Numerical Modeling of Unsaturated Layered Soil for Rainfall-Induced Shallow Landslides

Abstract

In this paper, a pioneer study on numerical modeling of rainfall-induced shallow landslides in unsaturated layered soil using the variably saturated flow equation is presented. To model the shallow landslides, the infinite slope stability analysis coupled with the hydrological model with the consideration of the fluctuation of time-dependent pore water pressure and Gardner equation for soil water characteristic curve was developed. A linearization process for the nonlinear Richards equation to deal with groundwater flow in unsaturated layered soil is derived using the Gardner model. To solve one-dimensional flow in the unsaturated zone of layered soil profiles, flux conservation and the continuity of pressure potential at the interface between two consecutive layers are considered in the numerical discretization of the finite difference method. The validity of the proposed model is established in three numerical problems by comparing the results with the analytical and other numerical solutions. Application examples have also been conducted. Obtained results demonstrate that the fluctuation of pore water pressure in unsaturated layered soil dominates slope stability of landslides and the lowest factor of safety may occur at the interface between two consecutive layers. The findings observed in this study are a fundamental contribution to environmental protection engineering for landslides in areas with higher occurrence and vulnerability to extreme precipitation.

Analysis of water retention in soil horizons of two open trenches on a slope of Serra do Mar, Brazil, susceptible to landslides

“…The saturation of the horizons, however, will be hampered by the high porosity of these horizons, mainly the macro. Thus, destabilization will probably occur by decreasing the shear strength of these horizons B or C with increasing moisture content, without reaching saturation [15].…”

Modeling of Transient Flow in Unsaturated Geomaterials for Rainfall-Induced Landslides Using a Novel Spacetime Collocation Method

“…The advantages of the proposed method are that the highly accurate results can be obtained and the convergence problem can be avoided since the one-dimensional transient example is solved without using the traditional time-marching scheme. 6 Geofluids…”

“…Increased precipitation events associated with extreme weather conditions affect the stability of slopes and can lead to a variety of geoenvironmental hazards [3,4]. Consequently, shallow landslides may often occur within the vadose zone under unsaturated soil conditions [5][6][7]. The prediction of flow in transient conditions is important in engineering practice while considering the stability of unsaturated soil slopes [8][9][10][11][12] or poromechanical coupling influence for rainfall-induced shallow landslides in unsaturated soils [13,14].…”

“…Adopting the Gardner exponential model, the linearized Richards equation for the one-dimensional transient Richards equation can be derived as follows [6,10,43,45].…”

Modeling Transient Flows in Heterogeneous Layered Porous Media Using the Space–Time Trefftz Method

“…A variety of mesh-generated techniques, such as the boundary element method [13], finite element method [14,15], finite volume method [16,17], and finite difference method [18,19], have been proposed to analyze heterogeneous layered porous media. In contrast with conventional mesh-generated techniques, meshfree approaches have attracted much attention in recent years because of their characteristics of simplicity, meshfree, and the capability to deal with engineering problems with complex geometry [20][21][22][23][24][25][26].…”