Trong bài báo này, phương pháp giảm cường độ cắt được sử dụng để xác định cơ chế hình thành, quá trình phát triển, khả năng dịch chuyển cũng như vị trí chính xác của vùng biến dạng dẻo trên bề mặt trượt của mái dốc. Mô hình mái dốc 3D được xây dựng, phân tích, tính toán hệ số an toàn cũng như xác định vùng biến dạng dẻo gây nguy cơ trượt lở mái dốc bằng phần mềm Midas GTS NX tích hợp phương pháp giảm sức chống cắt.

Application of Machine learning and Kriging methods in the geological investigation of ion-adsorption rare earth deposits

2026-01-07T08:55:25+07:00

Ion-adsorption type rare earth element (REE) deposits are of strategic significance and commonly occur within deeply weathered profiles in tropical humid regions. However, evaluating their resource potential and delineating prospective zones remain challenging due to complex spatial variability and limited sampling data. In this study, modern techniques including geostatistical interpolation (Kriging) and machine learning models such as Random Forest (RF) and Support Vector Machine (SVM) were integrated to analyze geochemical data and model the spatial distribution of REE across a 10 km² study area.

Based on 30 field sampling points and a simulated grid of 10,000 locations, the RF and SVM models were trained to classify prospective zones using REE_sum concentrations. The classification

results revealed that the central area exhibited the highest probability of REE enrichment, consistently identified by both RF and SVM models. Kriging interpolation (on a log-transformed scale) showed a clear geochemical gradient with REE concentrations decreasing outward from the center, demonstrating strong spatial continuity. The study area was further subdivided into 500 m × 500 m blocks for resource estimation, resulting in a total calculated resource of approximately 11,300 tonnes of REE, predominantly concentrated in the central blocks. A 3D block model was constructed to support spatial visualization and aid in future mine planning.

This study demonstrates the effectiveness of integrating Kriging and machine learning models for spatial modeling and resource assessment of ion-adsorption rare earth deposits. Beyond its methodological contribution, the study provides scientific and practical significance by establishing a data-driven workflow applicable to similar REE_sum-based investigations in Vietnam, supporting strategic resource planning.

Study on establishing a set of criteria for identifying rare earth elements in weathering crusts

2026-01-07T09:03:53+07:00

Ion-adsorption type rare earth element (REE) deposits in weathering crusts represent a strategic class of mineral resources with high economic value and relatively simple mining and processing technologies. These deposits have been extensively discovered and exploited in China, Myanmar, and more recently in Vietnam. This paper presents a framework of six groups of geological–environmental identification criteria to support the investigation, exploration, and assessment of the potential of REE deposits in weathered crusts, including: (1) Characteristics of parent rocks, (2) Topography and geomorphology, (3) Chemical alteration indices, (4) Climatic conditions, (5) Composition of REE-adsorbing clay minerals, and (6) Forms of REE occurrence and field identification methods.

Through a synthesis of international literature and field data from Vietnam, this study emphasizes the controlling roles of REE-enriched felsic parent rocks, long-term tropical to subtropical humid climates, gentle hill topography, deep chemical weathering, and the presence of clay minerals with high cation exchange capacities (kaolinite, halloysite, illite, etc.). In addition, the paper proposes several supplementary criteria, such as the thickness of the weathering profile, HREE/LREE ratio, and Ce/Ce* anomaly, to assist in the rapid evaluation of orebody potential. These findings contribute to the development of a standardized identification framework for REE resources in Vietnam, in the context of increasing global demand for rare earth elements.