Resilient Modulus and Permanent Deformation Testing of Unbound Granular Materials

Resilient Modulus and Permanent Deformation Testing of Unbound Granular Materials
Author: Anuroopa Kancherla
Publisher:
Total Pages:
Release: 2005
Genre:
ISBN:

Numerous research efforts have been devoted to characterizing the behavior of granular materials, which is one of the main concerns of pavement engineers. For better understanding of this behavior, laboratory tests where in-situ stress conditions and traffic loads are adequately simulated are needed. This study makes use of an expanded test protocol called a performance test that includes resilient modulus as well as permanent deformation testing. This test protocol determines three nonlinear resilient modulus parameters (k1, k2, k3) and two permanent deformation parameters ([alpha], [mu]). The resilient modulus test results are required inputs in the Level 1 analysis of the proposed American Association of State Highway and Transportation Officials (AASHTO) Pavement Design Guide. In addition, both resilient modulus and permanent deformation test results provide material property inputs to pavement performance prediction models. This study also evaluated the within laboratory repeatability of the performance test and developed a within laboratory precision statement. Further, a statistical analysis was conducted on the test results to estimate the number of test specimens required for testing for specific reliability levels. Two test specimens are required for a reliability level of 15%. A within laboratory study was also conducted to investigate the influence of specimen size on test results. The specimen height was reduced from 12 in. (304 mm) to 8 in. (203 mm), and there was no difference in test results at a confidence level of 95%. The performance test was further used successfully in subsequent studies to evaluate the behavior of granular materials and the influence of various factors on their behavior. As fines content increased, the resilient modulus values decreased and permanent deformation increased. As the moisture content increased, the resilient modulus value decreased and the resistance to permanent deformation decreased. A simplified laboratory measurement tool that is repeatable, relatively cheap and easy to perform might prompt the use of laboratory measured values of resilient modulus in pavement design and facilitate correlation of these values to field measured values on a large scale. Use of measured data for the base properties rather than estimates would insure improved pavement designs and, in many cases, would save money in construction costs.

Resilient Modulus Testing for Pavement Components

Resilient Modulus Testing for Pavement Components
Author: Mary Stroup-Gardiner
Publisher: ASTM International
Total Pages: 274
Release: 2003
Genre: Pavements
ISBN: 0803134614

"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."

Prediction of the Resilient Modulus of Unbound Granular Base and Subbase Materials Based on the California Bearing Ratio and Other Test Data

Prediction of the Resilient Modulus of Unbound Granular Base and Subbase Materials Based on the California Bearing Ratio and Other Test Data
Author: Steven Michael Lusher
Publisher:
Total Pages: 724
Release: 2004
Genre: Pavements, Flexible
ISBN:

"The paper describes methods for predicting the reilient (elastic) modulus of unbound granular base and subbase materials used in flexible pavement construction based on California Bearing Ratio (CBR) and/or other test data. Current pavement design methods employ relationships that estimate the resilient modulus from CBR results. The most commonly referenced of these relationships are limited in that they were developed using roadbed soils with CBR values no larger than approximately 15%. Therefore, it could be helpful if a model were available that would reliably predict the resilient modulus over a wider range of CBR values and be more specific to unbound granular materials. In this study, four different Missouri aggregates were analyzed that are commonly used in pavement base layers. Two of the aggregates were gravels and two were crushed stone."--Abstract, leaf iii.

Modelling of the Resilient and Permanent Deformation Behaviour of Subgrade Soils and Unbound Granular Materials

Modelling of the Resilient and Permanent Deformation Behaviour of Subgrade Soils and Unbound Granular Materials
Author: Haithem Soliman
Publisher:
Total Pages: 0
Release: 2015
Genre:
ISBN:

Laboratory characterization of subgrade soils and unbound granular materials is an essential component of the Mechanistic-Empirical Pavement Design Guide (Pavement ME). The design thickness and performance of a pavement structure are highly dependent on the deformation behaviour of subgrade and granular material. Specifications for granular materials vary among transportation agencies based on the availability of materials, climatic conditions, and function. Specifications aim to provide durable materials that meet design requirements and achieve the target design life with cost effective materials. The objectives of the research are to: • evaluate resilient modulus of typical fine-grained soils under traffic loading. • evaluate resilient modulus, permanent deformation, and permeability of typical unbound granular materials. • evaluate the effect of moisture and fines fraction on the performance of unbound granular materials and subgrade soil. • develop prediction models for resilient modulus to improve reliability of Level 2 inputs in the Pavement ME. • provide test data in support of updating Manitoba Infrastructure and Transportation specifications for unbound granular materials to improve the performance of pavement structures. Resilient modulus tests were conducted on three types of subgrade soil (high plastic clay, sandy clay, and silty sand/sandy silt) at four levels of moisture content. Resilient modulus, permanent deformation and permeability tests were conducted on six gradations representing two types of granular material (100% crushed limestone and gravel) at two levels of moisture content. Prediction models were developed for resilient modulus and compared to the models developed under the Long Term Pavement Performance program. The proposed models provided more reliable predictions with lower root mean square error. The deformation behaviour of the granular materials was classified according to the shakedown and dissipated energy approaches. Among the tested fines contents, limestone and gravel materials with optimum fines contents of 4.5% and 9%, respectively, had better resistance to plastic deformation and higher resilient modulus. The dissipated energy approach can be used to determine the stress ratio for the boundary between post compaction and stable zones from multistage triaxial testing. Result of permeability tests showed that the hydraulic conductivity of unbound granular material increased as the fines content decreased.