Depth to Bedrock
Knowing the depth to bedrock is a critical parameter in geotechnical investigations as bedrock influences the stability of structures and transport of contaminants as they travel down gradient on bedrock surfaces.
One of the most common geophysical methods for depth to bedrock determination is refraction seismics . This is a non-invasive, easily deployed method that provides quantitative information about the spatial variability of depth-to-bedrock as well as producing quantitative information about the strength of bedrock through the use of acoustic velocity as a surrogate for rock density. Confirmation augering or drilling will always be required to “calibrate” seismic results, but, far more area can be covered with seismics in a much more affordable manner compared to drilling costs to cover the same area.
Depth to bedrock is also important in placer mining where paleo-channels eroded into bedrock are sought. Quick coverage with refraction seismics can provide maps of channels which help focus dredging and excavation on the high-pay zones.
Environmentally, knowledge of depth-to-bedrock in areas of historic spills will help in the mitigation stage by quantifying excavation volumes of contaminated material. Knowing the depth to bedrock also facilitates the understanding of fate and transport of contaminants as they tend to travel down gradient on a bedrock surface.
For more information on refraction seismics go here.