Location

Chicago, Illinois

Session Start Date

4-29-2013

Session End Date

5-4-2013

Abstract

A county road department in Southeastern Michigan was faced with the problem of stabilizing a slope along the Clinton River supporting a heavily trafficked roadway. The roadway and supporting slope had performed satisfactorily for over 50 years. However, a reinforced concrete seawall that had partially supported the slope deteriorated over time, contributing to progressive failure of the slope and resulting damage to the roadway. The site is situated within the glacial lake plain district of Southeastern Michigan. The site geology consists of approximately 7 feet of over-consolidated clays underlain by approximately 17 feet of normally consolidated glacial-lacustrine clays. Below the normally consolidated clay, highly over-consolidated sandy clay till and dense fine to medium sands are present. The sands contain a confined aquifer with a hydrostatic head on the order of 20 feet. The 14-foot high, 35 degree slope has experienced progressive, creep type movement since approximately the year 2000 resulting in settlement and cracking of the roadway shoulder and pavement. Maintenance procedures to maintain serviceability of the roadway created increased surcharge loads that appear to have precipitated further creep movement. Our analyses indicated the unreinforced slope possessed a factor of safety of approximately one or less with respect to global and direct sliding failure mechanisms under both drained and undrained conditions. A number of alternatives were considered to obtain the desired factory of safety values. Upon analysis, these alternatives were not considered satisfactory due to failure to meet the project objectives, typically cost and/or failure to obtain the desired factor of safety against slope failure. A multi-phased approach was selected that was aimed at both reducing the destabilization forces as well as increasing the resisting forces by replacing the upper portion of the slope with geogrid-reinforced lightweight, angular blast furnace slag, and intercepting the slope failure surface with passive piles extending into the highly over-consolidated sandy clay till and/or dense sands. This approach allowed the project objective to be met with the work being accomplished on schedule and within budget. A cost savings of approximately $400,000 was realized with respect to other stabilization alternatives.

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

Stabilization of a Failed Highway Slope: A Multi-Phased Approach

Chicago, Illinois

A county road department in Southeastern Michigan was faced with the problem of stabilizing a slope along the Clinton River supporting a heavily trafficked roadway. The roadway and supporting slope had performed satisfactorily for over 50 years. However, a reinforced concrete seawall that had partially supported the slope deteriorated over time, contributing to progressive failure of the slope and resulting damage to the roadway. The site is situated within the glacial lake plain district of Southeastern Michigan. The site geology consists of approximately 7 feet of over-consolidated clays underlain by approximately 17 feet of normally consolidated glacial-lacustrine clays. Below the normally consolidated clay, highly over-consolidated sandy clay till and dense fine to medium sands are present. The sands contain a confined aquifer with a hydrostatic head on the order of 20 feet. The 14-foot high, 35 degree slope has experienced progressive, creep type movement since approximately the year 2000 resulting in settlement and cracking of the roadway shoulder and pavement. Maintenance procedures to maintain serviceability of the roadway created increased surcharge loads that appear to have precipitated further creep movement. Our analyses indicated the unreinforced slope possessed a factor of safety of approximately one or less with respect to global and direct sliding failure mechanisms under both drained and undrained conditions. A number of alternatives were considered to obtain the desired factory of safety values. Upon analysis, these alternatives were not considered satisfactory due to failure to meet the project objectives, typically cost and/or failure to obtain the desired factor of safety against slope failure. A multi-phased approach was selected that was aimed at both reducing the destabilization forces as well as increasing the resisting forces by replacing the upper portion of the slope with geogrid-reinforced lightweight, angular blast furnace slag, and intercepting the slope failure surface with passive piles extending into the highly over-consolidated sandy clay till and/or dense sands. This approach allowed the project objective to be met with the work being accomplished on schedule and within budget. A cost savings of approximately $400,000 was realized with respect to other stabilization alternatives.