Synopsis_DTFH61-14-R-00001.docx

Federal Highway Administration Synopsis DTFH61-14-RI-00001

Title: Design and Analysis of Engineered Fills for Bridge Support

This synopsis is issued in accordance with FAR Part 5.203 in response to the mandatory requirement for a 15 day pre-solicitation notification. The purpose of this synopsis is to announce the Federal Highway Administration’s intent to issue a solicitation for a Full and Open Competition to procure the services of an Offeror for Design and Analysis of Engineered Fills for Bridge Support.

As a result of this solicitation, the FHWA intends to award one Cost Contract. The anticipated period of performance is TBD. The solicitation will be issued on or about November 25, 2013.

The Federal Highway Administration (FHWA) Turner-Fairbank Highway Research Center (TFHRC) and more specifically, the Geotechnical Research Program are seeking organizations interested in conducting a research study on the design and analysis of engineered fills for bridge support (both piers and abutments) to evaluate bearing resistance and deformations under in-service conditions. The use of engineered fills, which can include compacted granular fill (manufactured/borrowed aggregates) with or without layered reinforced soil systems, is an economical solution to reduce deformations and improve bearing resistance of shallow foundations.

Current AASHTO and FHWA design guidelines to evaluate the strength (e.g. bearing resistance) and service limit (e.g. deformations) of shallow foundations is based on elastic theory and is largely limited to methods developed for natural soil conditions. To apply these equations for engineered fills comprised of compacted granular fill, FHWA (2006) proposes making an assumption of the representative SPT blow count for use in the conventional settlement analysis methods (e.g. Hough or a modified Schmertmann method); however, the impact of different types of engineered fills and compaction effort is not accounted for in this guidance, which is available at the following website: http://www.csupomona.edu/~wakitch/library/FHWA_NHI-06-088.pdf.

For engineered fills comprised of geosynthetic reinforced soil used for bridge abutments, FHWA (2011) provides an empirical method using the results of a large-element load test in the laboratory (called a GRS performance test) to estimate post-construction settlement and bearing resistance. Then, to estimate lateral deformations, zero volume change is assumed based on the empirical settlement prediction. In addition, an analytical method is provided to evaluate bearing resistance; however, the analytical method is only validated for the range of materials tested to date. A summary of these methods is available at: http://www.fhwa.dot.gov/publications/research/infrastructure/structures/11026/.

The FHWA guidance available for GRS is limited to abutment applications with closely-spaced geosynthetic reinforcement; however, reinforced soil foundations (RSF) can also be used as a shallow foundation technology for pier support. While basic design guidelines are available that outline recommended spacing along with the geometry of the reinforcement layers for the shallow RSF, reliable methods to evaluate bearing resistance and deformations is lacking.

Regardless of the method selected for the service limit state, the current analyses primarily predict immediate settlement. While it is a common assumption that granular or engineered fills do not exhibit secondary deformation, it has been measured for in-service bridge abutment applications and large-scale laboratory test experiments.

Whether evaluating the strength or service limit check for shallow foundations on engineered fills, the resistance and movement of the native foundation soils underlying the engineered fills will need to be included. The stress distribution with depth through the engineered fills and into the foundation soil will impact the analysis; however, this soil strain with depth is not fully understood. The combined resistance and deformation of the native soils and engineered fill foundation is needed to ensure stability and tolerable movements of the superstructure.

The primary objectives of this requirement are to:

1. Develop practice-ready design tools to evaluate immediate and secondary settlement and lateral deformation of engineered fills used for bridge support.

2. Determine the stress distribution as a function of depth transferred by the engineered fill to the native foundation soils.

The solicitation will be released electronically via this Government Point of Entry (GPE) otherwise known as Federal Business Opportunities or www.fbo.gov. As such, no written, telephonic or other type of request for an advance copy of the solicitation will be entertained at this time. Potential Offerors are encouraged to register on www.fbo.gov to receive any further information in reference to the subject action inclusive of any announcements, and/or amendments to the solicitation after its release.

Offerors must have an approved accounting system to be eligible for award of a Cost Type Contract. This requirement is full and open competition pursuant to NAICS code 541712 with a size standard of 500 employees.

Any questions regarding this synopsis should be directed to Tamiko Aikens, Contract Specialist, via email at tamiko.aikens@dot.gov.