Utilizing the dynamic theory of 3D continuous medium and 1D elastic rod, this paper obtains a new close-formed solution for the torsional vibration of pipe piles, with regard to both the pipe pile defect and the surrounding soil radial heterogeneity effect. Firstly, combining Laplace transform and complex stiffess transfer method, the tangential stress on the pipe pile from the soils can be obtained. Secondly, the close-formed solution for the torsional vibration characteristics (TVC) of pipe pile head is derived, via combining the continuity conditions of the soil-pipe pile system and the transmissibility of impedance functions. Further, using the inverse Fourier transform (IFT) and the convolution theorem, a semi-analytical solution for the time-domain reflected signal function of pile head velocity is achieved. Finally, the accuracy of the reduced solutions derived in this paper is validated via a comparison analysis with existing theoretical solutions. Moreover, a parameterized analysis is implemented to discuss the impacts of different types of pile defects and radial heterogeneity effects on the TVC of pipe piles.

This study develops a three-dimensional fluid-particle coupling numerical model based on the discrete element method (DEM), incorporating point cloud volume sampling technology to achieve high-precision dynamic calculation of particle porosity. The model comprehensively considers the coupling effects of pore structure evolution on pore water pressure fields, establishing governing equations that couple porosity-change-induced (PI) and diffusion-induced (DI) pressurization/depressurization mechanisms. The accuracy of the proposed method is validated through three classical benchmark problems: Terzaghi’s one-dimensional consolidation, undrained triaxial tests, and the Mandel-Cryer effect. Using this approach, the complete process from liquefaction instability to reconsolidation densification in saturated loose sand is successfully simulated, accurately reproducing key liquefaction phenomena including excess pore water pressure accumulation and dissipation as well as microscopic pore structure reorganization. The study achieves quantitative separation of the relative contributions of PI and DI mechanisms during liquefaction, revealing that they synergistically constitute the fundamental control system of the entire process: the liquefaction triggering stage is primarily dominated by the PI mechanism, the development stage shows gradually increasing influence of the DI mechanism, and the reconsolidation stage is entirely controlled by the DI mechanism. This numerical framework provides a powerful tool for in-depth understanding of the fundamental physical mechanisms of soil liquefaction, offering significant theoretical and practical value for prediction and risk assessment of seismic liquefaction hazards.

This work proposes a novel mathematical model for floating pile group-layered soil interaction considering partial embedment to analyze the vertical dynamic response. The pile-pile interaction factor and dynamic impedance are analytically derived using the superposition method and transfer matrix method. The accuracy of the derived solutions is verified through comparisons with existing results. Subsequently, numerical examples are examined to thoroughly analyze the influences of key pile-soil parameters on the vertical vibration characteristics of floating pile groups. The results indicate that parameters such as the non-embedded length, fictitious soil pile length, and shear modulus of layered soil exert a significant influence on the dynamic response. The proposed mathematical model is more adaptable to partially embedded floating pile groups in layered soils.

A novel analytical approach is proposed to investigate the vertical vibration of closely spaced pipe pile groups, which considers both the soil plug and scattering effects of passive piles. Analytical solutions for the pile-to-pile interaction factor, scattering effect factor, and dynamic impedance of the pipe pile groups were determined using a five-step methodology. Subsequently, the effects of the pile spacing, soil plug height, inner-to-outer radius ratio, and pile-soil modulus ratio on the interaction, scattering effect, and dynamic impedance of the pipe pile groups were analyzed using parametric analysis. The results indicate that the soil plug and scattering of passive piles significantly influence the vertical vibration of pipe pile groups. Therefore, the proposed analytical method is suitable for addressing the vertical vibration problem of closely spaced pipe piles.

Hydraulic concrete is highly susceptible to cracking due to reservoir water pressure, freeze-thaw cycles, and carbonation, which compromise its durability and service life. This study investigates the use of enzyme-induced calcium carbonate precipitation (EICP) in combination with chitosan (CS) or sodium alginate (SA) for the repair of concrete cracks. The permeability tests, freeze-thaw tests, and carbonation tests were conducted to evaluate the influence of crack width, repair number, repair method, freeze-thaw cycles, and carbonation duration on its durability. The microstructure of repaired concrete was constructed by conducted XRD, FTIR, SEM, and EDS tests. Based on the test results, a Weibull distribution model was established to account for strength degradation due to freeze-thaw and carbonation effects. The results showed that surface spalling of concrete increased significantly with the freeze-thaw cycles, and the carbonation depth progressively increased with carbonation duration. When the repair number ranged between 20 and 60, the permeability coefficient of concrete declined from the order of 10-5 cm/s to 10- 7 cm/s, and EICP+SA treated concrete showed a 10.23 % reduction compared to EICP-repaired concrete. After 100 freeze-thaw cycles, the EICP-repaired concrete with 1.0 mm crack width exhibited a mass loss rate of 10.55 % and a compressive strength loss rate of 13.65 %. Furthermore, the EICP+SA repaired concrete showed better performance, with a mass loss rate of 8.96 % and a compressive strength loss rate of 10.08 %. After 18 d of carbonation, EICP+SA treated concrete with 0.50 mm crack width exhibited the carbonation depth of 5.6 mm, and the splitting tensile strength loss rate of 7.56 %, which is only 4.02 % lower than that of uncracked concrete. The mineral product of the EICP was calcite, and addition of CS or SA enhanced the intensity of calcite-specific peaks, promoting greater calcite formation and improving its crystallinity, thereby enhancing the overall repair effect of the concrete. The model predictions showed good agreement with experimental results, indicating that the model is suitable for predicting the strength degradation due to freeze-thaw and carbonation in repaired concrete. The findings offer valuable practical guidance for crack repair in hydraulic concrete.

Accurate seismic reliability analysis of subway stations is significant to ensure the normal operation of urban lifeline system. Nonetheless, traditional seismic reliability analysis of subway stations struggles to process high-dimensional stochastic space with respect to structural and geotechnical mechanical parameters, as well as physical parameters of ground motions, which cannot guarantee the completeness of data samples of seismic response. Hence, a novel approach to seismic reliability analysis of subway stations considering quantifiable hybrid uncertainties from both soil-subway station interaction (SSSI) effect and ground motion is proposed by integrating the adaptive sparse polynomial chaos expansion (SPCE) and probability density evolution method (PDEM). In this approach, a two-stage partition of probability space is first conducted to determine the optimal quantity of seismic response samples for reliability analysis and weights of samples for constructing SPCE model. Subsequently, the hyperbolic truncation scheme and probability space repartition-incorporated orthogonal matching pursuit algorithm are combined to establish adaptive SPCE model. Finally, the seismic reliability of subway stations is derived by implementing the SPCE and PDEM. Further, the applicability of the proposed approach with the adaptive SPCE model is validated through a case study. On this basis, the effects of completeness of seismic response data, hybrid uncertainties, and variability degree of geotechnical parameters on seismic reliability of subway stations are also investigated. Results indicate that the probability density curves of seismic responses under the hybrid uncertainties exhibit prominent multi-peak mode distribution characteristics, and ignoring the uncertainty of the SSSI effect will overestimate the seismic reliability of subway stations. Meanwhile, the incompleteness of seismic response data can weaken the characterization ability of statistical methods for the uncertainty of seismic response. Moreover, the sensitivity of seismic reliability of different central columns to the variability of geotechnical parameters shows significant difference with the variation of performance level, which highlights the complicated influence mechanism of geotechnical parameter variability on the seismic reliability of different components in subway station structures. The proposed approach and relevant conclusions can provide new technologies and practical guidance for seismic reliability assessment of subway stations.

Tripod bucket foundation for offshore wind turbines (OWTs) may fail under horizontal cyclic loading due to stiffness degradation and excessive accumulated rotation. However, relevant research remains limited, and its horizontal cyclic bearing characteristics has not been sufficiently understood. This study develops a threedimensional finite element model of tripod bucket foundation in PLAXIS 3D, employing the hardening soil model with small strain stiffness (HSS) and SANISAND-MS constitutive models to simulate the mechanical responses of clay and sandy seabeds, respectively, under complex loading. Two horizontal cyclic loading schemes, representing the serviceability and fatigue limit states, are applied to investigate the evolution of bearing capacity, unloading stiffness, and rotational deformation during loading. Results show that the single-bucket tension mode is the most unfavorable loading condition, with vertical loads transmitted to the bucket top contributing over 80 % of the total overturning moment. In clay seabed, unloading stiffness decreases monotonically, dropping to 96.3 % and 86.5 % of the initial value under the serviceability and fatigue limit states, respectively. In sandy seabed, stiffness initially rises to 121 % before decreasing to 109 % under the serviceability limit state, while it decreases monotonically to 94 % and then stabilizes under the fatigue limit state. Accumulated rotation in clay seabed increases continuously, whereas in sandy seabed, partial recovery occurs due to self-healing effect, but the maximum rotation under the fatigue limit state still reaches 0.417 degrees, exceeding the allowable limit. These findings provide theoretical and practical guidance for the design and operation of tripod bucket foundations for OWTs in the two typical seabed conditions.

By integrating the Novak's thin layer method (NTLM) with the Biot's two-phase medium model (BTPMM), the established analytical model in this paper offers a novel approach for analyzing the lateral dynamic behavior of the offshore piles with partial embedment (OPWPE) subject to wave loads, with comprehensive consideration of wave diffraction and the effects of the interaction between pile and water (IPW). First, for the above-mudline pile section, the IPW is incorporated by introducing radiation wave potential function, yielding a novel analytical solution for hydrodynamic pressure via variable separation method. Second, for the below-mudline pile section, applying potential function decomposition with pile-soil interface conditions, the analytical formulation of the reaction force from saturated seabed resistance is systematically derived. Finally, employing both the continuity conditions at the mudline and pile-fluid interface, the analytical solutions of the lateral vibration characteristics (LVC) can be easily obtained. Validation against existing theoretical solutions confirms the proposed method's accuracy and reliability. On this basis, parametric analyses are conducted to systematically investigate the influence patterns of the soil parameters, pile parameters, and wave parameters on the LVC of the OPWPE.

The inherent issue of small sample sizes in geotechnical data and the resulting epistemic uncertainty are objective realities in geotechnical engineering. To effectively assess the seismic response and reliability of metro stations under sparse geotechnical data, the adaptive sparse polynomial chaos expansion (ASPCE) is firstly utilized in a given probability space of basic variables to obtain the shared physical analysis information of seismic response. By incorporating the Bootstrap method and the principle of change of measure (CoM), the epistemic uncertainty induced by the sparse geotechnical data is further quantified within the framework of the probability density evolution method (PDEM), and an approach to seismic reliability interval estimation of metro stations considering geotechnical data sparsity is subsequently proposed. The effects of geotechnical data sparsity on the seismic reliability assessment are also investigated. Results indicate that the seismic reliability of metro stations under sparse geotechnical data exhibits complex non-Gaussian probabilistic characteristics, and the reliability interval can effectively incorporate the epistemic uncertainty introduced by data sparsity, thereby rendering the assessment results more reasonable. As the sparsity of geotechnical data decreases, the probability density function of seismic reliability of metro stations gradually evolves from multimodal distribution to unimodal distribution with markedly enhanced symmetry, and the reliability interval progressively converges to a stable interval. Moreover, the seismic reliability interval of metro stations for 'Repairable Operation' performance level is most sensitive to the sparsity of geotechnical data on both sides of the structure under rare earthquakes. The proposed approach ensures the efficiency and effectiveness of seismic reliability analysis for metro stations under multi-sources hybrid uncertainties, and the relevant findings can provide guidance for the seismic safety assessment of metro stations.

To address the disposal and resource recovery challenges of dredged sediment, this study developed MgO-SiO2 system utilizing solid waste-derived light-burned magnesia (LBM) and silica fume (SF) under carbonation-hydration curing. The effects of this synergistic approach on material properties were systematically investigated by adjusting the LBM/SF ratio and precarbonation time. The results indicated that this strategy effectively enhanced material strength and optimized microstructure. Specifically, specimens with an LBM/SF ratio of 6:4 and a precarbonation time of 0.5 h (6M4S0.5C) exhibited a 38% increase in 28 day strength compared to the hydration system. Microstructural analysis revealed that hydrated magnesium carbonates (HMCs) formed during moderate precarbonation served as structural skeleton, retaining the reactive Mg2+ and alkaline environment for subsequent reactions. This promoted the formation of hydrated magnesium silicate (M-S-H) gel and its interweaving, constructing a "gel-crystal" composite network that optimized pore structure and enhanced macroscopic strength. Based on thermogravimetric analysis data, a strength prediction model was further established using the mass loss ratio of the reaction products, achieving a quantitative correlation between multiphase composition and macroscopic properties. Sustainability assessments indicated that, compared to the ordinary Portland cement (OPC) system, 6M4S0.5C reduced CO2 emissions by 41.8% and lowered the sustainability index (CO2 emissions required to achieve 1 MPa of strength) by 40.5%. The research provided a theoretical foundation and technical approach for the low-carbon resource utilization of dredged sediment.

The complex evolutionary patterns of time-varying soil parameters in coastal engineering present a significant challenge, exacerbated by ineffective synergy between multi-source data and the updating mechanism for statistical characteristics of soil parameter probability distributions. To address this, a Time-variant Coupled Bayesian Structural Equation Model (TVC-BSEM) is proposed. Probabilistic evolution equations embedding a time-variant mean trend function and a coefficient of variation adjustment mechanism are developed, enabling a closed-loop feedback coupling between time-varying soil parameter evolution and cross-scale uncertainty, driven by multi-source data. The dynamic siltation environment was parametrically reconstructed taking the silted bank slope-piled wharf system as a case study. The results show that the silted soil parameters exhibit a three-stage nonlinear decay characteristic. The internal friction angle demonstrates a significant dependency on the data combination during its long-term evolution. The sensitivity of cohesion to the prior distribution type of latent variables is higher than that of the internal friction angle. Moreover, the influence weight of data heterogeneity on parameter estimation is substantially greater than that of the prior distribution type. This framework elucidates the mechanism by which synergistic effects of multi-source heterogeneous data influence parameter estimation and offers a novel approach for quantifying multi-scale uncertainties in soil-pile-structure interaction analysis.

Based on Novak's plane strain (NPST) and Biot's wave theories (BWT), this paper establishes an analytical approach for horizontal vibration of partially embedded offshore piles (PEOP) in layered soils, considering the combined impact of diffraction and distribution of wave loads under coupled axial static and wave loads. First, for the above-mudline portion of the PEOP, the hydrodynamic pressure is analytically derived through the variable separation method. Second, for the below-mudline portion, the dynamic equilibrium equations of the saturated soil are decoupled via potential function transformations. Combined with the boundary conditions of saturated soils and the interface continuity conditions between the pile and soil, the analytical expression of soil reaction forces around the pile is obtained. Furthermore, the horizontal dynamic impedance (HDI) at the PEOP head is solved by displacement continuity conditions at the mudline. The proposed analytical solutions are validated for accuracy through a comparative analysis with established theoretical solutions. Finally, a parametric investigation is undertaken to investigate the influence of distribution effects of wave loads (DEWL), axial static loads, and variations in soil parameters across different soil layers on the horizontal vibration characteristics (HVC) of the PEOP.

To investigate the influence of wind-wave correlation and multi-source uncertainties on the dynamic reliability of monopile-supported offshore wind turbines (MOWTs) under data scarcity, a novel reliability analysis framework is proposed fusing Bayesian Bootstrap theory, Copula theory, and the Probability Density Evolution Method (PDEM). First, Bayesian Bootstrap theory is employed to correct load marginal distributions and quantify epistemic uncertainty. Second, combining Copula theory and the Dimension-Reduction Spectral Representation method, a joint wind-wave probability model is constructed. Finally, using this model as the input for stochastic excitation, the influence of multi-source uncertainties and load correlations on the dynamic reliability of MOWTs is systematically analyzed based on PDEM. The results indicate that: (1) Ignoring wind-wave load correlations and uncertainties may lead to increased uncertainty in risk assessment and an overestimation of structural failure risk; (2) Under normal operating conditions, the failure probability exhibits minimal fluctuation, whereas in the 50-year extreme condition, epistemic uncertainty has a significant impact on the failure probability; (3) The proposed framework effectively quantifies the propagation laws of multi-source uncertainties within the wind turbine structural system, providing a scientific basis for the refined design of MOWTs under complex sea states.

The resource utilization of marine-dredged sediment is considered a sustainable approach to its disposal. This paper investigates the preparation of non-sintered ceramsites from marine-dredged sediments and CSA cement via cold-bonded pelletization. The study examines the effects of various preparation conditions on the engineering properties, phase compositions and microstructures of non-sintered ceramsites. The results indicate that preparation conditions significantly influence the particle size distribution of non-sintered ceramsites. The early-strength development of non-sintered ceramsites prepared from CSA cement is remarkable, with the PCS achieving approximately 60% and 80% of the 28-day strength within 3 days and 7 days, respectively—a marked contrast to OPC. Response surface methodology analysis reveals significant interaction effects between the disc rotation angle, rotational speed, and duration of rotation on the PCS of non-sintered ceramsites. The open-ended porosity of non-sintered ceramsites exhibits greater sensitivity to changes in preparation parameters compared to closed-ended porosity and total porosity. The preparation conditions have negligible impact on the hydration process of CSA cement in non-sintered ceramsites. For both ellipsoidal and plate-like marine-dredged soil particles, ettringite and the AH3 phase provide effective pore-filling and binding effects in the microstructures of non-sintered ceramsites. These findings imply that low-carbon utilization of marine-dredged sediments through the preparation of non-sintered ceramsites offers a nature-based solution for sustainable management in coastal systems.

Dredged marine sediment (DMS) is a solid waste with high salinity and water content, currently disposed of via natural stockpiling or ocean dumping, both of which pose significant threats to environmental health. Given its inherent characteristics, particularly its silico aluminate phases, valorizatng DMS to produce building materials as emerged as a promising strategy to address above issues. This approach not only achieves DMS waste disposal but also reduces the industry's heavy reliance on nature geomaterials. Following the PRISMA methodology, the paper reviews 64 research studies on the DMS resource utilization in building materials through August 2025. The review unveils that the technologies for DMS resource utilization are primarily classified into sintering and hydration routes. The former corresponds to sintered bricks, while the latter covers specific applications involving non-sintered bricks, supplementary cementitious materials (SCMs), precursor materials and aggregates. Subsequently, the effectiveness of DMS in various applications is evaluated across various applications based on multi-dimension features, with an in-depth analysis of their underlying mechanisms. Among these applications, sintered bricks exhibits the highest level of technology maturity and specific DMS consumption capacity. However, their industrial potential remains limited due to insufficient policy support and low economic viability. In contrast, DMS used as SCMs exhibits stronger comprehensive competitiveness, making it more suitable for large-scale industrialization. Furthermore, several technical challenges impeding industrialization are summarized, including low chemical activity, neglected salt risks, and excessive water-retention. In response, this paper proposes further research directions based on the characteristics of DMS itself and various building materials.

Structural damages during an earthquake are typically controlled by seismic demands, which are represented by the combination of amplitude of ground motion and cyclic load effects. Since traditional methods normally assume the lognormal distributions of seismic demands and resistance parameters, uncertainties are inevitably induced in the seismic fragility analysis. In this paper, the Copula function and adaptive bandwidth kernel density estimation method (ABKDE) are used to establish a novel multidimensional seismic fragility analysis framework. Based on the results of incremental dynamic analysis for subway station structures, ABKDE is adopted to establish single-parameter seismic fragility curves for both the maximum inter-story drift ratio (MIDR) and cumulated dissipated hysteretic energy (CDHE), respectively. Subsequently, the Copula function is used to formulate a bivariate seismic fragility function considering the correlations among seismic demand measures and establish the corresponding fragility curves. Finally, comparative analyses are conducted to evaluate seismic fragility curves using Copula-based dual and single-parameter damage models as well as the traditional damage models. It is found that the seismic fragility analysis method using the Copula function has the ability to gain a comprehensive consideration of the MIDR and CDHE during the damage process of subway station structures. Moreover, this newly developed seismic fragility analysis framework can capture the influence of the correlation between deformation and energy under various peak ground accelerations on structural damage. Thus, this framework can provide a scientific basis for predicting structural damage in subway stations subjected to varying intensities of ground motion while considering multiple damage indicators.

In seismic regions, many underground structures are inevitably partially embedded in liquefiable sites, which may cause complex seismic response mechanisms due to the varying distribution of liquefiable soil layers. This study investigates dynamic interaction between underground structures and liquefiable soils employing three-dimensional nonlinear finite element models. The seismic response of both standard and connection sections of the subway station–tunnel of underground structures in liquefiable sites is evaluated to reveal the seismic response patterns of the soil–structure system under different liquefiable soil distribution forms. The results revealed that compared to homogeneous liquefiable sites, liquefiable interlayer sites can cause greater seismic damage to underground structures, potentially leading to failure along the entire length of the subway station. Therefore, the post-earthquake failure modes of the structure and site should be comprehensively considered based on the site layers distribution characteristics.

A reasonable seismic capacity model is crucial for establishing the seismic performance level system and evaluating the seismic reliability of subway station structures. However, the deterministic structural and geotechnical mechanical parameters are usually applied to calibrate the seismic performance levels of subway station structures in the traditional seismic capacity analysis, which ignores the stochasticity of the soil-subway station interaction system. To overcome the challenge caused by the stochastic interaction system, the probability space partition method and stochastic pushover analysis method are combined to develop a calibration strategy of seismic performance levels considering the complete probabilistic information of the stochastic interaction system, and the non-parametric probabilistic seismic capacity models of the subway station structure are further established based on the principle of probability conservation in this paper. A subway station is also taken as the prototype to investigate the applicability of the proposed strategy and the influence of system randomness on the seismic capacity of the subway station structure. The results demonstrate that the seismic performance levels calibrated according to the proposed strategy can effectively consider the complete probabilistic information of the interaction system, which are more rigorous than the existing performance levels. Meanwhile, the probability density evolution of the bearing capacity of the subway station structure is essentially a non-stationary stochastic process, and the non-parametric probability density curves of seismic capacity display noticeable multi-peak characteristic. Moreover, the seismic capacity for LP1 and LP2 levels is more sensitive to the variability of geotechnical parameters above and below the structure, while the former for LP3 and LP4 levels is more sensitive to that on both sides of the structure. The relevant conclusions can provide some guidance for seismic design and improvement of the performance limits of underground structures in the related codes.

Nanoindentation assesses micro-mechanical properties through load-induced surface responses, and molecular dynamics (MD) simulations can explore atomic-scale mechanics, yet MD simulations of nanoindentation for ettringite remain unexplored. This paper presents MD simulations of ettringite nanoindentation, examining the effects of modeling and loading conditions on the outcomes and investigating the anisotropic nanomechanical properties of ettringite. The results indicate that indentation modulus values, derived from both peripheral constraints and three-layer models, could align with referenced experimental ranges. Larger indentation radii increase ettringite's indentation modulus, while excessively smaller radii, such as 8 & Aring;, can result in simulated values below experimental ranges. Increasing the loading rate and indentation depth in MD simulations results in a higher indentation modulus for ettringite, and the indentation modulus of ettringite from simulations could match referenced experimental values at loading rates of 100-400 m/s and indentation depth of 8-12 & Aring;. The initial relaxation of ettringite during nanoindentation mainly occurs in the first few thousand steps of the holding stage, with later steps having little effect on the indentation modulus. Indentation on different crystal planes of ettringite yields significant variations in atomic density distributions for various atom types and alterations in the radial distribution functions curves among different atom pairs, culminating in the anisotropic nanoindentation behavior of ettringite. Accounting for this anisotropy, the simulated indentation modulus, obtained with an indenter radius of 12 & Aring;, a loading rate of 200 m/s and an indentation depth of 10 & Aring;, closely matches the average referenced experimentally determined value for ettringite.