Joint separation in reinforced concrete pipes (RCPs) can cause leakage, groundwater infiltration, soil erosion, and loss of local structural support. Cured-in-Place Pipe (CIPP) rehabilitation restores continuity across separated joints, but the liner spanning the unsupported joint region remains susceptible to groundwater-induced external-pressure buckling. This study investigated the local buckling behavior of CIPP liners in separated RCPs through a full-scale external-pressure test and 3D FE analysis incorporating cohesive interface elements. Based on the resulting FE dataset, an FE–Kolmogorov–Arnold Network (KAN) model was further developed to derive a simplified equation for predicting the buckling pressure. The test identifies a response process comprising pressure rise, post-buckling pressure drop, and pressure recovery. The validated FE model was then used to evaluate the effects of interface modulus, liner thickness, joint rotation, liner equivalent elastic modulus, and joint separation distance. The results show that liner thickness is a primary factor controlling buckling resistance, whereas interface modulus mainly affects deformation compatibility and post-buckling restraint. Joint rotation increases the initial buckling pressure but reduces the post-buckling capacity. Increasing the liner equivalent elastic modulus improves buckling resistance, although the improvement becomes limited beyond approximately 6000 MPa. Increasing joint separation distance reduces the buckling pressure, with a more rapid decrease below approximately 0.4 m. The proposed FE–KAN equation provides reliable buckling-pressure predictions within the investigated parameter range.

The performance of polymer-reinforced geostructures is fundamentally governed by the mechanical behavior of the soil-polymer interface, yet a predictive constitutive framework for its shear failure remains a critical challenge. This study bridges this gap by introducing a novel elasto-plastic-damage constitutive model grounded in comprehensive direct shear experiments. A key innovation lies in the unification of a hump-shaped function for pre-peak hardening and a mechanically-enhanced Lubliner formulation with a dedicated residual stress term for post-peak softening, achieving seamless characterization of the entire failure process. Furthermore, a unified parameterization scheme is established, where a global optimization scheme derives explicit relationships between model parameters and normal stress, granting the model exceptional predictive power beyond its calibration domain. The model’s computational viability is demonstrated through implementation as an ABAQUS user-element subroutine (FRIC), with finite element simulations exhibiting remarkable fidelity to experimental results. Collectively, this work provides a robust and predictive numerical framework that significantly advances the analysis and design of geotechnical systems incorporating polymer reinforcements, offering clear advantages over conventional empirical or simplified theoretical approaches.

The mechanical behavior of pressure pipelines rehabilitated with polymer liners under surface loads remains poorly understood. In this study, a three-dimensional model of a pressure pipeline repaired with a polymer liner is developed and validated against existing results. The effects of various factors—such as position, burial depth, load offset distance, host pipe (pressure pipe) diameter, surface load, host pipe thickness, liner thickness, liner elastic modulus, internal pressure, and the friction factor between the host pipe and liner—on the axial strain and displacement distribution of the pressure pipeline are analyzed. The findings reveal that the load's influence on the pipeline is confined to within 5 meters of the load center. As the offset distance increases, the strain and vertical displacement at the pipe crown decrease, while the lateral displacement at the pipe crown initially increases before decreasing. Additionally, the lateral displacement at the pipe springline reverses direction. This study offers valuable insights for the operation and maintenance of pressure pipelines.

To investigate the mechanical performance and failure modes of Prestressed Concrete Cylinder Pipe (PCCP) bell-and-spigot joints under conditions such as differential settlement, this study conducted a full-scale rotation test on a DN1400 PCCP joint and established a three-dimensional non-linear finite element model using ABAQUS. The experimental results indicate that when the relative rotation angle reaches approximately 1.92 degrees, the primary failure mode is the slipping of the rubber gasket from the spigot groove, leading to sealing failure. Meanwhile, the strains in the concrete, mortar coating, and prestressing wires at the joint increase significantly with the rotation angle. The finite element simulation results align well with the experimental data, with an average error of 1.88%. Based on the validated model, a parametric analysis was performed on PCCP joints with diameters ranging from 1400 mm to 4000 mm. The study determined the ultimate relative rotation angle for different diameters based on the concrete visible crack criterion and revealed a significant size effect, characterized by a decrease in the ultimate rotation angle with increasing pipe diameter. These findings provide a theoretical basis for the design, construction, and safety assessment of PCCP pipelines.

Curved pipe jacking is a satisfying technique for laying the buried pipeline in trenchless crossing scenarios. Estimation of frictional resistance in curved pipe jacking exhibits a more complex pipe-soil interaction compared with linear drives. Deflection differential equations for curved pipes embedded on a Pasternak foundation are established, and the finite difference method is used for estimating the foundation reaction force and frictional resistance. As verified, the proposed model exhibits good rationality compared to a practical drive. Parametric analysis indicates that small-radius curvature induces a larger foundation deformation, while the easement curvature restricts the constraints influence of pipe boundaries on frictional resistance along the axial direction. Limited pipe diameter weakens the influence range of the foundation reaction force on the normal pipe-soil interaction. The axial force transfer within the shear layer diminishes as the foundation reaction coefficient enlarges, while the integral value of the foundation reaction follows a decrease-then-increase pattern. Moreover, increased shear stiffness enhances the force transfer performance among the soil springs in the shear layer, but declines the normal contact behavior between the pipe and foundation, contributing to an expanding frictional resistance.

Current analytical programs for estimating stresses in underground concrete pipes do not consider structural defects or the coupling effects of complex loads, thereby restricting their applicability under realistic burial conditions. In this study, 3D FE methods were employed to generate a dataset of 300 cases, involving 12 physical parameters and the corresponding maximum stresses in concrete pipes. The simulation results were validated against full-scale experimental tests. However, directly constructing a predictive model for the pipe’s maximum stress based on this dataset risked overfitting and poor generalization. To mitigate this issue, the dataset was further augmented using fitted empirical formulas, yielding a total of 3900 scenarios. Traditional machine learning models typically extract information from data through weighted summations of feature variables, while neglecting the interaction effects among them. Mathematically, they lack contribution information expressed in the multiplicative form of feature interactions. To overcome this limitation, a physics-constrained neural network (PCNN) framework was developed. In this framework, one-dimensional signals were input into a multi-layer perceptron (MLP), while two-dimensional product signals were processed using a convolutional neural network (CNN). The aggregated outputs from both models were subsequently introduced into a physics-constrained fully connected layer, thereby constructing a neural network prediction model for assessing the maximum stress in concrete pipes. Global SHAP value analysis of the proposed model shows that, except for groundwater level and backfill soil strength, which exhibit negative correlations with the model output, all other parameters display positive correlations. Local SHAP analysis further elucidates the mechanisms by which individual features interact with others to influence the prediction. Moreover, the proposed model demonstrates strong application potential in predicting the interaction responses between any two physical features and the maximum stress of concrete pipes, as well as in estimating the remaining service life of the pipes.

The coexistence of defects such as internal corrosion, cracks, and surrounding voids is frequently observed in concrete pipes. However, the mechanical response of concrete pipes subjected to the combined influence of these defects remains insufficiently understood. This study develops three-dimensional simulation models of pipe-soil systems, incorporating internal corrosion, longitudinal crack, and surrounding void, both individually and in combination. The investigation evaluates the effects of individual defects as well as their combined impact on the longitudinal behavior of concrete pipes. Numerical results for the combined defects are validated through comparisons with experimental data. The results indicate that corrosion, crack, void, and combined defects increase the peak stress at the crown by 31%, 10%, 33%, and 37%, respectively, and at the invert by 11%, 22%, 33%, and 56%, respectively, compared to intact pipes. Moreover, combined defects further elevate the peak stress at the crown by 5%, 25%, and 3% and at the invert by 36%, 28%, and 18%, relative to pipes with corrosion, crack, and void defects, respectively.

Water-rich sand layers are frequently encountered as adverse geological conditions during underground construction. Polymer slurry grouting has been widely recognized as an effective technique for reducing permeability and enhancing the stability of such strata. In this study, a mathematical model is established to describe the diffusion behavior of polymer slurry in porous media under dynamic water conditions and is further validated through laboratory experiments. The theoretical formulation of the slurry permeation process is developed based on Darcy’s law, the Hagen–Poiseuille flow principle, and the physicochemical characteristics of the slurry. The derivation primarily focuses on analyzing the dynamic response of the slurry under the influence of water flow, considering the effects of flow velocity, grouting pressure, and sand-layer porosity on diffusion behavior. To verify the proposed model, a visualized grouting simulation system was designed to observe the diffusion process of polymer slurry in water-rich sand layers. The results demonstrate that slurry diffusion is significantly affected by grouting pressure, porosity, and water flow velocity. The observed staged diffusion characteristics, dynamic evolution patterns, and directional effects are in good agreement with theoretical predictions. Furthermore, the average relative deviations between the theoretical and experimental results for diffusion pressure and diffusion distance are both less than 25%, confirming the reliability of the proposed model. Additionally, this study identifies distinct differences in slurry diffusion between porous and void media. In porous media, slurry propagation encounters greater hydraulic resistance, leading to rapid pressure attenuation and a limited diffusion range. Conversely, diffusion in void media occurs more smoothly due to the continuous cavity structure, resulting in slower pressure decay and a substantially larger diffusion radius. These findings elucidate the mechanisms governing slurry diffusion under dynamic water conditions and provide a theoretical basis for optimizing grouting parameters and improving construction efficiency in water-bearing strata.

Prestressed concrete cylinder pipe (PCCP) is a critical structural component widely employed in large-scale water supply systems. Prestressed steel wire serves as the primary load-bearing material in PCCP. Over time, as the structure ages, these wires are prone to rupture. Employing carbon fiber-reinforced polymer (CFRP) liners to rehabilitate PCCP with broken wires offers a trenchless repair solution that significantly enhances the pipe's load-bearing capacity. However, the mechanical behavior of CFRP-reinforced PCCP under combined external and internal pressure remains inadequately understood. This study utilizes the finite element method to develop a three-dimensional model of CFRP-lined PCCP. The model is validated against experimental data and analytical benchmarks, followed by an in-depth analysis of how various parameters influence the pipe's structural performance. Results indicate that once external pressure is applied, subsequent reduction in internal pressure does not restore the pipe's original mechanical integrity. Based on the serviceability limit state, reinforcing the pipe with eight layers of CFRP can elevate its external pressure capacity by up to 72.4%.

Urban water supply networks commonly suffer from corrosion, perforation, and structural degradation during long-term service, posing significant risks to system safety. As a representative trenchless rehabilitation technology, Cured-in-Place Pipe (CIPP) has been widely applied in engineering practice. However, the pressure-bearing responses under typical internal pressure conditions in corroded water-supply steel pipes remain insufficiently quantified. To address this gap, a 3D FE model of a CIPP-lined corroded pipe incorporating a zero-thickness cohesive interface was developed and validated against internal pressure tests. On this basis, the effects of internal pressure, pipe diameter, corrosion radius, corrosion depth, and the thickness and elastic modulus of the CIPP liner on the pressure-bearing response were systematically investigated, and the interaction between corrosion depth and CIPP liner thickness was further analyzed. The results show that corrosion defects significantly alter the stress distribution on both inner and outer pipe boundaries, with perforation leading to the most severe stress concentration and representing a critical failure-prone condition. Under perforated conditions, the CIPP liner reduces the maximum stress by more than 63%, demonstrating a substantially enhanced stress-mitigation effect compared to non-perforated cases. Within typical service pressure ranges, CIPP exhibits limited influence on peak stress but effectively alleviates stress gradients and improves structural stiffness. Among the parameters, liner thickness has a more pronounced effect than elastic modulus. A clear interaction between corrosion depth and liner thickness is observed, indicating that excessive thickness may not always yield optimal performance under severe damage conditions. These findings provide insight into the pressure-bearing mechanisms and key controlling factors of CIPP-lined corroded steel pipes, offering a theoretical basis for design optimization and parameter selection in water-supply pipeline rehabilitation.

Understanding the structural behavior of cured-in-place pipe (CIPP) liners under radial compression is essential for ensuring the long-term reliability of trenchless rehabilitation systems. This study presents a comprehensive experimental and numerical investigation of CIPP liners under radial compression, aiming to elucidate their material behavior, structural response, and design implications. Three-point bending and tensile tests were conducted to characterize the mechanical properties and failure mechanisms of the liner material, consisting of three layers of fiberglass cloth. Full-scale radial compression tests examined the influence of loading speed, liner diameter, thickness, and loading times on ring stiffness and bearing capacity, revealing a progressive deformation process through initial, elliptical, and dumbbell stages, with failure governed primarily by geometric instability. To account for cumulative cyclic effects, a loading times correction factor was incorporated into a Spangler-based bearing capacity calculation, enabling quantitative evaluation of stiffness degradation and strength reduction under repeated loading. Sensitivity analysis indicated that liner thickness has the greatest influence on structural performance, followed by diameter, loading times, and loading speed. A three-dimensional finite element model was developed and validated against experimental data, accurately reproducing load–deformation behavior and stress evolution. The proposed calculation method and numerical model provide a reliable framework for optimizing liner design, predicting long-term performance, and supporting engineering safety assessment of CIPP rehabilitation systems.

Foamed polymer materials, known for their high expansion ratio, excellent impermeability, and environmental friendliness, are extensively applied in grouting repair engineering. However, the diffusion behavior within fracture networks is complicated by the expansive nature of polymer slurry. To address this, fracture curves with varying roughness were established, and a numerical model for polymer slurry diffusion in fracture networks was developed. The sealing rate and diffusion pressure distribution at fracture intersections were analyzed by adjusting the intersection angles within the network. Additionally, a physical model apparatus was designed to simulate flowing-water grouting under different fracture roughness conditions. Using an orthogonal experimental system, the dynamic diffusion and sealing mechanisms of polymer slurry in rough fracture networks were systematically investigated. Finally, scanning electron microscopy was employed to observe the microstructure of the solidified slurry under different conditions. The study reveals that: (1) The diffusion behavior observed in the polymer fracture network grouting model aligns well with experimental results. As the intersection angle of fractures increases, the diffusion pressure at the intersection rises, with the best sealing effect observed at a 60° intersection angle. (2) Increased fracture roughness significantly reduces the slurry sealing efficiency. (3) The sealing efficiency is correlated with the sealing area ratio, though variations arise depending on the slurry’s diffusion path and its effectiveness in sealing water flow channels. (4) SEM analysis reveals that the solidified structure near the grouting hole is denser with smaller pores, while farther away, the pores enlarge, and the surface becomes rougher.

Buried metallic pipelines, as essential components of urban underground transportation and utility systems, are typically installed beneath roadways and are continuously subjected to multiple coupled effects, including soil pressure, internal fluid pressure, stray current corrosion, and repeated traffic loads. These interacting factors give rise to complex multi-field coupling effects that significantly influence the stability and service performance of road structures and surrounding transportation infrastructure. This study establishes a refined three-dimensional finite element model that integrates the corroded pipeline, surrounding soil, and internal fluid domains to capture the coupled mechanical behavior under realistic loading conditions. The model is validated through full-scale experimental tests, demonstrating its capability in reproducing the stress and deformation characteristics of buried corroded pipelines beneath traffic loads. Parametric analyses are conducted to quantify the influence of corrosion geometry, pipe and soil properties, and loading conditions on the geotechnical-structural response. Furthermore, a Morris global sensitivity analysis identifies the most influential factors affecting pipeline stress and soil deformation, with corrosion depth, internal pressure, and corrosion length being dominant. The proposed multi-field coupling framework and sensitivity-based insights provide theoretical support for the geotechnical design, maintenance planning, and safety assessment of underground pipeline systems integrated within transportation infrastructure.

Traditional pipeline flow measurement methods encounter issues such as the challenge of identifying the characteristics of the gas-liquid interface in low-light environments and inaccurate segmentation of the cross-section of the flow. To address these shortcomings, a framework of multi-domain coupling model for intelligent flow measurement of drainage pipeline is constructed by integrating contour recognition in the visual domain, interface fitting in the control domain, and flow quantification in the fluid domain. Firstly, dual-domain perception dynamic enhancement sub-module and multi-scale attention residual fusion sub-module are established to prevent overexposure of the background and enhance the edge details of the water flow. Then, dual-constraint loss function and pipeline flow direction-aware feature alignment sub-module are formulated to prevent discontinuities during the interface segmentation process and improve the adaptability of the alignment approach. Finally, a pipeline flow velocity distribution and flow rate integration model incorporating a fluctuation correction coefficient is proposed to suppress fitting errors in irregular cross-sections and enhance the accuracy of pipeline flow calculations. The experiment results indicate that the proposed flow measurement model had the remarkable accuracy and robustness in different small-size datasets under noise interference, variable resolutions and unbalanced environment. Compared with other typical prediction methods based on machine vision, the mean accuracy degree of this study remains within the range of [95.8%, 97.1%], which is significantly higher than that of other flow prediction models by more than 6%. Meanwhile, the determination coefficients of this study is significantly higher than that of other flow prediction models by more than 0.12. The intelligent pipeline flow measurement method in this study can provide a technical basis for high-precision and full-coverage pipeline siltation diagnosis. Code is available at “https://github.com/Danyang1990/Flow-measurement.git”.

Urban road collapses caused by leakage of underground drainage pipelines have occurred with increasing frequency. However, the dynamic evolution of particle-scale migration and its implications for pavement settlement under the action of groundwater seepage have not yet been systematically revealed. This study focused on concrete drainage pipes buried in sandy soils under high groundwater conditions. Macroscopic experiments were conducted to investigate the progression and characteristics of soil erosion under varying leakage sizes and locations. Additionally, the continuum-discrete element method (CDEM)-an explicit numerical analysis approach that integrates finite element, block discrete element, and particle discrete element methods-was employed to examine soil erosion, void formation, and pavement subsidence from a microscopic perspective. The results indicate that soil erosion induced by pipe leakage undergoes initial leakage stage, void width expansion stage, and void depth expansion stage. The soil erosion volume, erosion area, and transverse span increase with larger leakage sizes and a shift in the leakage position from the crown to the springline. Under the influence of traffic loads, the maximum subsidence value of the pavement experiences a dramatic increase, with the extent of this increase diminishing as the leakage point shifts. Compared to the absence of traffic load, the maximum pavement subsidence increases by 7.88, 8.70, and 8.42 times for leakage sizes of 10.5 cm, 12.0 cm, and 13.5 cm, respectively, and by 8.70, 6.42, and 5.36 times for leakage positions of 0 degrees, 45 degrees, and 80 degrees, respectively.

With the ongoing advancement of urbanization, urban water distribution networks (WDNs) are increasingly challenged by asset aging, corrosion, and pipe bursts, which collectively threaten the safe and reliable operation of urban systems. Consequently, rigorous risk assessment of urban WDNs has become essential. It enables the identification of high-risk segments and hotspots, and provides an evidence base for maintenance prioritization and network optimization. In this study, research progress on risk assessment and failure analysis of urban WDNs over the past 25 years was systematically reviewed. Mainstream approaches, including indicator-based scoring, statistical modeling, and machine learning (ML), were emphasized, and their fundamental principles, methodological characteristics, applicable contexts, and reported practical performance were comprehensively summarized. Indicator-based scoring methods are valued for their transparent structure and ease of implementation, and have been widely adopted in engineering applications. Statistical methods leverage historical records to develop failure models with explicit probabilistic interpretability. ML methods can capture complex nonlinear relationships and show strong predictive capability in data-rich settings. Nevertheless, prevailing approaches continue to face persistent limitations, including incomplete and heterogeneous data, constrained model transferability across systems, and substantial computational demands. Building on these findings, this study highlights future research priorities in enhancing multidimensional models, developing interoperable data-sharing platforms, and conducting life-cycle-oriented risk assessment, with the goal of supporting intelligent and sustainable management of urban WDNs.

The cured-in-place pipe (CIPP) lining repair technology has been widely used in the field of trenchless repair of water supply steel pipes, where the bonding performance of the interface is critical to the stability of the composite structure. In order to elucidate the interfacial failure mechanism between the CIPP liner pipe and water supply steel pipe (SP), this paper innovatively studies the interfacial shear characteristics and damage behavior of CIPP and steel plate composite structure. The shear strength of the CIPP-SP interface under different working conditions was investigated by 33 sets of interface straight shear tests. The global displacement field and strain field of the interface were analyzed. A multiparameter prediction equation for the interface peak shear force was proposed. Sensitivity analysis was performed on each factor. The results indicate that the CIPP-PS interface exhibited a four-stage brittle failure. Increasing the pressure holding time, interface area, shear rate, and interface roughness significantly increased the interfacial shear strength, but the normal pressure and CIPP thickness had less effect. The softening properties of the lining material at low temperatures and short curing times reduced the interfacial shear strength. The impact of interface area, shear rate, CIPP thickness, pressure holding time, roughness, normal pressure, curing time, and curing temperature on the interface shear strength decreased in order of their influence. The interfacial displacement field exhibited a centrally reduced stratification, and the strain field was the first to show strain concentration at the fixed end of the composite structure.

Underground concrete pipelines, as critical components of urban lifeline systems, are susceptible to progressive performance degradation under long-term cyclic loading, leading to increased failure risk and secondary hazards such as road collapse. Enhancing the fatigue reliability of defective pipelines through targeted rehabilitation is therefore essential for system safety. This study investigated corroded and voided concrete pipes under coupled traffic loading and groundwater conditions. Fatigue experiments and refined numerical simulations were conducted to evaluate structural responses and failure mechanisms before and after rehabilitation using Cured-in-Place Pipe (CIPP) liners combined with polymer grouting. Key responses, including circumferential stress, circumferential bending moment, and vertical displacement, were analyzed. The effects of loading conditions, defect geometry, and rehabilitation parameters on fatigue life were systematically quantified, and an FE-assisted strain-based fatigue life prediction method was established for both pre- and post-rehabilitation conditions. The results revealed a five-stage fatigue failure process, including slow strain growth, rapid strain growth, axial crack propagation, radial crack propagation, and axial through-cracking. Under the tested conditions, the fatigue life after rehabilitation was approximately 2.1 times that before rehabilitation. Within the investigated parameter ranges, the numerical analysis indicated that fatigue resilience enhancement was more pronounced under shallow burial and groundwater levels near the pipe shoulder. The fatigue life gain coefficient (ηlife) decreased significantly when corrosion depth exceeded 25 mm, while critical thresholds of 90° and 1.0 m were identified for corrosion width and length, respectively. Larger void geometry led to greater fatigue life improvement. The gain coefficient exhibited non-monotonic variation with polymer density, liner thickness, and liner length, while no significant improvement was observed when the liner elastic modulus exceeded 8000 MPa. The proposed FE-assisted fatigue life prediction method yielded mean and maximum fatigue life prediction errors of 5.9% and 13.9%, respectively, demonstrating satisfactory predictive accuracy within the investigated cases and providing quantitative support for rehabilitation assessment.

A second-order multiscale framework has been proposed for designing equivalent piezoelectric behavior by utilizing microscale flexoelectric composites. Unlike conventional homogenization approaches that neglect strain-gradient effects, the proposed method incorporates higher-order electromechanical coupling, enabling a direct and rigorous transfer of flexoelectric responses from the microscale to the macroscale. By combining isogeometric analysis with the finite cell method, a second-order computational homogenization scheme is formulated and implemented, allowing accurate analysis of complex microstructural geometries while maintaining high computational efficiency. High-order periodic boundary conditions consistent with the Hill-Mandel energy equivalence principle are enforced to ensure thermodynamic consistency across scales. Based on a perturbation analysis, closed-form macroscopic constitutive relations are systematically derived, revealing the emergence of equivalent piezoelectricity from flexoelectric composites. Numerical studies demonstrate that microscale dielectric matrices embedded with tetrahedral flexoelectric inclusions can be engineered to exhibit tunable macroscopic piezoelectric properties. A representative volume element analysis further identifies a characteristic microscale length that balances local heterogeneity and global electromechanical response. The proposed framework establishes a unified and predictive pathway for multiscale design of equivalent piezoelectric materials beyond conventional piezoelectric and homogenization theories.