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Sensitivity of Shear and Longitudinal Velocity to Compression and Shear Stress Paths in Cohesive Soils.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Sensitivity of Shear and Longitudinal Velocity to Compression and Shear Stress Paths in Cohesive Soils./
作者:	McAneny, George T.
面頁冊數:	1 online resource (145 pages)
附註:	Source: Masters Abstracts International, Volume: 84-04.
Contained By:	Masters Abstracts International84-04.
標題:	Geotechnology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29326145click for full text (PQDT)
ISBN:	9798352912416

Sensitivity of Shear and Longitudinal Velocity to Compression and Shear Stress Paths in Cohesive Soils.
McAneny, George T.

Sensitivity of Shear and Longitudinal Velocity to Compression and Shear Stress Paths in Cohesive Soils. - 1 online resource (145 pages)

Source: Masters Abstracts International, Volume: 84-04.

Thesis (M.S.)--Tufts University, 2022.

Includes bibliographical references

Clays, whether deposited on the seafloor or resedimented in the lab, generally exhibit a type of anisotropy called transverse isotropy (TI) due to layering and grain/void orientation from compaction. Sediments also experience an array of stress states due to varying geologic conditions. It is important to systematically measure how velocity anisotropy evolves with stress path to improve subsurface geophysical models, understand dynamic stress-strain relationships, and perform informed geotechnical site characterizations. This research experimentally measured velocity anisotropy in intact vs resedimented Boston Blue Clay (BBC), as well as stress path velocity dependence, vertical velocities during undrained shear, and velocity anisotropy from 1 to 10 MPa of resedimented Gulf of Mexico Eugene Island Clay (RGoM-EI). Results for intact versus resedimented BBC agree, and all clays exhibited low horizontal vs vertical velocity anisotropy and inclined compressional wave anisotropy (Thomsen parameters ≤ 0.3). Shear stress was found to affect wave velocity immensely, and results suggest that stress path compression-derived equivalent velocity curves resemble Modified Cam Clay (MCC) iso-porosity ellipses. Undrained shear-derived iso-velocity curves agree with those from normal consolidation as well, implying that porosity/density controls vertical P-wave velocity (Vp) in normally consolidated clays.This thesis also improves upon shear and longitudinal (Vs and Vp) wave velocity measurement technologies developed at Tufts Advanced Geotechnical Laboratory and MIT. Prior technology exhibited signal noise issues that affected horizontal wave velocity interpretation. Additionally, apparatus compressibility was not considered in the previous studies, leading to offset velocity measurements. The signal issue in the horizontal wave arrivals was found to be caused by improper grounding, originating from a shared ground pin of both receiving and sending actuators. Apparatus compressibility was then measured, and for a uniaxial test at 10 MPa axial effective stress, the velocity offset was found to be 13.7 m/s. Since the P-wave velocity range of interest is greater than 1500 m/s in sea water, this deviation produces a 2.5% error in vertical P-wave velocity (VpV). This implies that all prior VpV were overestimated by up to 2.5 percent, though this error is now corrected for in post-processing.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798352912416Subjects--Topical Terms:

1018558
Geotechnology.
Subjects--Index Terms:

AnisotropyIndex Terms--Genre/Form:

542853
Electronic books.

Sensitivity of Shear and Longitudinal Velocity to Compression and Shear Stress Paths in Cohesive Soils.
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520 $a Clays, whether deposited on the seafloor or resedimented in the lab, generally exhibit a type of anisotropy called transverse isotropy (TI) due to layering and grain/void orientation from compaction. Sediments also experience an array of stress states due to varying geologic conditions. It is important to systematically measure how velocity anisotropy evolves with stress path to improve subsurface geophysical models, understand dynamic stress-strain relationships, and perform informed geotechnical site characterizations. This research experimentally measured velocity anisotropy in intact vs resedimented Boston Blue Clay (BBC), as well as stress path velocity dependence, vertical velocities during undrained shear, and velocity anisotropy from 1 to 10 MPa of resedimented Gulf of Mexico Eugene Island Clay (RGoM-EI). Results for intact versus resedimented BBC agree, and all clays exhibited low horizontal vs vertical velocity anisotropy and inclined compressional wave anisotropy (Thomsen parameters ≤ 0.3). Shear stress was found to affect wave velocity immensely, and results suggest that stress path compression-derived equivalent velocity curves resemble Modified Cam Clay (MCC) iso-porosity ellipses. Undrained shear-derived iso-velocity curves agree with those from normal consolidation as well, implying that porosity/density controls vertical P-wave velocity (Vp) in normally consolidated clays.This thesis also improves upon shear and longitudinal (Vs and Vp) wave velocity measurement technologies developed at Tufts Advanced Geotechnical Laboratory and MIT. Prior technology exhibited signal noise issues that affected horizontal wave velocity interpretation. Additionally, apparatus compressibility was not considered in the previous studies, leading to offset velocity measurements. The signal issue in the horizontal wave arrivals was found to be caused by improper grounding, originating from a shared ground pin of both receiving and sending actuators. Apparatus compressibility was then measured, and for a uniaxial test at 10 MPa axial effective stress, the velocity offset was found to be 13.7 m/s. Since the P-wave velocity range of interest is greater than 1500 m/s in sea water, this deviation produces a 2.5% error in vertical P-wave velocity (VpV). This implies that all prior VpV were overestimated by up to 2.5 percent, though this error is now corrected for in post-processing.
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538 $a Mode of access: World Wide Web
650 4 $a Geotechnology. $3 1018558
653 $a Anisotropy
653 $a Clay
653 $a Consolidation
653 $a Shear
653 $a Velocity
653 $a Cohesive soils
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690 $a 0428
710 2 $a ProQuest Information and Learning Co. $3 783688
710 2 $a Tufts University. $b Civil Engineering. $3 1020594
773 0 $t Masters Abstracts International $g 84-04.
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