Persistent Link:
http://hdl.handle.net/10150/193921
Title:
Viscous Effects on Penetrating Shafts in Clay
Author:
Mahajan, Sandeep Prakash
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
When a rigid shaft such as a jacked pile or the sleeve of a cone penetrometer penetrates soil, the soil mass at the shaft tip fails. This failed soil mass flows around the shaft surface and creates a disturbed soil zone. The soil in this zone, which is at a failure or critical state (CS), flows and behaves like a viscous fluid. During continuous penetration, the shaft surface is subjected to an additional viscous shear stress above the static shear stress (interfacial solid friction). The total resistance on the shaft in motion is due to the static and viscous shear components. Current methods of calculating the penetration resistance in soils are based on static interfacial friction, which determine the force required to cause failure at the shaft-soil interface and not the viscous drag. The main aim of this research is to understand the viscous soil resistance on penetrating shafts in clays.This research consists of two components. First, a theoretical analysis based on creeping flow hydrodynamics is developed to study the viscous drag on the shaft. The results of this analysis reveal that the size of the CS zone, the shear viscosity of the soil and velocity of the shaft influence the viscous drag stress. Large increases in viscous drag occur when the size of the CS zone is less than four times the shaft radius.Second, a new experimental procedure to estimate the shear viscosity of clays with water contents less than the liquid limit is developed. Shear viscosity is the desired soil parameter to estimate viscous drag. However, there is no standard method to determine shear viscosity of clays with low water contents (or Liquidity Index, LI). Soils can reach CS for water contents in the plastic range (LI<1) and exhibit viscous behavior. The fall cone test is widely used to interpret the index (liquid and plastic limit) and strength properties of clays. In this study the existing analysis of the fall cone test is reexamined to discern the viscous drag as the cone penetrates the soil. This reexamination shows that the shear viscosity of clays with low water contents (LI<1.5) can be estimated from time-penetration data of the fall cone. Fall cone test results on kaolin show that the shear viscosity decreases exponentially with an increase in LI.The results of this research can be used to understand practical problems such as jacked piles in clays, cone penetrometer sleeve resistance and advancement of casings in soil for drilling or tunneling operations.
Type:
text; Electronic Dissertation
Keywords:
viscosity; clay; fall cone test; jacked piles; critical state
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Civil Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Budhu, Muniram
Committee Chair:
Budhu, Muniram

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleViscous Effects on Penetrating Shafts in Clayen_US
dc.creatorMahajan, Sandeep Prakashen_US
dc.contributor.authorMahajan, Sandeep Prakashen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractWhen a rigid shaft such as a jacked pile or the sleeve of a cone penetrometer penetrates soil, the soil mass at the shaft tip fails. This failed soil mass flows around the shaft surface and creates a disturbed soil zone. The soil in this zone, which is at a failure or critical state (CS), flows and behaves like a viscous fluid. During continuous penetration, the shaft surface is subjected to an additional viscous shear stress above the static shear stress (interfacial solid friction). The total resistance on the shaft in motion is due to the static and viscous shear components. Current methods of calculating the penetration resistance in soils are based on static interfacial friction, which determine the force required to cause failure at the shaft-soil interface and not the viscous drag. The main aim of this research is to understand the viscous soil resistance on penetrating shafts in clays.This research consists of two components. First, a theoretical analysis based on creeping flow hydrodynamics is developed to study the viscous drag on the shaft. The results of this analysis reveal that the size of the CS zone, the shear viscosity of the soil and velocity of the shaft influence the viscous drag stress. Large increases in viscous drag occur when the size of the CS zone is less than four times the shaft radius.Second, a new experimental procedure to estimate the shear viscosity of clays with water contents less than the liquid limit is developed. Shear viscosity is the desired soil parameter to estimate viscous drag. However, there is no standard method to determine shear viscosity of clays with low water contents (or Liquidity Index, LI). Soils can reach CS for water contents in the plastic range (LI<1) and exhibit viscous behavior. The fall cone test is widely used to interpret the index (liquid and plastic limit) and strength properties of clays. In this study the existing analysis of the fall cone test is reexamined to discern the viscous drag as the cone penetrates the soil. This reexamination shows that the shear viscosity of clays with low water contents (LI<1.5) can be estimated from time-penetration data of the fall cone. Fall cone test results on kaolin show that the shear viscosity decreases exponentially with an increase in LI.The results of this research can be used to understand practical problems such as jacked piles in clays, cone penetrometer sleeve resistance and advancement of casings in soil for drilling or tunneling operations.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectviscosityen_US
dc.subjectclayen_US
dc.subjectfall cone testen_US
dc.subjectjacked pilesen_US
dc.subjectcritical stateen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineCivil Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBudhu, Muniramen_US
dc.contributor.chairBudhu, Muniramen_US
dc.contributor.committeememberHaldar, Achintyaen_US
dc.contributor.committeememberDesai, Chandrakant, S.en_US
dc.identifier.proquest1689en_US
dc.identifier.oclc137356754en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.