Search Results (294)

Accurate prediction of the temperature field around shallow-buried freezing pipes is important for the design and assessment of artificial ground freezing systems in shallow tunnel and underground structure construction. This study develops a semi-analytical series solution for the steady-state temperature field around a twin-pipe freezing unit in a semi-infinite domain under Dirichlet boundary conditions. The model assumes steady-state heat conduction in homogeneous and isotropic soil with prescribed pipe wall and ground surface temperatures; transient phase change, groundwater seepage, and thermo-hydro-mechanical coupling are not considered. Conformal mappings are used to transform the original semi-infinite and eccentric domains into bounded circular domains. The temperature field is decomposed into two subproblems by superposition, and the corresponding general solutions are expressed using Fourier series. The unknown coefficients are determined through boundary discretization and the solution of a finite linear algebraic system. The proposed method is compared with ANSYS Fluent results in the transformed domain at six selected points, yielding a pointwise NRMSE of 0.758% at a truncation order of 20. Parametric analyses further illustrate the qualitative sensitivity of the calculated temperature field to different ground surface temperatures, pipe radii, burial depths, and pipe spacings. The proposed method provides a preliminary semi-analytical framework for rapid quasi-steady temperature field estimation and qualitative parameter sensitivity analysis of shallow-buried twin-pipe artificial ground freezing systems. Full article

Urban ground collapse (UGC) threatens dense coastal cities because failures can occur abruptly beneath roads and buried lifelines. We developed a dynamic and interpretable machine-learning framework for UGC susceptibility assessment in Shenzhen, China. We integrated 1687 events from 2017 to 2024 with 20 predictors covering terrain, rainfall, drainage infrastructure and urban disturbance. Event-date rainfall was assigned to collapse samples, and background controls received year-constrained pseudo-event dates after spatial exclusion. Three tree-ensemble models were evaluated under random 75/25 testing, leave-one-district-out spatial validation and temporal hold-out testing. The selected LightGBM 1:5 model achieved ROC-AUC = 0.934, AP = 0.790 and BA = 0.860 in random testing, with more conservative ROC-AUC values of 0.905 and 0.884 under spatial and temporal validation. High-rainfall mapping expanded high and very high susceptibility zones from 4.60% to 15.26% and increased event capture from 19.32% to 58.92%. Grouped SHAP indicated comparable pipeline and rainfall contributions (26.01% and 25.13%). The leading predictors were pipe burial depth, road density and 30-day rainfall. PDP and spatial SHAP diagnostics highlighted high model responses where deep pipes coincided with high antecedent rainfall or dense roads in mature urban cores. This framework supports the rainfall-conditioned, mechanism-informed susceptibility diagnosis for early warning and mitigation. Full article

In Mediterranean countries such as Portugal, summer heatwaves increasingly threaten agricultural productivity by disrupting crop physiological processes. Greenhouse cultivation often exacerbates heat stress, while conventional cooling systems such as air conditioning and evaporative cooling impose unsustainable energy demands. This study investigates an Earth-to-Air Heat Exchanger (EAHE) system consisting of a five-tier helical PVC pipe configuration (29 m, buried at a depth of 3 m), installed in a prototype polycarbonate greenhouse in Covilhã, Portugal, and monitored under real summer conditions. Four ventilation scenarios were simulated in EnergyPlus 25.1, and a segmented NTU thermal model, implemented as a Python plugin via the pyenergyplus API, predicted the EAHE outlet temperature with CV(RMSE) values of 1.47% at 30 m³/h and 3.0% at 50 m³/h. The IPMA meteorological dataset provided the best simulation accuracy (RMSE = 2.31 °C, R² = 0.978). In simulations based on the experimentally calibrated models, EAHE preconditioning reduced accumulated heat stress degree-hours above 28 °C by 9.1 to 9.5% and lowered peak indoor temperature by up to 2.60 °C, at system COPs of 6.9 to 10.6, which are 2.3 to 3.5 times higher than conventional vapour-compression cooling; propagated measurement uncertainties confirm the robustness of this COP advantage. A model-based parametric scale analysis indicated that geometrically scaled circuits (DN200, DN400) achieve degree-hour reductions of 67 and 91%, supporting EAHE scalability through geometric proportioning, pending experimental validation at larger scales. Full article

External corrosion of buried ferrous water mains remains the dominant driver of structural failure in aging water distribution networks, yet the mechanisms linking soil physical and chemical heterogeneity to corrosion kinetics and product phase evolution have not previously been synthesized into a unified critical framework. This review evaluates three partially competing accounts of electrochemical degradation—anodic dissolution coupled to oxygen reduction within porous rust layers, redox cycling of iron oxide phases driven by seasonal soil moisture fluctuations, and microbially influenced corrosion (MIC) mediated by direct extracellular electron transfer (EMIC) and chemical metabolite pathways (M-MIC)—and assesses the weight of evidence for each. We demonstrate that corrosion products retain electrochemical activity long after formation, functioning as dynamic redox mediators that continue the reactions responsible for their own growth: the reduction of lepidocrocite under anoxic conditions regenerates Fe²⁺ ions that sustain anodic dissolution and catalyze oxygen reduction, while repeated soil moisture cycles drive the irreversible transformation of γ-FeOOH to Fe₃O₄, which fundamentally alters the conductivity and cathodic capacity of the rust layer. The widely cited universal critical-moisture threshold of 65% water-holding capacity (WHC) is evaluated and found to be a single-point approximation contradicted by texture-resolved experimental data that show the critical degree of saturation ranges from S_r ≈ 0.5 in sand to S_r ≈ 0.8 in clay. Modern machine learning analyses of field corrosion databases confirm that chloride content, pH, pipe-to-soil potential, and water content are the four highest-ranked predictors of maximum pit depth, consistent with the mechanistic framework developed here. The classical cathodic depolarization model of SRB-driven corrosion is evaluated against EMIC evidence and found insufficient: measured pure-culture SRB corrosion current densities range from 14 to 135 µA cm⁻², not the milliampere-level values reported in some earlier reviews. An explicit research agenda is proposed to address the five most consequential unresolved mechanistic questions. Full article

Agricultural steel pipelines are essential components of pressurized irrigation systems, yet localized corrosion-induced pinholes severely compromise their structural integrity by creating critical stress concentrations. To address the lack of performance-based maintenance guidelines, this study experimentally evaluates three repair techniques—a multi-joint hinge clamp, a GFRP composite sleeve, and overlay welding—applied to steel pipes containing simulated pinhole defects representing 6% and 10% circumferential damage. Four-point bending and uniaxial tensile tests were conducted to simulate transverse overburden and longitudinal axial loading encountered in buried pipelines. Results reveal that repair effectiveness strongly depends on both loading mode and damage severity. At 6% damage, all methods effectively restored bending capacity, with the GFRP sleeve achieving near-complete recovery. Under tensile loading, however, external-confinement methods provided limited ductility improvement because they lack a direct axial load-transfer path. In contrast, overlay welding consistently achieved substantial structural restoration by eliminating stress concentrations and shifting fracture to the parent pipe material. Furthermore, a significant transition in repair performance was observed near the 6% damage level, beyond which confinement-based repairs exhibited reduced efficacy. These findings demonstrate that repair performance cannot be reliably assessed from bending behavior alone and highlight the importance of considering both loading conditions and damage severity in rehabilitation design. The study provides a quantitative framework for load-specific pipeline rehabilitation strategies. Full article

Buried steel frame-reinforced polyethylene (SRPE) pipelines are vulnerable to bending-compression buckling, sectional distortion, and tensile rupture when crossing reverse faults. Nevertheless, their multi-mode failure mechanisms and strain evaluation frameworks have not been systematically clarified. Given this challenge, a three-dimensional nonlinear finite element model considering pipe–soil contact, material elasto-plasticity, and large deformation is established in this study to investigate the deformation characteristics, strain evolution, and buckling performance of SRPE pipelines under reverse fault inclination angles from 0° to 150°. The effects of internal pressure, steel frame diameter, and soil properties on pipeline mechanical behavior are analyzed, with the results being compared with the strain limits specified in the GB 50470-2017, CSA Z662-2023, and EN 13476-3 standards. The pipeline is subjected to a three-stage failure process involving local compressive buckling, overall bending, and tensile necking. Notably, coupled bending-compression failure is typical at low inclination angles, while high angles are dominated by shear-tension coupling. Excessive internal pressure increases the local buckling and concentration of compressive strains. An increase in the steel frame diameter contributes to an effective improvement in the buckling resistance. When the soil has higher cohesion and stiffness, the critical buckling displacement becomes larger. The standard constant strain limits currently adopted do not account for the transition in failure mode arising from inclination control and are therefore overly conservative for SRPE pipelines. This study provides a theoretical foundation and quantitative reference for the seismic design and safety assessment of SRPE pipelines crossing reverse fault zones. Full article

Buried pipelines with corrosion defects crossing reverse faults exhibit complex seismic responses under the combined effects of ground motion and fault displacement. Traditional finite-element analysis is computationally inefficient to comprehensively address such problems. This paper proposes a backpropagation neural network (BPNN)-based method for seismic response prediction and fragility assessment. A three-dimensional finite-element model is first employed to analyze the effects of corrosion depth-to-thickness ratio, diameter-to-thickness ratio, internal pressure, and burial depth on the axial compressive strain of the pipeline. Consequently, a BPNN model is constructed with these parameters, along with fault displacement, as inputs with the peak compressive strain as the output. The BPNN model demonstrated excellent predictive performance, with a maximum prediction error below 15%. The incremental dynamic analysis (IDA) method is then applied to map strength and damage indices of the pipeline, enabling quantitative evaluation of its failure probability and functional integrity under various conditions. It is found that higher diameter-to-thickness ratio (D/t) corresponds to a higher likelihood of the pipeline reaching adverse performance levels; this is also accompanied by a reduction in functional integrity. Specifically, as D/t increases from 72 to 144, the probability of pipe wall damage and the risk of transmission function loss rise significantly, highlighting the pronounced fragility of thin-walled pipelines subjected to fault movement. Moreover, corrosion defects exacerbate pipeline fragility: a corrosion depth equivalent to 10% of the wall thickness substantially amplifies strain responses, resulting in an approximately 80% probability of moderate damage, while a corrosion depth of 40% elevates the probability of severe damage beyond 60%. Full article

With the Green Deal and the Circular Economy Action Plan, the European Union aims to replace half of the fossil-based raw materials in plastics with sustainable alternatives by 2030. In the plastic pipe industry, the use of post-consumer recyclates (PCRs) remains very limited due to reduced material quality, economic hurdles, limited availability, non-specific classification requirements, and a lack of testing standards. This paper presents two interconnected contributions to the quality-assured use of PCR for buried utility infrastructure made from Polyethylene (PE), Polypropylene (PP), and unplasticized Polyvinyl Chloride (PVC-U). First, a methodological framework, based on EN 13476, defines suitability as the intersection of material classification and application-specific requirements profile. A review of the current regulatory and technical situation reveals a systemic discrepancy: requirements profiles are oriented toward virgin material, while the scope of classification for PCR remains insufficiently defined. As a result, PCR is either used without adequate suitability assessment or blended with fillers, thereby limiting recyclability. Secondly, the review focuses on additive strategies, including restabilization, compatibilization, chain modification, and recyclate-compatible functional additives. These strategies are among the main technical solutions for closing the gap between PCR properties and the product’s requirements, reducing filler dependency, and enabling the long-term use of PCR in safety-critical applications. Full article

Detecting and localizing leaks in buried pipelines typically requires direct access to the pipe, which is often impractical in real-world conditions. Although ground-surface vibration measurements offer a non-intrusive alternative, their potential for spatial leak localization remains underexplored, particularly in relation to frequency-dependent attenuation effects. This study investigates how frequency-dependent energy decay encodes spatial information in leak-induced ground vibrations. Experimental wok was conducted using an outdoor buried pipeline testbed, where surface acceleration data were collected with a movable array of piezoelectric sensors. The measurements were reorganized into L-shaped sensor trios to enable directional analysis and increase the number of spatial configurations. Energy-based features extracted from discrete frequency bands were used to represent the leak signatures, capturing both attenuation behavior and soil–pipe interaction effects. Artificial Neural Network and Random Forest models were trained to estimate leak coordinates in a local reference frame. The results demonstrate high localization accuracy at the centimeter scale and reveal consistent relationships between prediction error, distance, and signal-to-noise ratio. These findings show that frequency-dependent attenuation provides a robust basis for spatial inference, and that combining ground surface vibration measurements with lightweight machine learning models offers an effective and non-intrusive solution for leak localization in buried pipelines. Full article

Goaf gas drainage and residual-coal spontaneous-combustion prevention are often designed independently, even though both are controlled by the same leakage-flow, oxygen-transport and heat-release fields in a longwall goaf. This decoupled design may reduce methane accumulation while unintentionally enlarging the oxidation zone. Taking the No. 1217 fully mechanized working face of Zhongxing Coal Mine, Shanxi Province, China, as an engineering prototype, this study develops an integrated laboratory-field numerical framework to quantify the drainage-induced evolution of the three zones of spontaneous combustion. Programmed temperature-rise experiments on the No. 2 coal seam were used to determine the oxygen-consumption rate, heat-release intensity and apparent activation energy under oxygen concentrations of 3–21%, yielding a critical oxygen concentration of 5.9%. Bundle-tube monitoring and distributed optical-fiber temperature sensing delineated the in situ three-zone boundaries, and a three-dimensional CFD model coupling porous-media seepage, species transport and Arrhenius-type heat generation was validated against the field data, with most relative errors below 5%. Parametric simulations for buried-pipe depths of 20, 30 and 50 m and negative pressures of 15 and 20 kPa reveal a pronounced asymmetric response: drainage compresses and advances the return-side oxidation zone toward the working face, but drives the inlet-side oxidation zone deeper into the goaf by enhancing oxygen-bearing leakage. Within the investigated parameter space, a buried depth of 30 m and a negative pressure of 20 kPa provide the best compromise, reducing the return-side oxidation-zone width from 32 to 21 m and the upper-corner methane concentration from 6.80% to 0.58%. The results demonstrate that drainage design should be constrained simultaneously by methane dilution and oxidation-zone control, and provide a quantitative basis for coordinating gas extraction with fire prevention in gas-rich, oxidation-prone longwall panels. Full article

Horizontally buried rectangular hollow pipe barriers are investigated as a potential solution for mitigating ground-borne vibrations in densely built environments. This study combines high-fidelity three-dimensional finite-element analyses, a computationally efficient two-dimensional plane-strain modeling strategy, and a Python-based automated optimization framework to evaluate the effects of barrier geometry and material properties on vibration isolation performance. The results show that vertical vibration attenuation is consistently better than horizontal attenuation. Among the geometric variables, burial depth and barrier width are the dominant factors, with isolation benefits becoming marginal when the burial depth exceeds approximately 3 m and with barrier widths smaller than about 0.5 m leading to poor performance. The material parametric study indicates a threshold behavior for stiffness contrast: the improvement in isolation gradually saturates when the Young’s modulus ratio of barrier to soil exceeds about 5.12, suggesting that reinforced concrete provides a practical balance between structural reliability and engineering applicability. A comparison between the three-dimensional and two-dimensional models shows that the plane-strain approximation can reproduce the three-dimensional results with acceptable accuracy while substantially reducing the computational demand. The automated optimization further identifies high-performing design configurations for practical application. Overall, the study offers numerical insight and computational guidance for the preliminary design and evaluation of rectangular hollow pipe barriers for ground vibration mitigation. Full article

This study presents a compact controlled urban geophysics test site developed at the University of Malta to evaluate the response of complementary near-surface sensing methods under known shallow subsurface conditions. The experimental setup is designed to investigate buried target detection and the response to a simulated shallow leak, used here as a controlled water-release experiment in a shallow carbonate setting characterized by thin, laterally variable soil cover and anthropogenic disturbance. A preliminary passive seismic survey based on the horizontal-to-vertical spectral ratio (HVSR) method was used to compare candidate sectors and select the most suitable area for installation. The test site includes a buried iron plate and a perforated PVC pipe, the latter used to release water under controlled shallow conditions. Ground-penetrating radar (GPR), smartphone magnetometry, electrical resistivity tomography (ERT), and UAV-based thermal imaging were applied to assess target detectability and leak-related surface–subsurface responses. Results show that GPR provides the clearest response for static target detection, while smartphone magnetometry identifies the buried ferrous target under favourable conditions. For the simulated leak experiment, ERT provides the most robust subsurface evidence of moisture redistribution after water injection. UAV thermal imaging captures a complementary surface thermal response influenced by both moisture dynamics and local surface disturbance. The results show that a compact controlled test site can support the comparison of professional and low-cost sensing methods for shallow target detection and simulated leak assessment. In this configuration, the controlled water-release experiment provides a practical basis for evaluating leak-related surface–subsurface responses under known shallow conditions. The proposed setup has implications for methodological assessment, training, and near-surface environmental monitoring in heterogeneous urban settings. Full article

The behavior of buried pipes constructed on slopes is of great importance for the safety and sustainability of infrastructure systems. Slope movements, landslides, and soil displacements can significantly affect pipe–soil interaction, creating additional stresses on the pipes. Therefore, accurately determining the behavior of pipes under slope conditions is essential for improving engineering designs and preventing potential damage. In recent years, advanced experimental methods have been widely used in soil mechanics and geotechnical engineering studies to determine deformation and displacement fields. In this study, the behavior of buried pipes in reinforced and unreinforced sloping soils was experimentally investigated. Particle Image Velocimetry (PIV), an advanced image-based technique, was used to analyze soil deformation and displacement fields based on the images obtained during the model experiments. The results indicate that geogrid reinforcement has a significant effect on the behavior of the buried pipe and the deformation patterns of the soil. The study is primarily intended as a mechanism-oriented experimental investigation rather than an extensive parametric optimization study. Through PIV-based full-field displacement analyses, the evolution of deformation zones and failure surfaces around the buried pipe was evaluated in detail. Full article

Stray-current corrosion from DC-electrified railways drives premature failure of buried metallic infrastructure (pipelines, foundations, tunnel reinforcement), causing resource waste, repair-driven carbon emissions and service disruptions that undermine the sustainability of urban transit corridors. Conventional impressed-current cathodic protection (ICCP) design relies on uniform-anode rules of thumb or closed commercial codes that cannot quantify the trade-off between protection uniformity, energy use and hardware cost. We present an open MATLAB framework that couples a custom 3D finite element method (FEM) solver with multi-objective particle swarm optimisation (MOPSO) and minimises three competing objectives simultaneously: total impressed current, RMS deviation from the protection target, and number of active anodes. A laboratory-calibrated coupling factor ($\mathrm{CF}=1.98$, consistent with the image-method prediction of 2 for a highly conductive pipe inclusion) absorbs the pipe–soil interface kinetics into a single direct FEM solve, and a pre-computed Green’s-function basis accelerates each MOPSO evaluation by more than two orders of magnitude. The solver is validated against an instrumented prototype with RMSE $=14.9$ mV across ten Cu/CuSO₄ saturated reference electrode (CSE) measurements, and applied to a 500 m DC traction line. At an identical total current of 20.30 A across five anodes, the optimised design achieves an RMSE of 86.6 mV against the $-850$ mV NACE target, whereas a conventional uniform layout produces severe over-protection (RMSE $=1107$ mV)—a twelve-fold reduction. The framework is recommended as a transparent, reproducible engineering tool that simultaneously extends pipeline service life and reduces rectifier energy demand, supporting UN Sustainable Development Goals 9 and 11 for sustainable urban-rail infrastructure. Full article

This paper focuses on the application of ultrasonic guided waves in the defect inspection of buried pipelines, selecting circumferential cracks as the research object. Based on the three-dimensional finite element pipeline model, numerical simulation methods are employed to obtain defect echo signals for investigating the circumferential positioning accuracy, and the quantitative identification of the circumferential length and depth of crack geometries. For the circumferential positioning, a new circumferential positioning method is proposed. By introducing the circumferential position coefficient, the central angle is determined between the defect center point and the node corresponding to the maximum peak-to-peak amplitude of the echo signal. The maximum positioning error reaches 0.89% of the angle of the entire circle, achieving precise circumferential positioning of defects, and providing technical support for the development of future defect detection devices that use circumferential positioning. Regarding the identification of defect geometries, a back propagation (BP) neural network model is built for realizing the inversion of defect geometries, which is trained by using 13 feature indicators of numerical simulation datasets of defect echo signals in the time, frequency, and time–frequency domains. The trained model is then used to predict both the circumferential length and depth of cracks excluded from the dataset. The results demonstrate a maximum error of 0.46% of the pipe circumference for length and of 4% of the pipe wall thickness for depth. This high-precision inversion of the circumferential length and depth of cracks demonstrates that the model can significantly improve the detection accuracy of defect geometries in engineering applications. Full article