Factor of safety in a partially saturated slope inferred from hydro‐mechanical continuum modeling

Abstract

SUMMARYRainfall weakens an earth slope and triggers mass movement. Relevant triggering mechanisms are complex and include reduction of capillary pressure due to increased saturation and frictional drag on the sediment induced by fluid flow. Physics-based continuum models utilizing modern computational tools are useful for understanding the mechanisms of deformation in partially saturated slopes; however, they do not provide a scalar indicator called 'factor of safety' that measures the potential of a given slope for mass movement. In the present work, we employ sequential calculations consisting of a physics-based finite element model that couples solid deformation with fluid flow to quantify the stress and deformation fields in a steep hillside slope subjected to rainfall infiltration. This is followed by a limit-equilibrium calculation based on the method of slices that evaluates the desired factor of safety. The field condition investigated is similar to the steep experimental catchment CB1 near Coos Bay, Oregon, which failed as a large debris flow from heavy rainfall.

Hydro-mechanical coupling effect on surficial layer stability of unsaturated expansive soil slopes

“…In addition to the 1D seepage simplified model, the PWPs predicted using 2D numerical analyses were also used along with the infinite slope model to evaluate the stability of slope surficial layer (e.g. [5,11]). Furthermore, the measured in-situ PWP changes was input to the infinite slope formulation by Jeldes et al [33] to calculate the seasonal variation of FS of steep reclaimed slopes in Appalachian region in United States.…”

“…[5,17,66]), while, the elasto-viscoplastic and elasto-plastic model considering the plastic strains based on effective stress principle has been used by other researchers (e.g. [11,14,20]). Similar to the uncoupled hydraulic analyses above, the coupled analysis was usually followed by a calculation of FS based on the obtained PWP and/or the stress state within the slope profile.…”

“…[5,17,66]), and the traditional limit equilibrium methods (e.g. [5,11,14]). It is worth mentioning that Ehlers et al [20] obtained the localization of strains using the elasto-viscoplastic analysis directly instead of providing the slope FS.…”

3D stability of unsaturated soil slopes with tension cracks under steady infiltrations

“…The frequent occurrences of precipitation‐induced failures and landslides of unsaturated residual soils highlight the significance for explicit consideration of the suction in assessing the slope stability . However, because of the highly variable nature of the suction, it is difficult to model its effect on the slope stability …”

Stability Analysis of Unsaturated Soil Slope Considering Rainfall Infiltration by Two-Pahse Flow Model

“…가장 널리 사용되는 해석방법은 흙 의 응력-변형거동과 공기의 흐름을 무시하고 물만의 단상흐 름(single-phase)을 고려하는 Richard(1931)의 미분방정식의 해를 구하는 것이다(e.g., Ng and Shi, 1998). 강우의 사면으 로의 침투에 의한 역학적 거동을 연구하기 위하여 흐름-변형 이 연관된 해석이 수행되었지만 대부분 지반의 공기흐름이 물의 흐름에 비해 상대적으로 자유롭다는 가정을 바탕으로 지반의 공기압은 대기압과 같은 것으로 고려하고 있다 (Cho and Lee, 2001;Borja and white, 2010;Borja et al, 2012;Kim et al, 2012;.…”