GBG Australia undertook a geophysical investigation to map the subsurface conditions and structures beneath a multilane roadway, ACT. For this investigation MASW and Electrical Resistivity Tomography (ERT) was utilised to gain information on the depth of bedrock in addition to other subsurface structures.
MASW data was collected using the Gemetrics Geode seismic recorder. An array of 24 4.5Hz geophones was utilised. A sledgehammer striking a rubber plate was used to generate the low seismic energy.
The Resistivity Tomography was undertaken using a Syscal Pro 72 Switch Resistivity System. A Dipole-Dipole array was used with 3m electrode spacings. This setup resulted a maximium depth of penetration of beyond 30m.
All geophones/electrodes and shot locations were taken using a high accuracy DGPS and levels along the lines were taken using a laser level.
Figure 1: Site View.
Figure 2: A MASW survey being taken on the northbound lands.
Figure 3: A MASW survey being taken on the southbound lands.
Figure 4: The Geode, computer and auxillary cables were set up in the back of a ute. The MASW array was towed behind the same vehicle.
Figure 5: The ERT survey being conducted along the edge of the northbound entry ramp.