Design Memorandum



TO:                  All Design Section Staff

FROM:            Richard Stoddard
DATE:             April 20, 2006
SUBJECT:       CDF for Soldier Pile Tieback Walls


The following revisions are made to the construction of Soldier Pile Tieback Walls:

  • Specify CDF for soldier pile shafts (full height) when shafts are anticipated to be excavated in the dry

  • When under water concrete placement is anticipated for the soldier pile shafts, specify pumpable lean mix.

  • The Geotechnical Branch will provide temporary construction equipment loading to the Bridge Design for inclusion in the design. This loading shall be shown as part of design notes in the Plans.

  • Bridge design plans will show the maximum anticipated lateral deflection of the cantilevered piles so increases in quantity of the fascia wall concrete will be less likely to be in dispute with the Contractors.

  • Bridge Design, when appropriate, should consider shotcrete fascia walls in lieu of the comparatively more expensive cast-in-place concrete fascias, subject to structural and aesthetic requirements.


Background

The ADSC contractors had requested for us to use one type of concrete for the entire length of shafts. Past WSDOT practice was to place lean concrete or class 4000P in the toe and CDF in the exposed portion of the piles. During the course of the recent ADSC meeting, it was agreed that the CDF mix was appropriate for cantilevered soldier piles as well as soldier piles with PGAs provided shafts were dry. There were concerns that that CDF was not suitable for under water placement. However, some of our past contracts have specified CDF for wet shafts. The HQ Construction conducted a field survey of the recently constructed soldier pile walls and measure the lateral wall deflections. Based on the results shown below, there is no evidence that walls creep laterally when the CDF mix is used. However, further inquiries through the WACA concrete producers revealed that the prescribed recipe mix for CDF in the Standard Specification was not pumpable and the producers traditionally provided pumpable CDF mixes with cement contents in excess of 150 Lb/CY.

This new mix and its performance based acceptance criteria will be published in the August 7, 2006 amendments.


Performance of Soldier Pile Wall Projects with CDF Field Measurement Results:

The following walls were reviewed:

  • White Pass Fill Erosion, both cantilever and PGAs supported walls approx. 20 feet tall, no displacement over approx. one year.

  • 144th St. SE to 16th Ave. on SR 527, wall about 10 feet high with a noise wall constructed on top, built about 3 years ago, no movement.

  • Deception Pass Bridges, walls socketed into bedrock about 5 feet wall approx. 15 feet tall no movement evident.

  • Mud Slide project on SR 20 near Concrete, soldier pile wall approx. 10 feet tall, wall constructed in 2001, no movement.

  • Tenney Creek wall in southwest region on Salmon Creek Project, added by C.O. wall approx. 5 feet tall no movement over the last year.

  • SR 161 to Jovita Blvd., soldier pile wall approx. 15 feet tall, some discussion that the wall has moved up to 3 inches over the last 6 months; material in front of the wall has been removed and is 4 to 6 feet lower than designed.

  • In summary all of the walls checked did not move except the job on SR 161, and in this case they are unsure of the original alignment, it wasnít measured immediately after construction.

All of the walls had CDF placed around the piling and werenít loaded for approx. 2 weeks after the CDF placement.