Rock-Socketed Foundations for the Bridge at Pitkins Curve

A case history is presented on the design, construction, testing, and performance of drilled shafts for a bridge located at a difficult site on Highway 1 along California’s Big Sur Coast. The purpose of the bridge is to traverse a landslide that has been a long-term maintenance challenge for the California Department of Transportation (Caltrans). The site is underlain by rock of the Franciscan Formation and consists of metamorphosed siltstone and sandstone with inclusions of metabasalt. The rock is highly folded and fractured, difficult to sample in some locations, and exhibits wide variations in strength and quality. Construction challenges included the need to place bridge piers on a steep slope just outside the limits of active sliding and installation of drilled shafts into highly fractured rock prone to caving. The presence of perched water tables caused variable inflow of water to drilled shaft excavations. This paper describes how these constructability issues were addressed and how they influenced the selection and design of the foundations. This paper demonstrates a rational approach to a difficult design and construction problem, including: (1) the use of careful engineering geologic studies to design a structure with difficult access while traversing a major landslide (2) the need for careful attention to constructability for drilled shafts in highly fractured rock with variable groundwater, and (3) the interaction between load testing and site investigation and its application to Load and Resistance Factor Design (LRFD) design of rock-socketed drilled shafts.

• Record URL:
  • http://www.highwaygeologysymposium.org/wp-content/uploads/63_HGS-OPT.pdf
• 
• Supplemental Notes:
  • Copyright © 2012 Highway Geology Symposium (HGS). Abstract reprinted with permission of the HGS.
• Corporate Authors:

  Highway Geology Symposium

  ,   United States 
• Authors:
  • Turner, John P
  • Duffy, John D
  • Buell, Reid
  • Zheng, Xing
• Conference:
  • 63rd Highway Geology Symposium
  • Location: Redding California, United States
  • Date: 2012-5-7 to 2012-5-10
• Publication Date: 2012

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Photos; References; Tables;
• Pagination: pp 450-463
• Monograph Title: Proceedings of the 63rd Annual Highway Geology Symposium (HGS 2012)

Subject/Index Terms

• TRT Terms: Bridge foundations; Bridge piers; Fractured rock; Landslides; Load tests
• Uncontrolled Terms: Drilled shafts; Rock-socketed shafts
• Geographic Terms: Big Sur (California)
• Subject Areas: Bridges and other structures; Construction; Design; Geotechnology; Highways;

Filing Info

• Accession Number: 01661559
• Record Type: Publication
• Files: TRIS
• Created Date: Feb 28 2018 9:34AM