The mechanism of shield-soil interaction has always been a significant issue in academia and industry. For the active articulated shield, the presence of the active articulation system has an inevitable impact on shield-soil interaction. Therefore, a shield-soil interaction model considering active articulation was proposed and numerically solved using the time-incremental method. The model was validated through a case study of the Binzhong interval in Fuzhou Metro Binhai Express. The influence of active articulation on shield heading, resultant moment of earth pressure on shield shell, and resultant propulsion moment was carefully studied. Key conclusions include: (1) The shield-soil interaction during continuous excavation is more accurately reflected by the model and its numerical solution method. (2) Increasing the pitch articulation angle significantly reduces shield heading. (3) With a smaller coefficient of subgrade reaction, the articulation angle is approximately linearly correlated with the resultant moment of earth pressure; this relationship transitions to nonlinearity as the coefficient increases. In upper-soft lower-hard strata, the resultant moment varies with pitch articulation direction and becomes more pronounced with larger articulation angles. (4) Within the small-angle attitude correction range, a certain articulation angle reduces the resultant propulsion moment, enabling efficient attitude control. These findings provide theoretical support for shield axis deviation calculation and shield attitude control strategy.

Stratified rock slopes are prone to damage under strong earthquake, leading to geological disasters such as crumbling, landslides and debris flow, and their stability evaluation and support structure optimization are key issues for engineering construction and academic research. Based on field investigations, theoretical analyses, numerical simulations and physical model tests in strong earthquake regions, scholars at home and abroad have carried out a lot of fruitful researches on the damage mechanism and reinforcement measures of rock slopes in strong earthquake regions. Starting from four aspects, including destabilization and damage characteristics of laminated rock slopes, types of support structures, reinforcement mechanisms of support structures and new seismic support structures, the research status of rock slope support structures under strong earthquakes is systematically reviewed, the shortcomings in the current basic research and technical methods of support structures are indicated, and the future research and development directions of seismic support structures for slopes are prospected. This study provides theoretical support for revealing the instability mechanisms and reinforcement strategies of stratified rock slopes in strong earthquake regions, while establishing a scientific foundation for developing more reliable support structures.

Current machine learning models for recognizing geological conditions during shield tunneling heavily rely on precise geological data labelling, limiting their applicability in complex geological environments. To address this, we propose a continuous dynamic time warping (CDTW)-based agglomerative hierarchical clustering model (CDTW-Agglomerative), which integrates a linear interpolation framework to overcome DTW's discretization issues. An online learning mechanism is implemented for dynamic strata recognition. The model's accuracy and reliability are validated using Xiamen Metro Line 3 data, with generalization tested on Line 6 data. Results show recognition accuracies of 85% and 73% on the two datasets, demonstrating robust generalization. CDTW-Agglomerative outperforms DTW-Agglomerative, SoftDTW-Agglomerative, and CDTW-based models (K-means, K-medoids, Spectral clustering). Notably, it identifies cutterhead stratigraphy without requiring pre-labelled geological data, supporting intelligent decision-making for tunnelling parameters.

The problem of soil cutting widely exists in engineering fields such as tunnelling, port and waterway dredging, geological drilling, and civil construction. Accurately characterizing the three-dimensional soil failure surface in front of the cutting tool during the soil cutting process is of great significance for analyzing soil disturbance states, evaluating tool cutting performance, and understanding soil-tool interaction mechanisms. A nonlinear elastoplastic damage-based constitutive model is employed to describe the deformation and failure process of soil. Based on the characteristics of damage energy dissipation per unit area of the soil medium, a new numerical method is proposed to directly characterize the three-dimensional soil failure surface. Numerical simulations of flat-tool cutting processes under various operating conditions verify the effectiveness and robustness of the proposed characterization method. The influence of cutting angle and depth on the width, rupture distance, soil disturbance area, and shear failure angle of the three-dimensional soil failure surface is discussed in combination with theoretical calculations. Furthermore, the shape of the three-dimensional soil failure surface for complex-shaped tools obtained through this numerical method is consistent with experimental results, further validating the applicability of the proposed method for complex tool scenarios.

To investigate the stability of the excavation face during tunnel traversal through an upper-sand-lower-clay composite stratum, centrifugal model tests and numerical simulations were combined to analyze the displacement variation in instability zones, profile characteristics of final instability zones, earth pressure evolution patterns, and ultimate support pressure under different stratigraphic boundary positions and burial depth ratios. Test results indicate: Significant instability occurs when the stratigraphic boundary is at the tunnel face center, while stability is maintained when the boundary is at the tunnel crown. Displacements concentrate in the upper sandy layer with negligible changes in the clay layer, demonstrating that initial instability disturbance influences subsequent instability zone development. Analysis of normalized vertical earth pressure and excavation face retreat displacement curves reveals that increased burial depth ratios and clay layer thickness enhance formation resistance to disturbances. Support pressure ratio-displacement curves for two instability cases exhibit three distinct stages, with the upper side central point of the excavation face reaching ultimate support pressure first. When the burial depth ratio increases from 1.0 to 1.5, the ultimate support pressure shows minimal change. 3D finite element simulations of the excavation process validate the ultimate support pressure, failure patterns in instability zones, and earth pressure evolution, with numerical results showing good agreement with experimental data.

Combining bridge row piles with energy piles to create energy row piles can harness shallow geothermal energy for bridge deck deicing in winter and cooling in summer, respectively, while also supporting the mechanical loads of the bridge deck. This study investigates the thermo-mechanical response of energy row piles under heating-cooling cycles through field tests, and analyzes the interactions among energy row piles, slab, and unheated piles. An interface model considering the cyclic shear characteristics of the pile-soil interface is developed in a finite element software, and thermo-mechanical coupling numerical models of energy row piles are established to further explore the changes and mechanisms of long-term settlement of energy row pile under the combined effect of mechanical loads and heating-cooling cycles. The findings reveal that interactions among the energy row pile, slab, and unheated piles can result in load redistribution, leading to high thermally induced stresses of approximately 80% of the maximum thermally induced stress of the energy row pile (i.e. 1.1 MPa) at the top of the energy row piles due to strong restraining effects. Meanwhile, the slab experiences tensile stress exceeding the tensile strength of C30 concrete, reaching 3.75 MPa. Moreover, when the mechanical load is large, energy row piles progressively develop long-term settlement with an increasing number of thermal cycles, exhibiting a negative exponential growth pattern. This phenomenon is attributed to the mechanical load driving the pile-soil interface toward its limiting state, where cyclic shear at the interface readily induces plastic shear displacements, ultimately resulting in the long-term settlement of the energy row piles.

The variation in characteristic values of stress waves before and after passing through a material serves as a critical basis for evaluating its wave attenuation capacity. This can be characterized by the ratio of transmitted wave amplitude to the initial incident wave amplitude (i.e., transmission coefficient) in SHPB tests. However, due to the close correlation between the transmission coefficient and waveform parameters, it remains challenging to establish a quantitative characterization method for the transmission coefficient. Therefore, this study focuses on porous, irregular, and fragile calcareous sand as the research object. By combining physical experiments with numerical simulations, we investigate the influence of pulse width, platform duration, rising edge rate, falling edge rate, peak stress, and the central axis of symmetry on the transmission coefficient of calcareous sand. It is found that the transmission coefficient responds significantly to the coupling effects of the pulse width and the central axis of symmetry of the stress wave, the coupling effects of the platform section duration and the rising and falling edge rates, the coupling effects of the pulse width and the peak stress, as well as the coupling effects of the falling edge rate and the pulse width. Conversely, the response to the coupled effects of peak stress, rising edge rate, and falling edge rate is not pronounced. Owing to the difficulty in completely decoupling these waveform parameters, a prediction method is proposed for the transmission coefficient based on the gradient boosting algorithm, which effectively addresses multi-factor coupling issues. When the number of training samples reaches 91, the prediction accuracy exceeds 96%, which can effectively establish the mapping relationship between waveform parameters and transmission coefficients, providing a reference basis for the load design and calculation of protective engineering structures.