Characterization of Post-failure Movements of Landslides in Soft Sensitive Clays

Thakur, Vikas; Degago, Samson Abate; Oset, Frode; Aabøe, Roald; Dolva, Bjørn Kristoffer; Aunaas, Kristian; Nyheim, Trude; Lyche, Einar; Jensen, Odd Are; Sæter, May-Britt; Robsrud, A.; Viklund, Margareta; Nigussie, D; L’Heureux, Jean-Sébastien

doi:10.1007/978-94-007-7079-9_8

Cited by 22 publications

(16 citation statements)

References 29 publications

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“…Based on historical Canadian and Norwegian quick-clay landslides, a remolded shear strength cur < 1 kPa and a liquidity index IL > 1.2 may be used as an indicator on clays that pose a risk for large retrogressive landslides (Leroueil et al 1983;Thakur et al 2014). Re-establishing high salt contents in quick clays improve the cur so that the clay no longer appear as quick, and at the same time improve the Atterberg limits (Rosenqvist 1946(Rosenqvist , 1953(Rosenqvist , 1955Bjerrum 1955;Løken 1968Løken , 1970Moum et al 1968;Quigley 1980;Torrance 1983).…”

Section: Potassium Chloride As a Ground Improvement Agentmentioning

confidence: 99%

“…Risk of large retrogressive landslides increases in clays with a remolded shear strength (cur) of less than 1 kPa, and a liquidity index (IL) larger than 1.2 (Leroueil et al 1983;Thakur et al 2014). Therefore, these criteria are used in the following to define stabilized quick clay rather than the Norwegian quick-clay definition of cur < 0.5 kPa (Norwegian Geotechnical Society 2011).…”

Section: The Impact Of Kcl On Geotechnical Propertiesmentioning

confidence: 99%

“…Clay deposits with a remolded shear strength (cur) of less than 1 kPa, or a liquidity index (IL) exceeding 1.2, pose a risk to develop into successive retrogressive landslides if remolded (Leroueil et al 1983;Thakur et al 2014). The salt content in the pore water has a great impact on the remolded shear strength, and quick clays normally have salt contents of less than 2 g/L (Torrance 1979).…”

Section: Improved Geotechnical Properties Due To Changed Pore-water Cmentioning

confidence: 99%

“…Landslides comprising clays with a cur < 1.0 kPa and an IL > 1.2 may flow out of the initial slide pit, and develop into large backwards successive, retrogressive landslides (Leroueil et al 1983;Thakur et al 2014), such as the Rissa quick-clay landslide (Gregersen 1981). Improving the cur in clays to more than 1 kPa, the slide debris will not flow out of the initial slide pit, thereby preventing successive back-scarp failures.…”

Section: Recommendationsmentioning

confidence: 99%

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In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

Helle

Aagaard

Nordal

2017

J. Geotech. Geoenviron. Eng.

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Highly sensitive, low-saline clays, termed quick clays, represent a risk for large landslides. An in-situ experiment was conducted installing salt wells filled with potassium chloride (KCl) in order to study how salt wells can be used to reduce landslide risk. The salt-plume migration and the clay volume surrounding the salt wells were investigated by resistivity cone penetration tests (RCPTU), piston samples, conductivity divers and groundwater samples. Correlating the geotechnical properties to the occurring pore-water compositions, the remolded shear strength (cur) was improved beyond 1 kPa when the ratio of the sum of potassium, magnesium and calcium over the major cations exceeded 20%. The cur was improved to about 4-8 kPa 0.5 m from the wells within 3 years, and the liquidity index decreased from more than 3.4 to less than 1.2. A diameter of minimum 1.5 m around the wells was stabilized within 3 years. Thus, it is recommended to install the salt wells with a center-to-center distance of 1.5-2.0 m. The improved post-failure properties (cur and Atterberg limits) are considered permanent in an engineering time scale due to a lasting pore-water composition inhibiting development of high sensitivity. Salt wells can be installed without substantial disturbance of the soil, and can be used as landslide mitigation in quick-clay areas.

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Section: Potassium Chloride As a Ground Improvement Agentmentioning

confidence: 99%

Section: The Impact Of Kcl On Geotechnical Propertiesmentioning

confidence: 99%

Section: Improved Geotechnical Properties Due To Changed Pore-water Cmentioning

confidence: 99%

Section: Recommendationsmentioning

confidence: 99%

See 2 more Smart Citations

In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

Helle

Aagaard

Nordal

2017

J. Geotech. Geoenviron. Eng.

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“…Sensitive clays are characterized by rapid strength decrease during deformation [60], which translates to a low friction coefficient. Quinn et al [16], for example, suggest τ r / τ p =0.013 for subaerial sensitive clays in Quebec area (Canada).…”

Section: Examplesmentioning

confidence: 99%

Dynamic growth of slip surfaces in catastrophic landslides

2016

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This work considers a landslide caused by the shear band that emerges along the potential slip (rupture) surface. The material above the band slides downwards, causing the band to grow along the slope. This growth may first be stable (progressive), but eventually becomes dynamic (catastrophic). The landslide body acquires a finite velocity before it separates from the substrata. The corresponding initial-boundary value problem for a dynamic shear band is formulated within the framework of Palmer & Rice's (Proc. R. Soc. Lond. A 332, 527–548. (doi:10.1098/rspa.1973.004010.1098/rspa.1973.0040)) approach, which is generalized to the dynamic case. We obtain the exact, closed-form solution for the band velocity and slip rate. This solution assesses when the slope fails owing to a limiting condition near the propagating tip of the shear band. Our results are applicable to both submarine and subaerial landslides of this type. It appears that neglecting dynamic (inertia) effects can lead to a significant underestimation of the slide size, and that the volumes of catastrophic slides can exceed the volumes of progressive slides by nearly a factor of 2. As examples, we consider the Gaviota and Humboldt slides offshore of California, and discuss landslides in normally consolidated sediments and sensitive clays. In particular, it is conceivable that Humboldt slide is unfinished and may still displace a large volume of sediments, which could generate a considerable tsunami. We show that in the case of submarine slides, the effect of water resistance on the shear band dynamics may frequently be limited during the slope failure stage. For a varying slope angle, we formulate a condition of slide cessation.

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Retrogressive failure pattern and retrogression distance in sensitive clays induced by river erosion

Zhang

Wang

Liu

et al. 2023

Num Anal Meth Geomechanics

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The failure patterns and retrogression distances in sensitive clays induced by river erosion are two significant factors of concern in landslide risk assessment. For the former, empirical criteria, based on past events and numerical results, can hardly produce a unified guideline and explain their complex mechanism. For the latter, the capacity of the river cross section is rarely considered in existing studies, even though the failed soil would deposit on the riverbed and further affect upslope failure extension. The present study proposes an analytical method to quantitatively assess the failure patterns and retrogression distance by combining the shear band propagation method (SBP) with limit analysis on active block failure. A closed‐form active earth pressure (CAEP) and the shape function of the failure surface are proposed with the variational calculus method (VCM), providing a tool to understand the transformation mechanism of the failure patterns. The criteria for initiation failure positions and stages are formulated following the competition results between the induced minimum slope‐parallel force by foot unloading and the proposed CAEP. Further, the terminal retrogression distance is given considering two possible river cross sections. The proposed CAEP solution is validated against Buss's solution and further applied to a parametric study on the failure patterns. Finally, three practical cases are analyzed with the proposed method, and the predictions are shown to agree well with the field observations.

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Characterization of Post-failure Movements of Landslides in Soft Sensitive Clays

Cited by 22 publications

References 29 publications

In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

Dynamic growth of slip surfaces in catastrophic landslides

Retrogressive failure pattern and retrogression distance in sensitive clays induced by river erosion

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