The behaviour of a granular material under repeated loading

• Main Author: Boyce, John Rodney
• Format: Dissertation
• Language: English
• Published: University of Nottingham 1976
• Subjects: TA Engineering (General). Civil engineering (General)

A large number of repeated load triaxial tests were carried out on samples of a well graded crushed limestone, maximum particle size 38 mm. This material is commonly used for the base or sub-base layers of flexible highway pavements in the United Kingdom. The aim of the research was to measure the strains which occurred when the material was Subject to a wide range of stresses similar to those expected to occur in a pavement structure due to traffic loading. A review of previous work is presented and several new experimental techniques which were developed to achieve this aim are described. Resilient strain tests were performed in which a few cycles of load only were applied at each stress condition, including conditions of cyclic confining stress, in order to measure the resilient behaviour of the material without subjecting it to large permanent strains. The primary factors influencing resilient strain response were found to be the mean normal stress and the ratio of deviator stress to normal stress. Permanent strain tests were then performed in which large numbers of load cycles were applied at each stress condition. The permanent strain which developed was found to be largely dependent on the applied stress ratio and it was also found that large numbers of load cycles caused some anisotropy in the resilient behaviour. A model for the resilient strain response of the material is proposed, and the application of the results to pavement design is discussed.