Location

San Diego, California

Session Start Date

5-24-2010

Session End Date

5-29-2010

Abstract

A widely used method for evaluating the damage and possibility of soil liquefaction, called Liquefaction Potential Index (PL), was proposed by Iwasaki in 1982. The values of 5 and 15 are the critical boundaries of PL to describe the damage which soil liquefaction will occur. The method is also adopted in the building design codes in Taiwan. The index is computed in form of integration by mul-tiplying the danger function (i.e. 1 minus safety factor) and the depth weight function. Theoretically, the computation should adequately reflect the liquefaction potential for the depth interval calculated. If the danger function is calculated based on the CPT logs, the integration would be more desirable due to the continuity in the data. However, the SPT logs, not as continuous as CPT logs, are much more common and generally used in the engineering practices today. The danger function calculated by SPT logs would become erroneous (sometimes overestimated) in cases where the integration is performed by summing up the discontinuous SPT values with irregularly spaced depth intervals. If the SPT logs are uniformly spaced by depth, the calculation should be correct. A misjudgment would be made and sometimes lead to an overestimated PL if the SPT log is non-uniformly distributed. Accordingly, the study herein proposes a simple method in order to correct the above-mentioned issue. After verifying the method by the collected data in 1999 Chi-chi Earthquake in Taiwan, the result shows that the correction can reduce the computation error and have the calculated PL values fall into the right ranges.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fifth Conference

Publisher

Missouri University of Science and Technology

Publication Date

5-24-2010

Document Version

Final Version

Rights

© 2010 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 24th, 12:00 AM May 29th, 12:00 AM

Verification of Potential Flaws in Computing Liquefaction Po-Tential Index by 1999 Chi-Chi Earthquake in Taiwan

San Diego, California

A widely used method for evaluating the damage and possibility of soil liquefaction, called Liquefaction Potential Index (PL), was proposed by Iwasaki in 1982. The values of 5 and 15 are the critical boundaries of PL to describe the damage which soil liquefaction will occur. The method is also adopted in the building design codes in Taiwan. The index is computed in form of integration by mul-tiplying the danger function (i.e. 1 minus safety factor) and the depth weight function. Theoretically, the computation should adequately reflect the liquefaction potential for the depth interval calculated. If the danger function is calculated based on the CPT logs, the integration would be more desirable due to the continuity in the data. However, the SPT logs, not as continuous as CPT logs, are much more common and generally used in the engineering practices today. The danger function calculated by SPT logs would become erroneous (sometimes overestimated) in cases where the integration is performed by summing up the discontinuous SPT values with irregularly spaced depth intervals. If the SPT logs are uniformly spaced by depth, the calculation should be correct. A misjudgment would be made and sometimes lead to an overestimated PL if the SPT log is non-uniformly distributed. Accordingly, the study herein proposes a simple method in order to correct the above-mentioned issue. After verifying the method by the collected data in 1999 Chi-chi Earthquake in Taiwan, the result shows that the correction can reduce the computation error and have the calculated PL values fall into the right ranges.