ABSTRACT:

Conventional techniques such as boreholes and test pits have been used for geotechnical site investigation purposes for many years. These conventional techniques are invasive, time-consuming and expensive. To minimize costs and to complement intrusive investigation techniques, geophysical methods are now commonly employed for geotechnical investigations in karst terrain. One relatively new non-invasive geophysical technique is the active multichannel analysis of surface waves (MASW) tool. This paper explores the utility of using the active MASW tool in karst terrain. A 20-pound sledge hammer was used as an acoustic source; a Seistronix Ras-24 channel seismograph was used to record the MASW field data. MASW field data were processed with SurfSeis4 software; the output at each test location was a 10-layer shear-wave velocity profile of the subsurface. Borehole control and 2-D electrical resistivity tomography (ERT) data were used to verify and constrain the interpretations of the output 1-D shear-wave velocity profiles. The results show that MASW can reliably be utilized to map variations in the engineering properties of soil/rock and to estimate depth to top of rock in karst terrain.

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