Search Results (70)

Long-distance coal gangue slurry transportation pipelines are critical components of underground coal mine green backfilling systems, yet blockage failures severely threaten their safe and efficient operation. Existing distributed acoustic sensing (DAS)-based monitoring methods for such pipelines suffer from three key limitations: insufficient fixed-point quantitative accuracy, lack of verified blockage-specific characteristic indicators, and limited quantitative severity assessment capability. To address these gaps, this paper proposes a novel feature-level fusion monitoring method integrating DAS, fiber Bragg grating (FBG), and piezoelectric accelerometers for accurate blockage identification and quantitative evaluation in coal gangue slurry pipelines. A slurry pipeline circulation test platform with gradient blockage simulation (0% to 76.42%) and a synchronous multi-sensor monitoring system were developed. Through multi-domain signal analysis, three blockage-correlated characteristic frequencies were identified and cross-validated by synchronous multi-sensor data: 1.5 Hz (system background vibration), 26 Hz (blockage-induced fluid–structure resonance, verified by the Euler–Bernoulli beam theory with a theoretical value of 25.7 Hz), and 174 Hz (transient flow impact). The DAS phase change rate exhibited a unimodal nonlinear response to blockage degree, with the peak occurring at 40.94% blockage. On this basis, a sine-fitting quantitative inversion model was developed, achieving a high goodness of fit (R² = 0.985), and leave-one-out cross-validation confirmed its excellent robustness with a mean relative prediction error of 3.77%. Finally, a collaborative monitoring framework was built to fully leverage the complementary advantages of each sensor, realizing full-process blockage monitoring covering global blockage localization, precise quantitative severity calibration, and high-frequency transient risk early warning. The proposed method provides a robust experimental and technical foundation for real-time early warning, precise localization, and quantitative diagnosis of long-distance slurry pipeline blockages and holds important engineering application value for the safe and efficient operation of underground coal mine green backfilling systems. Full article

Subsequent backfilling mining methods are critical technologies for the safe exploitation of deep metal mines, while the resource utilization of ultrafine tailings is a core component of green mining practices. This study focuses on the ultrafine tailings from the Tianxing iron mine to investigate the preparation and optimization of backfill slurry. The goal is to develop a low-cost, high-strength slurry suitable for large-scale preparation and long-distance pipeline transportation. The main findings are as follows: the 6920-type anionic flocculant was identified as the optimal agent, with an optimal dosage of 20 g/t, achieving an underflow concentration of 70.1% under dynamic testing conditions; a novel cementitious material (NCM) exhibited a 28-day uniaxial compressive strength of 3.14 MPa at a low binder-to-tailings ratio of 1:10, outperforming ordinary Portland cement and Slag Micro-powder; and the optimal slurry concentration was determined to be 70%, which provides a favorable balance between mechanical strength and flowability. Furthermore, economic analysis indicates that adopting NCM can reduce annual backfilling costs by approximately 13 million RMB. By establishing an integrated technical framework that includes “property characterization–flocculation optimization–binder selection–rheological regulation,” this study addresses key technical challenges associated with ultrafine tailings backfilling, significantly reduces binder consumption and overall backfilling costs, and provides precise parameter guidance for industrial-scale applications. The proposed approach demonstrates significant practical value for promoting green and sustainable mining development. Full article

To address the safety and environmental challenges associated with deep mining, this study investigates the rheological behaviors and pipeline transport characteristics of cemented paste backfill (CPB) using unclassified tailings from a lead–zinc mine. Through the characterization of basic physicochemical properties—including chemical composition, particle size distribution, and specific surface area—combined with L-shaped pipeline simulation tests, the effects of slurry concentration and pipe diameter on rheological parameters and transport resistance were quantitatively analyzed. Furthermore, the mechanical performance and cost-effectiveness of four different cementitious binders were evaluated to identify the optimal material. The results indicate that the unclassified tailings possess a favorable particle size distribution with a significant fine-particle filling effect, making them suitable as backfill aggregates. Slurry concentration was identified as the critical factor influencing rheological performance; a concentration range of 68% to 72% was determined to be optimal, exhibiting superior fluidity and low pipeline resistance conducive to gravity flow. Additionally, increasing the pipe diameter was found to effectively reduce transport difficulty. Based on a comprehensive technical and economic analysis, Kunlun Mountain PO42.5 cement was selected as the optimal binder, achieving the required backfill strength with controlled costs. This study provides a theoretical basis and practical engineering guidance for the design and optimization of deep-well backfill pipeline systems. Full article

Cemented tailings backfill (CTB) is widely used in mining operations due to its operational simplicity, reliable performance, and environmental benefits. However, the poor consolidation of fine tailings with ordinary Portland cement (OPC) remains a critical challenge, leading to excessive backfill costs. This study addresses the utilization of modified manganese slag (MMS) as a supplementary cementitious material (SCM) for fine tailings from an iron mine in Anhui, China. Sodium silicate (Na₂SiO₃) modification coupled with melt-water quenching was implemented to activate the pozzolanic reactivity of manganese slag (MS) through glassy structure alteration. The MMS underwent comprehensive characterization via physicochemical analysis, X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) to elucidate its physicochemical attributes, mineralogical composition, and glassy phase architecture. The unconfined compressive strength (UCS) of the CTB samples prepared with MMS, OPC, tailings, and water (T-MMS) was systematically evaluated at curing ages of 7, 28, and 60 days. The results demonstrate that MMS predominantly consists of SiO₂, Al₂O₃, CaO, and MnO, exhibiting a high specific surface area and extensive vitrification. Na₂SiO₃ modification induced depolymerization of the highly polymerized Q⁴ network into less-polymerized Q² chain structures, thereby enhancing the pozzolanic reactivity of MMS. This structural depolymerization facilitated formation of stable gel products with low calcium–silicon ratios, conferring upon the T-MMS10 sample a 60-day strength of 3.85 MPa, representing a 94.4% enhancement over the T-OPC. Scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) analysis revealed that Na₂SiO₃ modification precipitated extensive calcium silicate hydrate (C-S-H) gel formation and pore refinement, forming a dense networked framework that superseded the porous microstructure of the control sample. Additionally, the elevated zeta potential for T-MMS10 engendered electrostatic repulsion, while the aluminosilicate gel provided imparted lubrication, collectively improving the flowability of the composite slurry exhibiting a 26.40 cm slump, which satisfies the requirements for pipeline transportation in backfill operations. Full article

Cemented paste backfill (CPB) is widely used in mining operations to enhance underground stope stability, production, and safety. Accurately predicting paste flow behaviours in backfill reticulation circuits is crucial for efficient delivery control and asset longevity. However, the predictions remain challenging due to complex rheology and flow-induced particle heterogeneities of CPB. This study develops a computational fluid dynamics (CFD)-based analysis framework to investigate flow dynamics of the CPB and the wear conditions of the pipes, considering slip layer and shear-induced particle migration. Experimental loop tests are conducted to measure pressure drops of CPB at different velocities, providing data for validating the developed CFD model. Simulation results are in good agreement with the measured pressure drops and wear rates of the internal pipeline wall. Furthermore, comparisons with existing models indicate that the developed model provides more accurate predictions. Microscopical analyses reveal that shear-induced particle migration leads to the formation of a distinct plug flow region, with particles accumulating near the unyielded boundary. Meanwhile, a low particle concentration near the pipe wall reduces local viscosity and pressure drop. Parametric studies reveal that increased flow velocity and reduced pipe diameter significantly elevate both pressure drop and wear rate, while higher solid concentrations induce nonlinear rheological effects. Full article

Subsea pipelines are critical lifelines for marine resource development, yet they face severe threats from accidental ship anchor impacts. This study addresses the scientific challenge of quantifying the “protection margin” of artificial rock-dumping layers, moving beyond traditional passive structural response to a “Critical Failure Intervention” logic. Based on the energy criteria of DNV-RP-F107, a critical velocity required to trigger Concrete Weight Coating (CWC) failure for a bare pipe was derived and established as the Safety Factor baseline (S = 1). Two groups of scaled model tests (1:15) were conducted using a Hall anchor to simulate impact scenarios, where impact forces were measured via force sensors beneath the pipeline under varying backfill thicknesses and configurations. Results show that artificial backfill provides a significant protective redundancy; a 10 cm coarse rock layer increases the safety factor to 3.69 relative to the H₀ baseline, while a multi-layer configuration (sand bedding plus coarse rock) elevates S to 27. Analysis reveals a non-linear relationship between backfill thickness and cushioning efficiency, characterized by diminishing marginal utility once a specific thickness threshold is reached. These findings indicate that while thickness is critical for extreme impacts, the protection efficiency optimizes at specific depths, providing a quantifiable framework to reduce small-particle layers in engineering projects without compromising safety. Full article

This study presents numerical results on 2D local scour around subsea pipelines positioned on sand wave seabeds under steady flow conditions, utilizing Flow-3D (v11.2) software. In the computational model, the flow dynamics surrounding the pipeline are resolved using the time-averaged 2D Navier–Stokes equations in conjunction with the Renormalization Group (RNG) k-ε turbulence model. The bed morphology is governed by the bedload transport rate, suspended load transport rate, and sediment mass balance equation. The research explores the influence of pipeline diameter and water depth on scour patterns over flat beds and investigates how the pipeline’s relative position to symmetrical sand waves affects the severity and morphology of scour. It is demonstrated that the non-dimensional scour depth decreases with an increase in pipeline diameter, whereas in shallower waters, the intensity of scour is greater for a given diameter. In the study of sand wave bed conditions, it was determined that the scour strength exhibits a hierarchical order from strongest to weakest as follows: pipeline located at the crest, downstream slope of the sand waves, pipeline situated on the upstream slope, and at the trough. It is noteworthy that the scour effect is marginally more pronounced at the crest compared to a flat seabed. Conversely, scour intensity diminishes at the other positions, particularly at the trough, where it often results in backfilling and the self-burial of the pipeline. Finally, the distributions of velocity and bed shear stress around the pipeline and seabed are presented to elucidate the flow mechanisms underlying the scour process. Full article

Gangue slurry pumping backfill offers a cost-effective and environmentally sound solution for coal mine solid waste disposal. Addressing the poor pumpability of pure gangue slurry, this study applied the Talbot gradation theory to a non-cemented gangue system by designing various particle size gradations and water-solid ratios (W/S). Through tests on rheological properties, slump, spread, and bleeding rate, the optimal proportion for pumpability of pure gangue slurry (PGS) within the scope of this study was determined. Tests were conducted on rheology, slump, spread flow, and bleeding rate to determine the optimal mix proportion for pumpability. The results show that: The slurry in this study demonstrates a strong correlation with the characteristics of a Bingham fluid. Its yield stress increases significantly as the W/S decreases. At a gradation index (n) of 0.4, particle packing is densest, resulting in the lowest yield stress. Slump and spread flow decrease with a lower W/S. They initially increase and then decrease as the gradation index increases, with optimal fluidity observed at n = 0.4. Bleeding rate increases with a higher gradation index but decreases with a lower W/S. Comprehensive optimization determined the optimal mix proportion as gradation index n = 0.4 and W/S of 0.18. At this ratio: Yield stress = 144.25 Pa, Slump = 255 mm, Spread flow = 60.1 cm, Bleeding rate = 2.21%. This meets the pumping requirements (Slump > 180 mm, Bleeding rate < 3%). The research results provide important experimental value for the practical pipeline transportation of PGS and the reduction in pumping friction resistance. Full article

HPMC, regulating slurry properties, is widely used in cement-based materials. Research on the application of HPMC in gangue slurry is still in its early stages. Moreover, the interactive effects of various factors on gangue slurry performance have not been thoroughly investigated. The work examined the effects of slurry concentration (X₁), maximum gangue particle size (X₂), and HPMC dosage (X₃) on slurry performance using response surface methodology (RSM). The microstructure of the slurry was characterized via scanning electron microscopy (SEM) and polarized light microscopy (PLM), while low-field nuclear magnetic resonance (LF-NMR) was employed to analyze water distribution. Additionally, industrial field tests were conducted. The results are presented below. (1) X₁ and X₃ exhibited a negative correlation with layering degree and slump flow, while X₂ showed a positive correlation. Slurry concentration had the greatest impact on slurry performance, followed by maximum particle size and HPMC dosage. HPMC significantly improved slurry stability, imposing the minimum negative influence on fluidity. Interaction terms X₁X₂ and X₁X₃ significantly affected layering degree and slump flow, while X₂X₃ significantly affected layering degree instead of slump flow. (2) Derived from the RSM, the statistical models for layering degree and slump flow define the optimal slurry mix proportions. The gangue gradation index ranged from 0.40 to 0.428, with different gradations requiring specific slurry concentration and HPMC dosages. (3) HPMC promoted the formation of a 3D floc network structure of fine particles through adsorption-bridging effects. The spatial supporting effect of the floc network inhibited the sedimentation of coarse particles, which enhanced the stability of the slurry. Meanwhile, HPMC only converted a small amount of free water into floc water, which had a minimal impact on fluidity. HPMC addition achieved the synergistic optimization of slurry stability and fluidity. (4) Field industrial trials confirmed that HPMC-optimized gangue slurry demonstrated significant improvements in both stability and flowability. The optimized slurry achieved blockage-free pipeline transportation, with a maximum spreading radius exceeding 60 m in the goaf and a maximum single-borehole backfilling volume of 2200 m³. Full article

As the demand for deep mineral resource extraction intensifies, optimizing pipeline transportation systems in backfill mining has become increasingly critical. Thus, reducing energy loss while ensuring the filling effect becomes crucial for improving process efficiency. Owing to variations among mines, accurately calculating pipeline resistance loss remains challenging, resulting in significant inaccuracies. The rapid development of Industry 4.0 provides intelligent and data-driven optimization ideas for this challenge. This study introduces a novel pipeline resistance loss prediction framework integrating generative artificial intelligence with a TransKAN model. This study employs generative artificial intelligence to produce physically constrained augmented data, integrates the KAN network’s B-spline basis functions for nonlinear feature extraction, and incorporates the Transformer architecture to capture spatio-temporal correlations in pipeline pressure sequences, enabling precise resistance loss calculation. The experimental data collected from pipeline pressure sensors provides empirical validation for the model. Compared with traditional mathematical formulas, BP neural networks, SVMs, and random forests, the proposed model demonstrates superior performance, achieving an R² value of 0.9644, an RMSE of 0.7126, and an MAE of 0.4703. Full article

The environmental hazards caused by the massive generation and improper disposal of industrial solid wastes (e.g., high calcium desulphurization ash, HCDA) and the growing safety risks posed by the increasing number of underground mine goafs generated by mining activities have become serious environmental and geotechnical challenges. To address the dual issues, this study develops a novel desulfurization ash–slag-based paste backfill (DSPB) material using HCDA and granulated blast furnace slag (GBFS) as primary constituents. The effects of cementitious material ratios, polycarboxylate superplasticizer (PCE), and sodium silicate (SS) on rheological properties of DSPB were investigated through a shear rheology experiment and fitting rheological model to assess the flow conditions in pipeline transportation. In addition, the mechanism was investigated through microanalysis. The results showed that with the decrease in desulfurization ash-to-slag ratio, the initial yield stress and plastic viscosity decreased by up to 88% and 34.9%, respectively; PCE via “card house” structural effects made the rheological parameters increase and then decrease, and a dosage of more than 1.2% significantly improved the rheological properties; and SS initially reduced the rheological parameters, but excessive doping (greater than 1.0%) led to an increase. These findings establish the relationship between DSPB composition and rheological properties, provide a practical solution for waste resource utilization and surface stabilization, and provide a scientific basis for the microstructure–rheology relationship of cementitious systems. Full article

Submarine pipelines laid across navigational channels are highly susceptible to anchor drop impacts, which can cause deformation and disrupt normal pipeline operations. In severe cases, anchor impacts may lead to oil and gas leaks, resulting in significant economic losses and environmental damage. To ensure the safe operation of submarine pipelines, artificial rock backfilling is widely employed as a protective measure. Compared with complex pipeline protection structures, this approach is both cost-effective and efficient. In the physical model experiment, a combination of total force sensors and thin-film sensors was used to measure the dynamic response of pipelines under anchor impact. Additionally, The FEM-DEM numerical method was used to simulate the dynamic response and interaction process of anchor impact on the rock protection layer and pipeline. Numerical results were compared with experimental data to analyze the effects of rock protection layer thickness, backfill rock particle size, and pipeline sublayer types on pipeline impact response. The results show a good agreement between the physical model tests and numerical simulation studies, revealing several factors that influence the mitigation effect of the rock protection layer. This study provides a valuable scientific reference for the installation of rock protection layers for pipelines. Full article

In practical engineering applications, the cold storage functional backfill cooling system is prone to pipe clogging due to the agglomeration and crushing effects of the components of the ice particle-containing filling slurry. In addition, the fluidity of the slurry becomes more complex due to the change in the particle size distribution (PSD) during the pipeline transportation of the filling slurry, which limits the practical application effectiveness of the system. In order to promote the application and sustainable development of mining solid waste resources, a CFD–PBM coupling model was established to simulate the flow of the ice-containing filling slurry in horizontal circular tubes. On this basis, the effects of the initial ice content, inlet flow rate, initial particle size of tailings, and filling slurry concentration on the caking phenomenon during pipeline transportation were analyzed. The distribution of the pressure drop along the pipeline was also analyzed and calculated. The results show that the higher the flow velocity, the lower the slurry concentration, the larger the tailings’ particle size, the lower the ice content, and the lower the likelihood of agglomeration during transportation of the filling slurry. Full article

Sanitary sewer pipelines frequently experience blockages, structural failures, and overflows, underscoring the dire state of U.S. wastewater infrastructure, which has been rated a D-, while America’s overall infrastructure scores only slightly better at C-. Traditional open-trench excavation methods or excavation technology (ET) for replacing deteriorated pipes are notoriously expensive and disruptive, requiring extensive processes like route planning, surveying, engineering, trench excavation, pipe installation, backfilling, and ground restoration. In contrast, trenchless technologies (TT) provide a less invasive and more cost-effective alternative. Among these, cured-in-place pipe technology (CIPPT), which involves inserting resin-impregnated fabric into damaged pipelines, is widely recognized for its efficiency. However, a comprehensive life cycle cost analysis (LCCA) directly comparing ET and TT, accounting for the net present value (NPV) across installation, maintenance, and rehabilitation costs, remains unexplored. This study aims to establish an LCCA framework for both CIPPT and ET, specifically for sanitary sewer pipes ranging from 8 to 42 inches in diameter. The framework incorporates construction, environmental, and social costs, providing a holistic evaluation. The key costs for ET involve pipe materials and subsurface investigations, whereas TT’s costs center around engineering and design. Social impacts, such as road and pavement damage, disruption to adjacent utilities, and noise, are pivotal, alongside environmental factors like material use, transportation, project duration, and equipment emissions. This comprehensive framework empowers decision makers to holistically assess economic and environmental impacts, enabling informed choices for sustainable sewer infrastructure renewal. Full article

With the advancement of backfill mining technology, cemented high-concentration backfill (CHB), composed of solid particles, such as high-concentration tailings or waste rock mixed with a small amount of binder, has gained widespread applications due to its superior filling performance. Given the complexity of the backfill pipeline network, studying the characteristics of pipe transportation is crucial. The local resistance in bending pipes represents an important parameter for CHB pipeline transportation. However, existing research on the local resistance characteristics of bending pipes lacks comprehensiveness and depth. This study proposes a novel definition of the local resistance coefficient as the ratio of pressure loss per unit length of a bend pipe compared to that of a straight pipe. Utilizing the computational fluid dynamics (CFD) method the impact of six different factors on the local resistance coefficient of the bending pipe is investigated: flow velocity, pipe diameter, slurry concentration, binder content, turning radius, and bending angle. The results indicate that the local resistance coefficient positively correlates with the flow velocity and pipe diameter but negatively correlates with the slurry concentration, turning radius, and bending angle. Among these factors, the slurry concentration exerts the most significant influence on the local resistance coefficient. The recommended approach to control the local resistance coefficient in the mine is to use CHB with a 76% solid fraction at a 1.5 m/s flow velocity, along with pipe parameters of a 0.15 m diameter, a 2.5 m turning radius, and bending angles between 90° and 150°. The findings provide a valuable reference for determining the optimal parameters for bend pipes and CHB and facilitate the theoretical calculation of resistance in complex filling pipeline networks. Full article