Previous earthquakes indicate that near-source canyon topographic effect (NCTE) can substantially amplify the seismic responses of canyon-crossing bridges (CCBs). While the conventional practices are to make disaster response decisions based on the deterministic approaches, it cannot provide a holistic view regarding the impacts of uncertainties of ground motions on CCBs. Thus, this study adopts the performance-based assessment in a probabilistic framework to evaluate the seismic fragility of CCBs considering NCTE. For this purpose, a numerical model of a typical tall-pier CCB across a V-shaped canyon is constructed using the OpenSees. Eighteen ground motions combined with NCTE are simulated using the region-matching method. PGA, Sa(T1), and PGV are compared to determine the optimal intensity measure (IM). The probabilistic seismic demand models and fragility curves are constructed. The results show that PGV is the optimal IM for ground motions considering NCTE. The NCTE can significantly increase the damage probability of CCBs. The damage probability of the side bearing is the most sensitive to NCTE among the vulnerable components. The side pier bearings and the side piers on the illuminated canyon side are the most vulnerable components in cases with and without consideration of NCTE, respectively.

Irregularities in the material or ground surface can cause the wave scattering and radiation, affecting the dynamic properties of the medium. This study proposes an innovative analytical solution to the problem of cylindrical SH wave scattering by multiple symmetric or asymmetric Vshaped canyons in half-space. The solution is derived using wavefunction expansion method combined with multi-region matching strategy. The proposed model overcomes the limitations of the previous single V-canyon models and addresses the issue of SH wave scattering by multiple Vcanyons. The model is validated by reducing it to the canonical single V-canyon models. Parametric analysis reveals that the multiple V-canyon topography exhibits continuous shielding effect on grazing incident waves and focusing effect on obliquely and vertically incident waves. These effects result in significant variations in surface ground motions, which are closely related to the topographic geometry and the characteristics of the incident seismic waves. Additionally, time-domain analysis of a realistic dual-canyon topography shows that the peak ground acceleration at characteristic points of the V-shaped canyons varies from -40 % to 65 % relative to that on a flat surface. These findings underscore the significant impact of multi-canyon topography on seismic input to engineering structures in mountainous areas, providing valuable insights for seismic design and risk assessment.

This study develops a three-dimensional tidal flow-graded sediment model based on a bidirectionally coupled CFD-DEM framework. The model can be used to investigate local scour evolution around offshore wind monopile foundations. Operating within an Eulerian-Lagrangian framework, the model allows for explicit tracking of particle trajectories and interaction forces, thereby capturing microscale sediment transport responses under alternating phases of scour and backfilling. The simulation results reveal a morphological transition in scour pit development, from shallow depressions to ring-like structures, as the dimensionless peak flow velocity increases, with flow reversal exerting a crucial regulatory influence in stabilizing the scour geometry. Additionally, the study proposes a new model that relates scour depth to flow velocity for estimating both scour evolution and maximum pit depth, emphasizing the stabilizing role of tidal backfilling across multiple flow cycles. This approach enhances engineering applicability by reducing dependence on empirical parameter tuning and complex boundary conditions. Collectively, these findings offer theoretical insights valuable for risk assessment and design optimization of offshore wind turbine foundations, while also laying a foundation for future research on particle-scale dynamics and multi-cycle coupled simulations.

This work presents a deep learning framework for the automatic detection and quantitative evaluation of tunnel cracks. Initially, a systematic data pre-processing method is proposed. By jointly leveraging SRGAN, Histogram Equalization, Contrast Limited Adaptive Histogram Equalization, the raw data is normalised and augmented prior to model training. A semantic segmentation method for tunnel lining cracks is developed, which is based on the object-detection network, the OTSU algorithm, and morphological algorithms. In the backbone network of the object detection, Swin Transformer and Sand Glass Block are integrated to concurrently account for both global perception and local feature representation capabilities. Furthermore, a Parallel Three-Channel Feature Extraction module (PTFE) and a Hierarchical Semantic Broadcast Feature Extraction module (HSB) are combined to enhance the responsiveness of the feature maps to critical regions. Based on the image data collected from actual tunnel engineering projects, the performance of the proposed method is evaluated using multiple evaluation indicators. The results demonstrate that the proposed method exhibits superior performance compared to Faster R-CNN, RetinaNet, and YOLO v5. Specifically, investigations are carried out to explore the impact of the PTFE and HSB module, data preprocessing techniques, and transfer learning on the proposed method.

Deep-sea mining vehicles (DSMVs) generate tremendous traction and provide excellent maneuverability, making them the preferred choice for deep-sea mining. The source of this immense traction lies in the shear forces generated by the interaction between the vehicle tracks and the deep-sea soil during underwater operations. Therefore, studying soil failure patterns caused by motion trajectories is crucial for evaluating the traction performance of DSMVs. In light of that, this study adopts the discrete-element method to investigate the influence of height/spacing ratio (r) on soil failure mode, putting into consideration the relationships among r, soil failure mode, and soil thrust in the analysis. Through analysis, it can be inferred that under the condition of a relatively large track height/spacing ratio, the failure of the soil behind the track can be approximately regarded as a direct shear failure mode. As the track height/spacing ratio decreases, the failure zone of the soil behind the track will exhibit uniformly distributed inclined shear surfaces. Based on the interaction between the track grouser and the soil and the failure mode of the soil behind the track, we have developed a new calculation model for the traction force of a crawler-type mining vehicle.

In response to the national strategic goals of "carbon peak and carbon neutrality," this experiment utilized recycled coarse aggregate (RCA) as the aggregate and metakaolin (MK) as a mineral admixture to replace a portion of cement. Compression analysis was carried out on recycled aggregate concrete (RAC) under various numbers of freeze-thaw cycles. Additionally, the mechanism of freeze-thaw deterioration and the effect of MK on the microstructure of RAC were investigated by electron scanning (SEM) and other microscopic instruments. Finally, a constitutive relationship for RAC subjected to freeze-thaw cycles was formulated utilizing the principles of statistical damage model. The results indicated that the physical expansion due to freeze-thaw cycles leads to continuous coarsening of RAC pores, leading to an ongoing reduction in its strength and elastic modulus, along with an escalation in the peak strain. The secondary hydration reaction and filling effect of MK significantly mitigated the effect of freeze-thaw cycles, enhancing RAC freeze resistance and strength. Taking into account the reinforcing effect of optimizing and adjusting the force-bearing skeleton at the mesoscale, the complete process of deformation and rupture was understood through the lens of effective stress, shedding light on the mesoscale reasons for the delay of the acoustic emission peak stage relative to the peak of the stress-strain curve, and distinguishing between the peak state and the critical state. The evolutionary laws between freeze-thaw damage parameters were quantitatively analyzed, verifying the rationality of the statistical damage model for use in freeze-thaw environments.

Oblique photography technology can provide high-fidelity three-dimensional (3D) models of large-scale building clusters, which has great application potential for 3D fire simulation in building clusters. However, it has not been applied to building fires. To this end, a 3D simulation method of fire spread for building clusters is proposed based on oblique photography and variable multi-grid. The method includes modeling, computing, and visualization. For modeling, the existing oblique photography model based on voxelization is directly converted into a computational fluid dynamics (CFD) model, which significantly reduces the modeling workload. For computing, the two-dimensional (2D) regional fire spread range is pre-assessed to reduce the computational domain for the 3D simulation. Moreover, a parallel computing algorithm with variable multi-grid (PCAVM) is developed to enhance the efficiency of the 3D fire simulation. For visualization, a highly realistic scene of fire spread in building clusters is generated using an oblique photography model combined with the 3D simulation results. The accuracy of the modeling method was validated by comparing the simulation results with actual experimental data. The application case demonstrated a 5.82-fold increase in computational speed, suggesting the efficiency of the proposed method. This method applies the oblique photography model to the 3D simulation of fire spread for building clusters, which can be used for fire prevention planning and virtual fire emergency training in key areas.

Tongzhou District is the urban sub-center of Beijing, and the importance of groundwater resources is increasingly prominent. Based on groundwater level data from 1980 to 2020 and water usage data from various sectors in Tongzhou District between 2011 and 2020, this paper utilizes continuous wavelet transform (CWT), geostatistical models, and grey relational analysis (GRA) to explore the spatiotemporal evolution patterns and influencing factors of groundwater levels in Tongzhou District. The study reveals that the groundwater level evolution in Tongzhou District exhibits two primary cycles, and it predicts that the groundwater level at Liyuan Station will decrease and eventually rebound. From 1980 to 2020, the overall trend of groundwater levels in Tongzhou District showed a decline. However, the groundwater levels in the central and southern regions exhibited an upward trend from 2000 to 2020. The groundwater level is mainly influenced by spatial structural factors, with minimal impact from external random factors. Domestic water consumption, water usage in the tertiary sector, and industrial water usage have the greatest impact on groundwater levels, attributed to the rapid growth of the population and regional economy. Agricultural water usage has the least grey relational grade, which is related to changes in agricultural development planning in the study area, as well as reductions in the area of crop planting and the actual utilization area of facility agriculture.

The soil and topographic amplification effects of a weathered canyon may pose a potential threat to the dynamic stability of the engineering structures (i.e., dams, buildings and bridges) located in such kind of sites. To reveal the influence of the surficial inhomogeneous viscoelastic soil layer of a weathered canyon on the ground motion, an analytical solution to scattering of SH waves by a semi-circular viscoelastic weathered canyon is presented in frequency domain in this paper using the wave function expansion method. Then, the frequency domain results are transformed into the time domain results using the inverse fast Fourier transform (iFFT) algorithm. The parametrical analysis indicates that the amplitude, duration and energy distribution during seismic wave propagation are significantly affected by the surficial inhomogeneous soil layer of the viscoelastic weathered canyon.

A general analytical solution for dynamic response of a multi-layered functionally graded lining (FGL) in a full space subjected to plane SH-, P- and SV- waves is presented using the wave function expansion method and transfer matrix approach. The accuracy of the proposed solution is verified by comparison with the past exact solutions. The influence of layer number, shear modulus, and thickness on the stress of the lining is discussed in the frequency domain to illustrate the mechanism of the seismic performance of FGL. Furthermore, a comparative evaluation of their dynamic response is conducted between the single-layered lining and FGL to reveal the effectiveness of FGL. The parameter analysis shows that FGL can effectively mitigate stresses in the lining and ensure a more uniform stress distribution.

Excavating tunnels in anisotropic rock induces greater stress concentrations at the excavation boundary compared to isotropic rock. However, existing analytical solutions for the shallow tunnel are founded on the simplifying assumption of isotropic rock masses. To clarify the deformation mechanism and mechanical behavior of the shallow tunnel, we proposed an analytical method for solving stress and displacement of the arbitrary-shaped shallow tunnel excavated in orthotropic rock mass, incorporating the effects of body forces and anisotropy of rock mass. Proposing the specific forms of the analytical functions for the shallow tunnel in anisotropic rock, which can reflect body forces and the anisotropy of the rock mass. A linear equation system, derived from stress boundary conditions at the surface and tunnel excavation, is solved by the boundary collocation method. In the solution process, conformal transformation techniques are employed to construct three polar coordinate systems, which aid in resolving boundary conditions. Subsequently, we analyzed the effects of tunnel depth and anisotropic parameters on the stress and displacement of a horseshoe-shaped tunnel and verified the correctness of the results through ANSYS software.

The bond strength between fibers and the matrix plays a crucial role in the tensile strength and post-cracking performance of ultra-high-performance concrete (UHPC). However, existing studies have not attempted to utilize machine learning models for the prediction of bond strength. In this study, machine learning techniques were employed to predict the bond strength of fibers in UHPC. A dataset comprising 658 experimental records was compiled and advanced unsupervised Isolation Forest techniques were utilized to identify and remove outliers, thereby ensuring the accuracy and reliability of the data. Six machine learning models, including ANN, GBDT and XGBoost are utilized in this study, with a focus on evaluating their performance in predicting the maximum pull-out force of fibers. The results indicate that the XGBoost model exhibits exceptional predictive performance, achieving R2 value of 0.98, which demonstrates the model's capability to accurately predict the fiber pull-out process. Furthermore, feature importance analysis, visualized through advanced techniques, reveals the significant influence of fiber tensile strength on the pull-out force. A new equation is proposed to predict the maximum pull-out force of fibers and correction factors for different fiber shapes are introduced, significantly enhancing the precision of the calculations. The newly proposed predictive equation has R2 value of 0.72, which increases to 0.74, 0.77, and 0.86 after the introduction of shape correction factors, significantly enhancing the accuracy of the computed results. This study not only provides an efficient and reliable method for predicting fiber bond strength in UHPC but also offers an innovative tool for calculating fiber pull-out force.

Deeply buried tunnels are often accompanied by high in situ stress, and rock burst is a common geological disaster during excavation in hard rock. This paper proposes a new rock burst discrimination criterion that is based on actual engineering and tests as well as the energy-release mechanism during a rock burst occurrence. By considering the elastic strain energy density gradient and the energy-release space together, the proposed criterion establishes a novel rock burst discrimination value, W. In addition, the elastic strain energy density gradient within isotropic surrounding rock is calculated using an improved complex variable function method. Rock burst discrimination calculation is performed for cases including both circular and noncircular tunnels. The results show that the rock burst risk decreases as the discriminant value W decreases, and that when W falls below the critical value (Wcr = 1), the surrounding rock ceases to experience rock burst failure. A comparative analysis with an existing rock burst discrimination criterion reveals that the proposed criterion exhibits better discrimination accuracy.

To investigate the dynamic interaction between irregular topography and the nearby structure, a rigorous analytical solution is derived for an asymmetric V-shaped canyon and a simplified structure under SH waves. The structure is represented by an idealized single-degree-of-freedom (SDOF) oscillator. The analytical model is validated by degrading into either a single SDOF oscillator model or an asymmetric V-shaped canyon model. Based on the proposed solution, the dynamic interaction between the V-shaped canyon and the nearby SDOF oscillator is analyzed in time domain. The results indicate that the canyon asymmetry can significantly influence the seismic response of the structure due to its “shielding effect” or “focusing effect” on seismic waves. In addition, the nearby structure either amplifies or attenuates the seismic responses at the canyon's shoulders and bottom.

The vast ocean floor holds abundant mineral resources, characterised by a wide variety, large reserves, and high grade. It has tremendous prospects for development and utilisation. Necessitating intensified efforts in key core technology development for deep-sea mineral resource exploitation. As crucial equipment in the field of deep-sea mining engineering, the performance and reliability of heavy-duty equipment for deep-sea mining play a critical role in the development of deep-sea resources. This paper provides a systematic analysis of the development status of deep-sea mining vehicles both domestically and internationally. Starting from the fundamental scientific issues of soil-vehicle interactions, it reviews the progress of research on the mechanical characteristics of deep-sea soft soil, stress response mechanisms under mining vehicle loading, and the behavior of track-soft soil interface contact. The evolution of the walking performance and motion behavior of deep-sea mining vehicles is summarized, and existing issues and future research priorities related to the coupling effect between deep-sea soft soil and dynamic equipment are identified.

Bolt is a safe and dependable engineering anchoring technique, and the stress transfer mechanism of the bolt has been the subject of research. Based on the bolt-grout interface deformation coordination relationship, this paper establishes physical equations using the Mindlin displacement solution and deduces the theoretical distribution of shear stress along the anchor length for fully grouted bolts. This paper also conducts an indoor bolt pullout test to verify the accuracy of the calculation results. The results show that when the bolt is subjected to tensile load, the shear stress shows a tendency to increase sharply and then decrease slowly. As the load increases, the shear stress also increases, with the extreme points gradually moving away from the pullout end. The distribution of shear stress is also directly related to the anchor length and diameter. By controlling the ratio of these two parameters, the shear stress on the bolt can be reduced by 50%-70%. Meanwhile, the ratio of the elastic modulus of the rock mass Ec to the elastic modulus of the bolt Es, Ec/Es, has a significant effect on the distribution of shear stress. The shear stress model established in this paper matches well with the experimental data, with a fitting coefficient R2 >= 0.9, which demonstrates high accuracy and applicability. In engineering practice, by taking into account the specific conditions of the construction site, the model developed in this study can be utilized to choose bolts of suitable size, thereby optimizing anchorage efficiency.

The requirements for transportation often make it unavoidable to excavate shallow multiple tunnels under slope terrain in mountainous areas. An analytical approximate solution of stresses and displacements around multiple shallow circular tunnels under slope terrain that takes the interactions among tunnels into consideration is proposed in this study. Using superposition principle, the original problem is decomposed into a slope plane without tunnels (solid slope) and several infinite planes containing only one tunnel loaded by virtual traction on the tunnel boundary. The solid slope is further divided into several half planes subjected to virtual tractions on the upper surfaces, Combined with complex variable method and Flamant’s solution, the virtual tractions acted on the half plane surfaces and tunnels boundaries are obtained through iterations, and thus the stresses and displacement around the tunnels are obtained. The analytical approximate solution is verified by the convergent iteration and the close agreement with the corresponding numerical and theoretical solutions. In addition, the effects of surcharge loads position, tunnels layout, tunnels radius and slope inclination on the ground responses are investigated through parametric analyses. The proposed analytical model is helpful for providing an alternative approach for the preliminary designs of shallow tunnels under slope terrain.

The pre-stressed UHPC bridge exhibits a trend towards thin-walled and lightweight, resulting in reduced crosssectional area in the anchorage zone, which restricts the anchorage space. Traditional anchorage configuration and design methods cause the crowding of steel bars, increase construction difficulty and reduce costeffectiveness. To fully utilize the excellent mechanical properties of UHPC, a lightweight UHPC anchorage system is proposed, in which anchorage zone the anchor devices was removed and the amount of skin reinforcement was minimized in this paper. Then, the experiment was conducted to study the local bearing performance of the lightweight UHPC anchorage zone. The results show that the bearing capacity of the lightweight anchorage zone is 14.0 % higher than that of the traditional anchorage zone. The combination of UHPC and spiral reinforcement can replace the anchor devices in the anchorage zone. Based on test results, a calculation method for the bearing capacity of the lightweight UHPC anchorage zone was proposed considering the contributions of fiber bridging effect, the residual tensile strength of UHPC after cracking, and the duct reduction effect. The ratio of calculation results of the proposed formula to the experimental results is 0.96, indicating high accuracy and safety of this calculation method. Data availability: Some or all data, models, or code generated or used during this study are available from the corresponding author by request.

Time-varying loading is a frequently encountered loading type in geotechnical engineering. As the deformation of viscoelastic soil is related to its loading history, studying the viscoelastic problems under time-varying loads has important practical engineering significance. In this paper, the stress and displacement of a layered soil with fractional-order viscoelastic model under time-varying loads were solved using the complex variable method and the corresponding principle. Under the assumption of quasi-static and linear elasticity, this paper derives the quasi-static elastic solutions of a layered soil under time-varying strip loads. By introducing the fractional-order viscoelastic model and using the corresponding principle, the Laplace-domain analytical solutions are obtained. Finally, numerical methods are utilized to perform the Laplace inverse transform and obtain the solutions in the physical domain. The correctness of this paper is validated by comparing the numerical results with the ANSYS software, as well as by comparison with previous literature. Based on the experimental data, the material parameters of frozen soil at two temperatures are fitted. The settlement patterns of soil under two engineering loads were analyzed through case studies. By controlling variables, the influence of parameters of the fractional viscoelastic model on elastic aftereffect was investigated.