Material Weakening of Slip Zone Soils Induced by Water Level Fluctuation in the Ancient Landslides of Three Gorges Reservoir

Abstract

This experimental study investigated the effect of repeated wetting and drying on the reduction of slip zone soils taken from the Huangtupo landslide in the Three Gorges Reservoir, China. The variation process of the physical property and substance composition of the slip zone soils under the wetting-drying cycles was studied through liquid and plastic limit test and X-ray diffraction test. The results indicate that (1) the shearing strength of the slip zone soil dramatically decreased after one wettingdrying cycle and then gradually decreased until reaching a relatively stable state at the fourth cycle; (2) the plasticity index of the slip zone soil varied with increasing number of cycles and a variation process opposite to that of the strength value was observed; and (3) the clay mineral content in the slip zone soil increased and the calcite and quartz contents relatively decreased with increasing number of cycles. The variations in the plasticity index of the slip zone soil, as well as the increase in its clay mineral content, play important roles in the strength reduction. The results of this study provide a foundation for revealing the deformation and damage mechanism of landslides in reservoir banks.

Using wavelet tools to analyse seasonal variations from InSAR time-series data: a case study of the Huangtupo landslide

“…Because rainfall is a well-known triggering factor of landslides (Bittelli, et al 2012, He, et al 2008, He, et al 2010, Jiang, et al 2011, Jiao, et al 2014, Wen and Chen 2007, (Jiang, et al 2011), this section assesses the relationship between rainfall and the Huangtupo slope displacements through XWT and WTC analysis. The plots for the four different slumping masses are shown in Figure 7.…”

“…Water can act in several ways: (a) reducing shear strength of the weak zones due to the physical and chemical interactions between the slip zones' materials and groundwater (He et al 2008, He et al 2010, Jiao et al 2014, Wen and Chen 2007 or due to pore pressure increase (i.e. a rise in pore-water pressure causes a drop in effective stress reducing the shear strength of a slope); (b) increasing the hydraulic gradient and seepage force of a landslide mass during water level lowering (Jiang et al 2011); (c) reducing soil suction (Bittelli et al 2012, Cascini et al 2014; (d) increasing soil unit weight; and/or (e) causing soil consolidation-swelling due to the changes of effective stresses on the landslide mass (Jiang, et al 2011).…”

Seepage, Deformation, and Stability Analysis of Sandy and Clay Slopes with Different Permeability Anisotropy Characteristics Affected by Reservoir Water Level Fluctuations

“…Huang et al [21] analyzed and discussed the seepage and stability characteristics of a slope with different soil permeability. However, the seepage variation under reservoir water drawdown is a typical saturated-unsaturated process; the reservoir water not only has static water pressure and buoyancy effect on slope soil [22][23][24][25] but also causes matrix suction change, dynamic water pressure, and excess pore water pressure [26][27][28][29][30][31]. The altering of pore water pressure caused by the flow of fluid in unsaturated soil and external water load changes the effective stress and seepage force, which means the stress distribution inside the soil changes, which causes the deformation and meanwhile causes a change of seepage.…”

Residual-state creep of clastic soil in a reactivated slow-moving landslide in the Three Gorges Reservoir Region, China

“…Previous studies conducted on the Huangtupo landslide, focus on subjects such as its soil properties (Jiao et al 2014;Wang et al 2012), stability (Cojean and Caï 2011), formation mechanisms (Deng et al 2000), triggering factors , and kinematic features (Tang et al 2015b;Tomás et al 2014). Despite these detailed investigations, landslide movement under various hydraulic boundary conditions represents one of the most pressing concerns for slope failure prevention and control.…”