Effect of soil suction on slope stability at Notch Hill

1989 ◽  
Vol 26 (2) ◽  
pp. 269-278 ◽  
Author(s):  
J. Krahn ◽  
D. G. Fredlund ◽  
M. J. Klassen
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Friction Angle ◽  
Soil Suction ◽  
Test Results ◽  
Surface Slope ◽  
Near Surface ◽  
Frictional Strength ◽  
Pore Water Pressures ◽  
Flat Ground

The side slopes of a railway embankment in central British Columbia, constructed with local lacustrine silt, on relatively flat ground, began to fail several years after construction. Shallow instability ultimately developed on both sides of the embankment over a distance of several kilometres. Initially, the soil had a significant apparent cohesive strength. With time, the strength appeared to diminish owing to the dissipation of negative pore-water pressures. The remaining frictional strength was not sufficient to maintain stability, since the slopes were constructed at angles close to the peak effective friction angle of the soil. This case history, together with the laboratory saturated and unsaturated strength test results and field suction measurements, demonstrates the dramatic effect of negative pore-water pressures on near-surface slope stability. Key words: soil suction, slope stability, nonsaturated soils, shear resistance, tensiometers.

scholarly journals Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

1986 ◽  
Vol 32 (110) ◽  
pp. 20-30 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Pore Water ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Friction Angle ◽  
Water Channels ◽  
Water Drainage ◽  
Short Term ◽  
Overburden Pressure ◽  
Melt Water ◽  
Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tan ϕ, where ϕ is the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such as h(x) = 3x1/2 (m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well below h(x) = 3x1/2.

scholarly journals Sensitivity Analysis of Factors Affecting Time-Dependent Slope Stability under Freeze-Thaw Cycles

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Zhiguo Chang ◽  
Qingxiang Cai ◽  
Li Ma ◽  
Liu Han
Keyword(s):  
Internal Friction ◽  
Slope Stability ◽  
Mass Density ◽  
Control Variable ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Open Pit ◽  
Test Results ◽  
Factors Affecting ◽  
Freeze Thaw

With open-pit mines excavated, the slopes will be exposed to the natural environment for a long time. Affected by factors like temperature, seepage, mining, freeze-thaw, etc., slope structural integrity and strength will gradually decline as slope exposure time extends. Besides, the development of defect structure within the rocks is closely correlated with time. In this paper, freeze-thaw cycle tests were conducted on the saturated sandstones collected from a certain open-pit mine. According to the test results, the mass density and longitudinal wave velocity gradually increased with more times of freeze-thaw cycles while mechanical properties such as internal friction angle, cohesion, elastic modulus, and uniaxial compressive strength decreased instead. The constitutive model of saturated rock deterioration was established by taking the volume of phase transition of water in microcracks as a variable. Based on the tests results and theoretical analysis, the sensitivity of the factors affecting slope stability under freeze-thaw damage was studied by Control Variable Method (CVM) and Orthogonal Design Method (ODM). It was determined that the internal friction angle and cohesion had a highly significant effect on the test results, while the mass density had a significant effect. The conclusions may play a certain role in guiding slope construction and protection.

Pore water pressures and slope stability: a joint geophysical and geotechnical analysis

2008 ◽  
Vol 5 (3) ◽  
pp. 323-337 ◽  
Author(s):  
Angela Perrone ◽  
Roberto Vassallo ◽  
Vincenzo Lapenna ◽  
Caterina Di Maio
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Pore Water Pressures

Thaw–Consolidation Tests on Undisturbed Fine-grained Permafrost

1974 ◽  
Vol 11 (1) ◽  
pp. 202-214 ◽  
Author(s):  
J. F. Nixon ◽  
N. R. Morgenstern
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Surface Temperature ◽  
Pore Water ◽  
Excellent Agreement ◽  
Test Results ◽  
Fine Grained ◽  
Arctic Soils ◽  
Thaw Consolidation ◽  
Pore Water Pressures

A series of thaw–consolidation tests on undisturbed frozen samples of Arctic soils is described. The tests were carried out in a special oedometer, and thawing was induced by the application of a sudden constant increase in surface temperature. Settlements, pore water pressures, and rates of thaw are measured, and interpreted in the light of current theories of heat transfer and thaw–consolidation. Excellent agreement is obtained between predicted and observed thaw rates, using published thermal properties. The observed pore pressures and settlements also are consistent with predicted behavior.These test results on a variety of undisturbed permafrost samples increase the level of confidence when applying the theory of consolidation for thawing soils to natural permafrost deposits.

scholarly journals Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

1986 ◽  
Vol 32 (110) ◽  
pp. 20-30 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Pore Water ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Friction Angle ◽  
Water Channels ◽  
Water Drainage ◽  
Short Term ◽  
Overburden Pressure ◽  
Melt Water ◽  
Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tanϕ, whereϕis the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such ash(x) = 3x1/2(m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well belowh(x) = 3x1/2.

scholarly journals Influences of Pore-Water Pressure on Slope Stability considering Strength Nonlinearity

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Di Wu ◽  
Yuke Wang ◽  
Fei Zhang ◽  
Yue Qiu
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Coefficient ◽  
Stability Evaluation ◽  
Slip Surfaces ◽  
Stability Of Slopes ◽  
Pore Water Pressures ◽  
Linear And Nonlinear

The pore-water pressure is a vital factor in determining the slope stability. To deal with the stability of slopes undergoing pore-water pressures, this paper used the pore-water pressure coefficient to develop the three-dimensional limit analysis method for slope stability evaluation with a nonlinear strength envelope. For numerical slope examples, the critical heights and corresponding critical slip surfaces associated with linear and nonlinear envelopes were derived by using a numerical optimization procedure. The influences of pore-water pressures on the slope stability were addressed by comparing the upper-bound solutions derived by linear and nonlinear strength envelopes (the linear and nonlinear results for short). The obtained two critical inclinations between the linear and nonlinear results both decrease and gradually approach with increasing pore-water pressure coefficient. For most slopes subjected to pore-water pressures, using the linear Mohr–Coulomb envelope will obviously overestimate the slope critical height. The overestimation resulted from the linear criterion will become more distinct for slopes with smaller widths. Besides, the presented results showed that the equivalent internal friction angle tends to have a weaker increasing trend for steeper slopes as pore-water pressure coefficient increases. Hence, when pore-water pressure coefficient increases, the critical slip surfaces of gentle slopes with nonlinear strength criteria become shallower, but the critical slip surfaces of steep slopes seem to have no consistent change law. These results and analyses can illustrate the significance of the application of nonlinear strength envelopes in slope stability evaluation considering pore-water pressures and provide certain reference advice in slope engineering design and landslide prevention.

scholarly journals Toe drain size and slope stability of homogeneous embankment dam under rapid drawdown.

Technobius ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 0001
Author(s):  
Timoth Mkilima
Keyword(s):  
Numerical Modeling ◽  
Slope Stability ◽  
Pore Water ◽  
Factor Of Safety ◽  
Potential Effect ◽  
Upstream Face ◽  
Design Team ◽  
Potential Influence ◽  
Embankment Dam ◽  
Pore Water Pressures

The slope stability of an embankment dam has been always a serious concern of any design team. Unfortunately, the information on the potential influence of a toe drain size on the slope stability of an embankment dam under rapid drawdown conditions is still scarce. This study investigated the potential effect of a toe drain size on the slope stability of a homogeneous embankment dam under rapid drawdown conditions. Three different sizes (5m, 10m, and 15m) of the toe drain were investigated under instantaneous (worst scenario) and 5 days (more realistic) drawdown rates with the help of numerical modeling in GeoStudio. From the results, it was observed that the pore-water pressures at the upstream face of the embankment decreased with the increase in the toe drain size, while the pore-water pressures at the downstream toe were increasing with the increase in the toe drain size. The factor of safety values were also observed to be affected by the changes in the toe drain size.

Postfailure analysis: Tramping Lake causeway, Saskatchewan, Canada

1989 ◽  
Vol 26 (4) ◽  
pp. 687-704
Author(s):  
J. L. Labossiere ◽  
E. K. Sauer ◽  
E. A. Christiansen
Keyword(s):  
Pore Water ◽  
Slip Surface ◽  
Friction Angle ◽  
Triaxial Tests ◽  
Lake Basin ◽  
Pore Water Pressures ◽  
Back Calculation ◽  
Vertical Subsidence ◽  
Sand And Gravel ◽  
Effective Friction

A traffic causeway placed on the sediments of saline Tramping Lake failed during construction in the summer of 1982. Vertical subsidence has continued until present (1988). The failure mechanism was controlled by sedimentary structure and artesian groundwater conditions. The shear zone is in a soft, near normally consolidated lacustrine sandy silt unit 22 m thick. The lake basin contains lacustrine, deltaic, and fluvial deposits of postglacial origin. Artesian conditions in the Upper Cretaceous Judith River Formation and postglacial fluvial sand and gravel dominate the hydrogeology at the site. The failure took place along a composite slip surface when excess pore-water pressures developed during loading [Formula: see text]. The estimated effective friction angle from triaxial tests and back calculation was 27° assuming c′ = 0. However, a parametric analysis showed that at very high pore-water pressures the effective friction angle required for equilibrium is very sensitive to small variations in ru. The calculated cohesion at [Formula: see text] required for equilibrium was 3.9 kPa, whereas the remolded vane strength measured in the field was 5.0 kPa. Key words: Foundation failure, artesian, saline environment, groundwater discharge, silty clays, postglacial fluvial and lacustrine deposits.

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