Application of seismic methods in pavement design and analysis

Abstract

An overview of the state-of-the-practice in the use of seismic methods in pavement design and analysis is presented herein. The primary parameter required for designing ahighway or an airfield pavement is a representative stiffness profile. This profile is used to predict the behavior and useful life of a pavement section subjected to wheel oads generated by vehicles or airplanes. Determining the stiffness profile consists of obtaining Young’s modulus and thickness of each layer in the pavement system. In terms of production testing, nondestructive methods are used for determining modulus profiles and other techniques are becoming obsolete. However, in terms of a research mode, testing methods that utilize cores, boreholes or test pits are used to verify the accuracy of the nondestructive methods. Seismic methods can be used for nondestructive t sting of pavements. Shear wave velocity of each layer is determined and used as an indicator of stiffness. Once the shear wave velocity is measured, Young’s modulus can be readily determined using the theory of elasticity. In this paper, the application of seismic methods to pavement design and analysis is discussed. The Spectral-Analysis-of-SurfaceWaves (SASW) technique is one example of a well-suited seismic technique for pavement evaluation. Seismic methods used in engineering applications (like pavement design) are based upon the same theory as conventional seismic methods. However, the conventional methods typically need extensive modification for engineering use because the maximum depth under consideration (i.e. 1 to 2 m in pavement design versus tens of kilometers in conventional geophysics). Modifications to the theory and practice of conventional geophysical prospecting are discussed. Several case studies demonstrating the use of seismic testing in pavement analysis are included. These case studies demonstrate hat, if applied properly, seismic methods are clearly supeTior to other nondestructive methods utilized for pavement evaluation in many cases.