Waterfront and submarine retaining structures are normally exposed to catastrophic seepage conditions under the effect of tidal and occasionally heavy rainfall effect, resulting in a decreased passive earth thrust and thus the higher risk of instability of retaining structures. To examine the effect of seepage flow on the magnitude and distribution of passive earth thrust, this paper assumes a composite curved-planar failure surface and presents a modified method of passive earth pressure considering the seepage flow effect. The flow field and pore pressure are firstly solved by the two-dimensional (2D) Laplace equation using the Fourier series expansion. The effective reaction force acting on the composite failure surface is then obtained using a modified K & ouml;tter equation. Compared to conventional methods based on limit equilibrium, the present method facilitates a straightforward assessment of both the magnitude and distribution of passive earth thrust without the prior assumption of the application point. The outcomes highlight that the passive earth thrust decreases with the ratios of permeability coefficients. The greater effective friction angle and a smaller ratio of permeability coefficients result in the lower application point of the passive earth thrust.

Slope fractures play an important role in slope destabilization accidents induced by rainfall, but its influence on seepage field and slope stability is not fully studied, especially under the conditions of soil permeability anisotropy. This study aims to investigate the influence of anisotropic permeability property of soil and fractures on the seepage field and slope stability under rainfall conditions. The surface cracks of the slope are regarded as continuous medium, and the saturated-unsaturated seepage theory is applied to the numerical simulation of the fractured soil slopes with different anisotropic permeability ratios by Geo-studio software. The evolution of seepage field and slope stability under the rainfall conditions are investigated using finite element simulation tool. The simulation results reveal that fractures mainly impact the pressure distribution in the seepage field of the shallow layer of slope, and have little effect on the deep layer. Furthermore, the anisotropic permeability of the soil has a significant effect on the seepage field, safety factor, and fracture action of the slope under rainfall conditions. These findings provide critical insights into slope engineering and management under anisotropic soil conditions.

This study investigated active and passive lateral earth pressure in the presence of anisotropic seepage conditions. The soil was assumed to be granular and fully saturated. Three methods were used to solve the problem: (1) the upper bound limit analysis method (UBM); (2) upper and lower bound solutions of finite-element limit analysis (FELA); and (3) the stress characteristic method (SCM). The proposed analytical solution for the UBM employed the logarithmic spiral slip surface. The lateral earth pressure coefficients for the active and passive cases were calculated and presented, considering variations in the vertical-to-horizontal hydraulic conductivity ratio, friction angle, and soil-wall interface friction angle. The obtained results for the active and passive cases agree with those of previous studies. The results of the SCM showed that in the presence of seepage, the distribution of stress on the soil-wall interface is nonlinear. In addition, the failure zone obtained from different methods was compared and examined. The failure patterns obtained from the SCM and FELA were almost identical.