scholarly journals The Impact of Reservoir Fluctuations on Reactivated Large Landslides: A Case Study

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Javed Iqbal ◽  
Xinbin Tu ◽  
Wei Gao
Keyword(s):  
Slip Surface ◽  
Strength Reduction ◽  
Slope Instability ◽  
Water Level Fluctuations ◽  
Silty Mudstone ◽  
Jinsha River ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
The Impact

Filling of Xiangjiaba Reservoir Lake in the Southwest China triggered and reactivated numerous landslides due to water fluctuation. In order to understand the relationship between reservoirs and slope instability, a typical reservoir landslide (Dasha landslide) at the right bank of Jinsha River was selected as a case study for in-depth investigations. The detailed field investigations were carried out to identify the landslide with respect to its surroundings and to find out the slip surface. Boreholes were drilled to find out the subsurface lithology and the depth of failure of Dasha landslide. The in situ geotechnical tests were performed, and the soil samples from exposed slip surface were retrieved for geotechnical laboratory analysis. Finally, stability analysis was done using the 3D strength reduction method under different conditions of reservoir water level fluctuations and rainfall conditions. The in-depth investigations show that the Dasha landslide is a bedding rockslide which was once activated in 1986. The topography of Dasha landslide is relatively flat, while the back scarp and local terrain is relatively steep. The total volume of landslides is about 580×104 m3 with an average thickness of 20 m. Bedrock in the landslide area is composed of Suining Formation of the Jurassic age. The main rock type is silty mudstone with sandstone, and the bedding orientation is 300~310° ∠ 7~22°. The factor of safety (FOS) of Dasha landslide obtained by 3D strength reduction cannot meet the minimum safety requirement under the working condition of reservoir level fluctuation as designed, with effect of rainfall and rapid drawdown.

scholarly journals Sensitivity Analysis of Anchored Slopes under Water Level Fluctuations: A Case Study of Cangjiang Bridge—Yingpan Slope in China

2021 ◽  
Vol 11 (15) ◽  
pp. 7137
Author(s):  
Jinxi Liang ◽  
Wanghua Sui
Keyword(s):  
Sensitivity Analysis ◽  
Slope Stability ◽  
Water Level ◽  
Controlling Factors ◽  
Slope Instability ◽  
Water Level Fluctuations ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Slope Inclination ◽  
Main Controlling Factors

This paper presents an improved slope stability sensitivity analysis (ISSSA) model that takes anchoring factors into consideration in umbrella-anchored sand and clay slopes under reservoir water level fluctuation. The results of the ISSSA model show that the slope inclination and the layout density of anchors are the main controlling factors for sand slope stability under fluctuation of the water level, while the slope inclination and water head height are the main controlling factors for slope stability in the Cangjiang bridge—Yingpan slope of Yunnan province in China. Moreover, there is an optimum anchorage angle, in the range of 25–45 degrees, which has the greatest influence on slope stability. The fluctuation of the reservoir water level is an important factor that triggers slope instability; in particular, a sudden drop in the surface water level can easily lead to landslides; therefore, corresponding measures should be implemented in a timely manner in order to mitigate landslide disasters.

scholarly journals Numerical Analysis of Slope Stability under Reservoir Water Level Fluctuations Using a FEM-LEM-Combined Method

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Qingxiang Meng ◽  
Kun Qian ◽  
Lin Zhong ◽  
Jinjian Gu ◽  
Yue Li ◽  
...  
Keyword(s):  
Slope Stability ◽  
Water Level ◽  
Large Scale ◽  
Numerical Study ◽  
Soil Strength ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
The Impact

Large-scale slopes at the banks of reservoirs pose a serious threat to the safety of hydropower stations. The fluctuation of the reservoir water level is a key factor in the slope stability. However, the parameters to describe the relationship among water content, matric suction, and soil strength are difficult to measure using unsaturated soil strength theory. To solve this problem, a simple FEM-LEM-combined scheme considering pore pressure, seepage force, and strength weakening is presented to calculate the safety factor. A numerical study on the impact of reservoir water level fluctuations on stability of a glaciofluvial deposit slope is implemented. Two typical profiles are used to estimate the stability of the glaciofluvial deposit slope in response to rising and lowering water levels. The results indicate that this method proposed a simple and efficient tool for water level-induced slope stability analysis.

scholarly journals A Simplified Solution for Calculating the Phreatic Line and Slope Stability during a Sudden Drawdown of the Reservoir Water Level

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Guanhua Sun ◽  
Shan Lin ◽  
Wei Jiang ◽  
Yongtao Yang
Keyword(s):  
Slope Stability ◽  
Water Level ◽  
Slip Surface ◽  
Laplacian Matrix ◽  
Safety Factors ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
The Three Gorges ◽  
Simplified Solution

On the basis of the Boussinesq unsteady seepage differential equation, a new simplified formula for the phreatic line of slopes under the condition of decreasing reservoir water level is derived by means of the Laplacian matrix and its inverse transform. In this context, the expression of normal stress on the slip surface under seepage forces is deduced, and a procedure for obtaining the safety factors under hydrodynamic forces is proposed. A case study of the Three Gorges Reservoir is used to analyze the influences of the water level, decreasing velocity and the permeability coefficient on slope stability.

scholarly journals Stability Analysis of Hydrodynamic Pressure Landslides with Different Permeability Coefficients Affected by Reservoir Water Level Fluctuations and Rainstorms

Water ◽  
2017 ◽  
Vol 9 (7) ◽  
pp. 450 ◽  
Author(s):  
Faming Huang ◽  
Xiaoyan Luo ◽  
Weiping Liu
Keyword(s):  
Water Level ◽  
Permeability Coefficient ◽  
Hydrodynamic Pressure ◽  
Water Level Fluctuations ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Stability Coefficient ◽  
Permeability Coefficients ◽  
Landslide Stability ◽  
The Stability

It is significant to study the variations in the stability coefficients of hydrodynamic pressure landslides with different permeability coefficients affected by reservoir water level fluctuations and rainstorms. The Sifangbei landslide in Three Gorges Reservoir area is used as case study. Its stability coefficients are simulated based on saturated-unsaturated seepage theory and finite element analysis. The operating conditions of stability coefficients calculation are reservoir water level variations between 175 m and 145 m, different rates of reservoir water level fluctuations, and a three-day continuous rainstorm. Results show that the stability coefficient of the hydrodynamic pressure landslide decreases with the drawdown of the reservoir water level, and a rapid drawdown rate leads to a small stability coefficient when the permeability coefficient ranges from 1.16 × 10−6 m/s to 4.64 × 10−5 m/s. Additionally, the landslide stability coefficient increases as the reservoir water level increases, and a rapid increase in the water level leads to a high stability coefficient when the permeability coefficient ranges from 1.16 × 10−6 m/s to 4.64 × 10−5 m/s. The landslide stability coefficient initially decreases and then increases as the reservoir water level declines when the permeability coefficient is greater than 4.64 × 10−5 m/s. Moreover, for structures with the same landslide, the landslide stability coefficient is most sensitive to the change in the rate of reservoir water level drawdown when the permeability coefficient increases from 1.16 × 10−6 m/s to 1.16 × 10−4 m/s. Additionally, the rate of decrease in the stability coefficient increases as the permeability coefficient increases. Finally, the three-day rainstorm leads to a significant reduction in landslide stability, and the rate of decrease in the stability coefficient initially increases and then decreases as the permeability coefficient increases.

scholarly journals Interpretasi Instrumentasi Piezometer Dalam Rangka Pemantauan Keamanan Bendungan Kedung Ombo

2021 ◽  
Vol 7 (2) ◽  
pp. 131-145
Author(s):  
Gerald Guntur Pandapotan Siregar ◽  
Fajar aldoko Kurniawan
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Level Fluctuations ◽  
Embankment Dam ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Embankment Dams ◽  
The World ◽  
Earthfill Dams

The embankment dam is the most widely built dam in the world, especially in Indonesia. However, embankment dams are also prone to collapse. Dam failures due to the piping process through the dam body account for 30.5% of the total dam collapses worldwide. Therefore, it is necessary to periodically monitor and evaluate the condition of pore water pressure and seepage in a dam which is usually carried out using installed instrumentation. Very little has been done on instrumentation interpretation of earthfill dams in Indonesia, which is a very worrying condition. It is possible that old or even new dams have shown behavior that leads to a decrease in safety. This condition can be monitored by instrumentation in the dam if interpreted properly. Kedung Ombo Dam as an old embankment dam but has a fairly complete instrumentation can be evaluated for safety related to pore water pressure and phreatic line (seepage line). Pore water pressure evaluation is carried out by collecting piezometer readings and reservoir water level fluctuations over a period of several years. The results of the research on the interpretation of piezometer readings indicate that the overall safety of the Kedung Ombo dam is still good in terms of pore water pressure conditions. However, there are some anomalous conditions that should be investigated further

scholarly journals Limitation of the Reservoirs’ Water Level Alteration Rate in Hydro Electric Power Stations Operational Mode Control in Accordance with Safety Rules for Water Work Facilities

2012 ◽  
pp. 65-73
Author(s):  
Keyword(s):  
Electric Power ◽  
Water Level ◽  
Electric Power Station ◽  
Operational Mode ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Water Power ◽  
Power Stations ◽  
The Impact ◽  
Water Work

The impact of the reservoir water level alterations rate limitation upon its operational mode has been studied. These limitations impact upon the hydro electric power station performance has been assessed. It has been proposed to take into consideration the level alteration rate in water/economic and water/power production calculations.

Deformation and stability analyses of a near-dam rocky slope and its potential landslide-generated wave threats

2021 ◽  
pp. qjegh2021-018
Author(s):  
Ming-liang Chen ◽  
Xing-guo Yang ◽  
Shun-chao Qi ◽  
Hai-bo Li ◽  
Jia-wen Zhou
Keyword(s):  
Water Level ◽  
Rock Slope ◽  
Limit Equilibrium ◽  
Water Levels ◽  
Reservoir Rock ◽  
Water Diversion ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
The Impact

Occurrence of a reservoir landslide and its potential secondary hazards near a dam can result in significant losses and casualties, such as those that resulted from the Vajont landslide. In this study, a cataclinal rock slope in the Maoergai reservoir was taken as a case to study the characteristics of the gravitational deformation process and to analyze the potential threat. The stability of rock slope is analyzed by the limit equilibrium method, and the potential landslide movement and subsequent waves are also simulated. Results indicate that lithology, geological structure, reservoir water level changes and artificial activities all play an important role for the large deformation of rock slope deformation, which is characterized by a combination of bending-toppling and principally shear-slip. Pre-calculations of potential threats indicated that the impact of a landslide wave would be greater at dead water levels than at the normal water level and could result in blockage of the inlet to the water diversion structure on the opposite right bank. These findings provide implication for the control of reservoir rock slopes: (i) serious attention should be paid to the influence of water on rock strength in early and (ii) infiltration must be prevented during water level rise.Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

scholarly journals Influence of Rainfall Intensity on the Stability of Unsaturated Soil Slope: Case Study of R523 Road in Thulamela Municipality, Limpopo Province, South Africa

2020 ◽  
Vol 10 (24) ◽  
pp. 8824
Author(s):  
Fhatuwani Sengani ◽  
François Mulenga
Keyword(s):  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Extreme Rainfall ◽  
Limpopo Province ◽  
Slope Instability ◽  
Soil Slope ◽  
Numerical Software ◽  
The Impact

The purpose of this paper was to analyze the impact of extreme rainfall on the recurrence of slope instability using the Thulamela Municipality roads (R523) as a case study. To this end, the historical rainfall data of the area of study were analyzed between 1988 and 2018. The results show that a significant increase in rainfall is usually experienced in the summer months of December and January. Following this, the factor of safety (FoS) of slopes of silt clay, clay, and clay loam soils were estimated using the SLIDE simulator (Numerical software “Finite Element Method (FEM)”) under sunny to rainy conditions of the area. A complementary model, FLACSlope (Numerical software “Finite Difference Method (FDM)”), was utilized to simulate FoS and pore water pressure in sunny and rainy conditions of the area. Simulation results show that extreme rainfall has the ability to reduce the shear strength and resistance of the soil slope material. This may explain the recurrent landslides noted in the area. Finally, the water pore pressure has been simulated to increase with the increased water table, which generally pushes the soil particles apart and reduces the stress between the particles resulting in soil slope failure. Extreme rainfall alters the phase of the material solid in a manner that may require further research for a better understanding.

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