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

Abstract

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.

Sensibility Analysis of the Hydraulic Conductivity Anisotropy on Seepage and Stability of Sandy and Clayey Slope

“…Slope stability is an important engineering problem in the geotechnical field, for example, the slope stability of the excavation of a foundation pit [1], the regulation of a riparian slope [2], and the stability of a high slope under complex geological environment in a reservoir area [3], etc. Slope failures mainly include external and internal causes.…”

“…The main consequence for slope instability caused by rainfall is reflected in these two aspects: (1) Landslide causes damage to buildings in the area where the slope is located. (2) Landslide threatens the lives and properties of the residents around the disaster area. For example, on 16 September 2011, heavy rainfall (250 mm/day, cumulative 430 mm) in Nanjiang County, Sichuan Province, China, induced thousands of landslides, and on 29 April 2015, the groundwater level in Dangchuan, Heifangtai, Gansu Province, China, rose due to heavy rainfall, which caused a large-scale slope failure [26].…”

“…Duong T.T. [2] used the Geo-studio program to study the effects of soil hydraulic conductivity and rainfall intensity on riverbank stability. Muqdad Al-Juboori et al [47][48][49] conducted the machine learning research based on SEEP/W.…”

Assessment of the Influence of Mountain Flood Control Reservoir Operation on the Floodplain Stability During an Extreme Flood

“…When the water level drops in the saturated soil, a decline curve is formed because of water lag time, and excess pore pressure can lead to the bank destruction [Alfatlawi et al 2020]. A slope stability decrease is noted also in the works by [Xue et al 2016, Acharya et al 2016, Duong et al 2019, Liu et al 2015] that is related to the penetration of water into unsaturated soil during the rain. Water penetration into the soil depends on the geological structure of floodplain banks.…”

Assesment of selected empirical formulas for computation of saturated hydraulic conductivity

“…Habtamu et al (2019) evaluate saturated hydraulic conductivity with different land uses of disturbed and undisturbed soil, they developed an equation which replaces the time taking in-situ saturated hydraulic conductivity measurement. Duong et al (2019) clarify the effects of soil hydraulic conductivity and rainfall intensity on riverbank stability using a GeoSlope analysis. Říha et al (2018) present the verification of validity of various published porosity functions and empirical formulae with the use of the experimental data obtained from the glass beads.…”