A transient analysis of slope stability following drawdown after flooding of a highly plastic clay

1999 ◽  
Vol 36 (6) ◽  
pp. 1151-1171 ◽  
Author(s):  
G J Pauls ◽  
E Karl Sauer ◽  
E A Christiansen ◽  
R A Widger
Keyword(s):  
Stability Analysis ◽  
Pore Water ◽  
Factor Of Safety ◽  
Field Measurements ◽  
Stability Of Slopes ◽  
Pore Water Pressures ◽  
Seepage Model ◽  
Transient Seepage ◽  
The Stability ◽  
Plastic Clays

The stability of slopes at bridge abutments across the Carrot River in east-central Saskatchewan was not influenced significantly by drawdown after flooding in the spring of 1995. Traditional methods of analysis for rapid drawdown predicted the factor of safety of slopes on highly plastic clays of proglacial Lake Agassiz would drop to 0.65 from an initial value of 1.0. Deformation along a well-defined slip plane has persisted at a more or less constant, slow rate since the bridge was constructed in 1975. The river rose approximately 10 m during a flood in the spring of 1995, yet there was only minimal response in piezometers and no measurable increase in the rate of deformation recorded by inclinometers. Pore-water pressures from a steady state seepage model, which was calibrated from piezometer measurements, were integrated into a stability analysis. Changes in pore-water pressures caused by flooding and subsequent drawdown were characterized from a transient seepage model using the flood hydrograph as a flux boundary. The stability analysis integrated with the transient seepage model estimated the factor of safety would drop from 1.0 to 0.91 after drawdown. Field measurements indicated the reduction in factor of safety was even less.

A new approach to the stability analysis of thawing slopes

1980 ◽  
Vol 17 (4) ◽  
pp. 607-612 ◽  
Author(s):  
Luis E. Vallejo
Keyword(s):  
Stability Analysis ◽  
Water Content ◽  
Pore Water ◽  
Active Layer ◽  
Necessary Conditions ◽  
Mass Movements ◽  
New Approach ◽  
Pore Water Pressures ◽  
The Stability ◽  
Excess Pore

A new approach to the stability analysis of thawing slopes at shallow depths, taking into consideration their structure (this being a mixture of hard crumbs of soil and a fluid matrix), is presented. The new approach explains shallow mass movements such as skin flows and tongues of bimodal flows, which usually take place on very low slope inclinations independently of excess pore water pressures or increased water content in the active layer, which are necessary conditions in the methods available to date to explain these movements.

An analysis of the stability of thawing slopes, Ellesmere Island, Nunavut, Canada

2000 ◽  
Vol 37 (2) ◽  
pp. 449-462 ◽  
Author(s):  
Charles Harris ◽  
Antoni G Lewkowicz
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Active Layer ◽  
Factor Of Safety ◽  
High Arctic ◽  
Ellesmere Island ◽  
Sensitivity Analyses ◽  
Pore Water Pressures ◽  
Hot Weather ◽  
The Stability

Active-layer detachment slides are locally common on Fosheim Peninsula, Ellesmere Island, where permafrost is continuous, the active layer is 0.5-0.75 m thick, and summer temperatures are unusually high in comparison with much of the Canadian High Arctic. In this paper we report pore-water pressures at the base of the active layer, recorded in situ on two slopes in late July and early August 1995. These data form the basis for slope stability analyses based on effective stress conditions. During fieldwork, the factor of safety within an old detachment slide on a slope at Hot Weather Creek was slightly greater than unity. At "Big Slide Creek," on a slope showing no evidence of earlier detachment failures, the factor of safety was less than unity on a steep basal slope section but greater than unity elsewhere. In the upper slope, pore-water pressures were only just subcritical. Sensitivity analyses demonstrate that the stability of the shallow active layer is strongly influenced by changes in soil shear strength. Possible mechanisms for reduction in shear strength through time include weathering of soils and gradual increases in basal active layer ice content. However, we suggest here that soil shearing during annual gelifluction movements is most likely to progressively reduce shear strengths at the base of the active layer from peak values to close to residual, facilitating the triggering of active-layer detachment failures.Key words: detachment slides, Ellesmere Island, pore-water pressures, gelifluction.

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.

Infiltration characteristics of two instrumented residual soil slopes

2003 ◽  
Vol 40 (5) ◽  
pp. 1012-1032 ◽  
Author(s):  
Illias Tsaparas ◽  
Harianto Rahardjo ◽  
David G Toll ◽  
Eng-Choon Leong
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Field Measurements ◽  
Residual Soil ◽  
Rainfall Runoff ◽  
Rainfall Events ◽  
Pore Water Pressures ◽  
Soil Slopes ◽  
Pressure Changes

This paper presents the analysis of a 12 month long field study of the infiltration characteristics of two residual soil slopes in Singapore. The field measurements consist of rainfall data, runoff data of natural and simulated rainfall events, and pore-water pressure changes during infiltration at several depths and at several locations on the two slopes. The analysis of the field measurements identifies the total rainfall and the initial pore-water pressures within the two slopes as the controlling parameters for the changes in the pore-water pressures within the slopes during infiltration.Key words: infiltration, rainfall, runoff, pore-water pressure, field measurements.

Field measurement of anchor forces, ground temperatures, and pore-water pressures behind a retaining structure in northwestern Ontario

1992 ◽  
Vol 29 (1) ◽  
pp. 112-116
Author(s):  
K. D. Eigenbrod ◽  
J. P. Burak
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Retaining Wall ◽  
Field Measurements ◽  
Strain Gauges ◽  
Ground Temperatures ◽  
Northwestern Ontario ◽  
Pore Water Pressures ◽  
Load Increase

Anchor forces, ground temperatures, and piezometric pressures were measured at a retaining wall in northwestern Ontario over a period of 2 years. The anchor forces were measured with strain gauges attached in pairs directly to the anchor rods. This method appeared practical in the field for time periods of less than 2 years as long as the strain gauges were carefully protected against moisture. The anchor forces increased from an average of 5 kN initially up to values of 50 kN during the winter periods and dropped during the summer periods back to the same values measured initially. The anchor forces were largely independent of pore-water pressure variations behind the wall. Rapid drawdown conditions, however, which were experienced during the second summer, were reflected in a load increase that was equivalent to the associated unloading effect in front of the wall. The pore-water pressures behind the wall were not noticeably affected by rapid drawdown, possibly due to the restraining effect of the anchors and the high rigidity of the low sheet pile wall. Ground temperatures at or below the groundwater table never dropped below 0 °C thus restricting the depth of frost penetration. Key words : anchor loads, freezing pressure, retaining walls, pore-water pressures, ground temperatures, field measurements.

Unsaturated Seepage and Fluid-Solid Coupling Analysis of Rainfall Infiltration of Slope

2011 ◽  
Vol 255-260 ◽  
pp. 3488-3492
Author(s):  
Bao Lin Xiong ◽  
Jing Song Tang ◽  
Chun Jiao Lu
Keyword(s):  
Pore Water ◽  
Unsaturated Flow ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Rainfall Infiltration ◽  
Medium Permeability ◽  
Stability Of Slope ◽  
Transient Seepage ◽  
The Stability ◽  
Unsaturated Seepage

Rainfall is one of the main factors that influence the stability of slope. Rainfall infiltration will cause soil saturation changing and further influence pore water pressure and medium permeability coefficient. Based on porous media saturation-unsaturated flow theory, the slope transient seepage field is simulated under the conditions of rainfall infiltration. It is shown that change of pore water pressure in slope soil lag behind relative changes in rainfall conditions. As the rainfall infiltrate, unsaturated zone in top half of slope become diminution, the soil suction and shear strength reduce, so stabilization of soil slope is reduced.

Approaches to the study of hillslope development due to mass movement

1993 ◽  
Vol 17 (1) ◽  
pp. 32-49 ◽  
Author(s):  
S.M. Brooks ◽  
K.S. Richards ◽  
M.G. Anderson
Keyword(s):  
Internal Friction ◽  
Pore Water ◽  
Water Table ◽  
Soil Cover ◽  
Slip Surface ◽  
Mass Movement ◽  
Slope Angle ◽  
Geological Time ◽  
Stability Of Slopes ◽  
Pore Water Pressures

Slope-angle histograms have traditionally provided a data base for the evaluation of changing angles over geological time. Ideas relating to hillslope development due to mass movement have considered a lowering in regolith shear resistance due to weathering, producing slope-angle decline. Decreasing values for angles of internal friction, along with increasing pore water pressures, have been suggested to explain slope-angle decline through time. These ideas have considered simple changes in undifferentiated regolith. This article considers the role of progressive pedogenesis in determining the changing stability of slopes. For this it is necessary to evaluate the changes which occur within individual horizons to produce an increasingly differentiated soil cover. Angles of internal friction alter at different rates and in different ways depending on whether the horizon is losing or gaining weathered material through translocation. Furthermore, the increasing internal differentiation of the soil cover has complex effects on its hydrological response. Instead of the two scenarios previously envisaged, one involving the water table below the slip surface and the other involving the water table at the ground surface, slope stability needs to be evaluated in the light of continually changing negative or positive pore water pressures. Each storm produces a different response, and this response alters with soil development, complicating the assessment of failure timing and depth. The study of evolving soil profiles is of fundamental significance to a range of geomorphological processes, requiring closer evaluation in the future.

Influence of the groundwater on the stability of a clay bank in Baie James, Québec

1985 ◽  
Vol 22 (3) ◽  
pp. 409-413
Author(s):  
Peter Rosenberg ◽  
Jacques Provençal ◽  
Guy Lefebvre ◽  
J.-Jacques Paré
Keyword(s):  
Pore Pressure ◽  
Factor Of Safety ◽  
Field Measurements ◽  
Failure Surface ◽  
Surface Failure ◽  
Failure Morphology ◽  
Critical Failure Surface ◽  
Groundwater Regime ◽  
The Stability ◽  
River Banks

The Rivière Broadback in northern Québec flows westward almost parallel to latitude 51 °N to discharge into Baie James at its southern end. Near the estuary the river banks are in clay. Surveys of the landsliding activity showed that many of the slides are superficial, with depths seldom greater than about 2 m, and are usually in the clay crust.Instrumentation revealed regional groundwater pattern close to the river banks that showed areas varying from those with significant underdrainage to those with hydrostatic pressure conditions. The stability of 26 m high river slopes inclined at 27° in an area of underdrainage was investigated.Triaxial testing on undisturbed tube samples was used to obtain the postpeak parameters. Stability analyses gave a factor of safety close to one for shallow failure surfaces. With underdrainage, the factor of safety for deep failure surfaces is appreciably higher. When hydrostatic pore pressure conditions are assumed, analysis gave a factor of safety for deep failure that was reduced by about 30%.The results of the analyses emphasize the relation between the morphology of the landslide activity and the groundwater regime. With underdrainage, effective stresses increase much faster with depth and the critical failure surface is always close to the surface, as confirmed by field observations. Key words: natural slope, clay, pore pressure, field measurements, stability failure surface, failure morphology.

Stability Analysis of a 3D Vertical Slope with Transverse Earthquake Load and Surcharge

2011 ◽  
Vol 90-93 ◽  
pp. 676-679 ◽  
Author(s):  
Ting Kai Nian ◽  
Ke Li Zhang ◽  
Run Qiu Huang ◽  
Guang Qi Chen
Keyword(s):  
Finite Element ◽  
Stability Analysis ◽  
Failure Mode ◽  
Factor Of Safety ◽  
Three Dimensional ◽  
Strength Reduction ◽  
Reduction Procedure ◽  
Interesting Issue ◽  
Earthquake Load ◽  
The Stability

The stability and failure mode for a 3D vertical slope with transverse earthquake load and surcharge have been an interesting issue, especially in building excavation and wharf engineering. In order to further reveal the seismic and surcharge effect, a three-dimensional elasto-plastic finite element(FE) code combined with a strength reduction procedure is used to yield a factor of safety and failure mode for a vertical slopes under two horizontal direction pseudo-static(PS) coefficient and surcharge on the slope top, respectively. Comparative studies are carried out to investigate the effect of seismic coefficient, surcharge intensity and location on the stability and the failure mechanism for a 3D vertical slope including an inclined weak layer. Several important findings are also achieved.

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