Settlement of an Embankment on Leda Clay

Burn, K. N.; Hamilton, J.

doi:10.1139/t68-002

“…Retrieving a perfectly undisturbed Champlain Sea clay sample is nearly impossible as the clay is susceptible to disturbance. Hence, the conventional laboratory determination may underestimate the in-situ pre-consolidation (Burn and Hamiltion 1968). On the other hand, the mobilized preconsolidation pressure, as proposed by Leroueil et al (1983a), can be determined by conventional oedometers on good quality samples taken with a 70 mm diameter piston sampler.…”

Section: Over-consolidation Andmentioning

confidence: 99%

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

Cong¹

2021

Preprint

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Soft clays are often associated with high compressibility due to their high void ratio, low shear strength, and creep behavior. Structures built on top of it can experience excessive settlement issues over a long period of time. The prediction of these settlements has attracted attentions from many researchers for over a century, but accurately predicting them still remains a difficult issue due to complex properties of soft clays, including plasticity, viscosity, anisotropy, soil structure and so forth. Therefore, studying the compressibility of soft clay is of significant importance. This dissertation aims to investigate the influence of plastic deviatoric strains on the compressibility of soft clays. First of all, the dissertation reviews a number of published incremental anisotropic consolidation tests on Finnish clays. The results demonstrate the dependence of soil compressibility on stress ratios. Based on the result, a modified yield surface size deviatoric softening law has been introduced. This softening law describes yield surface softening to be related to plastic deviatoric strain increments. Secondly, a new model named MEVP-DS, has been incorporated into the framework of Yin’s elaso-viscoplastic model to consider deviatoric softening, destructuration, and yield surface anisotropy of soft clay. Furthermore, the verification of MEVP-DS has been done through three phases. Phase one is the simulation of published incremental anisotropic consolidation tests on intact Finnish clay samples. The model results demonstrate MEVP-DS successfully captures the soil compressibility in response to different stress ratios. Phase two is the application of MEVP-DS in modeling 1-D consolidation tests on sensitive Champlain Sea clay. Model results highlight that using MEVP-DS is beneficial for predicting the compressibility and excess pore pressure response of the clay subject to constant rate of strain loading. Phase three is the application of MEVP-DS in simulating a real embankment dam on Champlain Sea clay. MEVP-DS not only simulates 40-year settlement measurements of the dam reasonably well, but also improves the prediction of lateral spreading of the dam. In summary, the MEVP-DS model proposed in this dissertation has shown to improve the simulation of soil compressibility of soft clays subject to 1-D, anisotropic and more complicated loading conditions.

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“…Retrieving a perfectly undisturbed Champlain Sea clay sample is nearly impossible as the clay is susceptible to disturbance. Hence, the conventional laboratory determination may underestimate the in-situ pre-consolidation (Burn and Hamiltion 1968). On the other hand, the mobilized preconsolidation pressure, as proposed by Leroueil et al (1983a), can be determined by conventional oedometers on good quality samples taken with a 70 mm diameter piston sampler.…”

Section: Over-consolidation Andmentioning

confidence: 99%

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

Cong¹

2021

Preprint

0

View full text Add to dashboard Cite

Soft clays are often associated with high compressibility due to their high void ratio, low shear strength, and creep behavior. Structures built on top of it can experience excessive settlement issues over a long period of time. The prediction of these settlements has attracted attentions from many researchers for over a century, but accurately predicting them still remains a difficult issue due to complex properties of soft clays, including plasticity, viscosity, anisotropy, soil structure and so forth. Therefore, studying the compressibility of soft clay is of significant importance. This dissertation aims to investigate the influence of plastic deviatoric strains on the compressibility of soft clays. First of all, the dissertation reviews a number of published incremental anisotropic consolidation tests on Finnish clays. The results demonstrate the dependence of soil compressibility on stress ratios. Based on the result, a modified yield surface size deviatoric softening law has been introduced. This softening law describes yield surface softening to be related to plastic deviatoric strain increments. Secondly, a new model named MEVP-DS, has been incorporated into the framework of Yin’s elaso-viscoplastic model to consider deviatoric softening, destructuration, and yield surface anisotropy of soft clay. Furthermore, the verification of MEVP-DS has been done through three phases. Phase one is the simulation of published incremental anisotropic consolidation tests on intact Finnish clay samples. The model results demonstrate MEVP-DS successfully captures the soil compressibility in response to different stress ratios. Phase two is the application of MEVP-DS in modeling 1-D consolidation tests on sensitive Champlain Sea clay. Model results highlight that using MEVP-DS is beneficial for predicting the compressibility and excess pore pressure response of the clay subject to constant rate of strain loading. Phase three is the application of MEVP-DS in simulating a real embankment dam on Champlain Sea clay. MEVP-DS not only simulates 40-year settlement measurements of the dam reasonably well, but also improves the prediction of lateral spreading of the dam. In summary, the MEVP-DS model proposed in this dissertation has shown to improve the simulation of soil compressibility of soft clays subject to 1-D, anisotropic and more complicated loading conditions.

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“…The Ottawa NRC site, located in the campus of the National Research Council of Canada in east Ottawa, has been previously documented by Eden and Hamilton (1956) and Eden and Law (1980). The Ottawa SP site is located at the Ottawa sewer plant in east Ottawa, near the Ottawa River, and has also been studied previously (Bozozuk 1963;Burn and Hamilton 1968;Eden and Bozozuk 1969). At 8.5 m depth, the overconsolidation (0; -a: , ) is relatively high, and the clay is affected by microfissures that appear upon breaking.…”

Section: Test Sites and Description Of Soilsmentioning

confidence: 99%

Evaluating K_o in Champlain clays with hydraulic fracture tests

Lefèbvre¹,

Bozozuk²,

Philibert³

et al. 1991

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Hydraulic fracture tests using piezometer tips 10-500 mm long were performed in Champlain clays at five different sites with overconsolidation ratios (OCR) varying from 1.6 to 4.8. Before the test, the piezometer fluid was replaced by a methylene blue solution (10 g/L) to dye the fissures resulting from the test. After the hydraulic fracture, the soil around the piezometer tips was recovered by means of a large-diameter sampler. For 300 and 500 mm long piezometers, the fissure pattern was radial and vertical, even in deposits with an OCR above unity, confirming that hydraulic fracturing is related to the total stress acting on the cavity walls. The results for the five sites define for the,Champlain clay deposits a KO-OCR relationship that gives higher KO values than generally proposed in the literature.Des essais de fracturation hydraulique ont Ct C rCalisCs dans les dCp8ts argileux de la mer Champlain a cinq sites diffkrents prisentant des degrCs de surconsolidation variant de 1,6 a 4,8. La longueur des piCzomktres utilisCs pour les essais a variC gCnCralement de 10 A 500 mm. ImmCdiatement avant l'essai de fracturation, le fluide dans les piCzomktres fut remplacC par une solution de bleu de mCthylkne (10 g/L) afin de bien marquer la fissuration rksultant de l'essai.Le sol entourant la pointe piCzomCtrique fut ensuite rCcupCrC au moyen d'un Cchantillonneur a grand diamktre. Pour les piCzomktres de 300 et 500 mm, la fracturation hydraulique crCe une fissuration radiale et verticale m&me lorsque le degrC de surconsolidation est supCrieur a 1'unitC confirmant que la fracturation rCsulte des contraintes totales appliquCes A la pCriphCrie de la cavitC. Les rCsultats des cinq sites permettent d'dtablir pour les dCpbts de lamer Champlain, une relation KO-OCR qui amkne des valeurs de KO passablement plus ClevCes que gCnCralement proposCes dans la littkrature.

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Settlement of an Embankment on Leda Clay

Abstract: /npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Cited by 7 publications

References 3 publications

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

Evaluating K_o in Champlain clays with hydraulic fracture tests

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Settlement of an Embankment on Leda Clay

Abstract: /npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Cited by 7 publications

References 3 publications

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

Evaluating Ko in Champlain clays with hydraulic fracture tests

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Evaluating K_o in Champlain clays with hydraulic fracture tests