Location

Chicago, Illinois

Session Start Date

4-29-2013

Session End Date

5-4-2013

Abstract

American Municipal Power is developing the Smithland Hydroelectric Project adjacent to the U.S. Army Corps of Engineers’ existing Smithland Locks and Dam on the Ohio River. The site geology is characterized by over 100 feet of variable alluvial deposits overlying karstic limestone. The investigation program revealed loose to medium dense sands and sandy gravels along with some interbedded clay. Large voids were encountered in rock and ground loss into solution features was believed to have created ‘chimneys’ of loosened soil. A project-specific seismic hazard evaluation determined that the maximum credible earthquake (MCE) is a 7.5M event associated with the New Madrid Seismic Zone. Site response analysis indicates that a peak ground acceleration of 0.52 g at the ground surface could be expected for the MCE, largely due to amplification within the soil column. The liquefaction cyclic softenng assessment indicated that the granular soils at the site would be susceptible to liquefaction, if left untreated. There was also concern about potential ground loss below the powerhouse and the migration of soil into rock under the powerhouse’s sheet pile cut-off wall. A ground improvement program was conducted to address these issues. Vibro-replacement was performed under the hardfill closure structures to minimize settlement and mitigate against liquefaction. Compaction grouting was performed overburden and rock to mitigate against liquefaction and ground loss below and adjacent to the powerhouse. Consoidation grouting was also performed along the cut-off wall.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Seventh Conference

Publisher

Missouri University of Science and Technology

Publication Date

4-29-2013

Document Version

Final Version

Rights

© 2013 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 29th, 12:00 AM May 4th, 12:00 AM

Ground Improvement for the Smithland Hydroelectric Project

Chicago, Illinois

American Municipal Power is developing the Smithland Hydroelectric Project adjacent to the U.S. Army Corps of Engineers’ existing Smithland Locks and Dam on the Ohio River. The site geology is characterized by over 100 feet of variable alluvial deposits overlying karstic limestone. The investigation program revealed loose to medium dense sands and sandy gravels along with some interbedded clay. Large voids were encountered in rock and ground loss into solution features was believed to have created ‘chimneys’ of loosened soil. A project-specific seismic hazard evaluation determined that the maximum credible earthquake (MCE) is a 7.5M event associated with the New Madrid Seismic Zone. Site response analysis indicates that a peak ground acceleration of 0.52 g at the ground surface could be expected for the MCE, largely due to amplification within the soil column. The liquefaction cyclic softenng assessment indicated that the granular soils at the site would be susceptible to liquefaction, if left untreated. There was also concern about potential ground loss below the powerhouse and the migration of soil into rock under the powerhouse’s sheet pile cut-off wall. A ground improvement program was conducted to address these issues. Vibro-replacement was performed under the hardfill closure structures to minimize settlement and mitigate against liquefaction. Compaction grouting was performed overburden and rock to mitigate against liquefaction and ground loss below and adjacent to the powerhouse. Consoidation grouting was also performed along the cut-off wall.