During an earthquake, the strong interaction between the surrounding rock and lining structure causes the lining susceptible to extrusion or shear damage. To evaluate the damping effect of the shock-absorbing layer on seismic loads and mitigate the deformation-induced damage of tunnel structures in loess regions, the dynamic mechanical properties of loess seismic-isolated tunnels subjected to P-wave seismic loading were investigated. In this work, the dynamic behavior of loess seismic-isolated tunnel under seismic loads was converted into a static problem. Analytical methods were employed to derive solution for internal forces within the lining structure using a mechanical analysis model. Additionally, the impact of loess hardness and seismic intensity on the performance of the shock-absorbing layer were analyzed based on the analytical solutions. Numerical methods were then applied to examine the influence of shock-absorbing layer parameters on the mechanical properties of loess seismic-isolated tunnel subjected to P-wave loads. The results indicate that the analytical solutions, simplified numerical solutions, and theoretical results in the literature exhibit strong numerical consistency and similar trends. The analytical results demonstrate that the internal forces in the lining structure increase linearly with seismic intensity, while the effect of loess hardness on the bending moment is more complex. As the loess hardness decreases, the damping effect of the shock-absorbing layer on the internal forces gradually diminishes. Numerical analysis further reveals that reducing the elastic modulus and increasing the thickness of shock-absorbing layer significantly enhance its damping effect on the axial force, although the bending moment slightly increases. Additionally, the shock-absorbing layer effectively reduces the peak stress and strain responses in lining structure, but the peak stress at the hance position increases, with this increase becoming more pronounced as the elastic modulus of the damping material decreases. Moreover, the shock-absorbing layer significantly reduces the peak acceleration response of lining structure but also leads to increased deformation, which progressively intensifies with the thickness of shock-absorbing layer. These findings provide valuable theoretical insights for the seismic design of tunnel structures in loess regions, emphasizing the importance of balancing damping efficiency and deformation control in the lining structure.

In this article, a one-dimensional non-isothermal diffusion model for organic pollutant in an unsaturated composite liner (comprising a geomembrane and an unsaturated compacted clay liner (CCL)) considering the degradation effect is established, which also includes the impacts of temperature on diffusion-related parameters, and employs a water content and pore-water pressure head relationship equation that better matches the experimental results. Subsequently, this model is addressed through a finite-difference technique, and its reasonableness is proved by comparing with the experiment measurements and two other calculation approaches. Following this, the analyses suggest that the diffusion coefficients' change induced by a rising temperature accelerates the diffusion rate, whereas such an alteration on partitioning coefficients has an opposite effect. Furthermore, the evaluation reveals that the non-isothermal state caused by an increasing upper temperature overall lowers the anti-fouling performance. The unsaturated composite liner's barrier function is weakened by an increment in residual water content of CCL, but enhanced by unsaturated layer thickness. It is also detected that the degradation effect should be considered if the degradation half-life <= 100 years. Lastly, a simplified approach for assessing the unsaturated composite liner's barrier performance is presented, which can provide guidance for its engineering design in a non-isothermal scenario.

The implementation of stone columns is a widely accepted method for improving the stability of liquefiable soil. A comprehensive understanding of the behavior of the composite ground is crucial for accurate design and calculation in practical applications. Several existing mathematical models were established to assess characteristics of the stone column-improved ground by typically ignoring the vertical seepage within liquefiable soil. This negligence will inevitably lead to significant calculation errors, particularly when the vertical permeability of liquefiable sites is high or the installation spacing of stone columns is large. In this context, a new mathematical model which accounts for coupled radial-vertical seepage within liquefiable soil is proposed to determine the reinforcement performance of stone columns. The equal strain assumption and new boundary conditions are incorporated to obtain numerical solutions with the finite difference method. Then the present solution is degenerated to the conventional calculation model to verify the reasonability of the proposed model. Finally, a parametric analysis is conducted to investigate the impacts of crucial parameters on the performance of stone columns for excess pore water pressure variation during soil liquefaction. The results reveal that the peak value of the maximum excess pore water pressure ratio increases with the increment of both the column spacing and cyclic stress ratio. Moreover, the increasing radial and vertical consolidation parameters Tb and Th will accelerate the dissipation rate of the excess pore water pressure of liquefiable sites. Furthermore, the conventional model neglecting the vertical seepage will underestimate the variation rate of the excess pore water pressure, and the calculation error will become larger with the increase of Th.