Evaluation of Intelligent Compaction at the Echo Dam Seismic Modification Project
Project ID: 406
Principal Investigator: Robert Rinehart
Research Topic: Improving Geotechnical Infrastructure Reliability
Funded Fiscal Years: 2013
Keywords: intelligent compaction, earthwork compaction quality control / quality assurance, echo dam seismic modification
Intelligent Compaction (IC) is an innovative earthwork construction control technology. In IC, roller compactor drum vibrations are monitored and related to soil properties through mathematical modeling, and these roller-measured values are available in real time and for 100% of the compacted area. Construction control is then based on the roller-measured values, rather than moisture-density spot test results (e.g., from nuclear gage or sand cone tests). IC holds tremendous benefit for Reclamation as it has the potential to result in a higher quality and more uniform product. The majority of IC research and development in the U.S. has been in the transportation infrastructure field and IC has had very little exposure in other earthwork areas – even though it holds such great potential benefit.
The earthwork specifications for the ongoing Echo Dam Seismic Modification project include provisions mandating that the contractor employ IC equipped rollers to collect and store IC data during compaction operations involving Zone 2 (filter sand) and Zone 2A (select transition), and Zone 4(select coarse fill) materials. Construction control for the compaction operations will still be by traditional means such as the sand cone density test. Accordingly, the IC data will not be used for project QC/QA, but rather collected as a means for Reclamation to evaluate the use of the technology within future projects.
The research being proposed here involves analyzing the IC data and producing a case study report detailing the use of IC at Echo Dam. This work will describe how IC compares to traditional earthwork QC/QA and how it could have been used for QC/QA purposes at Echo Dam, as well as highlight the benefits of this innovative technology. Given that the collection of the IC data is already written into the Echo Dam project specifications and represents no additional cost to the Science and Technology Program, this is very efficient research.
Need and Benefit
Implementation of IC technology into Reclamation earthwork construction holds several potential benefits. Direct benefits include:
1) 100% coverage: IC enables QA/QC with 100% coverage of the compacted area. Roller-measured values - which form the basis for QC/QA - exist wherever the roller has been operated. This is a substantial improvement in comparison to traditional spot testing which covers much less than 1% of the compacted area. This allows for inspectors to hone in on problem areas quickly and effectively. It also results in a final product with much lower uncertainty and risk because 100% of it has been inspected.
2) Phase out nuclear gage: Implementing IC decreases dependence on the nuclear moisture-density gage, as the roller becomes the primary QC/QA tool. This is desirable for several reasons including the increasing costs associated with purchasing, maintaining and storing gages, as well as the training and licensing of operators. Further, there is increasing risk associated with storing nuclear material and many agencies are looking for ways to phase out the use of the nuclear density gage for this reason.
3) Better documentation: IC technology provides GPS-position indexed QA data for the entire constructed area. This comprehensive electronic data can be stored long-term and referenced in the event that issues arise that require investigation into the as-built facility.
4) Test more materials: Materials such as pea gravel and rock fill are difficult and expensive to reliably test for moisture and density. These materials are often used by Reclamation and have traditionally been controlled by method specifications rather than by rigorous testing. However, IC is applicable to these materials, and the same level of control can be applied to them as to any other granular material.
Another, more indirect benefit of IC also exists. The operator of the roller compactor is able to view the roller-measured values in real time. This data is displayed on a screen onboard the roller and is color coded (i.e., green = good, red = bad) to give the operator immediate feedback regarding where more compactive effort is needed and where compaction is likely finished. This allows for more efficient and more uniform compaction operations. This is a great benefit to the contractor, but also to Reclamation as it results in more efficient construction and a more uniform product.
These benefits, both direct and indirect, result in higher quality products. QA has been performed for the entire compacted area and QA data can be easily stored for future reference. More uniform compaction operations are enabled and the use of the nuclear density gage is decreased. Materials that were previously not tested and controlled by method specifications are now rigorously tested.
The research proposed here will allow for Reclamation practitioners to be exposed to IC and to begin developing confidence in it. The documentation of the Echo Dam case study will be a significant step in Reclamation's adoption of IC as a preferred earthwork construction control methodology, and since the field data collection is paid for using project funds, the research is very efficient.
The results of the research will be presented in a formal case study report to the Science & Technology Program. To encourage technology transfer to all reaches of Reclamation, key results and highlights will be summarized in a Water & Power Solutions Bulletin. Further, given that this work represents the first use of IC technology on an embankment dam, results will be submitted for publication in the widely read, peer-reviewed literature.
This information was last updated on December 12, 2013
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