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Author:
Christopher Phillips
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2006-01-15 |
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As a geophysicist, I am dismayed by the lack of discussion in the geophysics forum.
There have been many advances in geophysics in the last number of years, with advances in equipment, research, and low cost of computing power.
We have conducted various geophysical projects for geotechnical clients, including:
- Investigation of extent of voids beneath concrete slabs
- Concrete integrity testing
- Pile Integrity Testing
- Pavement and Asphalt Thickness (Road GPR)
- Bridge Deck Investigations (Delamination/Deterioration mapping)
- Soil/Rock Stiffness profiling using SASW/MASW, crosshole seismic, VSP, and shear refraction
- Fracture detection and orientation mapping for joint set mapping of proposed open pit mines
This board (geophysics) has been pretty stagnant, with most discussion related to MASW.
I would like to try and open up this discussion forum with increased interest from geotechnical engineers with questions about how geophysics can help them with their specific problems.
There are a number of geophysical methods, including:
- MASW/SASW
- Seismic Methods
- Ground Penetrating Radar
- Electrical Resistiviy Methods
- Electromagnetic Methods
- Magnetic Methods
- Non Destructive Testing Methods
All of which have application to the geotechnical engineer and should be seen as another tool in your toolbox.
Please post in this forum if you have any questions about how geophysics can help with your specific problem, or help better approach a problem you often encounter. Post a problem and some information on the project and let the geophysics community see what we can do to provide you a solution that can help.
Thanks,
Christopher Phillips.
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Follow-up:
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Author:
Singh, P.
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2006-01-15 |
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Dear Chris,
I read your posting with interest. Sometime ago I inquired
about a geophysical method called electroseimics (or seismoelectrics) which utilises a coupling system -
seismics and electromagnetic waves in porous media.
There is a electrokinetic effect caused by the movement
of water with the creation a streaming potential.
There might be a no. of uses in field applications in underground excavation, ground water monitoring etc.
There is not much literature I could find on this method. Perhaps you might know something.
Best Wishes,
Singh, P.
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Follow-up:
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Author:
Christopher Phillips
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2006-01-15 |
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P. Singh,
Seismoelectrics exploits the physical phenomena that stress waves induce electrical currents in the ground. A seismic source is used to generate stress waves and the induced electrical currents are then mapped to determine variations in the layering of ground materials.
It is a method that is primarily used in the exploration for minerals as sulfides and ore bodies generate large electrical currents relative to background, but has been applied to shallower mapping of top of bedrock, although in these cases there are other methods that would probably be better suited to the task of bedrock delineation (true seismic methods, GPR, or electrical resistivity).
Hope that answers your question.
Chris.
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Follow-up:
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Author:
Vipul Nagar
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2006-01-17 |
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Dear Chris,
I am a Geophysicist. Your thoughts are very interesting.
I am also associated with geodiscussion from last few months. I am interested in nondistructive in-situ tests like SASW / MASW, its instrumentation, softwares etc.
I m involved in seismic, resistivity and electromagnetic techniques.
With best regards
Vipul Nagar
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Follow-up:
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Author:
Zivko Terzic
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2006-01-22 |
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I am glad to see someone's started this topic. I agree with you in this totally. We should be more aggressive in promoting geophysics' capabilities in solving geotechnical problems, especially in this computerized era. The cost and efficiency of geophysics increased dramatically in the last two decades. This is a good chance to make geophysics unavoidable in engineering practice.
I know many geotechnical engineers who are skeptics in regards to geophysics use in solving engineering problems. There are many though who are not that skeptic.
I recently conducted a resistivity survey coupled with GEM2 in order to resolve a geotechnical problem concerning a karst cavity. Based on results, we recommended some additional drillings with confirmative results in terms of cavity depth and size. Now we have lots of job offers in similar problems resolution.
I support the idea of geophysicists’ cooperation without frontiers. Therefore, I have a question. It is in regards to a shallow refraction survey. I am going to collect some refraction data next week. I was originally planning to use a conventional refraction method with very short geophone equidistance of 1-2 m. It is a good opportunity for me to try the MASW though. I will collect those data along the conventional refraction data as well. My question would be: What software has better reputation in processing the MASW data? And if possible what is the renting and/or licensing price?
Regards,
Zivko Terzic
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Follow-up:
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Author:
Dr. C. Krishnaiah
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2006-01-27 |
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Dear friends
I also agree with the following remarks.
Detailed discussions also have to be held regarding systematic data collection, processing and interpretaion of field data. Unlike deep seated oil exploration problems, shallow Engineering geophysics has lot of problems in the processing and interpretation and is challenging. These geophysical methods should be extensively used to not only geotechnical but also to groudwater exploration and exploitaion, modeling and environmental problems.
Krishnaiah. C
As a geophysicist, I am dismayed by the lack of discussion in the geophysics forum.
There have been many advances in geophysics in the last number of years, with advances in equipment, research, and low cost of computing power.
We have conducted various geophysical projects for geotechnical clients, including:
- Investigation of extent of voids beneath concrete slabs
- Concrete integrity testing
- Pile Integrity Testing
- Pavement and Asphalt Thickness (Road GPR)
- Bridge Deck Investigations (Delamination/Deterioration mapping)
- Soil/Rock Stiffness profiling using SASW/MASW, crosshole seismic, VSP, and shear refraction
- Fracture detection and orientation mapping for joint set mapping of proposed open pit mines
This board (geophysics) has been pretty stagnant, with most discussion related to MASW.
I would like to try and open up this discussion forum with increased interest from geotechnical engineers with questions about how geophysics can help them with their specific problems.
There are a number of geophysical methods, including:
- MASW/SASW
- Seismic Methods
- Ground Penetrating Radar
- Electrical Resistiviy Methods
- Electromagnetic Methods
- Magnetic Methods
- Non Destructive Testing Methods
All of which have application to the geotechnical engineer and should be seen as another tool in your toolbox.
Please post in this forum if you have any questions about how geophysics can help with your specific problem, or help better approach a problem you often encounter. Post a problem and some information on the project and let the geophysics community see what we can do to provide you a solution that can help.
Thanks,
Christopher Phillips.
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Follow-up:
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Author:
Brian Williams, P.E., P.G.
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2006-02-14 |
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Christopher:
I also agree with your position. I think one of the fundamental reasons for the lack of geophysical application in geotechnical engineering is that most engineers don't understand what geophysics is (like it's some black box thing) and therefore simply have no trust in the methods or results. From the geophysical side, it hasn't helped having people out there doing MASW or SASW (or shallow refraction, etc.) and those people coming up with off-the-wall results that are presented as valid data when they (the erstwhile geophysicist) doesn't know what a reasonable result should be.
There also seems to be a major disconnect between engineers and geophysicists- the geophysicists know how to measure a lot of different things (like shear wave velocity), but MOST engineers don't know what to do with the data beyond simple reference to something like the IBC charts to pick a site classification. A lot of this has to do with the basic formal education. Few advanced degree programs in the U.S. (elsewhere??) attempt to integrate any discussion of geophysics or geophysical data into engineering analysis, and the result is predictable.
How to fix this? Good question. We can try education. I've given several talks at regional engineering conferences in an attempt to educate people about geophysical applications in geotechnical engineering. Examples of "how I found the abandoned and buried piping at my building site" or "how to get definitive modulus values for use in settlement calculations" seem to get some interest. In many locales, I think it comes down to finding an application where geophysics provides better (and more cost effective) information than conventional testing.
As was discussed in other postings, knowledge of geophysical applications for geotechnical engineering provides a very powerful set of tools that can often provide data and/or interpretations that one simply cannot obtain without geophysical data.
I am open to further discussion through this forum or via my email: bwilliams@ntlengineering.com
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Follow-up:
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Author:
Matt
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2006-02-16 |
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RE: MASW
As a geotechnical engineer, I have hired a sub-consultant to perform MASW for site seismic class determination for the firt time.
Is anyone else using MASW for this? I'd like to know that I'm not the only one...
Thanks
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Follow-up:
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Author:
Christopher Phillips
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2006-02-17 |
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Hi Matt,
You're not the only one doing this. MASW is being used to a greater extent for seismic classification of sites. I think that this use and for foundation design are the two most common requests we get for MASW.
Chris.
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Follow-up:
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Author:
Derek Irving
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2006-03-09 |
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Hello Christopher, what is the main geotechnical and geological application of MASW? Can it record S adn P wave simultaneously?
Is it possible to do shallow on land Seismic Reflection and Refraction simultaneously?
Where can I find in internet firms that can do this type of job including Seismic Reflection on water?
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Follow-up:
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Author:
Derek Irving
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2006-03-09 |
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Christopher; What is the price range for a seismic reflection - refraction survey with MASW, using the conventional method and the tomographic method? Lets say for a total of 14 Km.?
Regard,
Derk Irving
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Return
to subject 'Geophysics'
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Follow-ups:
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»
Singh, P., 2006-01-15
»
Christopher Phillips, 2006-01-15
»
Vipul Nagar, 2006-01-17
»
Zivko Terzic, 2006-01-22
»
Dr. C. Krishnaiah, 2006-01-27
»
Brian Williams, P.E., P.G., 2006-02-14
»
Matt, 2006-02-16
»
Christopher Phillips, 2006-02-17
»
Derek Irving, 2006-03-09
»
Derek Irving, 2006-03-09
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Subject:
Geophysics for Geotechnical Applications 