Search Results (23)

Buried pipelines in permafrost areas are affected by harsh environments, especially those with defects and damages, which are prone to failure or even leakage accidents. However, current research is limited to single-factor analysis and fails to comprehensively consider the interaction relationships among temperature fields, moisture fields, and stress fields. Therefore, based on the thermodynamic equilibrium equation and the ice–water phase transition theory, this paper constructs the temperature field equation including the latent heat of phase transition, the water field equation considering the migration of unfrozen water, and the elastoplastic stress field equation. A numerical model of the heat–water–force three-field coupling is established to systematically study the influence laws of key parameters such as burial depth, water content, pipe diameter, and wall thickness on the strain distribution of pipelines with defects. The numerical simulation results show that the moisture content has the most significant influence on the stress of pipelines. Pipelines with defects are more prone to damage under the action of freeze–thaw cycles. Based on data analysis, the safety criteria for pipelines were designed, the strain response surface function of pipelines was constructed, and the simulation was verified through experiments. It was concluded that the response surface function has good predictability, with a prediction accuracy of over 90%. Full article

In recent years, controlling the integrity of shallow-buried natural gas pipelines within surface subsidence zones caused by high-intensity underground longwall mining in the Daniudi Gas Field of China’s Ordos Basin has emerged as a critical challenge impacting both mine planning and the safe, efficient co-exploitation of coal and deep natural gas resources. This study included field measurements and an analysis of surface subsidence data from high-intensity longwall mining operations at the Xiaobaodang No. 2 Coal Mine, revealing characteristic ground movement patterns under intensive extraction conditions. The subsidence basin was systematically divided into pipeline hazard zones using three key deformation indicators: horizontal strain, tilt, and curvature. Through ABAQUS-based 3D numerical modeling of coupled pipeline–coal seam mining systems, this research elucidated the spatiotemporal evolution of pipeline Von Mises stress under varying mining parameters, including working face advance rates, mining thicknesses, and pipeline orientation angles relative to the advance direction. The simulations further uncovered non-synchronous deformation behavior between the pipeline and its surrounding sand and soil, identifying two distinct evolutionary phases and three characteristic response patterns. Based on these findings, targeted pipeline integrity preservation measures were developed, with numerical validation demonstrating that maintaining advance rates below 10 m/d, restricting mining heights to under 2.5 m within the 260 m pre-mining influence zone, and where geotechnically feasible, the maximum stress of the pipeline laid perpendicular to the propulsion direction (90°) can be controlled below 480 MPa, and the separation amount between the pipe and the sand and soil can be controlled below 8.69 mm, which can effectively reduce the interference caused by mining. These results provide significant engineering guidance for optimizing longwall mining parameters while ensuring the structural integrity of shallow-buried pipelines in high-intensity extraction environments. Full article

Pipe–soil interaction encompasses the study of stress distributions and deformation mechanisms occurring between buried pipelines and their surrounding soil. Understanding the mechanical behavior of this coupled system is essential for the analysis of deformation patterns and failure modes in buried pipelines, thereby providing critical guidance for construction design and risk assessment protocols. Traditional analytical approaches have relied on classical mechanics theories and experimental methodologies; however, these approaches often incorporate excessive simplifications and assumptions that inadequately represent the complex properties of both soil and pipeline structures. Numerical simulation methodologies have emerged as viable alternatives for investigating pipe–soil interaction. Among these numerical approaches, Smoothed Particle Hydrodynamics (SPH)—an advanced Lagrangian meshless particle method—offers distinct advantages in modeling complex behaviors, including free surfaces, deformable boundaries, and large deformation scenarios that characterize pipe–soil interaction. This research establishes a pipe–soil interaction model for buried pipelines utilizing the SPH method, incorporating elastic–plastic constitutive relationships to represent soil behavior. The investigation examines lateral interaction mechanisms, vertical interaction responses in sandy soils, and the parametric influence of various soil properties on pipe–soil interaction characteristics. This study contributes insights into the application of meshfree numerical simulation techniques for pipe–soil interaction analysis, offering both engineering utility and theoretical advancement for pipeline infrastructure design and safety assessment. Full article

Resilient water distribution system is crucial for sustainable urban water management. Evaluating the inherent resilience of the buried water infrastructure is key to ensuring reliable water distribution. The water distribution network maintains water quality and supplies sufficient water to users. Evaluating the system’s resilience under varying failure conditions is crucial to guarantee continued service delivery. This study investigates the resilience of the water distribution network for the University City, Sharjah, United Arab Emirates subjected to failure conditions caused by pipe failure, water contamination, and water excess demand. This research quantifies the corresponding performance under these stressors and develops an innovative resilience index by using the global resilience analysis (GRA) approach. The corresponding strain is in the form of node failure, chlorine decay, and pressure failures among all the pipes throughout the network. A survey was conducted with the water company to identify recovery time for the designated water distribution network. Another survey was conducted among the experts to evaluate the relative significance of all the strains in contribution towards resilience. Based on the resilience index, four levels (high, moderate, low, and very low) of resilience were defined. The study revealed Sharjah water distribution network has up to 40% of its stress categorized as low resilience and 60% of its stress categorized as very low resilience. The study also presented a management plan for the improvement of the designated water distribution network. Full article

The stress analysis of buried pipe culverts is a complex task, and accurately characterizing the deterioration of mechanical properties caused by corrosion poses significant challenges. In this study, the finite element analysis software PLAXIS 3D was employed to construct a numerical simulation model of a pipe culvert. By varying the stiffness and thickness of either the entire structure or specific sections, different degrees of corrosion were simulated to investigate the influence of various cross-sectional shapes on corrosion effects. Multiple experimental controls were set to analyze both the bearing capacity and deformation characteristics under different conditions. The findings reveal that different levels of corrosion have distinct impacts on the deformation behavior of pipe culverts. Overall corrosion has the most significant effect on the overall deformation, while crown and middle corrosion show a similar effect on stiffness-related deformations. In contrast, invert corrosion has minimal impact on the stiffness-related deformation. Corrosion affects circular and elliptical pipe culverts similarly. However, the circular pipe culvert is evidently influenced by overall corrosion more significantly than the elliptical ones due to the combined effects from overall and local corrosion in their deformations. Through finite element numerical simulation, it can be used as a reference for practical engineering design and construction. Full article

Uniform support from the surrounding soil is important for maintaining the stable operation of buried pipelines. For segmented prestressed concrete cylinder pipe (PCCP), localized soil voids around the joint due to leakage or engineering activities make the pipe unsupported partially and threaten its integrity and strength. In this paper, the impact of a localized soil void on a pipe joint is qualitatively assessed using a beam-on-elastic-spring approximation model. It further provides quantitative analysis through a nonlinear finite element (FE) model of PCCPs and the surrounding soil. The derived algebraic solutions indicate that a unilateral local void induces shear force and rotation at the joint, whereas shear force becomes negligible when the void spans the joint, leading to increased rotation. Moreover, the rotation angle shows a positive correlation with soil load and a negative correlation with pipe diameter. Numerical analysis reveals that void elongation along the pipe length has a more pronounced effect on structural response than void depth and angle. When the void length reaches 2.5 m, the maximum principal stress on the mortar layer of the PCCP increases approximately eight-fold compared to the scenario without voids. Due to the rigidity and safety factor of the PCCP, small voids in the bedding typically do not cause immediate pipe damage or joint leakage; however, they can significantly alter the stress distribution within both the pipe and surrounding soil. As the void develops, the soil may collapse and compromise support, leading to additional secondary disaster risks and potential threats to pipeline safety. This research emphasizes the importance of effective pipe-soil interactions and provides theoretical insights for developing repair strategies for PCCP. Full article

Buried pipelines are widely used, so it is necessary to analyze and study their fracture characteristics. The locations of corrosion defects on the pipe are more susceptible to fracture under the influence of internal pressure generated during material transportation. In the open literature, a large number of studies have been conducted on the failure pressure or residual strength of corroded pipelines. On this basis, this study conducts a fracture analysis on buried pipelines with corrosion areas under seismic loads. The extended finite element method was used to model and analyze the buried pipeline under seismic load, and it was found that the stress value at the crack tip was maximum when the circumferential angle of the crack was near 5° in the corrosion area. The changes in the stress field at the crack tip in the corrosion zone of the pipeline under different loads were compared. Based on the BP algorithm, a neural network model that can predict the stress field at the pipe crack tip is established. The neural network is trained using numerical model data, and a prediction model with a prediction error of less than 10% is constructed. The crack tip characteristics were further studied using the BP neural network model, and it was determined that the tip stress fluctuation range is between 450 MPa and 500 MPa. The neural network model is optimized based on the GA algorithm, which solves the problem of convergence difficulties and improves the prediction accuracy. According to the prediction results, it is found that when the internal pressure increases, the corrosion depth will significantly affect the crack tip stress field. The maximum error of the optimized neural network is 5.32%. The calculation data of the optimized neural network model were compared with the calculation data of other models, and it was determined that GA-BPNN has better adaptability in this research problem. Full article

This study undertakes a comprehensive experimental and numerical analysis of the structural integrity of buried RC sewerage pipes, focusing on the performance of two distinct jointing materials: cement mortar and non-shrinkage grout. Through joint shear tests on full-scale sewer pipes under single point loading conditions, notable effects on the crown and invert of the joint were observed, highlighting the critical vulnerability of these structures to internal and external pressures. Two materials—cement–sand mortar and non-shrinkage grout—were used in RC pipe joints to experimentally evaluate the joint strength of the sewerage pipes. Among the materials tested, cement–sand mortar emerged as the superior choice, demonstrating the ability to sustain higher loads up to 25.60 kN, proving its cost-effectiveness and versatility for use in various locations within RC pipe joints. Conversely, non-shrinkage grout exhibited the lowest ultimate failure load, i.e., 21.50 kN, emphasizing the importance of material selection in enhancing the resilience and durability of urban infrastructure. A 3D finite element (FE) analysis was also employed to assess the effect of various factors on stress distribution and joint deformation. The findings revealed a 10% divergence between the experimental and numerical data regarding the ultimate load capacity of pipe joints, with experimental tests indicating a 25.60 kN ultimate load and numerical simulations showing a 23.27 kN ultimate load. Despite this discrepancy, the close concordance between the two sets of data underscores the utility of numerical simulations in predicting the behavior of pipe joints accurately. This study provides valuable insights into the selection and application of jointing materials in sewerage systems, aiming to improve the structural integrity and longevity of such critical infrastructure. Full article

This paper addresses the challenges associated with steel pipes used for transporting liquid fluids within buried sections of mining facilities, specifically in areas with heavy mining vehicles. While existing design standards, such as AW-WA M11, and manufacturer recommendations largely consider loads from vehicles like the AASHTO HS20 or Cooper E-80, both weighing below 35 tons, these guidelines inadequately represent the actual loads experienced on certain mining roads, notably those accommodating heavy vehicles, like haul roads. The research presented here focuses on the interaction between soil and buried steel pipes under the substantial loads exerted by mining vehicles with a maximum gross load of up to 612 tons, inclusive of hauled material weight. Utilizing a parametric study with the finite element method, the paper identifies critical variables influencing efforts and deflections calculations in these facilities. The analysis of 108 models, varying parameters related to trench pipe installation conditions, offers insights that empower designers to refine soil trench parameters in mining facilities, mitigating pipe failures and optimizing installation costs. Ultimately, the key influential variables affecting pipe deflection and stress are identified as the trench backfill height and the elasticity modulus of the trench lateral fill. Full article

Buried flexible pipes are allowed to deflect up to 2–5% of the pipe diameter, which can become problematic for the connected direct-bury, large-diameter butterfly valves. The complex behavior of the pipe–valve–soil system makes it difficult to predict the deflection of the pipe/valve system. In the absence of field/experimental studies, the application of finite element analysis (FEA) seems necessary to predict deflection and stresses and to avoid potential downtime associated with disruption of service. This paper described the FEA of a large-diameter pipe–valve system, with different backfills under gravity, overburden, and internal pressure loads. The effects of modeling different components of the system (e.g., flanges, bearing housing, gate disc, etc.) were described and investigated. The goal of this study was to provide insight into the design and installation of direct-bury pipe–valve systems and evaluate current installation methods in the absence of guidelines. In addition, the level of modeling details required for FEA to yield accurate results was discussed. Full article

In order to ensure the safe operation of buried polyethylene pipelines adjacent to blasting excavations, controlling the effects of blasting vibration loads on the pipelines is a key concern. Model tests on buried polyethylene pipelines under blasting loads were designed and implemented, the vibration velocity and dynamic strain response of the pipelines were obtained using a TC-4850 blast vibrometer and a UT-3408 dynamic strain tester, and the distribution characteristics of blast vibration velocity and dynamic strain were analyzed based on the experimental data. The results show that the blast load has the greatest effect on the circumferential strain of the polyethylene pipe, and the dynamic strain response is greatest at the section of the pipe nearest to the blast source. Pipe peak vibration velocity (PPVV), ground peak particle velocity (GPPV), and the peak dynamic strain of the pipe were highly positively correlated, which verifies the feasibility of using GPPV to characterize pipeline vibration and strain level. According to the failure criteria and relevant codes, combined with the analysis of experimental results, the safety threshold of additional circumferential stress on the pipeline is 1.52 MPa, and the safety control vibration speed of the ground surface is 21.6 cm/s. Full article

Landslides are one of the most serious geological disasters in oil and gas pipelines. According to investigations, the cross-cutting relationship between landslides and pipelines can be divided into three types: pipeline longitudinal crossing landslide, pipeline transversely crossing landslide, and pipeline oblique crossing landslide. This different cross-cutting relationship is one of the important factors affecting pipeline landslide disasters. As a result, it is necessary to study the stress and deformation characteristics of oil and gas pipelines under different cross-cutting relationships, which is of great significance for the prevention and control of oil and gas pipeline landslides. In this paper, an ideal pipe-soil coupling interaction model of oil and gas pipeline oblique crossing landslide was established using FLAC3D. The influence of the buried depth of the pipeline, the displacement of the sliding body, and the different intersection angles of landslide and pipeline on the deformation and stress of the pipeline under the action of a landslide is analyzed, and a typical case of pipeline oblique crossing landslide is used for analysis. The results demonstrated that the stress of pipeline oblique crossing landslide is complex, and the stress concentration is obvious at the shear outlet and the trailing edge of the landslide. The stress at the shear outlet is the largest, which should be regarded as the key location. The displacement and stress of pipeline oblique crossing landslide are obviously affected by the displacement of the sliding body and the buried depth of the pipeline. The displacement and stress of the pipeline increase significantly with the increase of the displacement of the sliding body. With the increase of pipeline buried depth, the displacement of the pipeline shows an overall decrease, and when the buried depth of the pipeline is 3–3.5 m, the displacement and stress are close to the peak, indicating that the buried depth is of great risk. The intersection angle between the pipeline and landslide has a significant effect on the stress of the pipeline. The smaller the intersection angle, the safer the pipeline is. Full article

Sensitivity analysis aids in determining important factors affecting pipeline safety. Sensitivity analysis of stress inside gas pipelines with corrosion defects in a landslide region can provide a theoretical basis for the safe operation of pipelines. This study considered an X80 high-grade steel gas pipeline model with corrosion defects using finite element analysis (ABAQUS software) under lateral landslide conditions. Particularly, we studied the six major engineering elements of soil cohesion to understand the stress variations in buried gas pipelines and performed a sensitivity analysis of each influencing parameter. The calculation results revealed that all the factors influencing the stress in corroded gas pipelines during landslide conditions were positively correlated to the internal pipe stress, except for the axial position of corrosion defects. The factors in the descending order of influence on the sensitivity coefficient are stated as follows: landslide displacement, axial position of corrosion defect, soil cohesion, depth of corrosion defect, pressure, and length of corrosion defect. The results of this study will aid in the design and implementation of such pipelines in mountainous or other landslide-prone terrains. Full article

When a pipe roof is used as a pre-support for the surrounding rock in a shallowly buried tunnel, accurate prediction of the support effectiveness of the pipe roof is important in order to ensure the rationality of the pipe roof structure design. Based on analysis of pipe roof pre-support effects, considering the construction time of pipe roof structures and the interaction mechanisms between the steel pipes of the pipe roof and the surrounding rock, we establish a calculation model of the surrounding rock pressure acting on each steel pipe of the pipe roof on the semi-circular pre-support boundary. Through comparison and analysis with the measured results, we demonstrate that the calculation model for surrounding rock pressure and the calculation model for stress and deformation of the pipe roof are reasonable. According to the deformation coordination conditions between the steel pipe of the pipe roof and the surrounding rock on the pre-support boundary and alongside the Peck formula, we establish a theoretical analysis method for pipe roof pre-support effectiveness based on the indexes of the ground loss rate, settlement trough width, and maximum ground surface settlement, thereby realizing a quantitative evaluation of pipe-roof pre-support effectiveness. At the same time, the effects of steel pipe diameter, circumferential spacing, and excavation footage length on the pre-support effectiveness of the pipe roof are analyzed. The conclusions can be used as a basis for the design and optimization of pipe roofs and as a guide for the application of pipe roofs. Full article

In the Huainan and Huaibei mining areas, a layer of calcareous clay is buried deep in the surface soil layer (at approximately 400 m). This layer is in a high-stress state and is prone to freezing pipe fractures in the freezing method. To obtain the true triaxial mechanical properties of this clay in its frozen state, this study conducted a cross test (L₁₆(4⁵)) to explore the change law of the strength of frozen calcareous clay under the influence of multiple factors. The results showed that the true triaxial stress–strain curve of frozen calcareous clay was divided into three stages: the strain within 0.5% showed linear elasticity. Under compressive stress, ice crystals and their cements were damaged or melted and shrank. At approximately 5%, they showed plastic hardening. The soil particles and ice crystals in the frozen soil recombined and became denser, resulting in irreversible deformation. As the compression progressed, cracks bred and swelled. The failure stage was manifested as strain hardening due to the test loading conditions. As the deformation increased, the stress also slightly increased. The consistent strength-influencing factors could be obtained through range and hierarchy analyses. The primary and secondary order of influence of σ₁ was the confining pressure σ₃, water content ω, temperature T, Bishop parameter b, and salt content ψ. The influence weight of each factor was quantitatively calculated. In the significance analysis, when the interaction was not considered, the effects of the pressure and moisture content on the strength were always significant. The effect of temperature was significant only when the significance level Ω > 0.05. The salt content and b value had no significant influence on the strength, and the significance of each factor followed the order of the results of the range analysis method and analytic hierarchy process; when considering the interaction, the interaction factors had different effects on the strength. When Ω > 0.01, the influence of factor A (temperature T) × B (water content ω) on the strength showed significance, even exceeding that of temperature. This demonstrated that when studying the strength characteristics of frozen soil, it is necessary to comprehensively consider the various factors and their interaction to more accurately characterize the mechanical behavior of frozen solids. Full article