Application of Geophysical Techniques in Civil Engineering
Before we discuss further about geophysical techniques; first of all, what is geophysics? Generally, geophysics is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis (SEG wiki).
In Engineering and Environmental Geophysics, geophysics can be defined as subsurface site characterization of the geology, geological structure, groundwater, contamination, and human artifacts beneath the Earth’s surface, based on the lateral and vertical mapping of physical property variations that are remotely sensed using non-invasive technologies.
Geophysical Techniques & Civil Engineering
Civil engineering is a broad field which covers several disciplines such as construction engineering, water resources engineering, structural engineering, environmental engineering, transportation engineering, geotechnical engineering, material engineering, urban engineering, and coastal engineering.
Geophysical techniques have been a part of the construction engineering toolbox for decades. Even though adoption of the technology over this time has been slow, their use on major infrastructure projects has now become routine. Most construction engineering projects generally require information on subsurface ground conditions to maximum depths of only 50 meters or just below the ground surface. This zone can contain soil, unconsolidated sediments, groundwater, weathered rock, boulders and bedrock. It can also contain utilities, buried waste, man-made structure, and contaminants. By understanding of what lies beneath before breaking ground can save significant costs to a construction project.
Geophysical techniques also offer the chance to overcome some of the problem inherent in conventional ground investigation techniques. In addition, it is also non-invasive techniques, less time consuming and cost effective.
Q&A about Geophysical Techniques and Civil Engineering
Q: What is the geophysical technique suitable in construction or geotechnical engineering?
A: Seismic refraction, MASW or resistivity survey can be applied to get subsurface information such as thickness layer, type of material and depth to the bedrock. Seismic refraction can provide rippability of the earth material which is very useful information in excavation process. A correlation between geophysical techniques and borehole exploration method can increase the effectiveness of site investigation information.
Q: What is the geophysical technique suitable in environmental(groundwater) engineering?
A: Electrical resistivity imaging or resistivity survey is the most effective method in mapping groundwater aquifer. It can provide accurate location of fresh groundwater zone or aquifer.
Q: What is the geophysical technique suitable in pavement engineering?
A: Ground Penetrating Radar (GPR) technique is the most suitable in mapping or profiling the pavement thickness. It is can produces real-time result and rapid ground coverage.
Q: How about the cost?
A: Geophysical techniques are cost effective; where detailed information about the subsurface can be obtained in little time compared to the cost of obtaining similar information purely through manual excavation or drilling method. These techniques can also profile up to hundreds of meters per day for detailed cross-section investigation.
Q: Are they safe to our environment?
A: Most of the geophysical techniques are non-invasive and minimal disturbance to environment. The equipment also are not harmful to workers and people surrounding as long as the standard field survey practices are followed.