Location

Arlington, Virginia

Session Start Date

8-11-2008

Session End Date

8-16-2008

Abstract

A 70m-high slope is currently under construction near the entrance of a cut-and-cover tunnel in the inner loop highway of City of Patras – a seismically active area in Western Greece (PGA = 0.24g). The slope consists of marl layers dipping inwards and exhibiting distinct sets of joints. The landscape provides evidence that the site has been subjected to a major landslide at an unknown time in the past. Geotechnical investigation detected a sheared zone at about 15m below ground surface, and a water table a few meters below the planned toe of the slope. The angle and position of the slope surface together with the estimated position of the sheared zone provide a chair-like potentially unstable volume with convex plan view. In addition to the general stability problem, surface instabilities due to the aforementioned sets of joints create the potential of smaller wedge-type failures near the surface of the slope. Following a detailed geotechnical investigation, nonlinear stress finite-element analyses considering both gravitational and earthquake loads were performed. The analyses encompassed a number of different assumptions about: (a) depth to water table, (b) soil strength and (c) geometry of slope and soil layer interfaces. Results show that adequate safety can be achieved using a combination of piles and passive anchors. The effects of various factors/assumptions on the safety of the slope are discussed.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Sixth Conference

Publisher

Missouri University of Science and Technology

Publication Date

8-11-2008

Document Version

Final Version

Rights

© 2008 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Aug 11th, 12:00 AM Aug 16th, 12:00 AM

Stability Analysis of a 70m-High Cut at an Ancient Landslide Area in Patras, Greece

Arlington, Virginia

A 70m-high slope is currently under construction near the entrance of a cut-and-cover tunnel in the inner loop highway of City of Patras – a seismically active area in Western Greece (PGA = 0.24g). The slope consists of marl layers dipping inwards and exhibiting distinct sets of joints. The landscape provides evidence that the site has been subjected to a major landslide at an unknown time in the past. Geotechnical investigation detected a sheared zone at about 15m below ground surface, and a water table a few meters below the planned toe of the slope. The angle and position of the slope surface together with the estimated position of the sheared zone provide a chair-like potentially unstable volume with convex plan view. In addition to the general stability problem, surface instabilities due to the aforementioned sets of joints create the potential of smaller wedge-type failures near the surface of the slope. Following a detailed geotechnical investigation, nonlinear stress finite-element analyses considering both gravitational and earthquake loads were performed. The analyses encompassed a number of different assumptions about: (a) depth to water table, (b) soil strength and (c) geometry of slope and soil layer interfaces. Results show that adequate safety can be achieved using a combination of piles and passive anchors. The effects of various factors/assumptions on the safety of the slope are discussed.