The statutory provisions are crucial for safeguarding safety and productivity in mining and averting loss of life and property. Adherence to these rules is obligatory. The integration of artificial intelligence (AI), natural language processing (NLP), and large language models (LLMs) may improve safety, efficiency, and real-time decision-making in the mining industry. This research investigates the creation of a chatbot using the natural language toolkit (NLTK), cosine similarity, and subsequently, a retrieval-augmented generation (RAG) framework with transformer-based models, such as bi-directional encoder representation from transformers (BERT) and large language model meta AI 2 (LLaMA 2). The system analyses regulatory documents using pre-processing, tokenisation, chunking, embedding creation, and semantic search to provide precise, contextually relevant replies. By transforming legal documents into vector embeddings, the chatbot achieves a retrieval accuracy of 95% and reduces query response time by 70%. This approach demonstrates a scalable, machine learning-based compliance tool that enhances operational efficiency and decision-making by automating access to critical safety information.
Loess is a typical water-sensitive soft soil widely distributed in northwest China. It typically exhibits low cohesiveness and easy subsidence when immersed in water, thus severely restricting the development of infrastructure construction such as highways, railways, and bridges. To solve the issues of high carbon emissions, low economic benefits, and increased environmental alkalinity caused by conventional cement-based curing materials, alkali-activated slag/fly ash (S/F) geopolymers (referred to as “geopolymer”) were adopted to improve collapsible loess in this study. The influence laws of the precursor S/F mass ratios (i.e., 0∶10, 2∶8, 4∶6, 5∶5, 6∶4, 8∶2, and 10∶0), alkaline activator (i.e., sodium hydroxide/sodium silicate, N/G), mass ratios (i.e., 0∶10, 1∶4, 4∶1, and 10∶0), and curing age (i.e., 7 d and 28 d) on the physical and mechanical properties of solidified loess were systematically investigated through measurements of unconfined compressive strength (UCS) tests, moisture content, and dry density. The strength-formation mechanism of solidified soil was revealed through X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The results show that as the proportion of slag in the precursor increases from 0% to 100%, the UCS of solidified loess increases significantly. The UCS of solidified soil increases significantly with curing age, i.e., the UCS of the 28-d solidified sample is 2.1 ～ 3.8 times higher than that of the 7 d solidified sample. After 7 d of curing, the moisture content of the solidified samples decreases as the slag proportion increases. By contrast, the change in moisture content of the solidified samples after 28 d of curing shows the opposite law. The proportion of alkali activator imposes a threshold effect on the solidified soil: the UCS of the high-slag system (the slag content exceeding 80%) first increases and then decreases as the proportion of sodium hydroxide increases, whereas that of the high-fly-ash system (the fly-ash content exceeding 80%) increases continuously with the proportion of sodium hydroxide. Microstructure characterization based on XRD and SEM analyses shows that the alkali-activated S/F geopolymers in the solidified samples primarily generate hydrated calcium silicate (C–S–H) and hydrated calcium aluminosilicate (C–A–S–H) gels, which cement the soil particles. The cementation effect of these gels is identified as the dominant mechanism for strength enhancement (particularly the C–S–H/C–A–S–H in slag system), whereas the pore filling effect is a secondary contributing factor. The optimized formula (S∶F = 8∶2, N∶G = 8∶2) results in a 28 d UCS of 8.69 MPa, which significantly exceeds the performance of conventional cement-stabilized loess while offering favorable economic benefits. Alkali-activated solidification improvement reduces the collapsibility of loess as well as enhances its strength, bearing capacity, and road usability. This study provides a scientific basis for the resource utilization of industrial solid waste and the green reinforcement of loess subgrade. Additionally, it demonstrates the feasibility and superior performance of geopolymer technology.
Rock masses have complex hierarchical structures, and the deformation of rock masses under both static and dynamic conditions is primarily concentrated at weak structural layers, which provides the possibility for the whole translation and rotation of rock blocks, and may induce a new type of nonlinear-alternating displacement waves that are completely different from traditional seismic waves, namely the pendulum-type waves (including longitudinal and transverse pendulum-type waves) and rotational waves. Pendulum-type waves have the characteristics of low frequency, low velocity, large amplitude and high energy, which can cause strong compression and anomalously low friction effect in weak layers of rock masses, and may lead to overall instability and lateral sliding of the roadway structure, thereby inducing the rockburst disasters. At present, the study of pendulum-type waves has obtained many achievements and is gradually being applied in engineering, but there are still many problems to be solved. Therefore, it is necessary to systematically review and summarize the pendulum-type wave phenomenon in blocky rock masses. Firstly, a systematic summary of domestic and foreign research achievements related to the pendulum-type waves is conducted, and the discovery, verification, on-site tests, laboratory tests, theoretical modeling and application of pendulum-type waves are briefly described. Secondly, the research achievements of the author's team in the field of pendulum-type waves in recent years are briefly introduced. Through theoretical analysis and experimental research, the propagation laws and typical characteristics of pendulum-type waves in 1D and 2D blocky rock masses have been thoroughly studied, and the influence of hierarchical structures on pendulum-type wave propagation in blocky rock masses is determined. Furthermore, the application of pendulum-type wave theory in anti-impact support of roadway is analyzed, and the mechanism of low-frequency and low-velocity characteristics, rock rotation and the disaster induced by pendulum-type waves are revealed. Finally, the future research focus and development trend of pendulum-type waves in blocky rock masses are prospected, which can provide reference for related researchers.
Mixed-grains magnesium alloy plates with soft-hard-soft layered structure, fabricated by corrugated plate rolling, exhibit simultaneous improvements in both strength and ductility. The corrugated and flat sides primarily consist of twins, necklace grains and recrystallized grains, while the middle layer is dominated by coarse grains with a small amount of twins and necklace grains. As the average strain rate increases, the twin density and shear band decrease. At a constant average strain rate, from the valley-to-peak, the twin density and the number of coarse grains gradually decrease, while the recrystallization fraction gradually increases. At an average strain rate of 4.3 s−1, the corrugated rolled plates with R = 3 mm achieve an optimal balance of strength (262.6 MPa) and ductility (30.6 %). The corrugated side and flat side contribute to strength through fine grain strengthening and orientation strengthening, while the middle layer with coarse grains provides plasticity. The ordered orientation gradient “sandwich” texture further ensuring ductility. The hard-soft-hard layered structure and the configuration of coarse grains surrounded by fine grains synergistically lead to exceptional mechanical properties.
Ismail Zabeeullah Kolimi, Julie Marteau, Salima Bouvier
et al.
This study presents a comprehensive multi-scale investigation of the microstructural and mechanical properties of a large Ti–6Al–4V block fabricated via Additive Friction Stir Deposition (AFSD). AFSD is a solid-state additive manufacturing process with growing industrial relevance. While AFSD has been widely studied for small deposited blocks, its scalability and ability to maintain uniform properties across large build volumes remain underexplored. To address this, a large (250 × 30 × 80 mm3) Ti–6Al–4V block was deposited and systematically characterized through optical microscopy, SEM, EBSD, XRD, EDS, and full-field measurement using Digital Image Correlation (DIC)-assisted tensile testing. Alternating bands were observed across the deposited block; however, no elemental segregation, microstructural, or mechanical differences were observed across layers. The build demonstrated a consistent lamellar α+β microstructure with minimal retained β-phase with no defects or porosity. An isotropic and weak texture was seen throughout the deposition. Mechanical testing revealed uniform hardness (346–358 HV0.5), yield strength (∼906 MPa), and elongation (∼13 %) across both longitudinal and transverse directions. Full-field measurements revealed deformation to be homogeneous. Fractographic analysis confirmed ductile failure with a complete absence of porosity. When compared to prior AFSD and fusion-based studies, this work establishes the largest reported defect-free AFSD Ti–6Al–4V build to date with homogenous microstructure and consistent mechanical properties, achieved without post-processing or heat treatment. These findings validate AFSD's scalability and process stability for manufacturing large-scale components with microstructure and properties on par or above those of wrought or fusion-based AM.
Objective and SignificanceAs the coal mining depth increases, coal mining faces increasingly prominent challenges including coal and gas outbursts, rock bursts, and compound dynamic disasters. Deepening the understanding of disaster-causing mechanisms and developing diversified prevention and control technologies are significant for the safe production of coal mines. Employing the key technologies for coalbed methane (CBM) production to control gas-related dynamic disasters is an inevitable course for the safe production of coal mines. However, large-scale, suitable technology systems are yet to be developed. MethodsFrom the perspective of the application of key technologies for surface CBM production, this study systematically reviews the development history and research advances in technologies including well drilling and completion for CBM production and fracturing. From the angle of coal mine safety, this study organizes the disaster-causing mechanisms and critical control technologies for gas dynamic disasters over the past 70 years. In combination with the characteristics of CBM production technologies and the demand for the prevention and control of dynamic disasters in coal mines, this study proposes some suggestions for theoretical innovation and technological breakthroughs. Results and ConclusionsIn terms of theoretical research, it is necessary to deepen the comprehensive exploration of coals and CBM and conduct fine-scale geological studies by integrating multiple approaches. Regarding control technologies, efforts should be made to further explore the control technologies for coal and gas outbursts and rock bursts, with the former including (1) outburst elimination using cavity-type tube wells+high-pressure air/liquid nitrogen/CO2 scrubbing + negative-pressure drainage and (2) multistage fracturing of L-shaped surface horizontal wells+production and the latter including (1) multistage hydraulic fracturing of roofs using L-shaped wells and (2) proppant injection-based multistage hydraulic fracturing for roofs using L-shaped wells+production. Accordingly, advanced technologies such as multistage fracturing of L-shaped wells for CBM production should be employed to conduct on-site experiments on gas dynamic disaster control. It is necessary to explore the applicability of varying prevention and control theories and technologies under different geologic conditions based on scientific research and engineering integrated engineering and projects and develop technology systems for the prevention and control of gas dynamic disasters in coal mines, thus providing robust support for the safe production of coal mines in China.
Abstract To analyze the relationship between macro and meso parameters of the gas hydrate bearing coal (GHBC) and to calibrate the meso-parameters, the numerical tests were conducted to simulate the laboratory triaxial compression tests by PFC3D, with the parallel bond model employed as the particle contact constitutive model. First, twenty simulation tests were conducted to quantify the relationship between the macro–meso parameters. Then, nine orthogonal simulation tests were performed using four meso-mechanical parameters in a three-level to evaluate the sensitivity of the meso-mechanical parameters. Furthermore, the calibration method of the meso-parameters were then proposed. Finally, the contact force chain, the contact force and the contact number were examined to investigate the saturation effect on the meso-mechanical behavior of GHBC. The results show that: (1) The elastic modulus linearly increases with the bonding stiffness ratio and the friction coefficient while exponentially increasing with the normal bonding strength and the bonding radius coefficient. The failure strength increases exponentially with the increase of the friction coefficient, the normal bonding strength and the bonding radius coefficient, and remains constant with the increase of bond stiffness ratio; (2) The friction coefficient and the bond radius coefficient are most sensitive to the elastic modulus and the failure strength; (3) The number of the force chains, the contact force, and the bond strength between particles will increase with the increase of the hydrate saturation, which leads to the larger failure strength.
Thanh-Dat Nguyen, Chetan Singh, You Sub Kim
et al.
This study investigates the mechanical properties of a friction-stir-welded (FSW) AA6061-T6 aluminum alloy at ultra-low temperature (ULT) of 20 K. In-situ neutron diffraction and orientation imaging microscopy were employed to compare the tensile deformation behavior of the base metal (BM) and heat-affected zone (HAZ) in the FSW aluminum plate. The results demonstrate that compared to room-temperature (RT), ULT induces a significant improvement in tensile strength and ductility in both the BM and HAZ. The enhanced mechanical properties in BM at ULT result from a more homogeneous deformation than occurs at RT. On the other hand, HAZ at ULT exhibits an even lower yield strength than at RT, but the strain hardening rate (SHR) is the most significant among the alloys, leading to a tensile strength of 346 MPa and the highest ductility of 46.8%. The lowest yield strength corresponds to the lowest-hardness zones in HAZ, caused by dissolved/coarsened precipitates during the FSW process. The highest SHR in HAZ at ULT is attributed to the hardening of the {111} grain families and finer dislocation cell structures. The dislocation densities of both the BM and HAZ increased considerably during tensile deformation at ULT, which accounts for the improvement in tensile strength. Revealing the mechanism behind the remarkable improvement in the mechanical properties of FSW AA6061-T6 at ULT suggests its applicability for cryogenic applications.
Microbial induced calcium carbonate precipitation (MICP) is considered as an environmentally friendly microbial-based technique to remove heavy metals. However, its application in removal and recovery of rare earth from wastewaters remains limited and the process is still less understood. In this study, a urease-producing bacterial strain DW018 was isolated from the ionic rare earth tailings and identified as Lysinibacillus based on 16S rRNA gene sequencing. Its ability and possible mechanism to recover terbium was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and fourier transform infrared spectroscopy (FTIR). The results showed that the urease activity of DW018 could meet the biomineralization requirements for the recovery of Tb3+ from wastewaters. The recovery rate was as high as 98.28% after 10 min of treatment. The optimal conditions for mineralization and recovery were determined as a bacterial concentration of OD600 = 1.0, a temperature range of 35 to 40°C, and a urea concentration of 0.5%. Notably, irrespective of CaCO3 precipitation, the strain DW018 was able to utilize MICP to promote the attachment of Tb3+ to its cell surface. Initially, Tb3+ existed in amorphous form on the bacterial surface; however, upon the addition of a calcium source, Tb3+ was encapsulated in calcite with the growth of CaCO3 at the late stage of the MICP. The recovery effect of the strain DW018 was related to the amino, hydroxyl, carboxyl, and phosphate groups on the cell surface. Overall, the MICP system is promising for the green and efficient recovery of rare earth ions from wastewaters.
A positioning grid is a key clamping structure for fixing the transverse and axial positions of fuel assemblies in nuclear reactors, and it is generally prepared by the transverse stamping of a Zr-4 sheet. However, the texture formed in the processing process of Zr-4 sheets can affect formability, resulting in cracking in the stamping process. Therefore, the relationship between the formability of Zr-4 sheets and the normal Kearns factor (Fn) of basal texture was studied in this paper. The results showed that the Zr-4 sheet with an Fn equaling 0.720, prepared by an isobaric reduction rolling process, would crack in the stamping process. To avoid the cracking during stamping, the formability improvement of Zr-4 sheets based on texture optimization was discussed. By using the finite element model (FEM) and a visco plastic self-consistent (VPSC) model coupled simulation, the relationship between the initial textures and formabilities of Zr-4 sheet is established. It is found that the hardening exponents (n) decreased with increasing Fns in VPSC simulations. Meanwhile, as the Fn increases, cracks are prone to occur at the bottom corner of the stamped sheet in finite element simulation. Given the results from FEM and VPSC simulations, it is proposed that the Fn should be controlled to be less than 0.7 for preventing cracks in the sheet during stamping. Additionally, a new rolling process named non-isobaric reduction rolling was designed in which the Fn of the Zr-4 sheet is successfully reduced to 0.690. The stamping results indicate that the sheet is free of cracks under an Fn of 0.690. Therefore, texture optimization with the proposed rolling process can improve the formability of Zr-4 sheets, which effectively solves the cracking problem of Zr-4 sheets.
This is an essay in the field of mineral processing engineering. The flotation method is applied to reduce ash content and purify pyrolysis carbon black from waste tires in this study. The effect of different operating factors on carbon black flotation was explored, and the phase and morphology of different flotation products were measured by various characterization methods. Results show that 62.32% yield of clean carbon black and 17.29% ash content for flotation concentrate were obtained, and 37.68% yield of flotation tailing and 23.32% ash content were obtained as well under the optimal flotation conditions were of 20 g/L of concentration, 500 g/t of collector, 1500 g/t of foaming agent, 9 min of froth skimming time and 0.25 m3/h of aeration amount, and the removal rate of quartz is 75.49% and the removal rate of calcium carbonate is 66.23%. Minerals including quartz and calcite were effectively removed by flotation, The amount of aeration had more significant impact on the test. This study indicates that flotation can be well used for reducing ash content of pyrolysis carbon black from waste tires which is proved to be an effective ash reduction pretreatment method.
Aiming at the reservoir damage of low-yield coalbed methane wells in Junggar Basin block during the drainage stage, in this paper, the drainage situation of typical coalbed methane wells in the block is systematically analyzed and reservoir damage types and prevention and control methods of coalbed methane wells in the drainage stage are discussed. The results show that the main types of reservoir damage at the drainage stage in the study area include stress sensitivity, velocity sensitivity and water lock damage. The low mechanical strength of coal reservoirs, improper fracturing fluid, and high drainage intensity are the important reasons for these damages. During the drainage stage of CBM wells, drainage is carried out according to the “continuous, slow and stable” guidelines, increasing the expansion range of the pressure drop funnel and keeping the fluid flow rate below the particle start flow rate will help prevent the three types of reservoir damage. In addition, the use of low-damage fracturing fluid with low surface tension and strong wettability can promote the rapid sedimentation and aggregation of particles. The pore capillary pressure is significantly reduced in the reservoir in the reconstruction stage, thereby inhibiting reservoir velocity sensitivity and water blocking damage. Meanwhile, the coal reservoir is retrofitted by surrounding rock, which helps to reduce the impact of stress-sensitive damage on the production of coalbed methane.
Maraging steel components fabricated by laser powder-bed fusion, which is a technique of additive manufacturing, are expected to be used widely because of their high strength, hardness and toughness. To apply maraging steel manufactured by laser powder-bed fusion in wider industrial fields and prevent the components from fracture, a study was conducted to improve the wear resistance and fatigue properties of the steel by an atmospheric-controlled induction-heating fine particle peening surface modification technique. The technique developed can create hard intermetallic compound layers and introduce peening effects, which are expected to improve the wear resistance and fatigue properties of maraging steel fabricated by laser powder-bed fusion. The prepared specimens were examined using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, laser microscopy, X-ray diffraction, micro-Vickers hardness testing, nano-indentation testing, reciprocating ball-on-disk wear tests and axial fatigue tests. It was revealed that atmospheric-controlled induction-heating fine particle peening using mechanically milled particles formed Fe–Al intermetallic compound layers with high hardness, introduced compressive residual stresses and increased the hardness of the maraging steel substrate owing to age hardening. In conclusion, atmospheric-controlled induction-heating fine particle peening can simultaneously improve the wear resistance and fatigue properties of maraging steel fabricated by laser powder-bed fusion within a few minutes. These achievements can expand applications of maraging steel fabricated by laser powder-bed fusion.
Gap-graded mixtures are one of the areas of improving the permanent deformation strength of hot-mixed asphalt mixtures. Additional filler materials can be needed due to the high bitumen amount and the less fine aggregate amount in the mixture. In this study, the effects of filler additives on moisture susceptibility of the gap-graded hot-mixed asphalt mixtures and mixing methods are investigated. Filler additives such as class C and class F fly ashes and hydrated lime are used 0.5 %, 1.0 %, 2.0 %, and 4 % of the total weight of mixture instead of mineral filler. Design mixtures are prepared according to the Turkish Highway Technical Specifications (THTS). To determine the effect of mixing methods, dry and wet (slurry) methods are used to mix the filler materials. Modified Lottman method (AASHTO T283) are used to determine the moisture susceptibility. An indirect tensile strength test is the measurement of bitumen film thickness which is also conducted. Test results showed that class C fly ash is significantly improved the moisture susceptibility of mixtures. While the slurry method does not give the expected improvement on class C fly ash added mixtures, it shows a positive effect on class F fly ash and hydrated lime added mixtures.