Experiment and theory research on the pore pressure unloading characteristics of saturated clay under isotropic consolidation conditions

Shu Wang Yan, Jing Jing Zhang, Ying Hui Tian, Hao Chen

Research output: Contribution to journalArticle

Abstract

When a gravity structure, such as a caisson or a jackup spudcan, is pulled out from the saturated soft clay foundation, a negative pore pressure will be developing, which may greatly increase the pullout force. Therefore, it is very important to estimate the negative pore pressure developed in the soil during the unloading process. The development of excess pore pressure is studied based on the triaxial extension tests under the isotropic consolidation conditions. By combining the modified Cambridge model with the Henkel's approach, the mechanism of negative pore pressure generation is revealed and a method is developed to predict the magnitude of the negative pore pressure. Meanwhile, the development rule of pore pressure under the isotropic consolidation conditions is obtained and explained why there will be a change of pore pressure from negative to positive. The research indicates that under the unloading conditions, the generalized shear stress induces positive pore pressure and the averaged principal stress generates negative pore pressure in the soil samples. The superposition of these two effects results in negative pore pressure in the initial unloading stage, and then becomes positive with the increase of strain. The research results can be used to predict the required force to pull out a structure from saturated clay foundation.

Translated title of the contributionExperiment and theory research on the pore pressure unloading characteristics of saturated clay under isotropic consolidation conditions
Original languageChinese
Pages (from-to)775-781
Number of pages7
JournalYantu Lixue/Rock and Soil Mechanics
Volume39
Issue number3
DOIs
Publication statusPublished - 10 Mar 2018

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Pore pressure
unloading
Unloading
Consolidation
pore pressure
consolidation
Clay
clay
experiment
Experiments
Soils
Caissons
caisson
soft clay
gravity
shear stress
Shear stress
Gravitation
soil sampling
soil

Cite this

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title = "等向固结饱和黏土卸载孔压特性的试验与理论研究",
abstract = "When a gravity structure, such as a caisson or a jackup spudcan, is pulled out from the saturated soft clay foundation, a negative pore pressure will be developing, which may greatly increase the pullout force. Therefore, it is very important to estimate the negative pore pressure developed in the soil during the unloading process. The development of excess pore pressure is studied based on the triaxial extension tests under the isotropic consolidation conditions. By combining the modified Cambridge model with the Henkel's approach, the mechanism of negative pore pressure generation is revealed and a method is developed to predict the magnitude of the negative pore pressure. Meanwhile, the development rule of pore pressure under the isotropic consolidation conditions is obtained and explained why there will be a change of pore pressure from negative to positive. The research indicates that under the unloading conditions, the generalized shear stress induces positive pore pressure and the averaged principal stress generates negative pore pressure in the soil samples. The superposition of these two effects results in negative pore pressure in the initial unloading stage, and then becomes positive with the increase of strain. The research results can be used to predict the required force to pull out a structure from saturated clay foundation.",
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等向固结饱和黏土卸载孔压特性的试验与理论研究. / Yan, Shu Wang; Zhang, Jing Jing; Tian, Ying Hui; Chen, Hao.

In: Yantu Lixue/Rock and Soil Mechanics, Vol. 39, No. 3, 10.03.2018, p. 775-781.

Research output: Contribution to journalArticle

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