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GUIDE SPECIFICATION FOR GROUND MODIFICATION METHODS

Description:

Over the last half century, public transportation agencies have greatly increased the use of ground modification methods to enable the use of construction sites that contain marginal geomaterials and to mitigate the risk of failure or poor performance of constructed facilities. More recently ground modification has been selected to meet challenges associated with accelerating construction in difficult geotechnical circumstances.

Ground modification methods have been widely used to provide both proactive and reactive geotechnical solutions for a wide range of issues including mitigation of soft or loose ground, or potential geohazards; increasing the speed of construction; and improving efficiencies in design of highway features. Ground modification methods are commonly used in all areas of transportation including structure foundations, pavement subgrades and bases, cut slopes, embankments, and earth retaining structures, and are used to provide practical solutions that mitigate geotechnical risks, remediate poor feature performance, and improve long-term durability of transportation assets.

The Federal Highway Administration (FHWA) and several state departments of transportation (DOTs) have conducted research and have developed guidance documents and other resources to remove the mystique surrounding these solutions, which have typically been developed by contractors in search of innovative approaches to complex geotechnical issues. Research efforts have successfully summarized design methods and quality assurance (QA) procedures developed for commonly used ground modification methods and have demonstrated the design methods based in accepted geotechnical practice. Design and construction methods, equipment needs, technical feasibility, and acceptance criteria have been widely implemented through products, such as the FHWA Demonstration Project 116, and subsequent reference manual updates that have now become Geotechnical Engineering Circular (GEC) 13 – Ground Modification Methods. Training courses provided through the FHWA’s National Highway Institute (NHI) have assisted state DOTs in developing and implementing design manuals to govern the use of ground modification methods regionally and, most recently, the development and deployment of GeoTechTools as a solution-based web tool continues to assist with increased safe, reliable, and cost-effective use.

At present, there is not a home in AASHTO for minimum guidance on the use of ground modification methods for application on bridge and highway projects. This is likely due to the wide applicability of solutions for both structure and earthworks, and large number of methods commercially available for ground modification. For continued promotion and cost-effective use, a guideline specification for the use of ground modification methods would provide agencies with a minimum and consistent standard for the selection, design, construction, and acceptance for commonly used techniques in transportation applications.

Objective:

The objective of this research is to develop an AASHTO guideline specification to assist public transportation agencies with the selection, design, construction, and acceptance of appropriate ground modification methods for transportation applications.

Benefits:

Guideline specifications have the potential to dramatically increase the efficiency and cost-effectiveness of ground modification solutions by assisting designers with specification language that could help avoid common issues, such as incorrect application of methods, a lack of understanding of mechanisms for improvement, and reliable metrics for acceptance and payment of constructed solutions. A significant problem faced by state DOTs is the lack of a standard for selecting from many methods available and proper application for the problem or issue being addressed.

Related Research:

As noted, there have been several efforts that have summarized research performed for the development of ground modification methods to group technologies based on function or application, and to remove the mystique from design methodologies and acceptance procedures. There is also a wealth of research to understand and quantify mechanisms for improvement, and to improve guidance. The development of the GeoTechTools web tool under the Second Strategic Highway Research Program (SHRP2) project R02 provides a venue for vetting and implementation of this technology specific research.

GeoTechTools is an online technology selection tool and resource for construction of ground modification solutions and is available at http://www.geoinstitute.org/geotechtools/. The SHRP2 report “Geotechnical Solutions for Soil Improvement, Rapid Embankment Construction, and Stabilization of the Pavement Working Platform” provides an excellent description of how GeoTechTools was developed including how technologies were selected for inclusion. The SHRP2 research effort provides a great resource not previously available but does not drill down to provide complete guidance for agencies.

Schafer, V.R. and Berg, R.R. (2014) “Geotechnical Solutions for Soil Improvement, Rapid Embankment Construction, and Stabilization of the Pavement Working Platform.” SHRP2 Report S2-R02-RW-1. Transportation Research Board, National Academies of Science, Washington, D.C.

In addition, references below provide additional information about the classification and application of common ground modification methods.

Schafer, V.R.; Berg, R.R.; Collin, J.G.; Christopher, B.R.; DiMaggio, J.A.; Filz, G.M.; Bruce, D.A.; and Ayala, D. (2016). “Geotechnical Engineering Circular No. 13 Ground Modification Methods, Volume I.” FHWA-NHI-16-028, Federal Highway Administration, Washington, D.C.

Schafer, V.R.; Berg, R.R.; Collin, J.G.; Christopher, B.R.; DiMaggio, J.A.; Filz, G.M.; Bruce, D.A.; and Ayala, D. (2016). “Geotechnical Engineering Circular No. 13 Ground Modification Methods, Volume II.” FHWA-NHI-16-028, Federal Highway Administration, Washington, D.C.

Tasks:
  1. Literature review.

  2. Develop clear, consistent nomenclature related to performance specifications for ground modification methods and in alignment with AASHTO.

  3. Identify, classify, and group existing ground modification methods and transportation applications that are likely to be included in the guideline specifications.

  4. Determine selection criteria, identify recommended design and construction methods, and determine acceptance and payment criteria for ground modification methods based on technology groupings and application classifications. Determine the impact of implementing recommendations on the performance and reliability of constructed highway features; speed of installation; degree of establishment of technologies in U.S. transportation practice; and disruption to public for construction.

  5. Develop guidance for agencies to select technology based, at a minimum, on the application, time in design life of installation (i.e., during design or in remediation), complexity of the technology, quality assurance (QA), availability of an accepted design methodology, regional availability, and cost.

Publish the final AASHTO guideline specification on recommended practice.

Implementation:

Implementation of the guideline specification will be accomplished through adoption as an AASHTO ballot. Because ground modification affects all areas of highway design, this will require presentations at the AASHTO Committees on Bridges and Structures (COBS), Design, and Materials and Pavements (COMP), as well as at various regional and national meetings and conferences, including the TRB annual meeting. Challenges will include aversion to the real or perceived risks by both agencies and contractors, lack of trained personnel, risk averse cultures and institutional bias to known technology, and perceived high initial costs. Inconsistent terminology related to design and QA will also present challenges by inhibiting effective communication of design and construction intent.

Relevance:

FHWA

Sponsoring Committee:AKG50, Transportation Earthworks
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Antonio Marinucci, PhD, MBA, PE; V2C Strategists, LLC; (347) 670.2006; amarinucci@v2cstrategists.com Silas C. Nichols, PE, Principal Geotechnical Engineer, FHWA; (202) 366.1554; silas.nichols@dot.gov
Date Posted:02/28/2021
Date Modified:04/12/2021
Index Terms:Specifications, Guidelines, Geotechnical engineering, Soil stabilization, Foundations, Subgrade (Pavements), Slopes, Embankments, Earthwork,
Cosponsoring Committees: 
Subjects    
Highways
Construction
Geotechnology
Bridges and other structures

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