BACKGROUND

Over the last half century, public transportation agencies have greatly increased the use of ground modification methods due to a need to use marginal sites with poor soil conditions for new construction purposes and to mitigate the risk of failure or the poor performance of constructed facilities. More recently, ground modification has been used to meet challenges associated with accelerating construction in difficult geotechnical circumstances.

Design and construction methods, equipment needs, technical feasibility, and acceptance criteria have been widely implemented through products developed by the Federal Highway Administration (FHWA). Technical assistance provided through the FHWA has helped state departments of transportation (DOTs) in developing and implementing design and construction documents to govern the use of ground modification methods regionally. Most recently, the development and deployment of GeoTechTools as a solution-based web tool continue to support increased safe, reliable, and cost-effective use.

Research is needed to develop consistent guidance to aid states in the implementation and use of ground modification methods for application on bridges, retaining structures, and other geotechnical features on transportation projects.

OBJECTIVE

The objective of this project is to provide performance-based guidelines for the selection, design, construction, and acceptance of appropriate ground modification methods for transportation applications. 

Accomplishment of the project objective will require at least the following tasks.

TASKS

PHASE I—Planning

Task 1. Conduct a literature review of state-of-the-practice research and documents on design philosophies and assumptions, construction procedures and specifications, and acceptance rationale for common ground modification methods used in transportation applications. The review shall include published and unpublished documentation and research conducted through the NCHRP; FHWA; and other national, international, state, and pooled-fund sponsored research.

Task 2. Synthesize the results of the literature review to identify knowledge gaps related to the research objective. These gaps should be addressed in the final product or the recommended future research, as budget permits. 

Task 3. Propose the methodology to be executed in Phase II to achieve the research objective. At a minimum, the research methodology shall develop:

• A clear, consistent nomenclature related to ground modification methods, functions, and performance applicable for the design and construction of bridges, retaining structures, and other geotechnical features;
• An approach for grouping common ground modification methods for a common function, application, acceptance procedure, or other that would facilitate the development of a guideline;
• An approach for the selection of method based on performance requirements;
• Performance-based requirements for design and construction; and 
• Proposed acceptance and payment criteria for common ground modification methods.

Task 4. Prepare a preliminary outline and table of contents for the draft language of guidelines for recommended ground modification methods for transportation applications such as bridges, retaining structures, and other geotechnical features for consideration by AASHTO to incorporate the research results in the appropriate AASHTO specifications (hereafter called AASHTO Deliverable). Include an annotated description of each section and subsection along with the proposed level of details of each subsection (i.e., brief, moderate, or extensive).

Task 5. Prepare Interim Report No. 1 that documents Tasks 1 through 4 and provides an updated work plan for the remainder of the research no later than 4 months after the contract award. The updated plan must describe the process and rationale for the work proposed for Phases II through IV.

PHASE II—Execution

Task 6. Execute the methodology according to the approved Interim Report No. 1 and update the preliminary outline and table of contents of the AASHTO Deliverable after consideration of the panel’s review comments.

Task 7. Develop a complete sample section of the AASHTO Deliverable to be selected by the NCHRP. This section should be publication-ready with the appropriate level of details.

Task 8. Prepare Interim Report No. 2 that documents Tasks 6 and 7 and provides an updated work plan for the remainder of the research no later than 4 months after the acceptance of Phase I. The updated work plan must describe the process and rationale for the work proposed for Phase III.

PHASE III—Draft Language Development

Task 9. Develop the remaining sections of the AASHTO Deliverable according to the approved Interim Report No. 2. Include illustrations (e.g., flowcharts, graphs) as needed to demonstrate interdependencies with existing products.

Task 10. Identify any inconsistencies between the AASHTO Deliverable and the AASHTO LRFD Bridge Design Specifications, the AASHTO LRFD Bridge Construction Specifications, and other AASHTO publications.

Task 11. Prepare Interim Report No. 3 that documents Tasks 9 and 10 and provides an updated work plan for the remainder of the research no later than 6 months before the contract end date. The updated work plan must describe the process and rationale for the work proposed for Phase IV.

PHASE IV—Final Products

Task 12. Revise the AASHTO Deliverable after consideration of the panel’s review comments.

Task 13. Plan and conduct an in-person workshop to review the draft AASHTO Deliverable. Revise the draft AASHTO Deliverable according to the outcomes of the workshop. Workshop participants shall be approved by the NCHRP.

Task 14. Submit the final deliverables including (1) the AASHTO Deliverable, (2) a final report that documents the entire research effort, and (3) a stand-alone technical memorandum titled “Implementation of Research Findings and Products.” 

STATUS: Research in Progress.