scholarly journals Physical Model Experiments on Water Infiltration and Failure Modes in Multi-Layered Slopes under Heavy Rainfall

2020 ◽  
Vol 10 (10) ◽  
pp. 3458
Author(s):  
Junfeng Tang ◽  
Uchimura Taro ◽  
Dong Huang ◽  
Jiren Xie ◽  
Shangning Tao

To assess the influence of an intermediate coarse layer on the slope stability during heavy rainfall, knowledge about water movement and how slope failure occurs is important. To clarify the characteristics of water infiltration in a multi-layered slope and assess its influence on the slope failure modes, eight groups of physical slope models were investigated. It was found that the unsaturated hydraulic conductivity in the coarse layer (5.54 × 10−6 cm/s) was much lower than that of the fine layer (1.08 × 10−4 cm/s), which resulted in the capillary barrier working at a lower water content. Intermediate coarse layers embedded between finer ones may initially confine the infiltration within the overlying finer layers, delaying the infiltration and eventually inducing a lateral flow diversion in the inclined slope. Two different failure modes occurred in the model experiments: surface sliding occurred at the toe in the single-layer slope group and piping occurred at the toe in the multi-layered slope as the rainfall water accumulated, was diverted along the interface, and then broke through in the downslope direction of the intermediate coarse layer. The lateral flow diversion caused by the capillary barrier and the tilt angle may be the major factors influencing the difference of the failure modes. The result also revealed that the coarser layers may have negative effects on the slope stability.

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 73
Author(s):  
Panagiotis Sitarenios ◽  
Francesca Casini

This paper presents a three-dimensional slope stability limit equilibrium solution for translational planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr–Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural and smooth transition from the unsaturated to the saturated regime and vice versa. The proposed analytical solution is evaluated by comparing its predictions with the results of the Ruedlingen slope failure experiment. The comparison suggests that, despite its relative simplicity, the analytical solution can capture the experimentally observed behaviour well and highlights the importance of considering lateral resistance together with a realistic interplay between mechanical parameters (cohesion) and hydraulic (pore water pressure) conditions.


2016 ◽  
Vol 16 (6) ◽  
pp. 1309-1321 ◽  
Author(s):  
Ching-Jiang Jeng ◽  
Dar-Zen Sue

Abstract. The Huafan University campus is located in the Ta-lun Shan area in northern Taiwan, which is characterized by a dip slope covered by colluvium soil of various depths. For slope disaster prevention, a monitoring system was constructed that consisted of inclinometers, tiltmeters, crack gages, groundwater level observation wells, settlement and displacement observation marks, rebar strain gages, concrete strain gages, and rain gages. The monitoring data derived from hundreds of settlement and displacement observation marks were analyzed and compared with the displacement recorded by inclinometers. The analysis results revealed that the maximum settlement and displacement were concentrated on the areas around the Hui-Tsui, Zhi-An, and Wu-Ming buildings and coincided with periods of heavy rainfall. The computer program STABL was applied for slope stability analysis and modeling of slope failure. For prevention of slope instability, a drainage system and tieback anchors with additional stability measures were proposed to discharge excess groundwater following rainfall. Finally, threshold value curves of rainfall based on slope displacement were proposed. The curves can be applied for predicting slope stability when typhoons are expected to bring heavy rainfall and should be significant in slope disaster prevention.


2021 ◽  
Author(s):  
Liang Wang ◽  
Xue Zhang ◽  
Stefano Tinti

AbstractThis paper presents the failure analysis of layered clayey slopes with emphasis on the combined effect of the clay’s weakening behavior and the seismic loading using the particle finite element method (PFEM). Diverse failure mechanisms have been disclosed via the PFEM modelling when the strain-weakening behavior of clay is concerned. In contrast to a single layered slope exhibiting either a shallow or a deep failure mode, a layered slope may undergo both failure modes with a time interval in between. Seismic loadings also enlarge the scale of slope failure in clays with weakening behavior. The failure of a real layered slope (i.e. the 1988 Saint-Adelphe landslide, Canada) triggered by the Saguenay earthquake is also studied in this paper. The simulation results reveal that the choice of the strain-softening value controls the slip surface of the landslide and the amplification effect is important in the triggering of the landslide.


2016 ◽  
Author(s):  
C.-J. Jeng ◽  
D.-Z. Sue

Abstract. The Huafan University campus is located in the Ta-Lun Shan area in northern Taiwan, which is characterized by a dip-slope covered by colluvium soil of various depths. For slope disaster prevention, a monitoring system was constructed that consisted of inclinometers, tiltmeters, crack gages, groundwater level observation wells, settlement and displacement observation marks, rebar strain gages, concrete strain gages, and rain gages. The monitoring data derived from hundreds of settlement and displacement observation marks were analyzed and compared with the displacement recorded by inclinometers. The analysis results revealed that the maximum settlement and displacement were concentrated on the areas around the Hui-Tsui, Zhi-An, and Wu-Ming Buildings and coincided with periods of heavy rainfall. The computer program STABL was applied for slope stability analysis and modeling of slope failure. For prevention of slope instability, a drainage system and tieback anchors with additional stability measures were proposed to discharge excess groundwater following rainfall. Finally, threshold value curves of rainfall based on slope displacement were proposed. The curves can be applied for predicting slope stability when typhoons are expected to bring heavy rainfall and should be significant in slope disaster prevention.


Author(s):  
Panagiotis Sitarenios ◽  
Francesca Casini

The paper presents a three-dimensional slope stability limit equilibrium solution for translational, planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr – Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural and smooth transition from the unsaturated to the saturated regime and vice versa. The proposed analytical solution is evaluated by comparing its predictions with the results of the Ruedlingen slope failure experiment [1]. The comparison suggests that despite its relative simplicity the analytical solution can capture well the experimentally observed behaviour and highlights the importance of lateral resistance consideration together with a realistic interplay between mechanical parameters (cohesion) and hydraulic (pore water pressure) conditions.


2015 ◽  
Vol 72 (3) ◽  
Author(s):  
Gambo Haruna Yunusa ◽  
Azman Kassim ◽  
Ahmad Safuan A. Rashid

Residual soil slope failure due to rainfall infiltration is one of geotechnical hazards receiving much attention in many tropical climate countries. The infiltrating water eliminates matric suction in the residual soil slope and results in slope failure. A capillary barrier is used to prevent excessive rainfall infiltration and preserve matric suction in the residual soil slope and hence prevent rainfall-induced slope failure. A numerical study to examine the performance of a transport layer in a two-layered slope using capillary barrier principle was presented in this paper. Material properties of tropical residual soils consisting of Grade V (silty gravel) and Grade VI (sandy silt) were used and modelled a two-layered slope. These material properties were obtained from representative soil sample of Balai Cerapan slope in Universiti Teknologi Malaysia, Johor Bahru campus. A granite chips (Gravel) was also incorporated to act as a transport layer in the numerical model. The simulated slope model was then subjected to three different rainfall intensities of 9 mm/h (rainfall 1), 22 mm/h (rainfall 2) and 36 mm/h (Rainfall 3) representing short, medium and high intensity rainfalls, respectively. A total of six numerical schemes were performed by restricting the thickness of the transport layer to 0.1 m. However, to assess the effect of the transport layer thickness on suction distribution; the thickness was increased to 0.2 m. The results of the study show that inclusion of gravelly transport layer enables the top layer of fine sandy silt residual soil to retain the infiltrating water as a result of capillary break developed at the interface and also divert it above the interface towards the direction of the toe of the slope. Similarly the transport layer is found to be effective in preventing water breakthrough occurrence into the underlying coarser soil layer of the two-layered slope, especially when the thickness of the transport layer is optimum.


2014 ◽  
Vol 501-504 ◽  
pp. 8-11
Author(s):  
Jing Sheng Bian ◽  
Chao Sheng Bian ◽  
Zhi Ming Zhu

Rainfall is one of the most important factors of the slope stability. After the "5.12" earthquake, there are a large number of loose solid produced by earthquake on the mountain, which leads to the soils strength loss in the earthquake disaster zones. and induces landslides and collapses easily in the heavy rainfall condition. The soil parameters obtained from the tests, the scene investigation of the Erman mountain landslide of Han Yuan County, the new developed control of ArcGIS to obtain intuitive landslide warning graphs have been carried out. Results show that the picture of hazard grade is consistent with the actual situation of landslide on Erman mountain. It will provide a scientific way to analyze the influence of heavy rainfall on slope stability.


2021 ◽  
Author(s):  
Shixin Zhang ◽  
Li Li ◽  
Dongsheng Zhao ◽  
Bo Ni ◽  
Yue Qiang ◽  
...  

Abstract Rainfall-induced landslide is a typical geological disaster in the Three Gorges reservoir area. The air entrapment in the pores of soils has a hindrance to the infiltration of the slope. It is mainly reflected in the hydraulic hysteresis after rainfall and the decrease of the slope anti-sliding force. A method considered the air entrapment of the closed gas in soil particles’ pores is developed to study the time-delay effect and slope stability under the rainfall process. The Green-Ampt infiltration model is used to obtain the explicit analytical solution of the slope infiltration considering air entrapment. Moreover, the relationship between the safety factor, the rainfall duration, and the depth of the wetting front under the three rainfall conditions (qrain=12, 26, 51 mm/h) is discussed. The results show that the air entrapment causes a significant time-delay effect of the landslide, and the hydraulic hysteresis is the strongest under the condition of heavy rainfall (qrain= 51mm/h). The time-delay effect lasts longer than low rainfall and heavy rainfall when the rainfall intensity (qrain= 26 mm/h) is slightly greater than saturated hydraulic conductivity Ks. Parameter analysis shows that when air entrapment is considered, the smaller the slope angle and the effective internal friction angle, the more significant the air entrapment has on the slope stability; the smaller the effective cohesion, the longer the air resistance lasts. Finally, the application of the Bay Area landslide is consistent with the actual state of the landslide.


Sign in / Sign up

Export Citation Format

Share Document