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Applications of Masw and Mhvsr Techniques for Infrastructure Evaluation with a Focus on the Effects of Different Transformation Techniques and Near-Field Effects on Derived Dispersion Data.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Applications of Masw and Mhvsr Techniques for Infrastructure Evaluation with a Focus on the Effects of Different Transformation Techniques and Near-Field Effects on Derived Dispersion Data./
作者:	Rahimi, Salman.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	284 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-04, Section: B.
Contained By:	Dissertations Abstracts International83-04B.
標題:	Civil engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28649142
ISBN:	9798460422203

Applications of Masw and Mhvsr Techniques for Infrastructure Evaluation with a Focus on the Effects of Different Transformation Techniques and Near-Field Effects on Derived Dispersion Data.
Rahimi, Salman.

Applications of Masw and Mhvsr Techniques for Infrastructure Evaluation with a Focus on the Effects of Different Transformation Techniques and Near-Field Effects on Derived Dispersion Data. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 284 p.

Source: Dissertations Abstracts International, Volume: 83-04, Section: B.

Thesis (Ph.D.)--University of Arkansas, 2021.

This item must not be sold to any third party vendors.

This dissertation is aimed at understanding two aspects of active surface wave methods to improve the accuracy and reliability of this method. These include (1) the performance of four common wavefield transformation methods for the multichannel analysis of surface wave (MASW) data processing and (2) near-field effects. Toward this end, extensive field measurements were conducted considering different factors affecting these two topics. The MASW and microtremor horizontal to vertical spectral ratio (MHVSR) were then employed to examine their efficiency for infrastructure health monitoring. Regarding the performance of the four common transformation techniques, it was observed that for sites with a very shallow and highly variable bedrock topography with a high-frequency point of curvature (>20 Hz), the Phase Shift (PS) method leads to a very poor-resolution dispersion image compared to other transformation methods. For sites with a velocity reversal, the Slant Stack (p) method fails to resolve the dispersion image for frequencies associated with layers located below the velocity reversal layer. Overall, the cylindrical frequency domain beamformer (FDBF-cylindrical) method was determined to be the best method under most site conditions. This method allows for a stable, high-resolution dispersion image for different sites and noise conditions over a wide range of frequencies, and it mitigates the near-field effects by modeling a cylindrical wavefield. However, the FDBF-cylindrical was observed to be dominated by higher modes at complex sites. Therefore, the best practice is to use more than one transformation method (FDBF-cylindrical and FK methods) to enhance the data quality. Regarding the near-field effects for active surface wave methods, it was observed that near-field effects are independent of surface wave type (Rayleigh and Love) and depth to impedance contrast. For sites with a very shallow impedance contrast, the FDBF-cylindrical transformation technique outperforms others in terms of dispersion resolution by significantly mitigating near-field effects. It is also revealed that source type is an important parameter, influencing the normalized array center distance criteria required to mitigate near-field effects. The best practical criteria for near-field mitigation include a normalized array center distance of 1.0 or greater for low-output impulsive sources such as a sledgehammer and a normalized array center distance of 0.5 for high-output harmonic sources such as a vibroseis. These criteria should not be violated when using a limited number of source offsets (≤2). But, if the multiple source offset approach (≥3 source offsets) is used where some of the source offsets meet the criteria, the near-field criteria can be violated for other source offsets. Additionally, it is recommended to use the multiple source offset approach along with the FDBF-cylindrical for data processing to mitigate near-field effects. For health monitoring of earthen hydraulic infrastructures, MASW was determined to be effective for detecting weak zones of such structures. In this regard, it is very important to use the reference shear wave velocity profiles to avoid misinterpretation of the results. Additionally, the grid pattern MHVSR method was determined to very effective for landslide evaluations for sites with shallow and complex bedrock topography, where bedrock is a key feature in the slope stability model.

ISBN: 9798460422203Subjects--Topical Terms:

860360
Civil engineering.
Subjects--Index Terms:

Horizontal to Vertical Spectral Ratio

Applications of Masw and Mhvsr Techniques for Infrastructure Evaluation with a Focus on the Effects of Different Transformation Techniques and Near-Field Effects on Derived Dispersion Data.
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245 1 0 $a Applications of Masw and Mhvsr Techniques for Infrastructure Evaluation with a Focus on the Effects of Different Transformation Techniques and Near-Field Effects on Derived Dispersion Data.
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500 $a Source: Dissertations Abstracts International, Volume: 83-04, Section: B.
500 $a Advisor: Wood, Clinton.
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506 $a This item must not be sold to any third party vendors.
520 $a This dissertation is aimed at understanding two aspects of active surface wave methods to improve the accuracy and reliability of this method. These include (1) the performance of four common wavefield transformation methods for the multichannel analysis of surface wave (MASW) data processing and (2) near-field effects. Toward this end, extensive field measurements were conducted considering different factors affecting these two topics. The MASW and microtremor horizontal to vertical spectral ratio (MHVSR) were then employed to examine their efficiency for infrastructure health monitoring. Regarding the performance of the four common transformation techniques, it was observed that for sites with a very shallow and highly variable bedrock topography with a high-frequency point of curvature (>20 Hz), the Phase Shift (PS) method leads to a very poor-resolution dispersion image compared to other transformation methods. For sites with a velocity reversal, the Slant Stack (p) method fails to resolve the dispersion image for frequencies associated with layers located below the velocity reversal layer. Overall, the cylindrical frequency domain beamformer (FDBF-cylindrical) method was determined to be the best method under most site conditions. This method allows for a stable, high-resolution dispersion image for different sites and noise conditions over a wide range of frequencies, and it mitigates the near-field effects by modeling a cylindrical wavefield. However, the FDBF-cylindrical was observed to be dominated by higher modes at complex sites. Therefore, the best practice is to use more than one transformation method (FDBF-cylindrical and FK methods) to enhance the data quality. Regarding the near-field effects for active surface wave methods, it was observed that near-field effects are independent of surface wave type (Rayleigh and Love) and depth to impedance contrast. For sites with a very shallow impedance contrast, the FDBF-cylindrical transformation technique outperforms others in terms of dispersion resolution by significantly mitigating near-field effects. It is also revealed that source type is an important parameter, influencing the normalized array center distance criteria required to mitigate near-field effects. The best practical criteria for near-field mitigation include a normalized array center distance of 1.0 or greater for low-output impulsive sources such as a sledgehammer and a normalized array center distance of 0.5 for high-output harmonic sources such as a vibroseis. These criteria should not be violated when using a limited number of source offsets (≤2). But, if the multiple source offset approach (≥3 source offsets) is used where some of the source offsets meet the criteria, the near-field criteria can be violated for other source offsets. Additionally, it is recommended to use the multiple source offset approach along with the FDBF-cylindrical for data processing to mitigate near-field effects. For health monitoring of earthen hydraulic infrastructures, MASW was determined to be effective for detecting weak zones of such structures. In this regard, it is very important to use the reference shear wave velocity profiles to avoid misinterpretation of the results. Additionally, the grid pattern MHVSR method was determined to very effective for landslide evaluations for sites with shallow and complex bedrock topography, where bedrock is a key feature in the slope stability model.
590 $a School code: 0011.
650 4 $a Civil engineering. $3 860360
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653 $a Multichannel analysis of Surface Wave (MASW)
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653 $a Surface wave methods
653 $a Transformation technique
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710 2 $a University of Arkansas. $b Civil Engineering. $3 2094097
773 0 $t Dissertations Abstracts International $g 83-04B.
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791 $a Ph.D.
792 $a 2021
793 $a English
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