Search Results (1,791)

The loss of sand foundation often induces differential settlement in immersed tunnel segments, potentially causing structural damage and reducing structural resilience. Accurately assessing the damage characteristics and their effects on resilience during sand foundation loss is essential for ensuring tunnel safety. This study adopts a typical immersed tunnel project as a case study. Long-term structural deformation data acquired by distributed optical fiber sensing technology and sand foundation detection data are adopted to analyze the response characteristics and damage state of the tunnel. A refined three-dimensional tunnel–stratum interaction model is established and validated against monitoring data to investigate mechanical response characteristics, including deformation and bending moment distributions. A redundancy factor is proposed as a quantitative index for tunnel resilience under foundation loss, and a multi-level resilience grading framework is established accordingly. Furthermore, the evolution of tunnel resilience under various displacement recovery ratios, which represent the extent of differential settlement remediation, is investigated using the refined numerical model. Field detection results show that over 50% of the foundation area is affected by loosening or voids. These defects are highly consistent with regions of abnormal structural deformation, leading to a bending–torsional deformation mode, with a maximum joint differential settlement of 106.7 mm. Stress concentration occurs in the tunnel floor above denser sand zones, with a maximum crack width of 0.43 mm. The tunnel is classified as severely damaged (low resilience) based on the proposed standard, with a redundancy factor of 1.59. Bending-torsional deformation and stress concentration are gradually mitigated as the displacement recovery ratio increases. The redundancy factor exhibits a parabolic relationship with the recovery ratio, indicating that tunnel resilience can be restored to a relatively high level when the displacement recovery ratio exceeds 70%. The proposed redundancy factor and grading framework provide quantitative guidance for designing and optimizing resilience improvement strategies following sand foundation loss. Full article

Mine leachate and saline industrial wastewater streams are often treated as liabilities to be remediated or disposed of. These flows often contain substantial water and dissolved mineral resources that can be reclaimed. In this work, a waste-heat-assisted falling-film evaporation reactor was developed and assessed for application as a pre-concentration step before water and mineral recovery processes. Two case studies were considered: synthetic saline wastewater containing 80 g/L Na₂SO₄ and 70 g/L NaCl for salt recovery, and iron-rich mine water containing approximately 4000 mg/L Fe²⁺, 95 mg/L Fe³⁺, and 13,000 mg/L acidity as CaCO₃ for downstream pigment and magnetite recovery. Saline water or mine leachate flows down a bank of vertical conduit pipes as a thin film while air flows through the pipe cores. Heat is transferred to the system from industrial waste gas externally. Psychrometric relationships, heat transfer, energy balances, and techno-economic analysis were used to assess the impact of air temperature, conduit diameter, column height, pipe material, and waste-gas temperature on overall reactor performance. Experiments were carried out to confirm expected psychrometric operation and establish appropriate operating temperatures while confirming the impact of conduit geometry on heat-transfer characteristics. A benchmark case of design evaporation rate equal to 100 L/h was chosen for comparison of all tests. Dry air operation was shown to be technically possible but severely limited by the moisture capacity of air; at 26 °C and 101.3 kPa, approximately 205,000 m³/h of air was required. When using industrial waste heat, the operation changed from psychrometric/mass-transfer-limited to heat-transfer-controlled. Using waste gas entering at 144 °C and exiting at 80 °C reduced airflow requirements to approximately 880 m³/h, allowing a much more compact reactor design with approximately 635 (12 mm diameter) conduit pipes. Relative to the 40 °C air benchmark, electrical power was reduced from approximately 24.7 kW to 2.9 kW, and screening-level reactor cost by ~84%. Findings demonstrated that appropriate waste heat enables the application of evaporation if there is sufficient local heat flux. Smaller conduit diameters, sufficient column height, and greater waste-gas inlet temperatures were all beneficial. Choice of material required trade-offs between heat-transfer coefficient, corrosion, and material cost. Full article

The reactive transport of hexavalent chromium (Cr(VI)) in anthropogenically disturbed sites (e.g., mine waste rock dumps, chromium salt industrial sites) is critically influenced by physico-chemical heterogeneity, yet the interplay between physical and chemical heterogeneities remains poorly understood. This study employed a series of experiments and numerical modeling to investigate the transport of Cr(VI), focusing on the implications of physical heterogeneity—represented by preferential flow paths—and chemical heterogeneity—characterized by reductive mineral lenses. Key findings indicate that physical heterogeneity accelerates Cr(VI) breakthrough by 1.4 to 2.1 pore volumes (PV) relative to homogeneous columns. The presence of pyrite lenses delays breakthrough by 0.6–1.2 PV under neutral pH and 1.6–2.0 PV under acidic pH. At a flow rate of 3.0 m/day, the apparent sorption capacity decreases by ~62.5% compared to 0.3 m/day, indicating that physical advection largely suppresses chemical retention under high-flux conditions. The above results demonstrate that physical heterogeneity governs flow paths and advection rates, whereas chemical heterogeneity impedes transport through heterogeneous adsorption and reduction in Cr(VI) to Cr(III) along these pathways. Furthermore, the presence of preferential paths leads to greater spatial variability, which subsequently influences the interaction dynamics between Cr(VI) and reactive minerals in the aqueous environment. The dominance shifts between physical/chemical controls based on flow rates and pH. At higher flow rates, the influence of physical heterogeneity becomes more pronounced, diminishing chemical reactions due to insufficient residence time of Cr(VI). Conversely, a lower pH environment enhances pyrite dissolution, which decouples the dependency on physical heterogeneity by promoting homogeneous reactions. Further evidence was obtained through X-ray photoelectron spectroscopy (XPS) analysis. The experimental observations are complemented by TOUGHREACT-based reactive transport simulations, which further reveal that the apparent dominance shifts arise from competing timescales between advection and surface reaction. The insights gained from the study emphasize the necessity of integrating both physical and chemical spatial variability in risk assessments, transport modeling, and designing targeted remediation strategies. Full article

Groundwater ingress threatens the serviceability and durability of underground structures, particularly when hydrogeotechnical conditions and waterproofing details are considered separately. This study presents a diagnosis-driven assessment of a reconstructed underground shooting range tunnel where leakage persisted despite reconstruction and previous repairs. The objectives were to identify the cause-and-effect mechanism of water ingress and select a targeted, low-impact remediation strategy. The investigation combined archival analysis, three site inspections, ultrasonic testing at 24 locations, eight tomographic scans, targeted destructive verification, and three geotechnical boreholes extending to 7.5 m. Ultrasonic measurements indicated good concrete homogeneity, with a mean estimated compressive strength of 36.9 MPa and a coefficient of variation of 5.86%. Tomography indicated a 25 cm bottom slab and a 20 cm lean concrete layer, compared with the designed 30 cm and 10 cm, respectively. The original geotechnical investigation was too shallow, and the ground conditions should have been classified as difficult, corresponding to geotechnical category II. Finally, leakage was linked to groundwater underestimation, water accumulation in the backfilled excavation, absence of drainage, waterproofing discontinuities, and ineffective previous injections. Targeted reinjection and joint sealing were selected, demonstrating how integrated diagnostics can support proportionate remediation while limiting excavation, demolition, material use, and operational disruption. Full article

High-speed railway track–bridge systems (HSRTBSs) in near-fault high-seismicity regions face combined threats from pulse-type seismic excitations, vertical earthquake components and track defects, which may trigger structural damage and deterioration of track regularity. This paper establishes refined OpenSEES coupled numerical models for a typical 32 m simply supported girder bridge equipped with CRTS II slab ballastless track, considering both conventional spherical steel bearings and friction pendulum bearings (FPBs). Nonlinear time-history analyses are performed with near-fault pulse-like and far-field non-pulse ground motions to explore the influences of peak ground acceleration (PGA), vertical-to-horizontal acceleration ratio (αVH), and CA mortar void length. The results demonstrate hierarchical controlling effects of these parameters. PGA dominates the overall seismic response; sliding layer damage follows the sensitivity sequence PGA > αVH > CA mortar void, whereas post-earthquake traffic capacity degradation obeys PGA > CA mortar void > αVH. Near-fault pulse-like ground motions produce more severe structural damage compared with far-field inputs. FPB isolation yields a maximum pier-top seismic reduction ratio of 86.73% and effectively mitigates structural deformation, but cannot eliminate track irregularity originating from CA mortar void defects. Conditional on the 0.2 g seismic level and the given structural configuration adopted in this study, αVH = 0.65 and the 1.95 m critical CA mortar void length for longitudinal track constraint failure can serve as reference values, though they are not universally applicable for all track–bridge systems. This work provides insights for seismic design, CA mortar defect remediation and post-earthquake traffic assessment of near-fault isolated HSRTBSs. Full article

Sudden tailings dam breaches trigger large-scale heavy metal compound pollution in coupled surface water–groundwater systems, requiring systematic full-cycle ecological damage quantification tools applicable to diverse contamination types. This study constructs an integrated full-cycle ecological damage assessment framework for sudden water pollution accidents, integrating three core modules: multi-model pollutant migration prediction, multi-scale aquatic biological damage diagnosis, and three-dimensional ecological-economic loss accounting. The framework adopts a modular design that can potentially accommodate heavy metals (Cd, Cr, As, Pb) and organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), with standardized molecular, individual, and population-level biological endpoints and corresponding pollutant dose–response templates reserved as reference calculation modules. However, applicability beyond this case has not been validated and requires case-specific calibration. To verify the operability and accuracy of the proposed integrated system, a typical tailings dam leakage incident dominated by hexavalent chromium (Cr(VI)) and arsenic (As) pollution was selected as the practical validation case; all field monitoring, pollutant simulation, and final economic loss quantification in this case exclusively rely on on-site measured Cr(VI) and As data, while Cd and PAH-related biological response curves and remediation cost formulas retained in the manuscript only serve as illustrative universal template components of the framework rather than case-measured results. For the Cr(VI)/As pollution case, the advection–diffusion model simulation revealed that the Cr(VI) contamination plume horizontally spread 250 m within 48 h and extended to 560 m after seven days, and anaerobic groundwater environments drove the transformation of toxic mobile trivalent arsenic (As(III)) from primary pentavalent arsenic. The calibrated SWAT model achieved Nash–Sutcliffe efficiency (NSE) coefficients of 0.75 for dissolved Cr(VI) and 0.68 for particulate As. The graph theory-based rapid prediction model cut computation duration down to minutes; when validated against independent field monitoring data, it yielded an average relative error of 14.2%, and its consistency with the SWAT model reached 10.5% relative deviation, satisfying the accuracy requirement for emergency early warning. Field biological monitoring demonstrated substantial ecological impairment: metallothionein (MT) expression in fish tissues was markedly elevated (the reported 6.2-fold induction value derives from standard Cd exposure template tests within the framework, with analogous MT upregulation also observed for field Cr(VI)/As co-stress), and benthic community Shannon diversity declined by over 50% in polluted river reaches. The standardized Ecological Damage Index (EDI) of the case was calculated as 480.2, indicating severe aquatic ecosystem damage, with total comprehensive ecological and economic losses reaching 17.25 million CNY. This study innovatively couples high-precision physical transport models with fast emergency prediction algorithms and establishes a complete multi-tier biological indicator chain linking molecular biomarkers to community integrity metrics; the three-dimensional loss accounting system integrating ecosystem service impairment, restoration expenditure, and post-pollution recovery loss realizes closed-loop full-cycle damage evaluation. The proposed framework, demonstrated for Cr(VI) and As pollution, has a modular design that may potentially be extended to other pollutants such as Cd and PAHs by adjusting model parameters, providing a quantitative reference for emergency disposal, pollution remediation, and ecological compensation of water contamination accidents, although further validation across different pollutants and hydrological settings is required. Full article

Gender bias in generative artificial intelligence (GenAI) is both a technical and a social phenomenon: it emerges from historically patterned data, model design, and interactions in institutional use, and it cannot be understood by engineering or by social critique alone. This critical integrative review develops a more differentiated account. It connects feminist epistemology, Science and Technology Studies, critical AI scholarship, natural language processing, and governance research to examine five levels: historical knowledge production, technical representation and generation, benchmark evaluation, institutional deployment, and accountability. The review explains tokenization, next-token prediction, transformers, and the transition from static embeddings to contemporary language models before assessing evidence from standard fairness tests—coreference tests (WinoBias), sentence-pair tests (CrowS-Pairs), and stereotype tests (StereoSet)—as well as open-ended generation, multilingual testing, and text-to-image systems. It shows that measured bias varies with task, prompt, language, model version, and metric. What a test records and what that record means are therefore distinct questions: measurements are situated and depend on the instrument, and their interpretation draws on theory rather than following from the numbers alone. Evidence from employment, education, healthcare, and translation further indicates that the relevant unit of analysis is the model-in-context—the model together with the institution and workflow in which its outputs are used. Technical mitigation can reduce specific harms but does not repair unequal criteria, incomplete evidence bases, or weak institutional accountability. The review proposes a multilevel governance approach combining technical evaluation, documentation, professional and community oversight, appeals, remedies, and public-interest knowledge infrastructure. Its distinctive contribution is to connect three observations usually kept apart—how bias is measured, how generative systems concentrate epistemic authority, and how statistical learning is oriented toward past data—and to show why democratic and feminist governance can keep alternative technological futures open. Full article

Persistent anthropogenic contaminants increasingly shape evolutionary processes across natural populations. While many pollutants can be metabolized, degraded, or eliminated, a subset of highly persistent compounds remains in ecosystems and organisms over ecologically and evolutionarily relevant timescales. Here, we propose the concept of Persistent Non-metabolizable Selective Agents (PeNSAs) to describe contaminants that exert chronic selective pressures while resisting biological degradation and effective elimination. Using per- and polyfluoroalkyl substances (PFASs) as a model case, we argue that exposure to PeNSAs creates a distinctive evolutionary regime in which adaptation is more likely to proceed through tolerance, physiological compensation, and damage mitigation than through contaminant removal. This dynamic generates a decoupling between adaptation and remediation, whereby populations may evolve increased fitness under exposure while contaminant burdens remain unchanged. We develop a conceptual framework describing the ecological and evolutionary consequences of PeNSA exposure, including energetic trade-offs, incomplete evolutionary resolution, maintenance of genetic variation, and heterogeneous adaptive outcomes among populations. We further derive testable predictions that distinguish PeNSA-driven evolution from classical models of resistance and detoxification. By integrating evolutionary biology, ecotoxicology, and environmental science, the PeNSA framework provides a foundation for investigating adaptation to persistent contaminants and highlights implications for environmental monitoring, risk assessment, and ecosystem management in the Anthropocene. Full article

The digitalization of sustainable energy systems increasingly relies on containerized Internet of Things services deployed across cloud–edge architectures. These services introduce software supply-chain risks associated with public container images and their dependencies. This study evaluates 22 container images representing 13 official or vendor-maintained technologies used for data storage and processing, communication, proxy and API services, and application runtime environments. Each image was analysed using Trivy and Grype, resulting in 44 vulnerability scans performed using vulnerability databases available on 14 June 2026. The effect of image minimization was assessed using five strictly matched standard–minimized pairs, while scanner agreement was evaluated for all images using unique CVE sets, the Jaccard coefficient, and symmetrical and directional Tversky indices. Across the complete sample, Trivy reported 7006 vulnerability findings and Grype reported 2299. Within the strictly matched sample, findings decreased from 5181 to 193 for Trivy and from 982 to 290 for Grype. However, these reductions were strongly influenced by the Ruby image, and the exact Wilcoxon signed-rank test did not confirm a statistically significant general minimization effect ($p=0.250$). Redis, HAProxy, and Ruby showed substantial reductions, whereas Caddy remained unchanged and both .NET SDK variants produced zero findings. The set-based analysis revealed incomplete and asymmetric agreement between the scanners, demonstrating that similar aggregate counts may represent different CVE profiles. Operational prioritization of six selected image variants further showed differences in remediation availability, EPSS scores, and CISA KEV inclusion. The results indicate that image minimization can reduce scanner findings but does not independently confirm container security. A multi-tool DevSecOps process combining immutable digest verification, Software Bills of Materials, vulnerability prioritization, image rebuilding, and continuous rescanning is therefore recommended. Full article

Agricultural soils in arid regions require assessment approaches that separate local element enrichment from actual ecological and human health relevance. Here, a site-prioritization framework is applied to potentially toxic elements (PTEs) in agricultural soils from Onaizah, central Saudi Arabia. The approach combines contamination indices, ecological-risk screening, deterministic health-risk estimates, Monte Carlo resampling, and relative ranking of management priorities. A total of 33 surface-soil samples collected from cultivated farms were examined for As, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn. The measured concentration ranges (mg/kg) were 1–5 (As), 1–12 (Co), 10–53 (Cr), 4–38 (Cu), 107–541 (Mn), 6–54 (Ni), 2–23 (Pb), 8–47 (V), and 11–168 (Zn). Based on their mean concentrations, the investigated elements decreased in the following sequence: Mn > Zn > Cr > Ni > V > Cu > Pb > Co > As. The P_N values ranged from 0.127 to 1.339, indicating 27 safe sites, 2 warning-line sites, and 4 slightly polluted sites, mainly controlled by localized Zn enrichment and, in one case, Pb. In contrast, mCd values of 0.099–0.676 indicated nil to very low contamination, while RI values of 2.743–15.701 confirmed low ecological risk across all samples. Non-carcinogenic risk was generally below the threshold of concern, with HI values of 0.204–1.018 for children and 0.024–0.119 for adults. Only one site showed a marginal child HI exceedance, emphasizing localized rather than widespread health concern. Children showed approximately 8.6-fold higher non-carcinogenic risk than adults, with Mn, Cr, As, and V as the main contributors. The total LCR values for As, Cr, and Pb ranged from 7.79 × 10⁻⁶ to 4.07 × 10⁻⁵ for children and from 3.48 × 10⁻⁶ to 1.82 × 10⁻⁵ for adults, within the commonly tolerable range of 1 × 10⁻⁶ to 1 × 10⁻⁴. Chromium was the dominant contributor to LCR. Monte Carlo resampling supported the deterministic risk classification, with only a 3.1% probability of child HI exceeding 1 and no simulated exceedance of the LCR threshold for either children or adults. From the standpoint of sustainable soil management, site 7 should undergo further health-risk assessment, while sites 30 and 33 require source verification and periodic monitoring before any remediation action is considered. Full article

The sustainable valorization of marine shell waste as functional additives for geopolymer materials represents a promising strategy for developing multifunctional materials for environmental remediation. In this study, metakaolin-based geopolymers were modified with calcium-rich particles obtained by calcination of five marine shell species (Chamelea gallina, Mya arenaria, Mytilus edulis, Pecten maximus, and Rapana venosa) under identical synthesis conditions to evaluate the influence of shell mineralogy on the structural, textural, adsorption, and antibacterial properties of the resulting composites. The materials were comprehensively characterized by Fourier transform infrared spectroscopy in attenuated total reflectance (ATR-FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption–desorption (BET/BJH) analyses. Functional performance was assessed through methylene blue (MB) adsorption experiments, adsorption kinetic modeling, and antibacterial tests against Escherichia coli (E. coli). ATR-FTIR and XRD analyses confirmed the formation of a stable amorphous geopolymer network containing residual crystalline phases together with shell-derived calcium carbonate, predominantly as calcite or aragonite depending on shell origin. The incorporation of shell-derived particles modified the pore architecture of the geopolymers. GP-SJ exhibited the highest BET specific surface area (94.30 m² g⁻¹) and the most developed mesoporous structure. Among the investigated formulations, GP-RP showed the most favorable overall combination of functional properties under the investigated conditions, exhibiting the highest methylene blue removal efficiency (63.97%) and experimental adsorption capacity at 160 min (9.60 mg g⁻¹), together with a comparatively high reduction in recoverable E. coli colonies during preliminary antibacterial screening. The combined structural and functional analyses demonstrate that the environmental performance of shell-modified geopolymers cannot be predicted from a single parameter such as BET surface area or calcium content alone, but results from the synergistic interaction between mineralogical composition, particle dispersion, pore accessibility, and matrix compactness. Under the investigated conditions, these findings provide evidence for proposed structure–property correlations under the investigated conditions and suggests that shell-derived calcium particles act as microstructural regulators of geopolymer matrices, providing a basis for the further development of sustainable multifunctional materials for simultaneous dye removal and bacterial reduction in wastewater treatment. Full article

Severely saline–alkaline land degradation poses a considerable challenge to sustainable agriculture, owing to high salinity, elevated pH, and nutrient deficiency. To address this, a salt-tolerant nitrogen-fixing bacterium (Bacillus sp.) and a microalga (Chlorella pyrenoidosa) were applied—alone, in combination, or with sheep manure—in a pot experiment with six treatments to examine their individual and combined effects on soil amelioration and wheat (Triticum aestivum L. cv. Jinchun 6) growth. We specifically assessed whether the three-component system outperforms single or dual applications. The bacterial–algal co-inoculation (BA) markedly outperformed single inoculations: shoot biomass increased by 117% and soil organic matter (SOM) by 130%, compared with the control. BA also alleviated oxidative stress, as evidenced by reduced malondialdehyde (MDA) content and elevated superoxide dismutase (SOD) and peroxidase (POD) activities. Scanning electron microscopy (SEM) observations confirmed tight bacterial attachment to algal surfaces. Incorporating sheep manure (BAM) further enhanced these benefits, achieving the lowest pH and electrical conductivity (EC), the highest SOM and available-nutrients, and the greatest wheat biomass. 16S rRNA sequencing showed that BAM increased microbial diversity, shifted community structure, and enriched beneficial genera (Sphingomonas, Flavihumibacter, and Fuscovulum) that were positively correlated with soil nutrient availability and plant stress tolerance, while the halophilic genus Halomonas declined. Collectively, the bacteria–algae–manure co-application establishes positive feedback between soil improvement and functional microbiome recruitment, offering a promising strategy for the remediation of severely saline–alkaline soil. Full article

Per- and polyfluoroalkyl substances (PFAS) represent a critical class of persistent environmental pollutants that challenge conventional remediation technologies. Metal–organic frameworks (MOFs), covalent organic frameworks (COFs), and the emerging metal–covalent organic frameworks (MCOFs) have attracted growing interest as tunable porous platforms for removing per- and polyfluoroalkyl substances (PFAS) from water. This review critically summarizes recent advances in the synthesis, structural characterization, and adsorptive performance of these three framework families. We examine key factors affecting adsorption, including solution chemistry and PFAS chain length, and elucidate the underlying mechanisms—hydrophobic/fluorophilic interactions, electrostatics, anion exchange, and coordination—through combined experimental and computational evidence. A comparative assessment evaluates adsorption capacities, kinetics, stability, and regenerability, identifying the distinctive advantages of each material class. Practical applications in fixed-bed columns and magnetic composites are also discussed. Finally, we highlight persistent challenges, particularly in the removal of ultrashort-chain PFAS, and outline future directions involving machine learning, defect engineering, and dual-functional adsorptive–catalytic platforms to guide rational adsorbent design. Full article

Heavy metal pollution in water bodies is a serious environmental and public health concern, as these contaminants are toxic, persistent and bioaccumulative in ecosystems and human tissues. Conventional remediation technologies are expensive, require constant monitoring and do not fully remove them. Recent studies have shown the potential, sustainability and cost-effectiveness of biosorption using algal biomass. This review gives a detailed assessment of the potential of algae and cyanobacteria as cheap biosorbents for the removal of heavy metals from wastewater. The sorption efficiency of algae and cyanobacteria is critically evaluated in terms of important operating parameters such as pH, temperature, initial metal concentrations, biomass loading and contact time. The diversity of metal-binding functional groups such as carboxylate, amine, imidazole, phosphate, sulfhydryl, sulfate and hydroxyl groups present on the surface of algal cells is discussed in detail, highlighting the complex algal biochemistry. Recent developments in functionalized algal materials are also discussed, with emphasis on their potential to improve adsorption capacity, selectivity, regeneration, and practical applicability. However, this review also identifies some limitations such as energy requirements for the drying of biomass, limitations of batch systems for microalgae applications, and challenges for large-scale implementation. Future research directions are suggested to highlight the urgent need for functionalized algal materials, optimization of large-scale applications, and integration of biosorption with other treatment technologies in the framework of a circular economy. Full article

Accurate identification and risk assessment of hidden defects in urban roads are essential for preventing road collapse and ensuring infrastructure safety. Based on a large-scale investigation of urban roads in Hunan Province, China, this study proposed a multi-scale collaborative detection framework integrating three-dimensional ground-penetrating radar (3D GPR) wide-area screening, manual interpretation, two-dimensional (2D) multi-frequency verification, and borehole endoscopic validation. Typical electromagnetic response characteristics of cavity, void, and loose-zone defects were summarized, and qualitative recognition criteria for different defect types were established. A total of 153 endoscopically validated defect cases, including 115 loose zones, 28 voids, and 10 cavities, were analyzed to investigate defect distribution and associated formation factors. The results show that underground pipeline damage, engineering disturbance, and inadequate backfill compaction are the main factors associated with defect development. Inadequate backfill compaction accounts for approximately 70% of all detected defects and is mainly related to early-stage defects, whereas pipeline damage is associated with nearly 90% of cavity cases despite accounting for only 30% of all cases. Risk assessment results show that cavities and voids are mostly high-risk defects, while loose zones are mainly moderate- to low-risk defects. The proposed framework provides a practical basis for subsurface defect identification, risk warning, targeted remediation, and preventive maintenance of urban roads. Full article