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.

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.

Vacuum preloading, as a widely adopted ground improvement method for saturated soft soils with high water content, is extensively applied in large-scale coastal reclamation projects. However, post-reinforcement bearing capacity remains insufficient in many engineering cases, particularly with limited strength improvement in deep soil layers. Numerous studies have demonstrated that the consolidation efficiency of vacuum preloading is constrained by two critical factors: depth-dependent attenuation of vacuum pressure and fine particle enrichment-induced clogging of drainage paths near prefabricated vertical drains. To address these challenges, this study integrates electro-osmosis with vacuum preloading (EVP) during the later stage of vacuum preloading in the dredger fill project of Yueqing Bay North Port Area. A large-scale model test pool was employed, where conventional vacuum preloading was conducted for 108 days until settlement stabilization, followed by a two-phase EVP intervention. The first phase lasted 11 days, after which electrode polarity was reversed for the second phase (6.5 days), totaling 17.5 days of EVP reinforcement. Post-EVP results revealed significant improvements: at depths of 20 cm, 60 cm, and 100 cm, soil water content decreased by 4.2%,4.84%, and 2.34%, respectively, while vane shear strength increased by 32%, 75%, and 61.1%. The test results indicate that superimposing the electro-osmosis method during the later stage of vacuum preloading can achieve a significant improvement in vane shear strength (with a water content reduction of less than 5%). Particularly for deep soil layers with low initial strength that are difficult to reinforce solely by vacuum preloading, the strength increased by 61%−75%, demonstrating effective reinforcement performance.

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.

The energy development projects in western China require the construction of a large number of vertical shafts in weakly cemented gravel layers with poor stability. Anchor rod support is an important means of controlling the deformation of surrounding rock. However, most of the current theories on anchor reinforcement have overlooked the lagging support of anchor rods. Therefore, based on the spatial constraint effect of the working face, elastic-plastic theory, and the anchor rod stress uniform distribution method, this study proposes a semi-analytical calculation method for the deformation and stress of the surrounding rock of vertical shaft anchor bolts considering the lag support of anchor bolts. The correctness of this method was verified by finite element method. Based on the proposed semi analytical solution, the influence of anchor parameters was further explored. The research results show that the larger the lag distance of the anchor rod, the greater the deformation of the surrounding rock, and the smaller the surrounding rock pressure borne by the anchor rod and other supporting structures. When the lag distance x_gs of the anchor rod is less than 1.5r_A (r_A represents the excavation radius of the vertical shaft), the deformation u_r(r=r_A) and safety factor s of the surrounding rock change greatly. When the lag distance x_gs of the anchor rod is greater than 3.0r_A, the deformation u_r(r=r_A) and safety factor s of the surrounding rock remain basically unchanged. Increasing the diameter of the anchor rod improves the shear strength, but the impact gradually decreases. When the length of the anchor rod L is less than 1.0r_A, the deformation of the surrounding rock u_r(r=r_A) and the safety factor s change greatly. When the length of the anchor rod L is greater than 1.0r_A, the change is slow, so it is not recommended to excessively use long anchor rods. Research suggests that when selecting support parameters, consideration should be given to the support lag distance to ensure the stability of the surrounding rock. This study successfully applied this theory to the vertical shaft engineering of pressure pipelines, and the research results provide a solid theoretical basis for the design of anchor rod support for the surrounding rock of the vertical shaft.

Current research on rock freeze-thaw damage mainly focuses on uniform freeze-thaw tests. However, the situation of unidirectional freeze-thaw action is widely present in cold region engineering, and there is a lack of sufficient understanding of the evolution of mechanical properties and damage models under unidirectional freeze-thaw conditions. Therefore, this study selected sandstone as the research object and conducted unidirectional freeze-thaw cycle tests and uniaxial compression tests. The elastic modulus, uniaxial compressive strength, stress-strain curves, and failure modes under uniaxial compression were analyzed for sandstone samples parallel and perpendicular to the freeze-thaw direction after undergoing freeze-thaw cycles. The results indicate that, following unidirectional freeze-thaw action, the compressive strength of sandstone parallel to the freeze-thaw direction is greater than that perpendicular to it, while the elastic modulus parallel to the freeze-thaw direction is smaller than that in the perpendicular direction. Both the peak stress and strain in the parallel direction are higher than those in the perpendicular direction. In uniaxial compression tests, the failure mode of sandstone parallel to the freeze-thaw direction remains consistent with that of samples that have not undergone freeze-thaw action, exhibiting X-shaped shear failure, whereas the failure mode perpendicular to the freeze-thaw direction manifests as splitting along the loading direction. Under unidirectional freeze-thaw action, the mechanical properties of sandstone transition from isotropy to anisotropy. Based on the aforementioned experimental observations, an anisotropic coefficient for unidirectional freeze-thaw was introduced, and a damage model for sandstone under unidirectional freeze-thaw conditions was established. The model was subsequently validated using experimental data.

The microbially induced calcite precipitation (MICP) technique can effectively enhance the mechanical properties of coral sand. To investigate the small-strain dynamic characteristics of MICP-treated coral sand, resonant column tests were conducted on specimens with varying biocementation cycles N_b and effective confining pressures and the development laws of dynamic shear modulus G and damping ratio λ were comparatively analyzed. The test results reveal that: at small strains, the dynamic shear modulus G increases significantly with both N_b and . The maximum dynamic shear modulus G_max exhibits a linear correlation with N_b and a power-law correlation with . A significant power-law relationship exists between G_max and unconfined compressive strength (q_ucs). As N_b increases, the reference strain γ₀ decreases gradually while the G/G_max-γ_d curves shift downward, indicating enhanced nonlinearity. Both minimum and maximum damping ratios increase, with the λ-γ_d curve moving upward and characterized by greater energy dissipation. In contrast, increasing produces opposite trends in both G/G_max-γ_d and λ-γ_d curves, exhibiting reduced nonlinearity and energy dissipation. Empirical relationships are established to quantify the nonlinear dynamic behavior and energy dissipation characteristics of MICP-treated coral sand. Scanning electron microscope (SEM) observations reveal that stiffness improvement primarily results from three mechanisms: contact cementation between sand grains, grain coating by calcite precipitates, and matrix supporting through pore filling.

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 stress analysis of sliding surface is the key link to evaluate the stability of slope and predict the risk of landslide. There are many methods to solve the sliding surface stress, but there is no reasonable method to evaluate these methods. In order to solve this problem, a sliding surface stress test device used in landslide model test was proposed. The structural characteristics and design principle of the device were introduced in detail. Three cases were designed to test the sliding surface stress by model test. Based on the correlation analysis and probability P value in the statistical analysis results of paired sample t-test, the applicability of Morgenstern-Price (M-P) method, elastic theoretical solution of sliding surface stress based on slope unloading and numerical analysis method in solving sliding surface stress was evaluated. The main conclusions are as follows: (1) The absolute error between the test results and the theoretical values of the 9 sliding surface test units is within 2.5%. The statistical analysis results show that the difference between the test results and the theoretical values is not significant, and the stability of the test results is good. (2) The elastic theoretical solution and numerical analysis method can accurately calculate the stress state of the sliding surface, but the calculation result of the M-P method has a large deviation from the actual one, which is not suitable for the calculation of slip surface stress in non-limit state. (3) The application of sliding surface stress elastic theory solution based on slope unloading in embankment slope is expanded, but this method still has great limitations. The sliding surface stress test device proposed in this paper expands the new method of sliding surface stress test, and provides a guarantee for the accuracy verification of sliding surface stress calculation and stability analysis theory.

The strength and deformation characteristics of rockfill materials are known to be closely related to their gradations. In order to predict the mechanical behavior of rockfill materials with different initial gradations, the influence of gradation on the mechanical properties of rockfill materials is first discussed within the framework of critical state constitutive theory. Subsequently, a method is proposed for rapidly predicting the initial and critical state void ratios for given gradations. Finally, by incorporating a state-dependent elastoplastic constitutive model, a prediction method for the gradation-related mechanical characteristics of rockfill materials is established. The results indicate that a good linear relationship exists between the minimum void ratio e_min and the critical state void ratio e_cs under low-stress conditions. Utilizing a particle packing algorithm, the critical state position of rockfill materials with specific gradations in the void ratio-pressure (e-p, e is the void ratio of the rockfill material in its current state, and p is the mean stress) space can be reliably predicted. Ultimately, this proposed prediction method facilitates the calibration of constitutive model parameters based on the test results of rockfill materials with known gradations, which subsequently allows for effective prediction of the mechanical behavior of other rockfill materials with different specified gradation profiles.