Geophysics
Traditional exploration services such as drilling, coring, sampling, and test pits provide very specific and detailed subsurface information but, only at a few discrete locations on a project site. Engineers and geologists must interpolate these results over wide areas between these discrete locations in order to develop a model of the subsurface. The subsurface model may not be adequate when budget, site access restrictions, or environmental issues make it necessary to limit the number of these traditional services performed, which could then ultimately widen the spacing between the locations even further. Traditional exploration services may also inadequately define subsurface conditions when the object/feature targeted, such as an underground storage tank or sinkhole, is small relative to the site area and the sampling spacing.
Experienced geophysicists use specialized non-destructive techniques to measure changes in the physical properties of materials such as soil, rock, pavement, concrete, or groundwater at the surface along one or more defined traverses across a site. By comparing these data to conventional exploration sampling services along the geophysical traverse, the subsurface model can be defined, more or less, continuously across a site along each traverse, especially when geophysics is used first to help guide the sampling program. Similar measurements can also be performed in boreholes.
S&ME has been providing geophysical services for over 10 years with a geophysical staff that brings more than 30 years of combined experience to their clients. Our geophysicists work directly with engineers and scientists from our other disciplines to select the survey approach that will provide the most valuable results. Surficial and borehole geophysical surveys are frequently used for a variety of geotechnical, environmental, cultural resources, construction, and transportation applications. Common uses of surficial geophysics include: buried debris and landfill delineation, underground storage tank location, bedrock profiling and rippability studies, site assessments for karst/sinkhole features, seismic site classification, and burial mapping. Geophysical methods are also used for identifying areas of concentrated ground water flow for use in dam seepage analyses, and to provide data for the design of grounding systems or identifying corrosion potential of soils. Other surficial applications include pavement thickness surveys, identification of voids below concrete and pavements, and bridge deck conditions assessments. Borehole geophysical logging is commonly used for lithology and fracture mapping, and hydrologic studies.
We continually strive to update our geophysical capabilities, which includes everything from hiring new technical staff to purchasing the latest equipment and software to help meet the needs of our clients. S&ME also owns and maintains most of the geophysical equipment used for our services. In addition, our geophysical personnel incorporates geo-referencing through the implementation of global positioning systems (GPS) for GIS applications. Three-dimensional modeling techniques are also used to improve visualization of the subsurface. A general list of our currently available geophysical techniques are listed below.
Geophysical Techniques
- Ground Penetrating Radar (GPR)
- Electrical Resistivity Tomography (ERT)
- Spontaneous Potential (SP)
- Multi-Channel Analysis of Surface Waves (MASW)
- Microtremor Array Measurements (MAM)
- Seismic Refraction (P-Wave and S-Wave)
- Downhole and Crosshole Seismic
- Time Domain Electromagnetics (TDEM)
- Frequency Domain Electromagnetics (FDEM)
- Wenner Four-Electrode Resistivity Measurements
- Borehole Televiewer and Geophysical Logging