Alternative rigid pavement models for the reduction of impulse response field data

• Main Author: Jackson, Hudson Victor Henry Aina
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2003
• Subjects: Civil engineering
• ISBN: 0496406515; 9780496406517

The Impulse Response (IR) method is a non-destructive method of testing used for the quality control/assessment of pavements, bridge decks and deep foundations. In the case of pavements, the pavement is excited at frequencies below or at its fundamental frequency and the response recorded. This method has been successfully used to determine the presence of voids or loss of support in rigid pavements. Voids underneath rigid pavements can be detected by monitoring changes in flexibility or stiffness due to loss of support. In the presence of voids, almost all the waves are reflected back to the surface, resulting in an increase in flexibility. The underlying assumption of the current data reduction procedure, that the dynamic response of the pavement-soil system can be represented as a single degree of freedom (SDOF) system, oversimplifies a complex dynamic problem and, although useful for practical purposes, introduces some inconsistencies and uncertainties in the interpretation of the results. The deficiencies of the SDOF system can be attributed primarily to a deviation of the shape of the impedance function for rigid pavement systems from the SDOF impedance function, especially at frequencies beyond the fundamental frequency. Results from an extensive parametric study show that the dynamic response of rigid pavements in nondestructive IR testing is highly frequency dependent. While the response is dominantly affected by the stiffness of the surface layer and subgrade, properties of the other pavement layers may play an important role. Two new sets of alternative models namely, the lumped parameter and the cone models are proposed for the reduction of IR data. The LP models consist of additional springs and dashpots in series and introduce an additional internal degree of freedom. The cone model assumes that the load is distributed as a cone through the pavement layers and accounts for the reflection within the individual layers. A comparison of the models using field data collected by the Seismic Pavement Analyzer indicates that the cone model provides a much better fit to the field data. Results from the LP model are in general comparable to those from the SDOF model while those from the cone model are much lowest.