Test for Detecting an Impermeable Water Barrier in an Earth‐Fill Dam in Austria Using MASW Method

Seismic methods were used to locate an impermeable water barrier (density body), constructed in front of a homogenous earth-fill dam (Prätisbach) in Eastern Styria, Austria. This detention reservoir, built in 1985/86, was constructed of locally mined materials. Key to this structures functionality is its impermeable core located within the upstream toe of the dam and parallel to the dam axis. This density body is reported to be composed of the same material as in the main structure, but has undergone intensive artificial compaction. Current pool level in the detention reservoir is consistent with the designed top of the density body, about 2 m below the surface. Seismic methods were attempted because no apparent anomaly was evident on electromagnetic data associated with the density body. Surface wave (MASW) and refraction seismic methods provided compressional (Vp) and shear-wave (Vs) velocities along a profile that should have crossed directly over the density body of the dam. With only a subtle increase in Vp velocity within the designed density body interval, the findings of the seismic survey appear consistent with the electromagnetic data. A loosely fitting relationship was developed providing a better understanding of the internal condition of the dam.