DYWIDAG Anchor Systems for Retaining Walls of the Sepulveda Pass, I-405 Project, Los Angeles

Interstate 405 is one of the principal highways in Southern California. Heavily traveled by commuters, I-405 has earned its place as one of the busiest freeways in the United States. The Sepulveda Pass section of I-405 serves hundreds of thousands of commuters between major urban centers of the Greater Los Angeles area.

A construction project on this section included adding a High Occupancy Vehicle Lane (HOV) or carpool lane for vehicles carrying more than one person, realigning existing on and off ramps, replacing and constructing a new bridge and several ramp structures, building approximately 29km (18miles) of retaining or sound walls and carrying out road improvements.

The California Department of Transportation (CALTRANS) and the Los Angeles Metropolitan Transportation Authority (Metro) jointly developed this project.

The retaining walls were designed and built by Drill Tech Drilling & Shoring, Inc. and incorporated permanent soil nails along the cut-off of the hills as well as permanent strand tieback walls along Sepulveda Boulevard that were part of the widening project.

Hundreds of Double Corrosion Protected (DCP) DYWIDAG Soil Nails and 500 Permanent 5-0.6" and 7-0.6” DCP DYWIDAG Strand Tieback Anchors were supplied for this project. The City of Los Angeles has requirements for load monitoring of the permanent tieback anchors, and the elasto magnetic DYNA Force® Sensor was the right choice to perform this function.

48 sensors were factory installed over individual strands on the stressing length, inside the corrugated sheathing. They were distributed at different heights of the two tieback wall locations and their lead wires conducted through the anchorage for easy connection to the readout box. They were used for additional load control during the performance/proof test and lock-off load transfer procedure. The walls were more than 350m long, and the lead wires are conducted along the wall length to a main control water-proof cabinet where multiplexer, modem and batteries are installed together with the readout box. The modem can send daily readings to a remote office location over the internet during the life of the anchor.

The DYNA Force® Sensor System is very easy to install and use, providing a reliable and accurate method to monitor the load of a strand or bar anchor. Construction work at this major project began in the spring of 2009 and is scheduled for completion in the spring of 2013.


California Department of Transportation (CALTRANS) Los Angeles Metropolitan Transportation Authority (Metro)

General Contractor

Kiewit Pacific Company, USA

Retaining Walls Subcontractor

Drill Tech Drilling and Shoring, Inc., USA

DSI Unit

DYWIDAG-Systems International USA Inc., BU Geotechnics, USA

DSI Scope

Supply of Double Corrosion Protected (DCP) DYWIDAG Soil Nails, 500 Permanent 5-0.6" and 7-0.6" DCP DYWIDAG Strand Tieback Anchors and of 48 DYNA Force® Strand Sensors; technical equipment

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