Comparison of traditional and new testing methods for riprap material quality

Project ID: 19119
Principal Investigator: Robert Rinehart
Research Topic: Improving Geotechnical Infrastructure Reliability
Funded Fiscal Years: 2019, 2020 and 2021
Keywords: None

Research Question

How do traditional riprap testing methods, based on testing 3/4-inch minus crushed material, compare to newer methods based on testing 2-inch thick slabs of design size blocks? This research will perform side-by-side comparisons of the two methods on identical samples to answer this question. Results will be used to inform design standards and construction specifications.

Need and Benefit

Need: Riprap is a construction material commonly used to armor soil slopes and protect them from erosion. Adequate
long term performance of the armoring stone is critical to the safety and longevity of structures. As nearly all of
Reclamation's water storage or conveyance structures has some sort of erosion protection, this research will benefit
all regions. It will particularly benefit new infrastructure projects where reliability of the riprap is an important design
As stated earlier, newer test methods attempt to reduce the scale effects inherent to laboratory testing. Translating
laboratory scale testing, where specimens need to fit into conventional equipment, into field scales is a challenge
inherent to all designs, but is particularly challenging with rock as increasing scale incorporates more defects. There is
a need to understand how the new testing procedure, incorporating larger specimens, can be compared to the older
testing procedure in order to guide our infrastructure designs and assessments.
This research will develop a fundamental understanding of riprap durability and testing to improve the reliability of
Reclamation's infrastructure projects.
Benefit: Reclamation will benefit from fundamental research into the assessment of rock durability as a function of
scale of specimens tested. This will guide how testing programs are specified and performed, leading to more robust
engineering designs and a reduced likelihood of riprap failure. The testing programs can then be optimized to
minimize costs to Reclamation for the best laboratory evaluations of longevity.
Urgency: This research is proposed at a time when the TSC laboratory has a number of riprap testing projects. The
project testing is primarily funded by the Dam Safety Office allowing S&T to leverage project funds to understand
fundamental behavior of construction materials. Additionally, the PI and co-PI are working with a number of other
USSD Embankment Dams Committee members to develop a state-of-the-art paper on the methods to evaluate and
design riprap. This research would be performed at a time when other funding would cover most of the laboratory
testing, and other professionals would be assisting in evaluating riprap testing and design methods, thereby
maximizing the impact of S&T funds.

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Last Updated: 6/22/20