Decalcification and residual shear strength reduction in Fuller's Earth Clay

Hawkins, A. B.; McDonald, Chad

doi:10.1680/geot.1992.42.3.453

Cited by 36 publications

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“…The low plasticity of solifluction sediments is also likely related to the high silt/sand content in the fine fraction, their low capacity for water retention (low V B , S S , A CB ), and their lack of true swelling clays (Locat, Lefebvre, & Ballivy, 1984;Lautrin, 1989;Santamarina et al, 2002;Chiappone et al, 2004). The low plasticity of the sediments could be explained by two additional factors: the presence of carbonates in the silt/clay fraction, which may act as dispersants (Fischer, Andersen, & Moum, 1978;Hawkins & McDonald, 1992;Cotecchia & Chandler, 1995), and a low organic matter content, which may induce low W L , W P , and I P (Booth & Dahl, 1986). Another factor that could explain the susceptibility of the sediments to solifluction is the low contribution of cohesion to their shear strength.…”

Section: Solifluction and Sediment Propertiesmentioning

confidence: 99%

Palaeoeskimo site burial by solifluction: Periglacial geoarchaeology of the tayara site (KbFk‐7), Qikirtaq Island, Nunavik (Canada)

Todisco

Bhiry

2008

Geoarchaeology

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The geoarchaeological study of the Palaeoeskimo Tayara site on Qikirtaq Island (Nunavik) has led to a better understanding of archaeological site formation in the arctic periglacial environment. The surrounding geomorphology (extra-site) is characterized by fine-grained, low plastic and leached postglacial glaciomarine sediments that have been reworked by sheet-like solifluction. This process buried the northern part of the Tayara site with mean annual rates between 1.68 and 2.86 cm/yr over approximately 350 years (1330-980 yr B.P.). The physicochemical and mineralogical properties of the frost-susceptible glaciomarine sediments may explain their susceptibility to solifluction. This process was probably enhanced by longer thawing periods or warmer/moister summer months that induced active layer thickening or rapid soil thawing. The dates we obtained in the downstream valley show that solifluction occurred during short warm periods in the Late Holocene between ca. 1500 and 1000 yr B.P., after 1000 yr B.P. (or after 500 yr B.P.) and recently (90-60 yr B.P.). Our data provide insights on the site factors and climate factors that govern site burial by solifluction. Solifluction promoted the preservation of the three superposed archaeological levels in the Tayara site; however, the waterlogging of the site related to solifluction also likely caused the subsequent abandonment of the site by the Palaeoeskimo people.

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Section: Solifluction and Sediment Propertiesmentioning

confidence: 99%

Palaeoeskimo site burial by solifluction: Periglacial geoarchaeology of the tayara site (KbFk‐7), Qikirtaq Island, Nunavik (Canada)

Todisco

Bhiry

2008

Geoarchaeology

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“…The mode of residual shear changes locally to sliding, with the consequent reduction in shear strength. Hawkins and McDonald (1992) studied the residual shear strength of weathered and unweathered Fuller's Earth Clay. Unweathered samples had significant amounts of sand and silt-sized particles composed of calcite.…”

Section: Introductionmentioning

confidence: 99%

The residual shear strength of tropical soils

Rigo¹,

Pinheiro²,

Bressani³

et al. 2006

Can. Geotech. J.

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Abstract:The paper discusses the residual shear strength of tropical soils. Ring shear tests have been performed with tropical soils from southern Brazil using the Bromhead apparatus. The data from the study are compared with data obtained in a comprehensive literature review of the subject. The residual friction angle of tropical residual soils from sedimentary formations decreases with increasing plasticity index following a general trend presented in the literature. Most of the residual soils described herein have also shown this trend. However, some of these residual soils, particularly basalt saprolitic soils, have shown quite low residual friction angles despite having low plasticity index and clay fraction values. It has been confirmed that the residual shear strength of tropical soils depends chiefly on mineralogy, particle size distribution, effective stress, parent rock, weathering degree, pedogenetic evolution and -when partly weathered minerals are present -degradation upon shearing. The substantial range of new data shown in the paper has allowed the definition of general boundaries of different soil behaviour in a chart of residual friction angle versus plasticity index. Each region has been associated with a different type of tropical soil.Key words: tropical soils, residual soils, residual shear strength, laboratory tests.Résumé : Cet article discute de la résistance au cisaillement résiduelle des sols tropicaux. La résistance au cisaillement des sols tropicaux du Sud du Brésil a été mesurée au moyen de l'appareil circulaire par torsion (appareil de Bromhead). Les données de l'étude sont comparées avec celles obtenues au cours d'une revue de littérature sur le sujet. L'angle de frottement résiduel des sols résiduels formés par l'altération des formations sédimentaires décroît avec l'augmentation de l'indice de plasticité selon une tendance générale présentée dans la littérature. La plupart des sols ré-siduels décrits ici ont également montré cette tendance. Cependant, certains de ces sols résiduels -particulièrement les sols de basalt saprolitique -ont montré des angles de frottement résiduels très faibles en dépit de leurs faibles valeurs d'indice de plasticité et de fraction argileuse. Il a été confirmé que la résistance au cisaillement résiduelle dépend principalement de la minéralogie, de la granulométrie, de la contrainte effective, de la roche-mère, du degré d'altération, de la pédogenèse, et -lorsque des minéraux partiellement altérés sont présents -de la dégradation au cours du cisaillement. La plage substantielle des nouvelles données montrées dans l'article a permis de définir des limites générales du comportement de différents sols dans un graphique de l'angle de frottement résiduel en fonction de l'indice de plasticité. Chaque région a été associée à un type différent de sol tropical.Mots clés : sols tropicaux, sols résiduels, résistance au cisaillement résiduelle, essais de laboratoire.[Traduit par la Rédaction] Rigo et al. 447

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“…Strength may increase accumulation of salt especially in coastal areas, precipitation of carbonates and iron compounds, and exchange of lower valence to higher valence cations (Kenney 1967;Chandler 1969;Hutchinson, 1969Hutchinson, , 1970Hawkins 1988;Moore 1991;Hawkins and McDonald 1992;Moore and Brunsden 1996;Hawkins 1998, 2002;Tiwari et al 2005). …”

Section: The Modification Of Strength After Failure (Landslide Reactimentioning

confidence: 99%

Slope stability in slightly fissured claystones and marls

Alonso

Pinyol

2014

Landslides

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ABSTRACT:The paper deals with the behaviour of some characteristic soft rocks found in the Iberian Peninsula. In geological terms they belong to Tertiary basins, the Keuper period and the Jurassic-Cretacic transition. The discussion is organized around the following aspects: (a) the intact material and its brittle behaviour; (b) the weathering action of atmospheric events; (c) the persistent discontinuities and scale effects; and (d) the modification of strength after failure. In all cases instability phenomena are addressed in connection with several case histories.Regarding material brittleness and the initial stress state, two cases of first time failures are discussed. Practical implications concerning the selection of operative strength will be given Field observations of the relevance of weathering and, also, on the rate of weathering, are given for a Weald claystone. Field observations emphasize the importance of sharp transitions between weathered and intact (or slightly weathered) levels A recent long term laboratory investigation on the nature of degradation will be summarized. Macroscopic variables such as stiffness and tensile strength have been found to be uniquely predicted by a degradation law in terms of the accumulated plastic deformations.Persistent discontinuities and, in particular, sedimentation planes, play a dominant role to explain slope failures not related to the shallow failures, usually associated with weathered profiles. The strength of discontinuities in a Weald formation was investigated by means of tests performed at two scales.Finally, the evolution in time of residual strength induced by chemical actions, associated with groundwater flow, is highlighted in connection with actual field data of unstable slopes.

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Decalcification and residual shear strength reduction in Fuller's Earth Clay

Cited by 36 publications

References 0 publications

Palaeoeskimo site burial by solifluction: Periglacial geoarchaeology of the tayara site (KbFk‐7), Qikirtaq Island, Nunavik (Canada)

Palaeoeskimo site burial by solifluction: Periglacial geoarchaeology of the tayara site (KbFk‐7), Qikirtaq Island, Nunavik (Canada)

The residual shear strength of tropical soils

Slope stability in slightly fissured claystones and marls

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