Numerical simulation of Qiaotou Landslide deformation caused by drawdown of the Three Gorges Reservoir,China |
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Authors: | Jiwei Jiang Dominik Ehret Wei Xiang Joachim Rohn Ling Huang Shaojun Yan Renneng Bi |
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Institution: | (1) Faculty of Engineering, China University of Geosciences, Wuhan, 430074, Hubei, China;(2) Department of Applied Geology, University of Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany |
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Abstract: | Landslides located beside reservoirs tend to be unstable or are characterized by large deformation during the drawdown process.
This has been accepted by many experts. In this paper, we use Qiaotou Landslide, which is located beside the Three Gorges
Reservoir (TGR), as a typical case study to investigate and predict the deformation mechanism during the drawdown process
of TGR in detail. According to field investigation, the landslide mass is mainly composed of thick, loose silt and clay mixed
with fragments of rock. Bedrock is mainly composed of silty sandstone. Field and laboratory tests indicate that the landslide
mass has a high permeability coefficient. If the water level declines fast, intense seepage force may result. Based on these
data, we establish a three-dimensional geological model of Qiaotou Landslide by FLAC3D and perform a numerical simulation using the saturated–unsaturated fluid–solid coupling theory. For the simulation, we assume
that the drawdown from 175 to 145 m takes place with a speed of 25 cm/day, which is based on the extreme water level regulation
program of TGR. The simulation shows that this causes a significant deformation in the landslide mass and that the maximum
displacement within the landslide is 24.2 cm. During the drawdown process, the maximum displacement zone is shifting from
the upper part of the landslide where bedrock surface is steeper and thickness of loose deposits is less to the middle part
of the landslide where bedrock surface is less steep and thickness of loose deposits is higher. The deformation mechanism
indicates that in the early stage of the drawdown the deformation of the landslide mass is mainly caused by seepage and in
the later stage mainly by consolidation. |
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