The resilient behavior is a significant parameter in the design, rehabilitation and serviceability of pavements. Resilient behavior is defined as the ratio of repeated deviator stress to that of recoverable strain. It has been found subgrade resilient modulus plays a vital role in the serviceability of flexible pavement and the object of this thesis to back calculate the subgrade resilient modulus of flexible pavements from data obtained from nondestructive testing using Dynaflect and Falling Weight Deflectometer(FWD)
A research procedure to determine the value of resilient modulus from nondestructive data is formulated. To conduct experiments in the laboratory for arriving at the characteristics of resilient modulus is elaborate, cumbersome, time consuming and it requires advanced equipments to simulate the conditions the pavement is undergoing during all seasons. To overcome this, nondestructive testing of pavements is selected for obtaining the material properties for rehabilitation and reconstruction. The FWD and Dyanaflect are the nondestructive devices used in this study.
The locations selected for this study are located at Auglaize, Fairfield and Vinton counties in Ohio. Nondestructive testing has been conducted on one flexible pavement at each county and the data is stored magnetic disks for analysis. Statistical analysis has been conducted for all data collected and a mean value of each sensor deflection is arrived to examine season and load variations. Using the Illipave finite element program and Illipave models the resilient modulus of subgrade material is back-calculated based on the interpretation of deflection measurements obtained from nondestructive testing.
In the back-calculation- technique deflection of pavements at distinct locations along the highway measured with nondestructive testing device is used as input. Soil response parameters are assumed for finite element solution. The predicted response is then compared with measured deflections and assumed values are adjusted until predicted values converge to measured deflections.The assumed parameters represent the material properties of flexible pavement when the measured and predicted deflections converge.
The results provide valid presentation of structural behavior of flexible pavement and can be used effectively to evaluate nondestructive test data and determine the material properties of existing pavements for for their rehabilitation strategies.