Comparison of Surface Wave Tests for Pavement System Thicknesses/Moduli

This paper discusses the comparison of the shear wave velocity results for the concrete, lime treated base and subgrade pavement layers obtained from two separate surface wave test methods at a concrete pavement site. The older Spectral Analysis of Surface Waves (SASW) and newer Multiple Impact of Surface Waves (MISW) test methods were performed at the same concrete pavement forensic investigation project for comparison purposes. Neither the SASW nor MISW test methods require the installation of boreholes to measure the shear wave velocity and layer thickness profiles of asphalt or concrete pavements, and the underlying base and subgrade layers, thus reducing the costs of the tests. The older SASW and newer MISW methods differ only slightly from one another in the equipment used, method of data collection, but involve significantly different data processing. This paper includes a comparison and discussion of the surface wave test results, as well as backgrounds of the MISW and SASW methods. The MISW method is able to provide much more accurate determinations of layer thicknesses (within 4–5 mm for the pavement surfaced layer) and layer thicknesses/moduli for the underlying less stiff base and subgrade layers than the SASW method which greatly overestimates moduli of less stiff base materials immediately below the stiffer asphalt or concrete pavement.