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 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.

Quantitative characterization of the anisotropy of rock joint roughness is crucial for evaluating joint mechanical properties. However, the complex structure of joint surfaces and the limitations of current analytical methods pose significant challenges to roughness calculation and anisotropy evaluation. This study focuses on shale from the Pengshui area in Chongqing, China, combining fractal topography theory and the joint roughness coefficient (JRC) to characterize the anisotropy of joint surfaces. Using a 3D laser scanner, the morphology of joint surfaces from shale samples fractured in different directions was captured. JRC and Fractal Dimension (D) of joint profiles were then calculated in various directions to compare joint surface anisotropy. The results indicate that: (1) JRC, which considers both fractal properties and amplitude characteristics of joint profiles, shows a stronger correlation with fracture orientation than D. Using the bedding plane of shale as a reference, a larger angle between the reference plane and the fracturing direction results in a higher JRC value for the joint surface. (2) The JRC values for a single joint surface can be approximated by an elliptical fit, with the area of the ellipse increasing as the angle between the rock bedding and the fracturing direction increases. This implies that when the fracturing direction is perpendicular to the bedding plane, the fracture surface is rougher. This research provides a reference for characterizing joint surface anisotropy and offers guidance for understanding the relationship between fracturing direction and joint surface roughness.

In order to investigate the influence of rock interface roughness on the characteristics of the charge induction signal during fault slip, the time-frequency characteristics of the multi-channel charge induction signal waveforms, the cumulative velocity of charge, the fractal dimension, and the primary and secondary frequency zones of the rock assemblage structure with different roughness during the slip process in the double-sided shear test under different vertical loads were investigated. The results show that: (1) The localized micro-rupture nucleation in the elastic deformation stage leads to multiple charge induction clusters with maximum values, which increase with the increase of interface roughness and vertical load, and then become dense and small-amplitude signals when entering into the start-slip stage. (2) With the increase of interface roughness and vertical load, the fluctuation of the accumulated charge velocity and fractal dimension are more obvious and highly correlated with the change of the waveform of the charge induction signal. In the elastic deformation stage, the accumulated charge velocity shows “slow increase in the main body and sudden increase in multiple points”, and each charge induction cluster is accompanied by the phenomenon of “first ascending and then descending” of the fractal dimension, with the main frequency area located in the low-frequency domain and the sub-main frequency area located in the high-frequency domain. In the start-slip stage, the accumulated charge velocity changes to an overall rapid increase and the fractal dimension fluctuates more obviously with the increase of fault interface roughness and vertical loading. During the start-slip stage, the charge accumulation rate changes to an overall rapid increase, and the fractal dimension is continuously downgraded, and the primary and secondary frequency regions show the phenomenon of “translational interchange”, with the primary frequency region shifted right to the high-frequency domain, and the secondary frequency region shifted left to the low-frequency domain, and the primary frequency of the charge signals at each slip stage falls into the frequency aliasing domain common to the whole process of slipping. (3) Comparing the time-frequency resolution and time-frequency focusing of the three time-frequency transform methods, wavelet transform, short-time Fourier transform and S transform, it is found that the wavelet transform performs the best in the low-frequency domain, the short-time Fourier transform the second, and the S transform the worst, while in the high-frequency domain, the S transform performs the best, the wavelet transform the second, and the short-time Fourier transform the worst. (4) Differences in charge signals of sensors at different locations during fault slip destabilization are mainly related to the aggregation of charges in specific regions caused by locally concentrated micro-ruptures before the start-slip phase, and are mainly caused by the change of misalignment of the relative positions between the slip surface and the sensors after the start-slip phase.

Mining disturbance can easily aggravate the creep instability of roadway surrounding rock, and its propagation mode in surrounding rock is damped oscillation disturbance. In order to explore the creep characteristics of rock under the damped oscillation disturbance, X-ray diffraction, nuclear magnetic resonance and pseudo-triaxial creep tests were carried out. Based on the test results, a discrete element numerical model of sandstone was established. The parameter calibration results show that the combination of linear parallel bond model and Burgers model can simulate the creep behavior of rock. Combining the sinusoidal disturbance function with the exponential function, a function expression for simulating the attenuation oscillation disturbance is proposed. The application of attenuation oscillation disturbance in numerical simulation is realized by Fish language, and the creep process of sandstone under attenuation oscillation disturbance is simulated. The simulation results show that compared with the undisturbed rock sample, the accelerated creep time of the rock sample under the action of attenuation oscillation disturbance is earlier and the creep deformation is larger. Before and after the disturbance is applied, the distribution of crack dip angle changes from concentration to dispersion, and the failure mode is tensile-shear composite failure mode. When the attenuation oscillation disturbance is applied, the creep deformation of rock shows a similar attenuation oscillation trend. The greater the deviatoric stress, the greater the influence of attenuation oscillation disturbance on rock deformation. The application of attenuation oscillation disturbance is more likely to lead to the fracture of contact bond between particles and accelerate energy dissipation. The attenuation oscillation disturbance element and the nonlinear viscoplastic body are introduced into the Burgers model, and an improved Burgers model is established. The theoretical curve is in good agreement with the experimental data. The model can better characterize the creep process of sandstone under attenuation oscillation disturbance.

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.

Evaluating the compaction quality of rock-filled subgrades rapidly and accurately poses a pressing challenge in highway engineering. To address this, this study establishes a discrete element-finite difference coupling model to simulate the response of rock-filled subgrades under impact loading. The primary parameters of the model are calibrated using indoor large-scale triaxial tests, and the model's accuracy is verified through comparisons between calculated and field data. Furthermore, this study conducts an in-depth analysis of the dynamic response results of five commonly used gradations of rock-filled subgrades under varying degrees of compaction, discussing the influence of gradation fractal dimension and porosity on subgrade deformation response. The findings are as follows: (1) A good exponential relationship between subgrade porosity and resilient modulus is identified, and the concept of settlement ratio is introduced, with a linear relationship between settlement ratio and subgrade porosity being verified. It is suggested that both resilient modulus and settlement ratio should be used as control indicators when evaluating subgrade compaction quality. (2) A prediction function for subgrade resilient modulus considering fill gradation and porosity is obtained, revealing that particle gradation has a significant impact on resilient modulus. Specifically, as the gradation fractal dimension approaches 2.31, the resilient modulus increases more rapidly with decreasing porosity. (3) A settlement ratio of zero corresponds to the ideal compaction state of the subgrade. This study establishes a prediction model for the critical resilient modulus of the subgrade in its ideal state, considering fill gradation, and finds that the critical modulus first increases and then decreases with increasing fractal dimension D, reaching a maximum when D=2.34. These findings aim to provide new methods and theories for evaluating the compaction quality of rock-filled subgrades in engineering.

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 cohesion effect induced by liquid bridges between particles, which promotes particle aggregation, is widespread in both natural environments and engineering applications. Understanding the migration and clogging processes of particles in fractured media under the influence of capillary-cohesion is crucial for advancing particle transport knowledge. Through visualization experiments and seepage calculations, the processes of capillary-cohesive particle migration and clogging are studied. A phase diagram of clogging patterns in the space of capillary-cohesion and flowrate is proposed. Experimental results show that capillary-cohesion induces particle agglomeration, increasing effective particle diameter and significantly enhancing fracture clogging. Stripe-like clogging patterns occur at high flow rates, while complete clogging patterns or entrance sealing patterns occur at low flow rates. Hydrodynamic analysis reveals that fluid velocity distributions control the growth of clogging stripes and the change in residual flow channels in the complete clogging patterns. Furthermore, Smoluchowski theory effectively describes the linear growth behavior of clogging stripes over time. These findings elucidate the mechanism of capillary-cohesive particle migration and clogging in rock fractures, providing theoretical and technical guidance for evaluating and controlling particle transport in fractured media.

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.