This study investigates the seismic stability of reinforced slope under a three-dimensional (3D) rotational horn-like failure mechanism, using the pseudo-dynamic approach and provides a new procedure to estimate factor of safety (FS) for slope. Such a procedure is able to figure out the influences of the seismic force, the soil property and the reinforcement by piles. Pseudo-dynamic approach is used to describe the seismic force in the time-to-spatial fields in unsaturated soils where matric suction works. Compared to the pseudo-static approach, the current approach considers the effects of time and spatial through the horizontal and vertical shear waves. For the pile driving, different insertion depths can yield various results, whether two work conditions of considering the pile resistance or not are discussed. FS of this study undergoes a decrement as the increase of the pile resistance and seismic force, indicating that the insertion depth affects FS where FS decreases in the early period of pile driving, after that increases and keeps constant in the late of pile driving, showing evident unimodal characteristics during the pile driving. The new expressions for slope reinforced by piles are presented for practical use in unsaturated soil engineering.

Currently, the study of analytical solutions for the seismic stability of slopes under anchorage conditions is one of the hottest subjects in engineering. In this paper, an analytical solution for the seismic safety of the three-dimensional (3D) two-stage rock slope reinforced with prestressed anchor cables governed by the nonlinear Hoek–Brown criterion was deduced, in which the analyses of seismicity were performed by the latest modified pseudo-dynamic method. This method supplements the consideration of the damping effect of the rock medium on seismic waves, which is more in line with the real seismic situation. A mathematical geometric model was developed for calculating the external forces work and internal energy dissipation acting on 3D rotating rock masses reinforced with prestressed anchor cables, in which the seismic work rate was calculated using a new layer-by-layer superposition summation method. The analytical solution of the safety factor could be collated as an explicit function of several variables, and then, the optimal value was obtained by the Particle Swarm Optimization (PSO) algorithm. To corroborate the accuracy of new analytical solutions, the results were contrasted with those of the pertinent literature. The results of the two comparisons were very close. Ultimately, the sensitivity analyses and coupling effects of seismic pseudo-dynamic factors and prestressing anchorage factors were carried out. It was found that even small seismic intensities had a large effect on the stability of rock slopes with developed joints. Increasing the number of steps and prestressing anchors can effectively improve the stability of rock slopes under seismic effects. The conclusions have significant implications for the anchorage design of the 3D two-stage rock slope as seismic events occur.

Aiming at the potential high-temperature packaging material of the wide band gap semiconductors, experimental and theoretical analysis on the compressive properties of sintered nano-silver was performed. The viscoplastic properties of sintered nano-silver were investigated by compressive experiments with five loading rates, and the effects of loading rate on the ultimate strength and elastic modulus of sintered nano-silver were analyzed. According to the microstructure characteristics of sintered nano-silver, the damage framework including void volume fraction was developed by extending the Gurson–Tvergaard–Needleman model, and the mathematical model between Bonora damage law and void volume fraction was proposed, in which the internal void was assumed to be sphere and cube. A modified constitutive model including the damage model was developed based on the unified creep and plasticity theory for describing the compressive properties of sintered nano-silver. The accuracy of the proposed model was verified by comparing it with the experimental data.

Current research has shown a nonlinear trend in the failure of soil, and the single tangent method is commonly adopted when coping with nonlinear problems of soil failure. However, the method equates a nonlinear criterion to an optimizable linear criterion, which may differ from the actual situation, resulting in conservative results. In this paper, two types of piece-wise log-spiral failure mechanisms for bearing capacity estimations, including symmetrical and unilateral mechanisms were proposed with the nonlinear Mohr-Coulomb criterion. The static bearing capacity of foundations was evaluated using the symmetric failure mechanism, while the seismic bearing capacity of foundations was evaluated adopting a modified pseudo-dynamic method based on the unilateral failure mechanism. The result shows that the bearing capacity calculated in the paper is smaller compared to the result using the linear Mohr-Coulomb criterion. For London clay, the static bearing capacity is reduced by about 45% at a foundation width equal to 1m. From the comparisons, it is found that the proposed approach of piece-wise log-spiral failure mechanism for bearing capacity estimation is effective. In addition, parametric studies show that the nonlinear parameters, the initial factor of seismic acceleration, the normalized frequency, and the damping ratio all have obvious effects on the seismic bearing capacity. A significant reduction in the seismic bearing capacity of the foundation occurs when the normalized frequency ω_sH/V_s is equal to (0.5 + n)π (n = 0, 1, 2, …). Considering that the approach proposed provides a strict upper bound to the bearing capacity, the result imparts confidence in the approach of analysis presented.

The shear strength of unsaturated soils exhibits significant nonlinearity, while previous studies often simplified it with linear strength models. The objective of this paper is to investigate the distinctions in the stability of three-dimensional (3D) tunnel faces when using linear and nonlinear strength models. A new 3D rotational failure mechanism and an extended form of the Mohr–Coulomb (M-C) failure criterion were integrated into the kinematically limited analysis (KLA) framework to describe the failure characteristics of tunnel faces. Subsequently, the factor of safety (FS) of the 3D tunnel faces was calculated using the strength reduction method (SRM). In the discussion section, the impacts of nonlinear shear strength, matric suction in the unsaturated soils, and the 3D geometric parameters of the tunnel on the stability of the tunnel face were analyzed. The outcomes indicate that, in unsaturated soil conditions, diverse nonlinear strength calculation models and soil types exert disparate influences on the FS of 3D tunnel faces. The main novelty of this study lies in establishing an effective method for assessing the stability of tunnel faces in unsaturated soils.

This paper aims to estimate the stability of tunnel faces in inclined layered soils under steady unsaturated seepage conditions, comparing the degree of correlation between the stability of the tunnel face and the influence of three types of parameters: unsaturated soil parameters, spatial geometric parameters of soil stratification, and other relevant factors. The study leverages the suction head distribution in multi-layered unsaturated soils, deriving a new formula to compute the effects of steady-state seepage forces with matric suction distribution in inclined stratified soil layers. A three-dimensional discrete rotational failure mechanism model is employed to calculate the critical support force at the tunnel face. The corresponding parametric analysis involves unsaturated soil parameters, spatial geometric parameters, and the variations in these parameters across different soil layers. Based on this analysis, the varying degrees of correlation between tunnel stability and changes in spatial angle parameters considering soil stratification, and the variations in unsaturated parameters across different soil layers are thoroughly investigated. The proposed framework serves as a valuable tool for quantitatively assessing the effects of unsaturated seepage forces on the stability of tunnel faces situated within complex, inclined, layered soil formations.