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"Resilient modulus indicates the stiffness of a soil under controlled confinement conditions and repeated loading. The test is intended to simulate the stress conditions that occur in the base and subgrade of a pavement system. Resilient modulus has been adopted by the U.S. federal highway administration as the primary performance parameter for pavement design. We thank those who prepared these papers, the reviewers who provided anonymous peer reviews, and those who participated in the symposium. We hope this STP encourages more work to improve the testing standard and the value of the Resilient Modulus test."
At head of title: National Cooperative Highway Research Program.
Field and laboratory testing programs were conducted to develop models that predict the resilient modulus of subgrade soils from the test results of DCP, CIMCPT, FWD, Dynaflect, and soil properties. The field testing program included DCP, CIMCPT, FWD, and Dynaflect testing, whereas the laboratory program included repeated load triaxial resilient modulus tests and physical properties and compaction tests. Nine overlay rehabilitation pavement projects in Louisiana were selected. A total of four soil types (A-4, A-6, A-7-5, and A-7-6) were considered at different moisture-dry unit weight levels. The results of the laboratory and field testing programs were analyzed and critically evaluated. A comprehensive statistical analysis was conducted on the collected data. The results showed a good agreement between the predicted and measured resilient modulus from the various field test methods considered. The DCP and CIMCPT models were enhanced when the soil moisture content and dry unit weight were incorporated. The results also showed that, among all back calculated FWD moduli, those back calculated using ELMOD 5.1.69 software had the best correlation with the measured Mr. Finally, the Mr values estimated using the approach currently adopted by the LADOTD were found to correlate poorly with the measured Mr values.
This report contains 27 papers that serve as a testament to the state-of-the-art of civil engineering at the outset of the 21st century, as well as to commemorate the ASCE's Sesquicentennial. Written by the leading practitioners, educators, and researchers of civil engineering, each of these peer-reviewed papers explores a particular aspect of civil engineering knowledge and practice. Each paper explores the development of a particular civil engineering specialty, including milestones and future barriers, constraints, and opportunities. The papers celebrate the history, heritage, and accomplishments of the profession in all facets of practice, including construction facilities, special structures, engineering mechanics, surveying and mapping, irrigation and water quality, forensics, computing, materials, geotechnical engineering, hydraulic engineering, and transportation engineering. While each paper is unique, collectively they provide a snapshot of the profession while offering thoughtful predictions of likely developments in the years to come. Together the papers illuminate the mounting complexity facing civil engineering stemming from rapid growth in scientific knowledge, technological development, and human populations, especially in the last 50 years. An overarching theme is the need for systems-level approaches and consideration from undergraduate education through advanced engineering materials, processes, technologies, and design methods and tools. These papers speak to the need for civil engineers of all specialties to recognize and embrace the growing interconnectedness of the global infrastructure, economy, society, and the need to work for more sustainable, life-cycle-oriented solutions. While embracing the past and the present, the papers collected here clearly have an eye on the future needs of ASCE and the civil engineering profession.
The mechanistic design of flexible pavement systems requires the specification of mechanical properties for asphaltic concrete, base course, and soil subgrade. The stiffness of the soil subgrade is represented by the resilient modulus, Mr, which is determined in the laboratory from cyclic triaxial tests and is usually a function of the level of applied stress. For a typical pavement project where numerous soils are encountered, cyclic triaxial testing to determine Mr for each subgrade soil may be too complex and time consuming to be applicable on a production basis. Therefore, alternative methods for the determination or estimation of Mr are appropriate and are in fact suggested in the 1993 AASHTO Guide for Design of Pavement Structures (AASHTO Guide 1993).