离散元法在计算滑坡土壤中饱和与非饱和渗流的应用及案例研究

A discrete element method for calculating saturated and unsaturated seepage in landslide soils and a case study

Abstract: Landslides influenced by rainfall and groundwater seepage often exist in a saturated–unsaturated state, making them susceptible to destabilisation. While the Discrete Element Method (DEM) is capable of predicting landslide failure, it does not currently account for the effects of saturated–unsaturated seepage on rock-soil masses. To address this, we use the theory of saturated–unsaturated seepage to investigate how water is conducted between particles within a landslide body. We then establish a relationship between macroscopic permeability and interparticle microconductivity and derive a discrete element equation for saturated–unsaturated seepage. Based on this, a DEM-based model that incorporates saturated–unsaturated seepage, hydrodynamic effects on the stress field and water-induced softening of the landslide body will be developed. This model aims to accurately predict the deformation evolution and ultimate collapse of a landslide due to rainfall and groundwater level change. To validate our approach, we apply the model to simulate the complete deformation process leading to the disintegration of the Tanjiahe landslide in the Three Gorges Reservoir area, China, under the influence of rainfall and reservoir water level changes. The results demonstrate that the intense rainfall penetrated deeply into the middle sliding mass, resulting in an increase in seepage forces near the sliding surface, a reduction in overall shear strength, and a loss of support in the middle sliding mass, which exerted pressure on the front sliding mass. Furthermore, the drop in reservoir water level led to a notable deformation of the front sliding resistance section, ultimately leading to landslide failure. Our method effectively predicts landslide deformation and instability under saturated–unsaturated seepage conditions.

Keywords: Saturated–unsaturated seepage; Discrete element method; MatDEM; Landslide run-out

Fig.7 Sand channel model seepage field calculation results: a sand channel model; b distribution of the total head at different moments calculated by MatDEM; c distribution of total head at different moments calculated by SEEP/W; d comparison of water level lines calculated by MatDEM and SEEP/W at different times; e monitoring curves of seepage field with different particle sizes.

Fig.8 Comparison between SEEP/W and MatDEM model results: a soil column model; b total boundary force and total weight change curves.

Fig.10 MatDEM numerical model of the Tanjiahe landslide.

Fig.12  Reservoir water level regulation (Condition 1): a total head and, b displacement distribution at different times

Chen, Y., Wang, S., Wang, L. et al. A discrete element method for calculating saturated and unsaturated seepage in landslide soils and a case study. Landslides (2025). https://doi.org/10.1007/s10346-025-02493-z