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The resilient modulus test is commonly used to determine the modulus of base or subgrade materials as well as to establish their nonlinear behavior. Since the resilient modulus test is time consuming, the number of tests performed for a given project is limited. For day-to-day operation of highway agencies, a more rapid test method is needed. The stress wave (or seismic) method is being considered in Texas for this purpose. Seismic methods of testing can rapidly and nondestructively provide fundamentally correct moduli at known states of stress. Unlike the resilient modulus test, comparative field testing methods are available for seismic methods that can provide similar results under similar conditions. This paper describes the seismic test procedure and its relationship to the resilient modulus test results. Also discussed are the repeatability and reproducibility of the results as a function of operator experience, type of soil, and preparation method.
"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."
Highways provide the arteries of modern society. The interaction of road, rail and other transport infrastructure with the ground is unusually intimate, and thus needs to be well-understood to provide economic and reliable infrastructure for society. Challenges include not only the design of new infrastructure (often on problematic ground), but inc
The Second International Symposium on Constitutive Modeling of Geomaterials: Advances and New Applications (IS-Model 2012), is to be held in Beijing, China, during October 15-16, 2012. The symposium is organized by Tsinghua University, the International Association for Computer Methods and Advances in Geomechanics (IACMAG), the Committee of Numerical and Physical Modeling of Rock Mass, Chinese Society for Rock Mechanics and Engineering, and the Committee of Constitutive Relations and Strength Theory, China Institution of Soil Mechanics and Geotechnical Engineering, China Civil Engineering Society. This Symposium follows the first successful International Workshop on Constitutive Modeling held in Hong Kong, which was organized by Prof. JH Yin in 2007. Constitutive modeling of geomaterials has been an active research area for a long period of time. Different approaches have been used in the development of various constitutive models. A number of models have been implemented in the numerical analyses of geotechnical structures. The objective of the symposium is to provide a forum for researchers and engineers working or interested in the area of constitutive modeling to meet together and share new ideas, achievements and experiences through presentations and discussions. Emphasis is placed on recent advances of constitutive modeling and its applications in both theoretic and experimental aspects. Six famous scholars have been invited for the plenary speeches of the symposiums. Some prominent scholars have been invited to organize four specialized workshops on hot topics, including “Time-dependent stress-strain behavior of geomaterials”, “Constitutive modeling within critical state soil mechanics”, “Multiscale and multiphysics in geomaterials”, and “Damage to failure in rock structures”. A total of 49 papers are included in the above topics. In addition, 51 papers are grouped under three topics covering “Behaviour of geomaterials”, “Constitutive model”, and “Applications”. The editors expect that the book can be helpful as a reference to all those in the field of constitutive modeling of geomaterials.
At head of title: National Cooperative Highway Research Program.
Design related project level pavement management - Economic evaluation of alternative pavement design strategies - Reliability / - Pavement design procedures for new construction or reconstruction : Design requirements - Highway pavement structural design - Low-volume road design / - Pavement design procedures for rehabilitation of existing pavements : Rehabilitation concepts - Guides for field data collection - Rehabilitation methods other than overlay - Rehabilitation methods with overlays / - Mechanistic-empirical design procedures.
Flexible Pavement is usually composed of several asphalt concrete layers, a granular base course and a soil subgrade. For mechanistic design of pavement systems based on elastic theory a modulus of elasticity must be designated for each design layer including the soil subgrade. The resilient modulus is used to characterize the soil in pavement design. The resilient modulus is defined as [equation] Where [symbol] is the deviator stress or the difference between the axial and confining stress, and [symbol] is the recoverable axial strain. The standard procedure for obtaining [symbol] is a repeated load tri-axial test at a constant confining pressure. There is not a singular resilient modulus value for a particular soil but rather the modulus is a function of the stress state. The standard test produces a range of resilient modulus values in a series of stress conditions. The resilient modulus test is inherently complicated, time consuming, and expensive. For these reasons, most commercial and design laboratories will not conduct these tests but instead rely on empirical relationships. Therefore, it has been recommended that alternative tests be developed to approximate resilient modulus. The Alternative Test Method was developed to be a simple and effective way of determining resilient modulus. The ATM design was based on a single degree of freedom, lumped mass spring system in which a hammer of known mass falls onto a volume of soil. Originally, there appeared to be good correlation between the Alternative Test Method and the standard test method for obtaining resilient modulus. However, subsequent testing failed to produce consistent results or confirm the correlation. Improvements have been made to the ATM to improve the overall consistency of results and correlation with the standard resilient modulus test results. The improvements to the ATM device include a new, more consistent drop mechanism, better data acquisition software, and a new calculation method. ATM tests were conducted on 4 different soils from TDOT research sites. Standard tri-axial resilient modulus tests were conducted for comparison with ATM resilient modulus tests. The improved ATM appears to measure a material response that correlates reasonably well with the standard triaxial resilient modulus test results for those soils tested. Furthermore, the Improved ATM produces much more consistent results than the Original ATM. It is also believed that the limitations of the device are outweighed by its simplicity and commonality with other lab tests. Therefore, the improved Alternative Test Method for resilient modulus of fine grained soils is believed to be a viable alternative to the standard test method for obtaining resilient modulus values.