scholarly journals The Influence of Horizontal Variability of Hydraulic Conductivity on Slope Stability under Heavy Rainfall

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2567
Author(s):  
Tongchun Han ◽  
Liqiao Liu ◽  
Gen Li
Keyword(s):  
Hydraulic Conductivity ◽  
Slope Stability ◽  
Coefficient Of Variation ◽  
Heavy Rainfall ◽  
Negative Impact ◽  
Wetting Front ◽  
Theoretical Derivation ◽  
Rainwater Infiltration ◽  
Horizontal Variation ◽  
Cumulative Infiltration

Due to the natural variability of the soil, hydraulic conductivity has significant spatial variability. In the paper, the variability of the hydraulic conductivity is described by assuming that it follows a lognormal distribution. Based on the improved Green–Ampt (GA) model of rainwater infiltration, the analytical expressions of rainwater infiltration into soil with depth and time under heavy rainfall conditions is obtained. The theoretical derivation of rainfall infiltration is verified by numerical simulation, and is used to quantitatively analyze the effect of horizontal variability of the hydraulic conductivity on slope stability. The results show that the variability of the hydraulic conductivity has a significant impact on rainwater infiltration and slope stability. The smaller the coefficient of variation, the more concentrated is the rainwater infiltration at the beginning of rainfall. Accordingly, the wetting front is more obvious, and the safety factor is smaller. At the same time, the higher coefficient of variation has a negative impact on the cumulative infiltration of rainwater. The larger the coefficient of variation, the lower the cumulative rainwater infiltration. The conclusions reveal the influence of the horizontal variation of hydraulic conductivity on rainwater infiltration, and then the influence on slope stability.

scholarly journals Assessing the Effects of Rainfall Intensity and Hydraulic Conductivity on Riverbank Stability

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 741
Author(s):  
Toan Thi Duong ◽  
Duc Minh Do ◽  
Kazuya Yasuhara
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soil ◽  
Rainfall Intensity ◽  
Groundwater Table ◽  
Wetting Front ◽  
Soil Hydraulic Conductivity ◽  
Rainwater Infiltration ◽  
Soil Hydraulic ◽  
Transient Seepage ◽  
Riverbank Stability

Riverbank failure often occurs in the rainy season, with effects from some main processes such as rainfall infiltration, the fluctuation of the river water level and groundwater table, and the deformation of transient seepage. This paper has the objective of clarifying the effects of soil hydraulic conductivity and rainfall intensity on riverbank stability using numerical analysis with the GeoSlope program. The initial saturation condition is first indicated as the main factor affecting riverbank stability. Analyzing high-saturation conditions, the obtained result can be used to build an understanding of the mechanics of riverbank stability and the effect of both the rainfall intensity and soil hydraulic conductivity. Firstly, the rainfall intensity is lower than the soil hydraulic conductivity; the factor of safety (FOS) reduces with changes in the groundwater table, which is a result of rainwater infiltration and unsteady state flow through the unsaturated soil. Secondly, the rainfall intensity is slightly higher than the soil hydraulic conductivity, the groundwater table rises slowly, and the FOS decreases with both changes in the wetting front and groundwater table. Thirdly, the rainfall intensity is much higher than the soil hydraulic conductivity, and the FOS decreases dominantly by the wetting front and pond loading area. Finally, in cases with no pond, the FOS reduces when the rainfall intensity is lower than hydraulic conductivity. With low hydraulic conductivity, the wetting front is on a shallow surface and descends very slowly. The decreasing of FOS is only due to transient seepage changes of the unsaturated soil properties by losing soil suction and shear strength. These obtained results not only build a clearer understanding of the filtration mechanics but also provide a helpful reference for riverbank protection.

scholarly journals Moisture Transfer Finite Element Modeling with Soil-Water Characteristic Curve-Based Parameters and its Application to Nhan Co Red Mud Basin Slope

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Nguyen Van Hoang ◽  
Hoang Viet Hung ◽  
Pham Van Dung
Keyword(s):  
Finite Element ◽  
Soil Moisture ◽  
Moisture Content ◽  
Slope Stability ◽  
Moisture Transfer ◽  
Characteristic Curve ◽  
Moisture Distribution ◽  
Wetting Front ◽  
Strength Parameters ◽  
Rainwater Infiltration

Since the year of 2017 landslides at the red mud basins in Nhan Co alumina factory, Dak Nong province have been occurring during the rainy seasons. The change of the soil physical and mechanical parameters due to rainwater infiltration has been considered as the main factor of the slope instability. The soil cohesion and angle of internal friction depend very much on the soil moisture: soil with a lower moisture content has a higher shearing strength than that with higher moisture content. The finite element modeling of moisture transfer in unsaturated soils through the relationship between soil moisture, soil suction, unsaturated permeability and soil-moisture dispersivity is capable of accurately predicting the wetting front development. The element sizes and time steps have been selected based on detailed analysis of analytical error estimation and on the numerical simulations with different element sizes numerical simulation errors. Soil samples had been taken and the soil different suctions and corresponding soil moisture values have been determined in the laboratory. The soil water characteristic curve (SWCC) parameters (a, n and m) have been determined by the best fitting using the least squared error method. The hydraulic conductivity of the saturated soil, one of the key input parameters was also determined. The results of the application to the study area's slope has shown that the wetting front depth can be up to 8 meters for 90 days of moisture transfer due to the rainwater infiltration The wetting front depth and the length of the intermediate part of the moisture distribution curve have increased with the infiltration time. The soil moisture distribution with a depth is an essential information to have soil strength parameters for the slope stability analyses. The slope stability analysis with the soil shear strength parameters which are strictly corresponding with the moisture change would provide the most accurate and reliable slope stability results and provide more reliable slope stabilization solutions.

Slope Stability Analysis under the Condition of Seepage

2012 ◽  
Vol 204-208 ◽  
pp. 241-245
Author(s):  
Yang Jin
Keyword(s):  
Finite Element Method ◽  
Shear Strength ◽  
Slope Stability ◽  
Negative Impact ◽  
Strength Reduction ◽  
Soil Slope ◽  
Failure State ◽  
Calculation Results ◽  
The Stability ◽  
Shear Strength Reduction

The stability of soil slope under seepage is calculated and analyzed by using finite element method based on the technique of shear strength reduction. When the condition of seepage or not is considered respectively, the critical failure state of slopes and corresponding safety coefficients can be determined by the numerical analysis and calculation. Besides, through analyzing and comparing the calculation results, it shows that seepage has a negative impact on slope stability.

Analysis of the Slope Stability in the Heavy Rainfall Condition

2014 ◽  
Vol 501-504 ◽  
pp. 8-11
Author(s):  
Jing Sheng Bian ◽  
Chao Sheng Bian ◽  
Zhi Ming Zhu
Keyword(s):  
Slope Stability ◽  
Heavy Rainfall ◽  
Strength Loss ◽  
Soil Parameters ◽  
Actual Situation ◽  
Earthquake Disaster ◽  
Rainfall Condition ◽  
Scene Investigation

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.

Simulating transient infiltration in unsaturated soils

1998 ◽  
Vol 35 (6) ◽  
pp. 1093-1100 ◽  
Author(s):  
J R McDougall ◽  
I C Pyrah
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soils ◽  
Flow Model ◽  
Unsaturated Flow ◽  
Surface Region ◽  
Infiltration Rate ◽  
Soil Suction ◽  
Wetting Front ◽  
Near Surface ◽  
Unsaturated Hydraulic Conductivity

Transient responses to various infiltration events have been examined using an unsaturated flow model. Numerical simulations reveal a range of infiltration patterns which can be related to the ratio of infiltration rate to unsaturated hydraulic conductivity. A high value of this ratio reflects a prevailing hydraulic conductivity which cannot readily redistribute the newly infiltrated moisture. Moisture accumulates in the near-surface region before advancing down through the soil as a distinct wetting front. In contrast, low values of the ratio of rainfall to unsaturated hydraulic conductivity show minimal moisture accumulation, as the relatively small volumes of infiltrating moisture are readily redistributed through the soil profile.Key words: numerical modelling, infiltration, unsaturated soil, soil suction, groundwater.

scholarly journals Stability and Time-Delay Effect of Rainfall-induced Landslide Considering Air Entrapment

2021 ◽  
Author(s):  
Shixin Zhang ◽  
Li Li ◽  
Dongsheng Zhao ◽  
Bo Ni ◽  
Yue Qiang ◽  
...  
Keyword(s):  
Time Delay ◽  
Slope Stability ◽  
Heavy Rainfall ◽  
Parameter Analysis ◽  
Three Gorges Reservoir Area ◽  
Actual State ◽  
Air Entrapment ◽  
Delay Effect ◽  
Hydraulic Hysteresis ◽  
Time Delay Effect

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.

scholarly journals Risk assessment of designated landslide-risky valleys against heavy rainfall based on geotechnical investigation and slope stability analysis

2013 ◽  
Vol 8 (1) ◽  
pp. 119-131 ◽  
Author(s):  
Shoichi KAWABATA ◽  
Takashi TSUCHIDA ◽  
Seiji KANO ◽  
Hiroki YURI ◽  
Takashi HANAOKA ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Stability Analysis ◽  
Slope Stability ◽  
Heavy Rainfall ◽  
Slope Stability Analysis ◽  
Geotechnical Investigation

scholarly journals A method for predicting the factor of safety of an infinite slope based on the depth ratio of the wetting front

2015 ◽  
Vol 3 (1) ◽  
pp. 791-836 ◽  
Author(s):  
B.-G. Chae ◽  
J.-H. Lee ◽  
H.-J. Park ◽  
J. Choi
Keyword(s):  
Steady State ◽  
Slope Stability ◽  
Unsaturated Soil ◽  
Landslide Susceptibility ◽  
Shallow Landslides ◽  
Rainfall Infiltration ◽  
Wetting Front ◽  
Operating Characteristics ◽  
Infinite Slope ◽  
Depth Ratio

Abstract. Most landslides in Korea are classified as shallow landslides with an average depth of less than 2 m. These shallow landslides are associated with the advance of a wetting front in the unsaturated soil due to rainfall infiltration, which results in an increase in water content and a reduction in the matric suction in the soil. Therefore, this study presents a modified equation of infinite slope stability analysis based on the concept of the saturation depth ratio to analyze the slope stability change associated with the rainfall on a slope. A rainfall infiltration test in unsaturated soil was performed using a column to develop an understanding of the effect of the saturation depth ratio following rainfall infiltration. The results indicated that the rainfall infiltration velocity due to the increase in rainfall in the soil layer was faster when the rainfall intensity increased. In addition, the rainfall infiltration velocity tends to decrease with increases in the unit weight of soil. The proposed model was applied to assess its feasibility and to develop a regional landslide susceptibility map using a Geographic Information System (GIS). For that purpose, the spatial databases for input parameters were constructed and landslide locations were obtained. In order to validate the proposed approach, the results of the proposed approach were compared with the landslide inventory using ROC (Receiver Operating Characteristics) graph. In addition, the results of the proposed approach were compared with the previous approach used steady state hydrological model. Consequently, the approach proposed in this study displayed satisfactory performance in classifying landslide susceptibility and showed better performance than the steady state approach.

scholarly journals Characteristics of ground motion and threshold values for colluvium slope displacement induced by heavy rainfall: a case study in northern Taiwan

2016 ◽  
Vol 16 (6) ◽  
pp. 1309-1321 ◽  
Author(s):  
Ching-Jiang Jeng ◽  
Dar-Zen Sue
Keyword(s):  
Slope Stability ◽  
Heavy Rainfall ◽  
Slope Failure ◽  
Drainage System ◽  
Threshold Value ◽  
Slope Instability ◽  
Disaster Prevention ◽  
Strain Gages ◽  
Slope Displacement ◽  
Northern Taiwan

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.

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