Electrical Resistivity Profiling for Groundwater Exploration
Eastern Mojave Desert, California
completed transient electromagnetic (TEM) soundings along several survey
lines setup across large desert basins. The TEM data were used to
generate multi-layer resistivity versus depth models at 1/4-mile
intervals. These results were used to prepare two-dimensional electrical
resistivity profiles along the survey lines.
Resistivity profiles such as the one shown below were compared with a resistivity versus depth model from a TEM sounding near an existing well. This "calibrated" model was used to interpret groundwater conditions along the survey lines, such as depth to top of saturated zone and relative groundwater salinity. These results were used by our client to locate test wells for further evaluation of groundwater resources.
Pulse Echo Testing of Piles
Alameda Train Corridor Project
Los Angeles County, California
completed shaft integrity testing using
the Pulse Echo Method in accordance ASTM D-5882 for hundreds of
cast-in-drill-hole, concrete piles installed for temporary support of the
trench wall. Test records were evaluated for reflection pulses
showing higher impedance reductions along the length of the pile shafts.
Such impedance reductions could be caused by reductions in cross-sectional
area or zones of decreased concrete density.
The velocity-amplitude versus time records below show testing results for piles with and without defects. The second test record shows an anomalous positive reflection pulse occurring before the toe reflection, indicating a probable shaft defect at 40 feet. These results were confirmed by several repetitive test records.