Vol17 No.5: 1128-1142
【Title】Formation mechanism of a rainfall triggered complex landslide in southwest China
【Author】HUANG Qiu-xiang1,2*; XU Xiang-tao1; P.H.S.W. KULATILAKE2,3; LIN Feng1
【Addresses】1 State Key Lab of Geohazard Preventionand Environment Protection (SKLGP), Chengdu University of Technology (CDUT) ，Chengdu 610059, China; 2 Rock Mass Modeling and Computational Rock Mechanics Laboratories, University of Arizona, Tucson, AZ 85721, USA; 3 School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China
【Corresponding author】HUANG Qiu-xiang
【Citation】Huang QX, Xu XT, Kulatilake PHSW, Lin F (2020)Formation mechanism of a rainfall triggered complex landslide in southwest China. Journal of Mountain Science 17(5). https://doi.org/10.1007/s11629-019-5736-9
【Abstract】This case study is about a landslide that occurred after 4 days of heavy rainfall, in the morning of June 29, 2012, in Cengong County, Guizhou Province of China, geographical coordinated 108°20′-109°03′E, 27°09′-27°32′N, with an estimated volume of 3.3×106 m3. To fully investigate the landslide process and formation mechanism, detailed geotechnical and geophysical investigations were performed including borehole drilling, sampling, and laboratory testscoupled with monitoring of displacement. Also, a combined seepage-slope stability modeling was performed to study the behavior of the landslide. After the heavy rainfall event, the sliding process started in this area. The landslide development can be divided into different parts. The man-made fill area, spatially distributed in the south side of the landslide area with low elevations, slid first along the interface between the slope debris and the strongly weathered bedrock roughly in the EW direction. Consequently, due to severe lateral shear disturbance, the slope in the main sliding zone slid next towards the SW direction, along the sliding surface developed within the strongly weathered calcareous shale formation located at a depth of 25-35 m. This means it was a rainfall triggered deep-seated landslide. Finally, retrogressive failure of a number of upstream blocks occurred, which moved in more than one direction. The initial failure of the man-made fill area was the ‘engine' of the whole instability framework. This artificial material with low permeability, piled up in the accumulation area of surface and sub-surface and destroyed the drainage capacity of the groundwater. The numerical modeling results agreed with the analysis results obtained from the laboratory and field investigations. A conceptual model is given to illustrate the formation mechanism and development process of the landslide.
【Keywords】Complex landslide; Man-made fill; Shale formation; Lateral shear failure; Conceptual model