To study the wetting deformation characteristics of undisturbed loess under true triaxial force-water path, the true triaxial apparatus with rigid-flexible-flexible loading boundary was used to carry out the true triaxial single-line humidification test of undisturbed loess in Xi'an under different spherical stresses, intermediate principal stress parameters and stress ratios. The influence of true triaxial force-water path on the humidification deformation characteristics of undisturbed loess was comprehensively analyzed. The test results show that the relationship curve between the wetting volumetric (deviatoric) strain and the spherical stress presents a three-stage of slow-steep-slow. When the spherical stress is in the second stage, the wetting collapsibility of the soil is the largest, and a large wetting deformation can occur. At a certain stress ratio, the wetting volumetric strain gradually increases with the spherical stress, and the increase of the wetting volumetric strain decreases when the spherical stress exceeds 200 kPa. Finally, the variation law between the intermediate principal stress and each humidification strain is analyzed, and the calculation expression of loess collapsible deformation considering the intermediate principal stress is given according to the test results.

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.

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.

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.

In the constructural backfill mining, the composite bearing structure of 'backfill body-immediate roof' structure will be subjected to different loading rates depending on the mining speed and other conditions. According to the loading rate of 0.15−2.40 mm/min, the uniaxial compression test of five groups of rock-backfill composite were carried out, and digital image correlation technology and acoustic emission monitoring were carried out to analyze the evolutionary characteristics of its energy loss. It can be seen from the experiment that the strength of siltstone is significantly greater than the strength of the rock-backfill composite and the backfill body, and the strength of the combination is closer to the strength of the filling body than the siltstone. It can be seen that 0.60 mm/min is the critical load for this group of experiments. When the loading rate of the rock-backfill composite is 0.15−0.60 mm/min, the rock-backfill composite ultimately realizes the synergistic deformation of the siltstone and the backfill body in the rock-backfill composite and destruction of the rock-backfill composite in the process of loading, and when the loading rates are 1.20−2.40 mm/min, rock-backfill composite failed to achieve the collaborative deformation damage of the siltstone and the backfill body parts. When the loading rate is lower than 0.60 mm / min, due to the strength difference between the siltstone and the filling body and the non-uniform deformation of the contact interface between the two, a large crack penetrates the whole specimen. It can be seen that the final failure mode of each group of specimens is a tensile and shear mixed failure mode. By analyzing the dissipation energy changes of the rock-backfill composite and the backfill body, it can be seen that when the loading rate is greater than the critical loading rate, the pre-peak dissipation ratio of the rock-backfill composite is greater than that of the backfill body, and the composite can be destroyed in a coordinated manner. By calculating the energy storage coefficient and energy storage limit of the rock-backfill composite under different loading rates, it is found that when the loading rate is less than 0.60 mm/min, the higher the loading rate, the higher the energy storage limit of the combination specimen, and the speed of absorbing elastic energy is also rising synchronously. Finally, the backfill body part is destroyed first, and the energy released by the instantaneous damage is transmitted to the siltstone part of the rock-backfill composite, so that the elastic energy absorbed by the siltstone part can reach the energy storage limit. The crack in the backfill body part extends into the sandstone to achieve synergistic damage. The results of this study are intended to provide suggestions for ensuring the stability of the composite bearing structure of ' backfill body-immediate roof 'structure under different mining and filling rates.

Tectonic fault cores are formed substantially of clay minerals. Even a slight change in mineral composition or in water saturation can result in a significant alteration of the sliding regime on the fault. We present results of laboratory experiments on a slider model set-up that was used to study the regularities of slip behavior in a model fault filled with gouge. The gouge consisted of quartz sand and clays of different types (bentonite, illite and kaolinite). The slip behavior essentially depended on gouge mineralogy. The accumulated stress could release via both fast and slow slips. The scaled kinetic energy for fast slips was 10⁻⁵–10⁻³, while that for the slowest slips was 10⁻⁹–10⁻⁷. Fast stick-slip is characteristic of model faults filled with quartz sand in dry and moistened conditions. A gradual transformation from stick-slip to stable sliding was observed for quartz sand/clay gouge as the clay content approached 20%. Under moistening clay, mineralogy played a key role. If the illite clay content was 5%, the moistening led to an increase in peak velocity by more than an order of magnitude; if the bentonite clay was 5%, it led to stabilization of sliding. While alteration in friction coefficient after moistening remained relatively small, the scaled kinetic energy could vary by several orders of magnitude.

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.

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.

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.

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.