Analysis of the Impact of Reservoir Water Level Fluctuation on the Stability of Cohesive Colluvial Landslide in the Three Gorges Reservoir Area

Author(s):  
Qiang Li ◽  
Youlong Gao

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhaodan Cao ◽  
Jun Tang ◽  
Xiaoer Zhao ◽  
Yonggang Zhang ◽  
Bin Wang ◽  
...  

The stability of the reservoir bank landslide is affected by a variety of external factors, and the fluctuation of reservoir water level is one of the important influencing factors. The Erdaohe landslide is a typically colluvial landslide in the Three Gorges Reservoir area with periodic reservoir water level fluctuations. According to landslide displacement data, the displacement of the Erdaohe landslide exhibits the significantly stepwise feature. Its failure mechanism was analyzed using strength reduction method by the FLAC3D package in the case of reservoir water level changes. The results indicate that the hydrodynamic pressure has an important impact on the initialization of the landslide failure. When reservoir water level rises rapidly or maintains constant at the lower level, the landslide stability would be higher. When the reservoir water level decreases rapidly or maintains constant at the higher level, the landslide stability will be smaller. When the reservoir water level was in the lowest elevation, the factor of safety (FS) reached the minimum value of 1.11. Findings in this paper can provide guidelines for the risk assessment of colluvial landslides.



2021 ◽  
Author(s):  
Zhiqiang Fan ◽  
Yanhao Zheng

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.



Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Nenghao Zhao ◽  
Bin Hu ◽  
Qinglin Yi ◽  
Wenmin Yao ◽  
Chong Ma

Rainfall and reservoir level fluctuation are two of the main factors contributing to reservoir landslides. However, in China’s Three Gorges Reservoir Area, when the reservoir water level fluctuates significantly, it comes at a time of abundant rainfall, which makes it difficult to distinguish which factor dominates the deformation of the landslide. This study focuses on how rainfall and reservoir water level decline affect the seepage and displacement field of Baijiabao landslide spatially and temporally during drawdown of reservoir water level in the Three Gorges Reservoir Area, thus exploring its movement mechanism. The monitoring data of the landslide in the past 10 years were analyzed, and the correlation between rainfall, reservoir water level decline, and landslide displacement was clarified. By the numerical simulation method, the deformation evolution mechanism of this landslide during drawdown of reservoir water level was revealed, respectively, under three conditions, namely, rainfall, reservoir water level decline, and coupling of the above two conditions. The results showed that the deformation of the Baijiabao landslide was the coupling effect of rainfall and reservoir water level decline, while the latter effect is more pronounced.



2017 ◽  
Vol 54 (5) ◽  
pp. 631-645 ◽  
Author(s):  
Guanhua Sun ◽  
Yongtao Yang ◽  
Shengguo Cheng ◽  
Hong Zheng

Rainfall and reservoir water level fluctuations are the main external factors of landslides in the Three Gorges Reservoir area. To improve the analysis of slope stability under the combined effect of reservoir water level fluctuations and rainfall, a simplified method for phreatic line calculation of slopes is proposed in this study. Based on the obtained phreatic line, the expression of normal stress on the sliding surface of the slope under the hydrodynamic forces is deduced, and a global analysis method to solve the slope safety factor under hydrodynamic force is proposed. Finally, the safety evolution of a slope in the Three Gorges Reservoir area is studied under the combined effect of reservoir water level fluctuations and rainfall.



2020 ◽  
Vol 12 (16) ◽  
pp. 6427
Author(s):  
Chun Li ◽  
Huiming Tang ◽  
Yankun Wang

Reservoir water level fluctuation is one of the main extrinsic factors that could change the stress field in landslides, as well as the mechanical strength of geomaterials, hence affecting the deformation and stability of landslides. The largest reservoir landslide in the Three Gorges Reservoir area was selected for a case study. The impact of reservoir water level fluctuation is represented by the dynamic change in the underground seepage field and was thereby analyzed with numerical modeling. The deformation behavior considering the rheological properties of the slip zone soil was studied. The sudden change in the displacement–time curve was selected as the failure criterion for the investigated landslide. The evolution process of the accelerated deformation stage was divided into slow acceleration, fast acceleration, and rapid acceleration stages. The Huangtupo landslide is characterized by a retrogressive landslide and is currently in the creep deformation stage; the deformation mechanism and deformation characteristics are closely related to the reservoir water level fluctuation. Research was carried out by means of field investigation, in situ monitoring, and numerical simulation to provide a true and reliable result for stability evaluation.



2021 ◽  
Vol 13 (2) ◽  
pp. 224
Author(s):  
Xin Liang ◽  
Lei Gui ◽  
Wei Wang ◽  
Juan Du ◽  
Fei Ma ◽  
...  

Since the impoundment of the Three Gorges Reservoir (TGR) in June 2003, the fluctuation of the reservoir water level coupled with rainfall has resulted in more than 2500 landslides in this region. Among these instability problems, most colluvial landslides exhibit slow-moving patterns and pose a significant threat to local people and channel navigation. Advanced monitoring techniques are therefore implemented to investigate landslide deformation and provide insights for the subsequent countermeasures. In this study, the development pattern of a large colluvial landslide, locally named the Ganjingzi landslide, is analyzed on the basis of long-term monitoring. To understand the kinematic characteristics of the landslide, an integrated analysis based on real-time and multi-source monitoring, including the global navigation satellite system (GNSS), crackmeters, inclinometers, and piezometers, was conducted. The results indicate that the Ganjingzi landslide exhibits a time-variable response to the reservoir water fluctuation and rainfall. According to the supplement of community-based monitoring, the evolution of the landslide consists of three stages, namely the stable stage before reservoir impoundment, the initial movement stage of retrogressive failure, and the shallow movement stage with stepwise acceleration. The latter two stages are sensitive to the drawdown of reservoir water level and rainfall infiltration, respectively. All of the monitoring approaches used in this study are significant for understanding the time-variable pattern of colluvial landslides and are essential for landslide mechanism analysis and early warning for risk mitigation.



2014 ◽  
Vol 955-959 ◽  
pp. 3287-3294
Author(s):  
Zheng Wang ◽  
Ying Liu

To improve water quality and alleviate pollution in Changshou-Fuling section of the Three Gorges Reservoir Area, an analysis methodology of regional key discharge outlet based on hydrodynamic-water quality model was developed. The EFDC model was used to study the impact of different discharge outlets on the transport of contamination in the study area by using the concept of pollutant mixing zone and pollutant mixing zone per unit load. Model calibration was conducted using observed data in 2008. Results indicated that EFDC could perfectly simulate hydrodynamics characteristics and contaminant transport process. Calculated results of pollutant mixing zone per unit load showed that the discharge outlet location in Fuling is more reasonable than that in Changshou. This study provides useful information for optimization of discharge outlets location and prediction of pollutant mixing zone in the study area, which is important for the government to make water pollution control measures.





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