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 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.

A widely distributed salinized silt in Northwest China exhibits the physical characteristics of both low-liquid-limit silt and saline soil, yet its long-term deformation behavior remains insufficiently understood. A series of uniaxial creep tests were conducted to investigate its creep properties under varying conditions of salt content, dry density, moisture content, and overburden stress. Test results indicate that, compared to salt-free soil, the creep rate of salinized silt accelerates significantly with increasing salt content, demonstrating more pronounced nonlinear creep characteristics. The final strain of the salt-washed soil was 10%, which increased to 14% at a salt content of 6.4%. To more accurately characterize the soil's creep behavior, the classical creep models were modified, leading to the proposal of two new models: an integer-order model and a fractional-order model. Comparative analysis between the experimental data and the improved models shows that both proposed models describe the actual deformation characteristics more accurately than the classical creep model. However, the integer-order model lacks refinement in describing the decay creep stage, whereas the fractional-order model demonstrates superior accuracy in capturing the detailed features of all creep stages and is therefore recommended for effectively predicting the creep behavior of salinized silt.

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.

This study investigated the dynamic response of a high steep rock slope with a double-layer ductile shear zone using the right bank slope of the Banda Hydropower Station dam site area in the upper reaches of the Lancang River as the research subject. Shaking table model tests were conducted to simulate seismic behavior by incorporating the dimensionless peak acceleration amplification factor for the slope and applying seismic waves of varying types, excitation directions, frequencies, and amplitudes. Experimental results showed that: (1) Increased frequency and amplitude enhanced the dynamic response, with frequency exerting greater influence than amplitude. (2) The slope model exhibited evident elevation amplification within the slope and nonlinear near-surface amplification on the slope surface. (3) Under horizontal seismic loading, thicker ductile shear zones demonstrated pronounced energy absorption and dissipation effects. (4) Under vertical seismic loading, thicker zones continued to absorb energy, while thinner near-surface zones amplified seismic wave amplitudes.

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.

Based on the dynamic theory of elastic media, the horizontal vibration of end-bearing piles embedded in a transversely isotropic soil is studied via an analytical scheme. By introducing displacement potential functions, the governing equations of the soil are decoupled, and the general solutions for the displacement and stress fields around the pile are derived using the method of separation of variables. Applying the continuity conditions at the pile–soil interface, the horizontal complex impedance of the surrounding soil is incorporated into the motion equation of the pile, leading to analytical solutions for the displacement, rotation angle, bending moment, and shear force of the pile. In addition, explicit expressions for the horizontal, rocking, and coupled horizontal–rocking dynamic impedances at the pile head are derived. Comparison with existing theoretical solutions confirms the accuracy and reliability of the proposed method. Furthermore, the influence of soil anisotropy parameters on the horizontal vibration characteristics of the pile is systematically analyzed. The results indicate that the anisotropic modulus ratio has a significant impact on the dynamic impedance at the pile head, as well as on the distribution of horizontal displacement, rotation angle, bending moment, and shear force along the pile depth.

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.

In rock-lined caverns with compressed air energy storage (CAES), the hoop tensile strength of rock is an important parameter for calculating the ultimate bearing capacity and long-term stability of the cavern. The existing methods for measuring the tensile strength of rock are direct tensile tests or indirect tensile tests, such as Brazilian splitting and point load bending tests, which cannot truly reflect the circumferential stress of rock under high internal air pressure. Based on this, a new measurement method is proposed. By injecting high-pressure air into the drilled rock sample, the rock burst pressure is obtained. Then a calculation formula for the rock tensile strength is proposed considering the rock pore stress. In the experiments, the inflation rate and the temperature are changed, and it is found that the rock burst pressure is negatively correlated with the inflation rate and positively correlated with the temperature. It is found that when the number of cycles is relatively small (n≤100), the rock burst pressure is positively correlated with the number of cycles. The results can guide the design and calculation of rock-lined caverns for CAES, which is conducive to the promotion and application of CAES technology and has important engineering application value.

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.