Three approximate analytical solutions for the problem of the seismic response of two rigid cantilever walls retaining a transversely isotropic poroelastic soil layer over bedrock are presented under conditions of plane strain and time harmonic ground motion. These approximate solutions come as a result of various reasonable simplifications concerning various response quantities of the problem, which reduce the complexity of the governing equations of motion. The method of solution in all the cases is the same with that used for obtaining the exact solution of the problem, i.e., expansion of response quantities in the frequency domain in terms of sine and cosine Fourier series along the horizontal direction and solution of the resulting system of ordinary differential equations with respect to the vertical coordinate in conjunction with the boundary conditions. The first approximate solution is obtained on the assumption of neglecting all the terms of the equations of motion associated with the fluid acceleration. The second approximate solution is obtained on the assumption that the fluid displacements are equal to the corresponding solid displacements. The third approximate solution is obtained as the sum of the second approximate solution for the whole domain plus a correction inside a boundary layer at the free soil. All three approximate solutions are compared with respect to their accuracy against the exact solution and useful conclusions pertaining the approximate range of the various parameters, like porosity, permeability and anisotropy indices, for minimization of the approximation error are drawn.

This paper presents a comprehensive investigation into the role of soil permeability variation on the stability of slopes reinforced by retaining walls, with a focus on the Huizhou slope failure as a case study. The study demonstrates that rising groundwater levels diminish the Factor of Safety (FoS) for retaining walls, with stability most compromised under combined loading from adjacent soil and lightweight concrete. These findings emphasize the need for enhanced drainage or structural support in retaining wall designs subjected to elevated groundwater conditions. It integrates advanced numerical simulations, utilizing Abaqus and GeoStudio, with empirical field data to analyze the interactions between soil permeability, pore water pressure, moisture content, shear strength, and the overall stability of the slope. The dynamics of water infiltration are influenced by permeability, moisture content, and the groundwater table. These factors change the pore pressure and decrease shear strength, which causes shear failure in the slope mass. This research also looks at how surcharge loading affects slope stability. Higher permeability soils cause faster infiltration rates, leading to higher pore pressures, lower effective shear strengths, and a higher likelihood of slope failure. The opposite is true for reduced permeability, which makes drainage more difficult and ultimately leads to hydrostatic pressure building up behind retaining walls, which in turn makes the slope even more unstable. This study demonstrates the critical need for optimized drainage systems to reduce the hazards of infiltration-induced failure and the role of precise permeability evaluation in geotechnical design. Geotechnical engineers can use these results to better understand how to construct and maintain slope stabilization systems.

Deciding on the inclusion of tiers and determining the optimal number of tiers are critical considerations in the design of reinforced soil retaining walls (RSRWs). In this study, the mechanical properties of RSRWs under seismic loading are discussed in depth, with special attention paid to the influence of tiered configuration effects on the seismic performance of RSRWs. The response characteristics of these structures under seismic loading were comparatively analyzed by conducting shaking table tests of single-tiered, two-tiered, and three-tiered modular geogrid RSRWs. The results show that localized modular misalignment mainly occurs at the top of the retaining walls of all tiers, and reasonable tiered design can enhance the stability, but too many tiers may instead reduce the structural stability. The tiered reinforced soil retaining walls (TRSRWs) exhibit higher natural frequencies and damping ratios, which increase with more tiers, and the natural frequencies and damping ratios of the upper-tiered walls are always higher than those of the lower-tiered walls. The acceleration amplification effect is more significant in the upper part of the retaining wall structure, and the tiered design can reduce the acceleration amplification effect to a certain extent, but the increase in the number of tiers does not have much effect on this. The horizontal displacement of the TRSRWs shows the distribution of upper large and lower small, and the two-tiered retaining wall effectively reduces the horizontal displacement of the wall facing, whereas the three-tiered retaining wall does not have a significant improvement effect. The tiered design significantly optimizes the settlement of the retaining walls, and the number of tiers has little effect on the settlement improvement. The seismic active soil pressure increased with the peak ground acceleration and loading frequency, and the tiered design changed its distribution, and the increase in the number of tiers helped to further reduce the soil pressure. The increment of reinforcement strain in TRSRWs was lower than that in single-tiered retaining walls, and the tiered design effectively reduced the reinforcement stress, but the number of tiers had a limited effect on the improvement of this effect. The upper part of the wall in the un-tiered design is prone to overall tilt and horizontal expansion, and the deformation of the upper-tiered walls of the TRSRWs is all in a composite deformation mode, while the lowest-tiered walls are in a single deformation mode. The tiered design has a positive effect in limiting the development of potential failure surfaces in the substructure, resulting in improved stability of the substructure. The results of the study can provide a reference for the design selection of RSRWs.

The tensioned reinforced soil retaining wall, a novel retaining structure, utilizes either anchors or geosynthetic materials as reinforcements that contribute to load-bearing and friction within the structure. This study aims to explore the tension distribution and strain patterns in the reinforcements, and their influence on the reinforced soil retaining walls. To this end, tensile, direct shear, and pullout tests were conducted on GeoStrap@5-50 geotextile strips and TGDG130HDPE geogrids to evaluate the tensile strength and interface strength between the reinforcement and the soil. The characteristics of the reinforcement-soil interface and the deformation behavior under stress were examined, with a comparative analysis of the technical merits of the two types of reinforcements. The results indicate that both the geotextile strips and geogrids enhanced the strength of the reinforced soil, primarily by increasing cohesion. The GeoStrap@5-50 geotextile strips exhibited superior tensile strength compared to the TGDG130HDPE geogrids; the reinforcement with the geotextile and geogrids both enhanced the cohesion of the standard sand, albeit with a slight decrease in the internal friction angle, by 4.6% and 3.1%, respectively, offering enhanced mechanical properties and economic value in reinforced soil retaining wall applications.

Retaining walls and other waterfront structures were seen to suffer severe damage due to soil liquefaction in previous earthquakes. As part of the LEAP project, cantilever retaining walls with loose, saturated backfill were tested at various centrifuge centres participating in this endeavour. The toe of the retaining wall penetrated about 0.5 m into the dense sand layer underlying the loose sand layer. Retaining walls with different ratios of the retained height h over the penetration depth d were tested. As part of the LEAP project, additional testing was carried out at Cambridge to consider the effect of the wall size on its deformation following liquefaction. It will be shown that a larger wall will suffer more rotation and wall top displacement than a smaller wall with the same h/d ratio. This can have implications for numerical modelling in terms of how well the constitutive models capture the suppressed soil dilatancy at higher confining pressures.

This study evaluates the earthquake-induced movement of geogrid earth-retaining (GER) walls. A thorough investigation was conducted on a GER wall model, utilizing a comprehensive finite element (FE) analysis. This research focuses on investigating and designing hollow prefabricated concrete panels and conventional gravitytype stone masonry GER walls. It also displays comparative studies such as the displacement of the wall, deflection of the wall, lateral pressure of the wall, settlement of the backfill reinforcement, vertical pressure of the backfill, lateral pressure of the backfill, vertical settlement of the foundation, and settlements of soil layers across the height and acceleration of the walls of the GER walls. The FE simulations used a three-dimensional (3D) nonlinear dynamic FE model of full-scale GER walls. The seismic performance of models has also been examined in terms of wall height. It was found that the seismic motion significantly impacts the height of the GER walls. In addition, the validity of the proposed study model was assessed by comparing it to the conventional reinforcement concrete and gravity-type GRE wall and ASSHTO guidelines using finite element (FE) simulation results. Based on the findings, the hollow prefabricated concrete panels were the most practical alternative due to their lower deflection and displacement. Based on the observation, it was also found that the hollow prefabricated GER wall is the most viable option, as the settlement and lateral pressure in the former type are high.

Fragility curves of retaining walls constitute an efficient tool for the estimation of seismic risk and can be utilized for prevention from potential damage or for immediate decision-making. In this work, fragility curves for cantilever retaining walls of three different heights are proposed, considering cohesionless soil materials. The seismic response of the soil-wall system, in terms of permanent vertical ground displacement of the backfill soil and permanent horizontal displacement of the wall's base, is estimated by conducting non-linear time history analyses, through the 2D finite element simulation method. Five initial conditions are investigated regarding the value of the global factor of safety (FS) under static conditions. An initial value of FS equal to 1.5 is considered for dry conditions. If the presence of the water table is taken into account, the corresponding FS drops to values ranging from 1.4 to 1.1. Parameters that characterize seismic intensity are evaluated based on criteria, in order to identify the intensity measures that best correlate with the system's response. Three damage states are adopted, corresponding to minor, moderate, and extensive damage. The approach of combined damage criteria is also investigated. Finally, fragility curves are derived demonstrating the degree of dependency on initial conditions.

Unsaturated soil, as a widely existing soil in nature, has significant differences in mechanical properties compared to saturated soil. Especially when considering water migration and changes, its stability issues become more complex .Therefore, in-depth research on the interaction mechanism and stability of unsaturated soil slopes and support structures is significant. This study first analyzes the mechanical properties of unsaturated soil and the influence of water migration on soil strength based on the principles of unsaturated soil mechanics. It establishes a mechanical model for unsaturated soil slopes. Subsequently, the pseudo-dynamic method was used to simulate the response of slopes under dynamic loads such as earthquakes and rainfall, and the deformation and failure modes of unsaturated soil slopes were explored. Regarding support structures, this article studies the interaction mechanism between retaining walls, anchor rods, and unsaturated soil slopes. A mechanical model of the interaction between the support structure and unsaturated soil slopes was established by analyzing the influence of the support structure on the distribution of soil pressure on the slope, as well as the stability and bearing capacity of the support structure itself. In terms of stability analysis, this article uses numerical analysis methods such as the limit equilibrium and finite element methods to evaluate the overall stability of unsaturated soil slopes and support structures. Suggestions for optimizing the design of support structures were proposed by comparing the stability performance of slopes under different support schemes. The experiment shows that increasing soil cohesion by 1kPa per unit area can increase the stability coefficient by about5%. The interface friction angle between the fill and the wall back increases by 1 degree, resulting in an increase of approximately 7% in the over turning stability coefficient.