Pregnant Mechanism and Mechanical Model of Rock Landslides in Chair-Shaped Cataclinal Bank Slopes

2014 ◽  
Vol 580-583 ◽  
pp. 2589-2599
Author(s):  
Xian Chun Ma ◽  
Xi Chang Chen ◽  
You Jun Feng
Keyword(s):  
Mechanical Model ◽  
Critical Value ◽  
Control Measures ◽  
Monitoring Methods ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Sliding Mechanism ◽  
Groundwater Supply ◽  
Rock Landslide ◽  
The Stability

The pregnant and sliding mechanism was firstly compared between Vajont and Qianjiangping large rock landslides, which happened in the chair-shaped cataclinal bank slopes. And then the essence of the landslides occurred was deduced. The pregnant and sliding process of the landslides was showed two stages. First, after the first impoundment of the reservoir, the soil and shallow rock at the front of the landslides were slipped and then caused posterior margin of the deep latent sliding surface cracks. So the groundwater supply condition was significantly changed. Second, with the rapidly increase of the groundwater recharge, its pressure on the front of the landslides was also rapidly rise to the critical value which the landslides occurred. Afterwards, the stability mechanical model of the chair-shaped cataclinal bank slopes and critical value formula of the groundwater pressure were established on the basis of the stability mechanical model of general chair-shaped cataclinal slopes, added reservoir water level which was a dynamic load. While working procedures to determine the groundwater pressure was put forward. Last, the theory was certified validity take Liangshuijing rock landslide of the Three Gorges Project area as an example and the monitoring methods and control measures for the landslide were proposed.

scholarly journals Unsteady Seepage Behavior of an Earthfill Dam During Drought-Flood Cycles

Geosciences ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 17 ◽  
Author(s):  
Ziyang Li ◽  
Wei Ye ◽  
Miroslav Marence ◽  
Jeremy Bricker
Keyword(s):  
Pressure Gradient ◽  
Water Level ◽  
Pore Pressure ◽  
Internal Erosion ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Upstream Slope ◽  
Earthfill Dams ◽  
The Stability ◽  
Pore Pressure Gradient

Climate change with extreme hydrological conditions, such as drought and flood, bring new challenges to seepage behavior and the stability of earthfill dams. Taking a drought-stricken earthfill dam of China as an example, the influence of drought-flood cycles on dam seepage behavior is analyzed. This paper includes a clay sample laboratory experiment and an unsteady finite element method seepage simulation of the mentioned dam. Results show that severe drought causes cracks on the surface of the clay soil sample. Long-term drought causes deeper cracks and induces a sharp increase of suction pressure, indicating that the cracks would become channels for rain infiltration into the dam during subsequent rainfall, increasing the potential for internal erosion and decreasing dam stability. Measures to prevent infiltration on the dam slope surface are investigated, for the prevention of deep crack formation during long lasting droughts. Unsteady seepage indicators including instantaneous phreatic lines, equipotential lines and pore pressure gradient in the dam, are calculated and analyzed under two assumed conditions with different reservoir water level fluctuations. Results show that when the water level changes rapidly, the phreatic line is curved and constantly changing. As water level rises, equipotential lines shift upstream, and the pore pressure gradient in the dam’s main body is larger than that of steady seepage. Furthermore, the faster the water level rises, the larger the pore pressure gradient is. This may cause internal erosion. Furthermore, the case of a cracked upstream slope is modelled via an equivalent permeability coefficient, which shows that the pore pressure gradient in the zone beneath the cracks increases by 5.9% at the maximum water level; this could exacerbate internal erosion. In addition, results are in agreement with prior literature that rapid drawdown of the reservoir water level is detrimental to the stability of the upstream slope based on embankment slope stability as calculated by the Simplified Bishop Method. It is concluded that fluctuations of reservoir water level should be strictly controlled during drought-flood cycles; both the drawdown rate and the fill rate must be regulated to avoid the internal erosion of earthfill dams.

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 Application of DInSAR-PSI Technology for Deformation Monitoring of the Mosul Dam, Iraq

2019 ◽  
Vol 11 (22) ◽  
pp. 2632 ◽  
Author(s):  
Arsalan Ahmed Othman ◽  
Ahmed F. Al- Maamar ◽  
Diary Ali Mohammed Al-Manmi ◽  
Veraldo Liesenberg ◽  
Syed E. Hasan ◽  
...  
Keyword(s):  
Deformation Rate ◽  
Hydrostatic Stress ◽  
Deformation Monitoring ◽  
Monitoring Methods ◽  
Persistent Scatterer Interferometry ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Efficient Operation ◽  
Spatial Coverage ◽  
Deformation Velocity

On-going monitoring of deformation of dams is critical to assure their safe and efficient operation. Traditional monitoring methods, based on in-situ sensors measurements on the dam, have some limitations in spatial coverage, observation frequency, and cost. This paper describes the potential use of Synthetic Aperture Radar (SAR) scenes from Sentinel-1A for characterizing deformations at the Mosul Dam (MD) in NW Iraq. Seventy-eight Single Look Complex (SLC) scenes in ascending geometry from the Sentinel-1A scenes, acquired from 03 October 2014 to 27 June 2019, and 96 points within the MD structure, were selected to determine the deformation rate using persistent scatterer interferometry (PSI). Maximum deformation velocity was found to be about 7.4 mm·yr−1 at a longitudinal subsidence area extending over a length of 222 m along the dam axis. The mean subsidence velocity in this area is about 6.27 mm·yr−1 and lies in the center of MD. Subsidence rate shows an inverse relationship with the reservoir water level. It also shows a strong correlation with grouting episodes. Variations in the deformation rate within the same year are most probably due to increased hydrostatic stress which was caused by water storage in the dam that resulted in an increase in solubility of gypsum beds, creating voids and localized collapses underneath the dam. PSI information derived from Sentinel-1A proved to be a good tool for monitoring dam deformation with good accuracy, yielding results that can be used in engineering applications and also risk management.

Stability Analysis of Accumulation Landslides in the Three Gorges Reservoir Area Under Reservoir Water Level Fluctuation Based on Multi-Circular Model

2021 ◽  
Author(s):  
Zhiqiang Fan ◽  
Yanhao Zheng
Keyword(s):  
Stability Analysis ◽  
Water Level ◽  
Three Gorges Reservoir ◽  
Three Gorges ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Landslide Stability ◽  
Slip Surfaces ◽  
The Three Gorges ◽  
The Stability

Abstract In the Three Gorges Reservoir (TGR) area, the accumulation landslide characterized by stepped slip surfaces is widely developed, and its stability is significantly affected by the fluctuation of reservoir water level. In this paper, the Shuping landslide, a typical accumulation landslide in the TGR area, was selected to study the effect of water level fluctuations on landslide stability. Based on Multi-Circular (M-C) model, it is found that the decline of reservoir water level was the dominant factor causing the decrease of landslide stability. At the end of the decline of reservoir water level, the landslide stability was minimum and the corresponding moment was the most dangerous. The effect of the drawdown speed of reservoir water level on the minimum value of landslide stability had a threshold effect, although the minimum stability coefficient of landslide decreased with the increase of drawdown speed. Under the most dangerous water level conditions, the stability of the piled landslide increased linearly with the increase of the net thrust of piles. Also, by comparing with other classical models, the effectiveness of the M-C model in evaluating landslide stability under the dynamic changes of reservoir water level was verified. The results could provide a reliable scientific basis for improving the stability analysis and reinforcement measures of the accumulation landslide with the multi-circular slip surfaces in the TGR area, as well as can be applied to similar landslides in reservoir areas.

Stability of No 7 Landslide Located at Ciha Gorge under the Condition of Reservoir Water Level Rise

2011 ◽  
Vol 368-373 ◽  
pp. 1482-1486
Author(s):  
Yan Hui Song ◽  
Ying Wang ◽  
Min Qi Huang
Keyword(s):  
Shear Strength ◽  
Water Level ◽  
Slip Band ◽  
Water Pressure ◽  
Work Conditions ◽  
Stability Factor ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Stability Calculation ◽  
The Stability

Engineering geology characteristics of No. 7 landslide located at Ciha Gorge is described and shear strength of the slip band soils is determined. Based on the above, unbalanced pushing force method is used to calculate the stability factor of the landslide the under different work conditions. It shows that the influence of the reservoir water level rising on the No. 7 landslide mainly includes two points: (1) water makes the shear strength of slip band soils reduced and thus result in the reduction of the stability factor; (2) the rising of reservoir water level also exerts water pressure to the surface of landslide body, and this is beneficial to landslide stability. Calculation results show that with the rising of reservoir water level the stability factor will experience beginning’s reducing followed by later increasing. The minimum stability factor in the process of impounding is 1.05 and it will be 1.08 when reservoir water level reaches to normal impounded level. This shows that No. 7 landslide will maintain elemental stability status in the all process of impounding.

scholarly journals The Impact of Microearthquakes Induced by Reservoir Water Level Rise on Stability of Rock Slope

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Dongliang Li ◽  
Xinrong Liu ◽  
Xingwang Li ◽  
Yongquan Liu
Keyword(s):  
Water Level ◽  
Shear Failure ◽  
Middle Part ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Water Level Rise ◽  
Soft Interlayer ◽  
Tensile Fractures ◽  
The Stability ◽  
The Impact

In order to study the impact of frequent microearthquakes induced by water level rise on the stability of rock bedded slopes in the Three Gorges Reservoir (TGR) area, Zhaoshuling Landslide (a representative slope) is selected to study. Safety factors based on probability statistics andFLAC3Dare used for numerical simulation (under the operating condition that five earthquakes of Intensity IV are applied to slope in succession after water level rises from 145 m to 175 m). Then the slope’s dynamic stability characteristics and failure mechanism are analyzed. The study shows that slope deformation is evidently the result of thrust load. The deformation starts from the steeply dipping segment in the middle part of slip mass and is controlled by the soft interlayer. Shear failure tends to occur along the soft interlayer and the horizontal slip displacement increases from the rear to the front of the slope. The steeply dipping segment shows a general downslide trend. Although the gentle slope platform on the rear edge is relatively stable, it is vulnerable to tensile fractures which are precursors of landslide. Under the same failure probability, as the number of microearthquake occurrences increases, the safety factor of slope under microearthquake action decreases gradually.

scholarly journals Theoretical and Case Studies of Interval Nonprobabilistic Reliability for Tailing Dam Stability

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Longjun Dong ◽  
Daoyuan Sun ◽  
Xibing Li
Keyword(s):  
Mechanical Parameters ◽  
Analysis Model ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Proposed Model ◽  
Tailing Dam ◽  
Calculation Results ◽  
Tailing Dams ◽  
Dam Stability ◽  
The Stability

The stability of the operation of a tailing dam is affected by reservoir water level, phreatic line, and mechanical parameters of tailings. The values of these factors are not a definite value in different situations. Meanwhile, the existence of the phreatic line makes it a more complex issue to analyze the stability of the tailing dam. Additionally, it is very hard to give a definite limit to the state of tailing dam from security to failure. To consider the uncertainty when calculating the stability of the tailing dams, interval values are used to indicate the physical and mechanical parameters of tailings. An interval nonprobabilistic reliability model of the tailing dam, which can be used when the data is scarce, is developed to evaluate the stability of the tailing dam. The interval nonprobabilistic reliability analysis model of tailing dam is established in two cases, including with and without considering phreatic line conditions. The proposed model was applied to analyze the stability of two tailing dams in China and the calculation results of the interval nonprobabilistic reliability are found to be in agreement with actual situations. Thus, the interval nonprobabilistic reliability is a beneficial complement to the traditional analysis method of random reliability.

Analysis of Dynamic Response of Landslide Stability to Reservoir Water Level Fluctuation Using Numerical Simulation

2012 ◽  
Vol 594-597 ◽  
pp. 407-414
Author(s):  
Wu Yi ◽  
Zhao Ping Meng ◽  
Guo Qing Li ◽  
Zhi Wei Jin
Keyword(s):  
Dynamic Response ◽  
Water Level ◽  
Water Level Fluctuation ◽  
Level Fluctuation ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Landslide Stability ◽  
Reservoir Drawdown ◽  
The Stability ◽  
Reservoir Water Level Fluctuation

Reservoir water level is one important factor influencing the stability of landslides. The dynamic response of landslide stability under reservoir water level function and its features are analyzed using theoretical and numerical methods. The results show that, in terms of reservoir water level fluctuation and landslide permeability, the seepage filed of landslide can be divided into four types: lag behind impoundment(X-Ⅰ), lag behind drawdown(T-Ⅰ), synchronization with impoundment(X-Ⅱ) and synchronization with drawdown (T-Ⅱ). Under lag behind drawdown, at a certain rate of reservoir drawdown, the stability drops with the permeability of landslide. Under lag behind impoundment, with the rise of water level, the lower the permeability of landslide is, the more stable the landslide is. Under synchronization with impoundment or drawdown, the stability of landslide drops with reservoir impoundment and rises with reservoir drawdown.

scholarly journals Application of Well Drainage on Treating Seepage-Induced Reservoir Landslides

2020 ◽  
Vol 17 (17) ◽  
pp. 6030 ◽  
Author(s):  
Zongxing Zou ◽  
Sha Lu ◽  
Fei Wang ◽  
Huiming Tang ◽  
Xinli Hu ◽  
...  
Keyword(s):  
Three Gorges Reservoir Area ◽  
Seepage Force ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Slide Mass ◽  
Landslide Stability ◽  
Water Head ◽  
Medium Permeability ◽  
Well Depth ◽  
The Stability

In the process of rapid drawdown of reservoir water level, the seepage force in the slide mass is an important factor for the stability reduction and deformation increment of many landslides in the reservoir areas. It is feasible to improve the stability of seepage-induced landslide by employing a drainage well to reduce or eliminate the water head difference that generates the seepage force. In this paper, the Shuping landslide, a typical seepage-induced landslide in the Three Gorges Reservoir area of China, is taken as an example. A series of numerical simulations were carried out to figure out the seepage field, and the Morgenstein–Price method was adopted to calculate the landslide stability. Then the influence of horizontal location of the drainage well, drainage well depth, drainage mode on the landslide treatment effect, and the applicability of drainage well were analyzed. The results show that: (1) landslide stability increases obviously with the well depth in the slide mass, while the increment of landslide stability with the well depth is limited in the slide bed; (2) the sensitivity of the stability improvement with the depth is greater than that with the horizontal positions of the drainage wells in the slide mass; (3) the drainage well is suggested to be operated when the reservoir water falls rather than operates all the time; and (4) the drainage method is most suitable for landslides with low and medium permeability. These results provide deep insights into the treatment of seepage-induced landslides.

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