Location
New York, New York
Date
16 Apr 2004, 8:00am - 9:30am
Abstract
Heavy rains in late December 2001 and January 2002 caused approximately 100 meters of roadway to settle approximately 0.5 meters within a week along Highway 1 on the Sonoma County Coast (Post Mile 30.3). This area has a complex landslide history involving two active landslides. These landslides coalesce on a narrow section of Highway 1 approximately 130 meters above the Pacific Ocean. A tieback wall, sheet piles and a lightweight fill embankment had previously been constructed at this location to try to stabilize and maintain the roadway. The subsurface material at the site is composed of a matrix of very weak and extremely fractured shale and mudstone with the inclusion of sandstone blocks and fragments. The landslides are mainly driven by erosion at their base caused by storm related flows in Timber Gulch Creek and wave action undermining the slopes below the roadway. The Office of Geotechnical Design West was requested to provide Geotechnical expertise for mitigating the landslide in an expeditious manner. Several mitigation measures were considered to stabilize the landslide. The selected repair strategy was to move the roadway approximately 30 meters inland behind the failure plane of the landslide. This required the construction of a 21-meter high soil nail wall and the excavation of approximately 100,000 cubic meters of rock material. In addition, a new tieback wall needed to be constructed on the outside shoulder of the new realigned highway to prevent the current landslide scarp from encroaching into the new roadway. Design of the mitigation system was completed by March 2002 and construction started early April 2002 and completed by June 2003. This paper describes the geology and landslide history of the site and the observations, design details, soil nail pull out testing data, and wallmonitoring data obtained during the construction of the soil nail and the soldier beam tieback walls. This project demonstrated the efficiency and flexibility of soil nail and post tensioned tieback anchors for mitigating large landslides in extremely unfavorable geologic and topographic conditions. California Department of Transportation sponsored the project.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
5th Conference of the International Conference on Case Histories in Geotechnical Engineering
Publisher
University of Missouri--Rolla
Document Version
Final Version
Rights
© 2004 University of Missouri--Rolla, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Momenzadeh, Mahmood; Wilcox, Grant; Nikoui, Hooshmand; and Pokrywka, Tim, "Landslide Mitigation on the Sonoma Coast in Northern California" (2004). International Conference on Case Histories in Geotechnical Engineering. 5.
https://scholarsmine.mst.edu/icchge/5icchge/session05/5
Landslide Mitigation on the Sonoma Coast in Northern California
New York, New York
Heavy rains in late December 2001 and January 2002 caused approximately 100 meters of roadway to settle approximately 0.5 meters within a week along Highway 1 on the Sonoma County Coast (Post Mile 30.3). This area has a complex landslide history involving two active landslides. These landslides coalesce on a narrow section of Highway 1 approximately 130 meters above the Pacific Ocean. A tieback wall, sheet piles and a lightweight fill embankment had previously been constructed at this location to try to stabilize and maintain the roadway. The subsurface material at the site is composed of a matrix of very weak and extremely fractured shale and mudstone with the inclusion of sandstone blocks and fragments. The landslides are mainly driven by erosion at their base caused by storm related flows in Timber Gulch Creek and wave action undermining the slopes below the roadway. The Office of Geotechnical Design West was requested to provide Geotechnical expertise for mitigating the landslide in an expeditious manner. Several mitigation measures were considered to stabilize the landslide. The selected repair strategy was to move the roadway approximately 30 meters inland behind the failure plane of the landslide. This required the construction of a 21-meter high soil nail wall and the excavation of approximately 100,000 cubic meters of rock material. In addition, a new tieback wall needed to be constructed on the outside shoulder of the new realigned highway to prevent the current landslide scarp from encroaching into the new roadway. Design of the mitigation system was completed by March 2002 and construction started early April 2002 and completed by June 2003. This paper describes the geology and landslide history of the site and the observations, design details, soil nail pull out testing data, and wallmonitoring data obtained during the construction of the soil nail and the soldier beam tieback walls. This project demonstrated the efficiency and flexibility of soil nail and post tensioned tieback anchors for mitigating large landslides in extremely unfavorable geologic and topographic conditions. California Department of Transportation sponsored the project.
