Use of surface waves for geotechnical engineering applications in Western Sydney

Abstract

Current in situ methods used to geotechnically characterize the ground are predominantly based on invasive mechanical techniques (e.g. CPT, SPT, DMT). These techniques are localized to the tested area thus making it quite time consuming and costly to extensively cover large areas. Hence, a study has been initiated to investigate the use of the non-invasive Multichannel Analysis of Surface Waves (MASW) and Multichannel Simulation with One Receiver (MSOR) techniques to provide both an evaluation of compacted ground and a general geotechnical site characterization. The MASW technique relies on the measurement of active ambient vibrations generated by sledgehammer hits to the ground. Generated vibrations are gathered by interconnected electromagnetic geophones set up in the vertical direction and in a linear array at the ground surface with a constant spacing. The MSOR technique relies on one sensor, one single geophone used as the trigger, and multiple impacts are delivered on a steel plate at several distances in a linear array. The main attributes of these non-invasive techniques are the cost effectiveness and time efficiency when compared to current in situ mechanical invasive methods. They were applied to infer the stiffness of the ground layers by inversion of the phase velocity dispersion curves to derive the shear wave velocity (Vs) profile. The results produced by the MASW and the MSOR techniques were verified against independent mechanical Cone Penetration Test (CPT) and Standard Penetration Test (SPT) data. This paper identifies that the MASW and the MSOR techniques could be potentially useful and powerful tools in the evaluation of the ground compaction and general geotechnical site characterization.