scholarly journals Infiltration, seepage and slope instability mechanisms during the 20–21 November 2000 rainstorm in Tuscany, central Italy

2006 ◽  
Vol 6 (6) ◽  
pp. 1025-1033 ◽  
Author(s):  
V. Tofani ◽  
S. Dapporto ◽  
P. Vannocci ◽  
N. Casagli
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Factor Of Safety ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Critical Time ◽  
Infiltration Rate ◽  
Slope Instability ◽  
Storm Event ◽  
Surface Boundary

Abstract. On 20–21 November 2000, a storm of high intensity, with a estimated return period of more than 100 years, triggered over 50 landslides within the province of Pistoia in Tuscany (Italy). These failures can be defined as complex earth slides- earth flows. One of the documented landslides has been investigated by modelling the ground water infiltration process, the positive and negative pore water pressure variations and the effects of these variations on slope stability during the rainfall event. Morphometric and geotechnical analyses were carried out through a series of in-situ and laboratory tests, the results of which were used as input for the modelling process. The surface infiltration rate was initially simulated using the rainfall recorded at the nearest raingauge station. Finite element seepage analysis for transient conditions were then employed to model the changes in pore water pressure during the storm event, using the computed infiltration rate as the ground surface boundary condition. Finally, the limit equilibrium slope stability method was applied to calculate the variations in the factor of safety during the event and thereby determine the critical time of instability. For the investigated site the trend of the factor of safety indicates that the critical time for failure occurs about 18 h after the storm commences, and highlights the key role played by the soil permeability and thickness in controlling the response in terms of slope instability.

scholarly journals Analysis of infiltration, seepage processes and slope instability mechanisms during the November 2000 storm event in Tuscany

2005 ◽  
Vol 2 ◽  
pp. 301-304
Author(s):  
V. Tofani ◽  
S. Dapporto ◽  
P. Vannocci ◽  
N. Casagli
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Factor Of Safety ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Critical Time ◽  
Infiltration Rate ◽  
Slope Instability ◽  
Storm Event ◽  
Surface Boundary

Abstract. On the days 20-21 November 2000, a storm of exceptional intensity triggered over 50 landslides within the province of Pistoia in Tuscany (Italy). These failures are mostly of complex type, originating as rotational or translational landslides, and transforming into flows. Two of these landslides were investigated in this paper by modelling the ground water infiltration process, the pore water pressure variations, both positive and negative, and the effects of these variations on slope stability during the rainfall event. Morphometric and geotechnical analyses were carried out for both sites through a series of in-situ and laboratory tests, the results of which were used as input for the modelling process. In a first step the surface infiltration rate was simulated using a modified Chu (1978) approach for the Green and Ampt (1911) equations in case of unsteady rainfall together with a surficial water balance. A finite element seepage analysis for transient conditions was then employed to model the changes in pore water pressure during the event, using the computed infiltration rate as the ground surface boundary condition. Finally, once again using the data from the previous step as input, the limit equilibrium Morgenstern-Price (1965) slope stability method was applied to calculate the variations in the factor of safety during the event and thereby determine the most critical time of instability. In both sites this method produced a curve for the factor of safety that indicated that the most critical time for failure occurred a few hours after the peak of rainfall.

scholarly journals Analysis of plant root–induced preferential flow and pore-water pressure variation by a dual-permeability model

2017 ◽  
Vol 54 (11) ◽  
pp. 1537-1552 ◽  
Author(s):  
Wei Shao ◽  
Junjun Ni ◽  
Anthony Kwan Leung ◽  
Ye Su ◽  
Charles Wang Wai Ng
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Factor Of Safety ◽  
Preferential Flow ◽  
Pore Water Pressure ◽  
Plant Root ◽  
Water Pressure ◽  
Planting Density ◽  
Permeability Model ◽  
The Impact

Vegetation can affect slope hydrology and stability via plant transpiration and induced matric suction. Previous work suggested that the presence of plant roots would induce preferential flow, and its effects may be more significant when the planting density is high. However, there is a lack of numerical studies on how planting density affects soil pore-water pressure and shear strength during heavy rainfall. This study aims to investigate the impact of plant root–induced preferential flow on hydromechanical processes of vegetated soils under different planting densities. Two modelling approaches, namely single- and dual-permeability models, were integrated with an infinite slope stability approach to simulate pore-water pressure dynamics and slope stability. Laboratory tests on soils with two different planting densities for a plant species, Schefflera heptaphylla, were conducted for numerical simulations. The single-permeability model overestimated the pore-water pressure in shallow soil and underestimated the infiltration depth. The dual-permeability model, which is able to model the effects of preferential flow, can better capture the observations of rapid increase of pore-water pressure and deeper pressure response in the vegetated soil. However, caution should be taken on the choice of pore-water pressure when using the dual-permeability model to assess the factor of safety. The dual-permeability model using the pore-water pressure in the preferential flow domain and that in the matrix domain would result in a lower and higher factor of safety, respectively.

scholarly journals Rainfall-induced landslides in the residual soil of andesitic terrain, western Japan

2011 ◽  
Vol 42 ◽  
pp. 137-152
Author(s):  
Ranjan Kumar Dahal ◽  
Shuichi Hasegawa ◽  
Minoru Yamanaka ◽  
Netra Prakash Bhandary
Keyword(s):  
Stability Analysis ◽  
Moisture Content ◽  
Slope Stability ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Slope Stability Analysis ◽  
Surface Boundary ◽  
Residual Soil ◽  
Western Japan

Rainfall triggered landslides are frequent problems in the residual soil of andesitic terrain in western Japan. Characteristics of residual soils over bronzite andesite, procedure of in situ permeability measurement, matric suction and soil moisture content change and stability analyses considering unsaturated-saturated soils as integral system are presented in this paper. The paper highlights two landslides of small andesitic hillock of western Japan and describes modelling of rainwater seepage, slope stability analysis and contributing parameters for landsliding in andesitic terrain. For both landslides, results of geomorphological and geotechnical analyses were used as a direct input to the numerical modelling. For transient conditions, a finite element analysis was used to model the fluctuations in pore water pressure during the rainfall, with the computed hourly rainfall rate as the surface boundary condition. This was then followed by the slope stability analysis using the temporal pore water pressure distributions derived from the seepage analysis. Obtained trend for the factor of safety indicates that the most critical time step for failure was a few hours following the antecedent moisture content of previously day peak rainfall. Time of failure estimated by modelling has shown good match with time declared by eyewitnesses.

scholarly journals The Effect of Bedrock Topography on Timing and Location of Landslide Initiation Using the Local Factor of Safety Concept

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1290 ◽  
Author(s):  
Shirin Moradi ◽  
Johan Huisman ◽  
Holger Class ◽  
Harry Vereecken
Keyword(s):  
Slope Stability ◽  
Water Flow ◽  
Pore Water ◽  
Factor Of Safety ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Subsurface Water ◽  
Local Factor ◽  
Bedrock Topography ◽  
2D And 3D

Bedrock topography is known to affect subsurface water flow and thus the spatial distribution of pore water pressure, which is a key factor for determining slope stability. Therefore, the aim of this study is to investigate the effect of bedrock topography on the timing and location of landslide initiation using 2D and 3D simulations with a hydromechanical model and the Local Factor of Safety (LFS) method. A set of synthetic modeling experiments was performed where water flow and slope stability were simulated for 2D and 3D slopes with layers of variable thickness and hydraulic parameters. In particular, the spatial and temporal development of water content, pore water pressure, and the resulting LFS were analyzed. The results showed that the consideration of variable bedrock topography can have a significant effect on slope stability and that this effect is highly dependent on the intensity of the event rainfall. In addition, it was found that the consideration of 3D water flow may either increase or decrease the predicted stability depending on how bedrock topography affected the redistribution of infiltrated water.

scholarly journals Characteristics of Rainfall-Induced Slope Instability in Cisokan Region, Indonesia

2021 ◽  
Vol 53 (5) ◽  
pp. 210504
Author(s):  
Sugeng Krisnanto ◽  
Harianto Rahardjo
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Groundwater Level ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Matric Suction ◽  
Slope Instability ◽  
Access Road ◽  
Level Increase ◽  
Long Access

A 25.5 km long access road has been constructed in a hilly area in Cisokan region. Several slope instabilities occurred during the rainy season, particularly at the end of heavy rainfall. A comprehensive study was performed to understand the characteristics of rainfall-induced slope instability. The study consisted of field observation, analyses of field and laboratory test data, and numerical analyses. The study revealed that in general there were two categories of slopes with instability characteristics: (i) slopes with a significant groundwater level increase during rainfall; (ii) slopes with an insignificant groundwater level increase during rainfall. In the first category, the slope instability was caused by a loss of matric suction and eventually the pore-water pressure, uw became positive as indicated by an increase of the groundwater level. In the second category, the slope instability was caused by a loss of matric suction without a rise in pore-water pressure, uw, to a positive magnitude. Two empirical curves of slope stability were developed as a preliminary guidance to assess slope stability during rainfall in the region.

scholarly journals Integrated Simulation Modeling Approach for Investigating Pore Water Pressure Induced Landslides

2022 ◽  
Author(s):  
Sahila Beegum ◽  
P J Jainet ◽  
Dawn Emil ◽  
K P Sudheer ◽  
Saurav Das
Keyword(s):  
Pore Water ◽  
Factor Of Safety ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Simulation Models ◽  
Integrated Simulation ◽  
Hill Slope ◽  
Slope Factor ◽  
The Stability ◽  
The Hill

Abstract Soil pore water pressure analysis is crucial for understanding landslide initiation and prediction. However, field-scale transient pore water pressure measurements are complex. This study investigates the integrated application of simulation models (HYDRUS-2D/3D and GeoStudio–Slope/W) to analyze pore water pressure-induced landslides. The proposed methodology is illustrated and validated using a case study (landslide in India, 2018). Model simulated pore water pressure was correlated with the stability of hillslope, and simulation results were found to be co-aligned with the actual landslide that occurred in 2018. Simulations were carried out for natural and modified hill slope geometry in the study area. The volume of water in the hill slope, temporal and spatial evolution of pore water pressure, and factor of safety were analysed. Results indicated higher stability in natural hillslope (factor of safety of 1.243) compared to modified hill slope (factor of safety of 0.946) despite a higher pore water pressure in the natural hillslope. The study demonstrates the integrated applicability of the physics-based models in analyzing the stability of hill slopes under varying pore water pressure and hill slope geometry and its accuracy in predicting future landslides.

Study on Slope Instability Disciplinarian on the Condition of Rainfall

2013 ◽  
Vol 353-356 ◽  
pp. 654-658
Author(s):  
Nan Tong Zhang ◽  
Xiao Chun Zhang ◽  
Hua Rong Wang ◽  
Chen Yan
Keyword(s):  
Slope Stability ◽  
Tensile Stress ◽  
Rainfall Intensity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Road Construction ◽  
Slope Instability ◽  
Slope Surface ◽  
Large Area ◽  
Break Zone

Slope stability is one of the problems of road construction which should be faced with and solve. Rainfall can reduce the shear strength of slope soil and raise the underground water level which can lead to increase slope soil pore water pressure. The influence of rainfall infiltration on slop is mainly to change the slope seepage field, increase dynamic and hydrostatic water load on the slope soil and decrease of soil shear parameters. More abundant rainfall of typhoon area could make the road slope stability more fragile. Based on Matoushan Mountain along 104 state roads in Taizhou city, Zhejiang province, slope instability disciplinarian on the condition of rainfall is studied using the method of numerical simulation in this paper. As the results, when the rainfall intensity was 0.006 m/h and continuous rain was in 24 hours, the slope surface compressive stress tends to zero which began to appear tensile stress area on the condition of self-weight. And when the rainfall intensity was 0.01 m/h and continuous rain was in 24 hours, the large area of the slope surface was tensile stress area which means to appear break zone in slope surface and likely to landslide at the same time.

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