Slope Stability Analysis based on Probabilistic Characteristics of Unsaturated Soil Properties of Weathered Granite Soil

Based on the FEM analysis of unsaturated slope seepage and strength of unsaturated soil, and adopted the assumption of rigid body limit equilibrium to calculate safe coefficient of landslides, a new slope stability analysis method is promoted and the calculation program called USSP is composed and verified. The method could consider the impact of rainfall and water change to slope stability. Compared with GeoSlope package, it is more practical in rainfall or variation of ground water level condition.

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Four-Year Monitoring Study of Shallow Landslide Hazards Based on Hydrological Measurements in a Weathered Granite Soil Slope in South Korea

Water ◽

10.3390/w13172330 ◽

2021 ◽

Vol 13 (17) ◽

pp. 2330

Author(s):

Kyeong-Su Kim ◽

Sueng-Won Jeong ◽

Young-Suk Song ◽

Minseok Kim ◽

Joon-Young Park

Keyword(s):

Slope Stability ◽

South Korea ◽

Shallow Landslide ◽

Soil Slope ◽

Weathered Granite ◽

Landslide Hazards ◽

Infinite Slope Stability Model ◽

Geological Conditions ◽

Weathered Granite Soil ◽

Granite Soil

To build a comprehensive understanding of long-term hydro-mechanical processes that lead to shallow landslide hazards, this study explicitly monitored the volumetric water content (VWC) and rainfall amount for a weathered granite soil slope over a four year period. From the 12 operational landslide monitoring stations installed across South Korea, the Songnisan station was selected as the study site. VWC sensors were placed in the subsurface with a grid-like arrangement at depths of 0.5 and 1.0 m. Shallow landslide hazards were evaluated by applying an infinite slope stability model that adopted a previously proposed unified effective stress concept. By analyzing the variations in the monitored VWC values, the derived matric suctions and suction stresses, and the calculated factor of safety values, we were able to obtain numerous valuable insights. In particular, the seasonal effects of drainage and evapotranspiration on the slope moisture conditions and slope stability were addressed. Preliminary test results indicated that continuous rainfall successfully represented the derived matric suction conditions at a depth of 1.0 m in the lower slope, although this was not the case for the upper and middle slopes. The significance of a future study on cumulative field monitoring data from various sites in different geological conditions is highlighted.

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Modeling the unsaturated soil zone in slope stability analysis

Canadian Geotechnical Journal ◽

10.1139/cgj-2013-0394 ◽

2014 ◽

Vol 51 (12) ◽

pp. 1384-1398 ◽

Cited By ~ 39

Author(s):

L. L. Zhang ◽

Delwyn G. Fredlund ◽

Murray D. Fredlund ◽

G. Ward Wilson

Keyword(s):

Shear Strength ◽

Stability Analysis ◽

Slope Stability ◽

Unsaturated Soil ◽

Unsaturated Soils ◽

Matric Suction ◽

Slope Stability Analysis ◽

Engineering Practice ◽

Rate Of Increase ◽

Nonlinear Shear

The linear form of the extended Mohr–Coulomb shear strength equation uses a [Formula: see text] parameter to quantify the rate of increase in shear strength relative to matric suction. When the [Formula: see text] value is unknown, a [Formula: see text] equal to 15° is sometimes used in the slope stability study to assess the influence of matric suction on the stability of a slope. In many cases, however, a [Formula: see text] value of zero is used, signifying that the effect of matric suction is ignored. Experiment results have shown that the relationship between the shear strength of an unsaturated soil and matric suction is nonlinear. Several semi-empirical estimation equations have been proposed relating the unsaturated shear strength to the soil-water characteristic curve. In this paper, the results of a study using two-dimensional slope stability analysis along with an estimated nonlinear shear strength equations is presented. The effects of using an estimated nonlinear shear strength equation for the unsaturated soils are illustrated using three example problems. Several recommendations are made for engineering practice based on the results of the example problems. If the air-entry value (AEV) of a soil is smaller than 1 kPa, the effect of matric suction on the calculated factor of safety is trivial and the [Formula: see text] value can be assumed to be zero. If the AEV of a soil is between 1 and 20 kPa, the nonlinear equations of unsaturated shear strength should be adopted. For soils with an AEV value between 20 and 200 kPa, an assumed [Formula: see text] value of 15° provides a reasonable estimation of the effects of unsaturated shear strength in most cases. For soils with an AEV greater than 200 kPa, [Formula: see text] can generally be assumed to be equal to the effective angle of internal friction, [Formula: see text], in applications where geotechnical structures have matric suctions around 100 kPa.

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