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| Critical deformation velocity of landslides in different deformation phases |
| LI Cong，ZHU Jiebing，WANG Bin，JIANG Yuzhou，LIU Xiaohong，ZENG Ping |
| (Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources，Yangtze River Scientific Research Institute，Wuhan，Hubei 430010，China) |
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Abstract Prediction and early warning is one of the difficult issues of landslide. Currently，no enough attention was paid to the elapsed time and the critical deformation velocity of landslides in different deformation phases. In order to further explore the warning criterion of deformation velocity of landslides，the process of landslide was divided into four phases including an initial deformation phase，a uniform deformation phase，and an accelerated deformation phase and a sharp deformation phase. The landslide database was studied with the statistical method. The accelerated deformation phase lasted from 18 days to 1 080 days，and the elapsed time of nearly half of the landslides was within 30 days to 90 days. The sharp deformation phase of majority landslides lasted less than 30 days. The elapsed time of landslides in different deformation phases related to the failure mode，the landslide volume and the sliding surface type. The elapsed time and the sliding surface type are most closely related. When the slip surface is a rigid structure，the acceleration and sharp deformation phases are shorter. When the slip surface is a weak bedding surface，the acceleration and sharp deformation phases are longer. In the acceleration deformation phase，the maximum width of crack is 1–50 cm. In the sharp deformation phase，the maximum width of crack is 4–126 cm. The cracks of soil landslide and talus slide are wider，and the crack of rock landslide is relatively narrow. The critical deformation velocity of landslide entering into the sharp deformation phase is not more than 50 mm/d. The threshold of toppling landslide is relatively large，and the threshold of landslide with the weak sliding surface is larger than the landslide with rigid sliding surface. The critical deformation velocities of various landslides entering into the acceleration deformation phase are not large which are closely related to the failure mode. The threshold of sliding landslide is basically no more than 4 mm/d，and the threshold of toppling landslide or collapse landslide is slightly larger，generally larger than 4 mm/d.
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2016, Vol. 35 
