Seismic Dilatometer (SDMT) is the combination of the standard Flat Dilatometer with a seismic module.
The probe is fitted with two sensors, spaced 0.5m, for measuring the shear wave velocity Vs. From Vs, one can determine the small strain shear modulus Go. SDMT provides profiles of Vs in a quick, precise, simple, and economical way.
Based on previous testing experience, we prefer to use geophones as the sensors in our SDMT, instead of accelerometers, as we found this produced a better seismic signal.
While accelerometers sense a wide spectrum and record high frequencies, this causes complex post-processing of the data and has little to do with shear wave.
At the moment, SDMT is the only in situ test, besides the self-boring pressure meter, that provides the low strain Go and the working strain M, hence two points in the G-Gamma curve. The availability of two points helps in the choice of the proper G-Gamma curve, unlike tests determining only Go.
An example of the results given from an SDMT is below.
