The September 5, 1987, landslide on the La Grande River, James Bay, Quebec, Canada

1991 ◽  
Vol 28 (2) ◽  
pp. 263-275 ◽  
Author(s):  
Guy Lefebvre ◽  
Peter Rosenberg ◽  
Jean Paquette ◽  
J. G. Lavallée
Keyword(s):  
Shear Strength ◽  
Ground Surface ◽  
Bank Erosion ◽  
Undrained Shear Strength ◽  
Silty Clay ◽  
James Bay ◽  
River Bank ◽  
River Erosion ◽  
Sensitive Clay ◽  
Undrained Shear

The September 5, 1987, landslide at kilometre 82.5 on La Grande River affected a slope about 60 m high inclined at about 35°. The site had been identified as presenting high risks of a major landslide and had been under observation for several years. The conditions existing before the landslide are relatively well documented from a deep boring put down in 1975 at the slide location and from prior observations and photographs of the river bank erosion. The overburden deposit, sand at the ground surface changing to a silty clay at depth, was normally consolidated but affected by a strong underdrainage. Stability analyses confirm the strong underdrainage deduced from the 1975 piezometric reading. The slide retrogressed 290 m from the river on a surface inclined at 6°. The location of the retrogression surface appears related to the undrained shear strength profile. Key words: landslide, earthflow, sensitive clay, groundwater, river erosion, slope stability.

scholarly journals Experimental investigations of using deep mixing method to stabilise problematic clays in Ontario

2021 ◽  
Author(s):  
Shuihan Li
Keyword(s):  
Shear Strength ◽  
Strength Properties ◽  
Undrained Shear Strength ◽  
Experimental Investigations ◽  
Silty Clay ◽  
Slag Cement ◽  
Mixing Method ◽  
Sensitive Marine Clay ◽  
Strength Improvement ◽  
Undrained Shear

Champlain Sea clay is a sensitive marine clay which can lose more than 90% of its strength when disturbed. Organic silty clay, commonly found in Ontario, has a high compressibility and a low shear strength. In this experimental study, different binders were applied to Champlain Sea clay and organic silty clay to improve its strength properties. The results indicate that cement and slag/cement can significantly improve the strength of these problematic clays. A cement dosage ranging from 150 kg/m3 to 250 kg/m3 can consistently improve the undrained shear strength of Champlain Sea clay and organic silty clay with the maximum strength improvement ratio of 10 and 18 respectively. A slag/cement dosage of 290 kg/m3 with a mass ratio of 3:1 can improve the undrained shear strength of Champlain Sea clay for more than 50 times. Lime was found to be effective in treating organic silty clay as well.

scholarly journals Geotechnical Centrifuge Modelling of Retrogressive Sensitive Clay Landslides

2020 ◽  
Author(s):  
Ray Kennedy ◽  
W. Andy Take ◽  
Gregory A. Siemens
Keyword(s):  
Shear Strength ◽  
Slope Angle ◽  
Physical Modelling ◽  
Failure Surface ◽  
Undrained Shear Strength ◽  
Stability Number ◽  
Surface Stability ◽  
Geotechnical Centrifuge ◽  
Sensitive Clay ◽  
Undrained Shear

Sensitive clay landslides represent a significant geohazard due to their well-known potential for extensive retrogressive failures, on the scale of multiple hectares, which could encompass surrounding communities and infrastructure. Interpretation of retrogression mechanisms is often limited since only forensic investigations are possible. This work presents the results of a physical modelling study to examine retrogressive failures, analysis of each failure episode, and interpretation of the results using published relationships. Five novel centrifuge model tests were conducted under a defined range of undrained shear strength and slope angle conditions. The models are constructed of a sensitive cement-soil mixture that allows for a consistent contractile material with bespoke shear strength. Results indicate the observed retrogression distance correlates with Taylor’s stability number. The addition of a 5-degree slope angle to invoke a static shear stress on the model provoked notably larger retrogression distances. Post-test undrained shear strength measurements quantified softening of the material along the failure surface. Stability analyses on each failure episode captured the observed failure geometry and factor of safety. Results indicate that the geometric parameters of a slope, specifically the slope angle, may be able to explain a component of the scatter for relating the Taylor’s stability number with retrogression distances.

scholarly journals Modeling of large-deformation behaviour of marine sensitive clays and its application to submarine slope stability analysis

2016 ◽  
Vol 53 (7) ◽  
pp. 1138-1155 ◽  
Author(s):  
Rajib Dey ◽  
Bipul Hawlader ◽  
Ryan Phillips ◽  
Kenichi Soga
Keyword(s):  
Shear Strength ◽  
Shear Band ◽  
Large Scale ◽  
Critical Length ◽  
Undrained Shear Strength ◽  
Model Parameters ◽  
Submarine Landslides ◽  
Weakened Zone ◽  
Sensitive Clay ◽  
Undrained Shear

Post-slide investigations suggest that many large-scale submarine landslides occur through marine sensitive clay layers. A nonlinear mathematical model for post-peak degradation of undrained shear strength of sensitive clay is proposed based on experimental results. A method for estimation of model parameters is presented. Incorporating the model, an analytical solution is developed to examine possible mechanisms of large-scale submarine landslides. Analyses are performed for mild infinite slopes where the failure initiates from a “fully weakened zone” of soil having undrained shear strength lower than the shear stress acting parallel to the slope. The driving force, in excess of resistance, generated from the fully weakened zone is then transferred to the surrounding soil elements resulting in shear band formation due to strain-softening behaviour of sensitive clays. When the length of the fully weakened zone is greater than a critical length, catastrophic shear band propagation (self-driven without any additional external force) occurs, which could result in large-scale offshore landslides. A simple design chart is developed to calculate the critical length. Compared with a 2005 study by Puzrin and Germanovich based on a linear post-peak shear strength degradation model, the present study gives a conservative estimation of critical length for catastrophic shear band propagation.

Excavation d'argile sensible au site de l'aménagement hydroélectrique LG-2

1985 ◽  
Vol 22 (2) ◽  
pp. 186-194
Author(s):  
J. J. Paré ◽  
J. G. Lavallée
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Strength Analysis ◽  
Site Conditions ◽  
Embankment Dams ◽  
Clay Deposits ◽  
Undrained Strength ◽  
Sensitive Clay ◽  
Tailrace Tunnel ◽  
Undrained Shear

This paper is a review of the design adopted to establish the slopes for deep clay excavations (3 000 000 m3) made for founding rockfill embankment dams on bedrock and for clearing the tailrace tunnel portals at the LG-2 hydroelectric site. The design and excavation of soft sensitive clay deposits down to 22 m had been undertaken at a period of time when very few precedents were existing (1974). During the excavation works, only a few minor slides occurred, indicating that the design approach, using undrained shear strength analysis, was appropriate for the site conditions. Methods of excavation and hauling of material to disposal areas are also described. Key words: slope, sensitive clay, undrained strength analysis, safety factor, excavation method, behaviour.

Origine de la préconsolidation des argiles du Saguenay, Québec

1983 ◽  
Vol 20 (2) ◽  
pp. 315-328 ◽  
Author(s):  
R. Bouchard ◽  
D. J. Dion ◽  
F. Tavenas
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Ground Surface ◽  
Undrained Shear Strength ◽  
Geological History ◽  
Eastern Canada ◽  
Geotechnical Data ◽  
Preconsolidation Pressure ◽  
Undrained Shear ◽  
Good Agreement

The clays of Eastern Canada, and in particular the Saint-Jean-Vianney clay in the Saguenay region, have often been described as clays with a preconsolidation due partly to cementation. In order to check this assumption, the geological history and the geomorphology of the Saguenay region have been analyzed. Further to the evidence of significant erosion, available geotechnical data in the form of variations of water content, undrained shear strength, and preconsolidation pressure have been analyzed to determine the elevation of the original ground surface in the hypothesis of a preconsolidation resulting from deposition and erosion. The results of this analysis are in good agreement with the geological and geomorphological data and they suggest that cementation has had a negligible effect on the preconsolidation of the Saguenay clays. A regional map of preconsolidation pressures is also presented. Keywords: clay, preconsolidation, geomorphology, erosion, shear strength. [Journal translation]

scholarly journals Determination of the Undrained Shear Strength of Sensitive Clay Using Some Laboratory Soil Data

2021 ◽  
Vol 8 (1) ◽  
pp. 14
Author(s):  
Tahar Ayadat
Keyword(s):  
Shear Strength ◽  
Soil Properties ◽  
Bearing Capacity ◽  
Fine Particles ◽  
Undrained Shear Strength ◽  
Clay Layer ◽  
In Situ Tests ◽  
Sensitive Clay ◽  
Undrained Shear

The undrained shear strength is a paramount parameter in determining the consistency and the ultimate bearing capacity of a clay layer. This resistance can be determined by in-situ tests, such as the field vane test or by laboratory tests, including the portable vane test, the triaxial, the simple compression test, and the consistency penetrometer test (i.e. the Swedish cone). However, the field vane test and the Swedish cone are the most commonly test used by geotechnical experts. In this paper, relationships between the field undrained shear strength of sensitive clay and some laboratory soil properties were developed. The soil properties consisted of the percentage of fine particles (less than 2 µm), the moisture content and the Atterberg limits. Furthermore, a correlation was proposed associating between the undrained shear strength of sensitive clay as obtained by the field vane test and the laboratory cone penetration test (Swedish cone). In addition, some applications of the proposed correlation on some geotechnical problems were included, such as the determination of the consistency and the bearing capacity of a clay layer. Comparison of the results of the developed correlations with the experimental results of the present investigation and the results reported in the literature show acceptable agreement.

scholarly journals Undrained shear strength from piezocone tests

1987 ◽  
Vol 24 (3) ◽  
pp. 392-405 ◽  
Author(s):  
J.-M. Konrad ◽  
K. T. Law
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Cavity Expansion ◽  
Pore Pressures ◽  
Clayey Silt ◽  
Tip Resistance ◽  
Sensitive Clay ◽  
Rigidity Index ◽  
New Interpretation ◽  
Undrained Shear

With the advent of piezocones — penetrometers measuring both the mechanical resistance and induced pore pressures near the tip during penetration into the soil — a new interpretation of penetrometer test data is possible. This paper presents a review of available interpretation methods for obtaining the undrained shear strength of soft soils, and introduces a new interpretation taking into account measured pore pressures. The undrained shear strength is considered to be solely related to the ultimate cavity expansion pressure, which is one of the components of the tip resistance. The other component is calculated assuming that effective friction is developed at the cone–soil interface.Parametric studies on the parameters required for strength determination based on the proposed method are also presented. Special self-boring pressuremeter tests to obtain relevant values of soil rigidity index, which is a key parameter for cavity expansion modelling, are described. Tests were conducted at three sites having the characteristics of soft sensitive clay, stiff sensitive clay, and clayey silt. The operational undrained strength mobilized during the cone insertion derived from the proposed model is equal to or lower than the CK0U triaxial strength, which depends on soil brittleness. The proposed approach yields results consistent with known soil behaviour at all three sites. Key words: piezocone penetrometer, pressuremeter, excess pore-water pressure, undrained shear strength, rigidity index, in situ tests, laboratory test.

scholarly journals Testing of Undrained Shear Strength in a Hollow Cylinder Apparatus

2015 ◽  
Vol 37 (2) ◽  
pp. 69-73 ◽  
Author(s):  
Grzegorz Wrzesiński ◽  
Zbigniew Lechowicz
Keyword(s):  
Shear Strength ◽  
Principal Stress ◽  
Hollow Cylinder ◽  
Laboratory Tests ◽  
Undrained Shear Strength ◽  
Cohesive Soils ◽  
Silty Clay ◽  
Hollow Cylinder Apparatus ◽  
Stress Directions ◽  
Undrained Shear

Abstract The paper presents the results of tests performed in a Torsional Shear Hollow Cylinder Apparatus on undisturbed cohesive soils. The tests were performed on lightly overconsolidated clay (Cl) and sandy silty clay (sasiCl). The main objective of the tests was to determine the undrained shear strength at different angles of rotation of the principal stress directions. The results of laboratory tests allow assessing the influence of rotation of the principal stress directions on the value of undrained shear strength that should be used during designing structure foundations

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