Search Results (55)

This study investigates the effectiveness of geopolymer-based binders for the stabilization of silty sand, aiming to improve its strength and durability under cyclic environmental conditions. A composite binder consisting of Ground Granulated Blast-furnace Slag (GGBS) and Recycled Glass Powder (RGP), modified with nano poly aluminum silicate (PAS), was used to treat the soil. The long-term performance of the stabilized soil was evaluated under cyclic wetting–drying (W–D) conditions. The influence of PAS content on the mechanical strength, environmental safety, and durability of the stabilized soil was assessed through a series of laboratory tests. Key parameters, including unconfined compressive strength (UCS), mass retention, pH variation, ion leaching, and microstructural development, were analyzed using field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Results revealed that GGBS-stabilized specimens maintained over 90% of their original strength and mass after eight W–D cycles, indicating excellent durability. In contrast, RGP-stabilized samples exhibited early strength degradation, with up to an 80% reduction in UCS and 10% mass loss. Environmental evaluations confirmed that leachate concentrations remained within acceptable toxicity limits. Microstructural analysis further highlighted the critical role of PAS in enhancing the chemical stability and long-term performance of the stabilized soil matrix. Full article

To study the optimization of construction parameters and schemes for complex connecting tunnels in extra-long highway tunnels in granite strata, the research team, relying on the construction project of the complex connecting tunnel between the Xiaolongmen Extra-long Highway Tunnel and the ultra-deep shaft, established an on-site monitoring scheme and a refined numerical simulation model. It systematically analyzed the impact of various construction parameters on the construction process of connecting tunnels and the main tunnel, and on this basis, optimized the construction scheme, improving construction efficiency. The research results show that (1) after the excavation of the connecting tunnel, the confining pressure at the top of the working face decreases rapidly, while the confining pressure on both sides increases rapidly; the extreme point of the confining pressure decrease is located at the central point at the top of the excavated working face. (2) For Class III surrounding rock excavated using the full-face blasting method, the maximum influence range of working face excavation on the stratum along the tunneling direction is approximately 4D (where D represents the excavation step). (3) The larger the excavation step of the connecting tunnel, the more obvious the stress concentration phenomenon at the central point of the working face arch crown, and the excavation step should be optimally controlled within the range of 2–3 m. (4) When explosives in the blast hole adopt decoupled charging, the ratio of borehole diameter to charge diameter can be increased to utilize the air gap to buffer the energy generated by the explosion. Full article

Ammonia is emerging as a promising zero-carbon marine fuel due to its high hydrogen density, low storage pressure, and long-term stability, making it well-suited for supporting sustainable maritime energy systems. However, its adoption introduces serious safety challenges, as its toxic, flammable, and corrosive properties pose greater risks than many other alternative fuels, necessitating rigorous risk assessment and safety management. This study presents a comprehensive investigation of potential ammonia leakage scenarios that may arise during the fuel gas supply process within confined compartments of marine vessels, such as the fuel preparation room and engine room. The simulations were conducted using FLACS-CFD V22.2, a validated computational fluid dynamics tool specialized for flammable gas dispersion and explosion risk analysis in complex geometries. The model enables detailed assessment of gas concentration evolution, toxic exposure zones, and overpressure development under various leakage conditions, providing valuable insights for emergency planning, ventilation design, and structural safety reinforcement in ammonia-fueled ship systems. Prolonged ammonia exposure is driven by three key factors: leakage occurring opposite the main ventilation flow, equipment layout obstructing airflow and causing gas accumulation, and delayed sensor response due to recirculating flow patterns. Simulation results revealed that within 1.675 s of ammonia leakage and ignition, critical impact zones capable of causing fatal injuries or severe structural damage were largely contained within a 10 m radius of the explosion source. However, lower overpressure zones extended much further, with slight damage reaching up to 14.51 m and minor injury risks encompassing the entire fuel preparation room, highlighting a wider threat to crew safety beyond the immediate blast zone. Overall, the study highlights the importance of targeted emergency planning and structural reinforcement to mitigate explosion risks in ammonia-fueled environments. Full article

With growing demands for improved blast resistance in concrete protective structures, developing new concrete materials that combine high toughness, impact resistance, and efficient energy dissipation is essential. This study replaces conventional aggregates with titanium slag and prepares three specimen groups: pure cement mortar (control), cement mortar with large titanium slag particles, and an optimized mix with titanium slag aggregates. Using Split Hopkinson Pressure Bar (SHPB) tests and AUTODYN finite difference simulations, stress-wave absorption and attenuation performance were systematically investigated. Results show that, under identical impact loading rates, the large-particle titanium slag group increased energy absorption by 23.5% compared with the control, while the optimized mix improved by 19.2%. Both groups maintained stable absorption efficiencies across different loading rates. Numerical simulations reveal that the porous titanium slag model attenuated stress waves by approximately 67.9% after passing through three slag layers, significantly higher than the 51.4% attenuation in the non-porous model. This improvement is attributed to multiple wave reflections and interferences caused by a two-order-magnitude difference in the elastic modulus between the slag and air interfaces, creating ring-shaped stress concentrations that disrupt wave propagation and dissipate impact energy. This research provides experimental support and mechanistic insights for titanium slag application in novel blast-resistant concrete. Full article

Variations in slag properties critically influence smelting operations and product quality. The effects of K₂O on the CaO-SiO₂-MgO-Al₂O₃-K₂O slag system at 1823 K were systematically analyzed through an integrated approach combining viscosity measurements, FTIR spectroscopy, and molecular dynamics simulations. The results revealed a rapid 52% decrease in slag viscosity and an 18.32 kJ/mol reduction in activation energy as K₂O content increased from 0% to 3%. K₂O releases O²⁻ ions that depolymerize Si-O network structures. Within the 3% to 5% range, structural network formation is promoted by the K₂O-SiO₂ reaction, resulting in increased slag viscosity and elevated activation energy. Molecular dynamics simulations elucidate the depolymerization of complex Si-O networks, accompanied by a proliferation of smaller [AlO₄] tetrahedral fragments. The diminished Si-O-Si bridging oxygen (BO) bonds contrast with the enhanced increase in Si-O-K non-bridging oxygen (NBO) linkages. When K₂O exceeds 3%, the diffusion capacity of K atoms becomes constrained as K₂O participates in structural network assembly, a phenomenon validated by FTIR spectroscopic analysis. Elevated K₂O concentrations enhance slag network polymerization, leading to increased viscosity. Therefore, the precise control of K₂O content is critical during smelting operations and by-product manufacturing (e.g., glass or mineral wool) to optimize material performance. These findings provide theoretical support for controlling the alkali metal content during the actual metallurgical process and thus further optimizing blast furnace operation. Full article

The iron and steel industry, as a major energy consumer, was critically required to enhance operational efficiency and reduce CO₂ emissions. Conventional blast furnace processing of vanadium–titanium magnetite (VTM) in China had been associated with persistent challenges, including suboptimal TiO₂ recovery rates (<50%) and elevated carbon intensity (the optimal temperature range for TiO₂ recovery lies within 1400–1500 °C). Shaft furnace technology has emerged as a low-carbon alternative, offering accelerated reduction kinetics, operational flexibility, and reduced environmental impact. This study evaluated the low-carbon PLCsmelt process for VTM smelting through energy–mass balance modeling, comparing two gas-recycling configurations. The process integrates a pre-reduction shaft furnace and a melting furnace, where oxidized pellets are initially reduced to direct reduced iron (DRI) before being smelted into hot metal. In Route 1, CO₂ emissions of 472.59 Nm³/tHM were generated by pre-reduction gas (1600 Nm³/tHM, 64.73% CO, and 27.17% CO₂) and melting furnace top gas (93.98% CO). Route 2 incorporated hydrogen-rich gas through the blending of coke oven gas with recycled streams, achieving a 56.8% reduction in CO₂ emissions (204.20 Nm³/tHM) and altering the pre-reduction top gas composition to 24.88% CO and 40.30% H₂. Elevating the pre-reduction gas flow in Route 2 resulted in increased CO concentrations in the reducing gas (34.56% to 37.47%) and top gas (21.89% to 26.49%), while gas distribution rebalancing reduced melting furnace top gas flow from 261.03 to 221.93 Nm³/tHM. The results demonstrated that the PLCsmelt process significantly lowered carbon emissions without compromising metallurgical efficiency (CO₂ decreased about 74.48% compared with traditional blast furnace which was 800 Nm³/tHM), offering a viable pathway for sustainable VTM utilization. Full article

Using the two-dimensional Particle Flow Code (PFC2D), a model of red sandstone containing fractures with different inclination angles under impact load was established to study the influence of fracture inclination angles on the dynamic compressive strength, stress wave attenuation, and crack evolution laws of the model. The results indicate that, under the same impact load, the dynamic compressive strength of the cracked specimens exhibits a “V”-shaped variation, with the specimen at a 45° inclination angle showing the lowest strength. The influence of inclination angles on strength is most significant in the 30° to 45° inclined specimens. As the inclination angle increases, the reflection coefficient rises, the transmission coefficient decreases, stress wave attenuation intensifies, and the time for specimen penetration shortens, making the specimen more prone to failure. The location of crack initiation shifts toward the middle of the fracture as the inclination angle increases, and the cracks tend to develop parallel to the impact load. When the inclination angle is ≥45°, stress concentration at fracture tips prolongs the shear-dominated phase during failure progression. However, the tensile ratio k consistently exceeds 0.7 at ultimate failure, indicating tensile mechanisms remain the dominant failure mode. Both absorbed energy and total crack number generally decrease with increasing inclination angle, while no clear correlation exists between absorbed energy and fragment number. Large fragments are distributed on both sides of the fracture during the fragmentation process. In contrast, small fragments concentrate near the through cracks. Specimens with 45° and 60° inclination angles exhibit a higher number of fragments and more significant fragmentation. In the initial loading stage, the specimen with a 90° inclination angle shows the weakest resistance to failure, while the 0° inclination angle specimen exhibits the strongest resistance. The research findings contribute to elucidating the dynamic failure mechanisms of fractured red sandstone, analyzing slope stability, and optimizing blasting designs. Full article

Gas control and extraction are essential for energy use and sustainable development. In order to study the gas diffusion and transportation law of high-gas tunnels after excavation and blasting and the influence of ventilation on gas concentration, an engineering example is used as a research object. We put forward the “energy concentrating device + digital electronic detonator”, a new type of peripheral hole in the joint initiation of explosive technology, applied to a tunnel in the plateau, studied through field tests and the original “detonating cord + digital electronic detonator” joint detonation technology after a comparative analysis of the blasting effect. On this basis, the characteristics of gas diffusion and transportation near the palm face were studied by numerical simulation under the two working conditions of ventilated and unventilated, and the law of gas diffusion and transportation near the palm face was obtained. The research shows that: with the “energy concentrating device + digital electronic detonator”, a new perimeter hole joint detonation technology compared to the original “detonating cord + digital electronic detonator” joint detonation technology, the explosive unit consumption reduced by 0.2 kg/m³, half-hole retention rate increased by 5%, average charging time shortened from the original 1.3 h to 1.0 h, and stabilizing the cycle of footage at the same time greatly reduces the cost of consumables, improving the tunnel surface blasting effect; numerical simulation shows that under the condition of no ventilation, the gas accumulation near the arch top and arch waist at the tunnel face is severe, with the gas concentration close to 30%, the gas concentration is higher up to 7 m from the face after the gas state is stabilized, and the gradient of the gas concentration in the area beyond 7 m is small. The gas concentration in the area can be reduced to the safe range after ventilation in about 30 s, but gas accumulation easily occurs in the foot and arch waist on the opposite side of the wind pipe. The results of this study can provide a reference basis for similar gas tunnel blasting construction and ventilation optimization and promote the sustainable development of energy. Full article

Placing empty holes between charging holes is widely used in blasting engineering to achieve directional fracture blasting. Studies have shown that the presence of a notch along the empty hole wall enhances stress concentration and supports improved control over crack propagation. The notch angle and length are the two main parameters influencing the impact of notch holes. Therefore, in this study, we used numerical simulations to investigate how varying notch angles and lengths influence the directional fracture blasting effect. The findings suggest that, among the different types of holes used in directional fracture rock blasting, notched empty holes have the most significant guiding effect, followed by empty holes, while the absence of empty holes yields the least effective results. In the directional fracture blasting of a notched empty hole, stress concentration occurs at the notch tip following the explosion. This alters the stress field distribution around the empty hole, which shifts from a compressive to a tangential tensile state. Additionally, this concentration of stress causes the explosion energy to be focused on that location, resulting in a directional fracture blasting effect. In blasting construction, selecting the appropriate notch hole parameters is necessary to achieve optimal effects and reduce damage to surrounding rocks. Based on the notch parameters assessed in this study, the optimal effect of directional fracture blasting is achieved when the notch angle is 30°. Full article

In order to address the issue of limited excavation footage in the drilling and blasting of a water diversion tunnel with a cross-section of approximately 10 m², which is unable to meet the demands of rapid construction, a blasting method combining long and short straight-hole cutting was proposed based on the theories of elastic mechanics, blasting craters, explosive gas and stress waves. A mechanical model was established to elucidate the parameter design method and cavity formation principle of the combined cutting. Numerical simulation and field tests were employed to analyze the rock-breaking process of combined cutting, with a view to comparing the blasting effect differences between the traditional inclined cutting method and the combined cutting method. The research results indicate that during the blasting process with combined long and short straight-hole cutting, the uncharged portion of the deep hole can serve as an empty hole during the subsequent blasting of the shallow hole. The concentration of stress at the wall of the empty hole and the superposition of reflected and incident waves serve to enhance the rock-breaking effect of the shallow hole, with the enhancement being influenced by the diameter of the hole and the distance between it and the empty hole. The preferential detonation of the shallow hole can provide a smaller resistance line and free surface distance for deep hole detonation, creating favorable conditions for rock fragmentation in deep hole blasting, making it easier for the rock in the cutting area to be thrown out and increasing the utilization rate of the blast holes. The shape of the formed cavity is a long strip-shaped cube, with its volume being influenced by the spacing between each group of deep and shallow holes. The rock mass damage is most severe in the vertical direction, while the rock mass damage at the center of the upper and lower edges is relatively weaker. In order to optimize the utilization of blasting energy, it is essential to select an appropriate spacing between each group of blast holes. In comparison to the utilization of traditional inclined cuts, the implementation of combined long and short holes has been observed to result in a greater extent of blasting footage and relatively lower explosive consumption. These research findings provide a reference point for the rapid and efficient construction of small-section tunnel engineering, as well as the design of straight-hole cut blasting with reduced consumption. Full article

Rockburst, one of the leading types of disaster in mining and rock engineering causing serious injuries and the loss of property, frequently occurs, involving various features and complex evolutionary mechanisms. Compared to rockbursts occurring at mining faces, those occurring in main roadways cause more serious problems for mine production. This paper first analyzes the characteristics of rockbursts in main roadways using two case studies involving the Gaojiapu and Cuimu coal mines. The causes of rockbursts in main roadways were studied using microseismic monitoring, energy density cloud maps, and seismic velocity tomography. During the mining of the 22306 working face in the Cuimu coal mine, targeted measures, such as deep-hole blasting of the roof strata and deep-hole blasting of the coal seam, were implemented to prevent rockbursts in the main roadways. The effectiveness of these measures was verified through long-term analysis of tremor activities. The study found that the influence of mining at two working faces on both sides of main roadways was significantly greater than that from a single-sided working face. The intensity of the tremor activities occurring near the main roadways was correlated with the distance from the working face to the main roadways. The closer the working face was to the main roadways, the stronger the tremor activities were near the main roadways. According to the distribution range of the tremors, the influence area of working face mining exceeded 800 m, with tremors distributed linearly along the main roadways. Even five months after the completion of working face mining, there were still a large number of tremors near the main roadways, which gradually disappeared after another five months. Mining activities were the main reason for the occurrence of main roadway rockbursts and the stress concentration within the main roadways themselves was another reason for the occurrence of rockbursts. The influence of working face mining could be reduced by deep-hole blasting of roof strata and the stress concentration within main roadways themselves could be reduced by large-diameter drilling. Those joint preventive measures effectively prevented the occurrence of rockbursts in main roadways. This study is of important theoretical and practical significance for further studies of rockburst mechanisms and prevention in regard to main roadways in coal mines, and the findings are significant in terms of the enhancement of safety in coal mines. Full article

Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 × 10⁻⁶ cm²/s–9.5 × 10⁻⁶ cm²/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 × 10⁻⁸ to 4.13 × 10⁻⁷ cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills. Full article

The occurrence of rock bursts due to penetrating faults are frequent in China, thereby limiting the safe production of coal mines. Based on the engineering background of a 501 working face in a TB coal mine, this paper investigates stress and energy evolution during the excavation of this working face due to multiple penetrating faults. Utilizing both theoretical analysis and numerical simulations, this study reveals the rock burst mechanism within the triangular coal pillar influenced by the penetrating faults. Based on the evolution of stress within the triangular coal pillar, a stress index has been devised to categorize both the rock burst danger regions and the levels of rock burst risks associated with the triangular coal pillar. Furthermore, targeted stress relief measures are proposed for various energy accumulation areas within the triangular coal pillar. The results demonstrate that: (1) the superimposed tectonic stress resulting from the T6 and T5 penetrating faults exhibits asymmetric distribution and has an influence range of about 90 m in the triangular coal pillar, reaching a peak value of 11.21 MPa at a distance of 13 m from the fault plane; (2) affected by the barrier effect of penetrating faults, the abutment stress of the working face is concentrated in the triangular coal pillar, and the magnitude of the abutment stress is positively and negatively correlated with the fault plane barrier effect and the width of the triangular coal pillar, respectively; (3) the exponential increase in abutment stress and tectonic stress as the width of the triangular coal pillar decreases leads to a high concentration of static stress, which induces pillar burst under the disturbance of dynamic stress from fault activation; (4) the numerical simulation shows that when the working face is 150 m away from the fault, the static stress and accumulated energy in the triangle coal pillar begins to rise, reaching the peak at 50 m away from the fault, which is consistent with the theoretical analysis; (5) the constructed stress index indicates that the triangular coal pillar exhibits moderate rock burst risks when its width is between 73 to 200 m, and exhibits high rock burst risks when the width is within 0 to 73 m. The energy accumulation pattern of the triangular coal pillar reveals that separate stress relief measures should be implemented within the ranges of 50 to 150 m and 0 to 50 m, respectively, in order to enhance the effectiveness of stress relief. Blasting stress relief measures for the roof and coal are proposed, and the effectiveness of these measures is subsequently verified. Full article

With the increasing depth of coal mining, the ground stress of coal seams rises, the gas content rises, and the permeability decreases, which is unfavorable to gas extraction and increases the possibility of gas accidents in coal mines. Blasting technology is often used to improve the permeability of coal seams and increase the effect of gas extraction, but it is difficult to control the blasting effect of ordinary flux coils, and the direction of the fissure and the degree of development of randomness, so it is important to study the effect of different flux coil structures on the blasting of coal seams to increase the permeability of the coal seam, in this paper, first of all, through the numerical simulation to analyze the effect of the blasting of the ordinary structure flux coils and the fissure change in the polygonal structure flux coils, and then make the experimental module. Then, we make the test module, build the test platform, and analyze the effect of blasting penetration of different drug coil structures by comparing the strain after blasting and the change in resistivity before and after blasting of two kinds of drug coil structures, and the results show that the polymerized drug coil can play the role of directional fracturing, and compared with the ordinary structure of the drug coil, the polymerized drug shows a better effect of fracturing and penetration increase. Full article

The cement industry is known for being highly energy-intensive and a significant contributor to global CO₂ emissions. To address this environmental challenge, this study explores the potential of using the waste materials of steel slag (SS) and eggshell powder (ESP) as partial replacements for cement in alkali-activated mortars (AAMs) production, activated by NaOH and Na₂SiO₃. Mortar samples are prepared with 50% of ordinary Portland cement (OPC) as part of the total binder, and the remaining 50% is composed of ESP, incrementally replaced by SS at levels of 10%, 20%, 40%, and 50%. The activation process was performed with an 8% NaOH concentration and a silica modulus of 2. Key findings include that the workability of AAMs decreased with increasing SS content, requiring admixtures like superplasticizers or additional water to maintain workability. At 50% SS replacement, the water consistency and slump flow values were 32.56% and 105.73 mm, respectively, with a setting time reduction of approximately 36%, losing plasticity within 2 h. Both absorption capacity and porosity decreased as SS content increased from 10% to 50% of ESP. Additionally, the bulk density, compressive strength, and uniformity of the hardened mortar samples were enhanced with higher SS content, achieving maximum compressive strength (28.53 MPa) at 50% SS replacement after 56 days of curing. Furthermore, OPC-based AAMs incorporating SS and ESP demonstrate good resistance to sulfate attack and thermal heating. Microstructural analysis reveals the presence of C–S–H, C–A–S–H, and N–A–S–H phases, along with minor amounts of unreacted particles, and the microstructure shows a dense, highly compacted, and homogeneous morphology. These findings suggest that replacing eggshell powder with up to 50% steel slag enhances the hardened properties of AAMs. Further research is recommended to explore cement-free alkali-activated granular ground blast furnace slag (GGBFS) with ESP for more sustainable construction solutions. Full article