Location

San Diego, California

Session Start Date

3-26-2001

Session End Date

3-31-2001

Abstract

To improve our understanding of the lateral load behavior of deep foundations in liquefied soil, a series of full-scale lateral load tests have been performed at the National Geotechnical Experimentation Site (NGES) at Treasure Island in San Francisco, California. The ground around the test piles was liquefied using explosives prior to lateral load testing. The goal of the project is to develop load-displacement relationships for bored and driven piles and pile groups in liquefied sand under full-scale conditions for improved and non-improved ground. The results of this investigation confirmed that controlled blasting techniques could successfully be used to induce liquefaction in a well-defined, limited area for field-testing purposes. Excess pore pressure ratios greater than 0.8 were typically maintained for 4 to 10 minutes after blasting. Data were collected showing the behavior of laterally loaded piles before and after liquefaction in non-improved ground. Following liquefaction, the stiffness of the soil-foundation system typically decreased by 70 to 80% of its pre-liquefaction value non-improved ground. Ground improvement with stone columns was then performed prior to an additional series of tests. Lateral load tests were again conducted before and after blasting to induce liquefaction. Cone penetration testing following the installation of stone columns found that the density was improved significantly. As a result, the stiffness of the foundation system following blasting was 2.9 to 3.6 times that in the liquefied soil. Subsequent tests involving more than twice as many piles or 50% larger piles provided less than 50% of the increased resistance produced by stone column treatment alone. This study provides some of the first full-scale quantitative results on the improvement of foundation performance due to ground improvement in a liquefiable deposit.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

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

Meeting Name

Fourth Conference

Publisher

University of Missouri--Rolla

Publication Date

3-26-2001

Document Version

Final Version

Rights

© 2001 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Mar 26th, 12:00 AM Mar 31st, 12:00 AM

Full-Scale Lateral Load Testing of Deep Foundations Using Blast-Induced Liquefaction

San Diego, California

To improve our understanding of the lateral load behavior of deep foundations in liquefied soil, a series of full-scale lateral load tests have been performed at the National Geotechnical Experimentation Site (NGES) at Treasure Island in San Francisco, California. The ground around the test piles was liquefied using explosives prior to lateral load testing. The goal of the project is to develop load-displacement relationships for bored and driven piles and pile groups in liquefied sand under full-scale conditions for improved and non-improved ground. The results of this investigation confirmed that controlled blasting techniques could successfully be used to induce liquefaction in a well-defined, limited area for field-testing purposes. Excess pore pressure ratios greater than 0.8 were typically maintained for 4 to 10 minutes after blasting. Data were collected showing the behavior of laterally loaded piles before and after liquefaction in non-improved ground. Following liquefaction, the stiffness of the soil-foundation system typically decreased by 70 to 80% of its pre-liquefaction value non-improved ground. Ground improvement with stone columns was then performed prior to an additional series of tests. Lateral load tests were again conducted before and after blasting to induce liquefaction. Cone penetration testing following the installation of stone columns found that the density was improved significantly. As a result, the stiffness of the foundation system following blasting was 2.9 to 3.6 times that in the liquefied soil. Subsequent tests involving more than twice as many piles or 50% larger piles provided less than 50% of the increased resistance produced by stone column treatment alone. This study provides some of the first full-scale quantitative results on the improvement of foundation performance due to ground improvement in a liquefiable deposit.