A new tool for the automated travel time analyses of bender element tests
ABSTRACT: Whilst bender elements are increasingly used in both academic and commercial laboratory test systems, there still remains a lack of agreement when interpreting the shear wave travel time from these tests. Given such interpretation is often subjective, a software tool was developed to automate the interpretation process using a number of analysis methods recommend in the literature.
The tool resulting from this development is accessed through two easy-to-use Microsoft Excel Add-Ins, allowing any digital bender element data to be interpreted. Initial assessment of the tool was provided by a series of tests conducted on a triaxial specimen of Leighton Buzzard sand at a mean effective stress of 100 kPa, with variation of the source element frequency. Travel times estimated from a time-domain cross-correlation showed relatively low scatter, equal to ± 7 µs, across a frequency range of 3.3 kHz to 14.3 kHz, whilst times estimated from a frequency-domain cross-spectrum calculation produced much larger scatter, equal to ± 138 µs. Finally comparisons with subjective observational analyses performed by a geotechnical academic showed good agreement, suggesting the tool can provide accurate, automated interpretation of bender element shear wave travel times.