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Seismic Tomography Between Exploratory Drifts For Dam Projects
Seismic Tomography Between Exploratory Drifts For Dam Projects
Dr. Sanjay Rana, Ashutosh Kaushik, Bhaskar Chendhoor (PARSAN Overseas Pvt Limited)
About Parsan
- An ISO 9001:2015 certified geophysical company
- Promoters recognized as leaders in region for launching new technology. Responsible for launch of:
- Ground Penetrating Radar Technology- 1996
- Shear Wave Seismic Refraction- 1997
- High Resolution Seismic Tomography- 1998
- Passive Seismic Tomography for Oil Exploration- 2008
- Innovative use of geophysical methods for high resolution non-destructive testing of dams- 1998
- Highly experienced and trained staff.
- Offices in Delhi, Kolkata, Bhopal, Bahrain, Saudi Arabia, Singapore
- Work experience in India, Nepal, Bhutan, Saudi Arabia, Bahrain, Kuwait, Oman, Afghanistan, Singapore, Greece, Iran, Algeria, Georgia...
About Speaker (Dr. Sanjay Rana)
- Professional Geophysicist, with 32 years of work experience. Chairman AF Academy & Managing Director, PARSAN, An engineering geophysics company
- Gold Medalist- 1990, University of Roorkee (Now IIT-Roorkee)
- Pioneered use of Near Surface Geophysics (Private Sector) in India in 1995.
- Pioneered use of Dam Geophysics in India in 1998.
- Successfully used integrated geophysical approach for investigations across flowing rivers & for dam safety
- Completed geophysical investigations of 72 hydro power projects.
- Member of various working committees for development of Code of Practices and Standards, including BIS, IRC.
- Principal author of:
- Guidelines on Geophysical Investigation of Dams
- Guidelines for Geophysical Investigation of Tunnels (TAI)
- Guideline for Geophysical Investigations for Bridges (IRC)
- Indian Code for Subsurface Utility Mapping.
The Engineers first problem in any design situation is to discover what the problem really is.
Difficult Ground Conditions?
1) Expertise & engineering solutions available for dealing with any (almost) ground condition
2) The problem is meeting the unexpected and uncertainty of ground conditions
Geophysical Investigation for Dam Sites...
- Study available geological maps
- Geological Mapping
- Geophysical Investigations
- Drilling (with geophysical logging)
- Slope stability analysis
- Hydrogeological studies
- Seismicity Study
- Burrow Areas
Necessary Investigation Steps...
-
Different types of geophysical studies should be performed in the dam site and reservoir area to indicate the following data:
- To indicate groundwater level.
- To indicate the mechanical properties of the rocks and the depth of the weathering zone.
- To detect faults/ fractures/ shear zones/ weak zones
- To investigate burrow areas
- To conduct slope stability studies
- To determine shear wave velocities for seismic hazard studies
Dam Site Investigations - Advanced Geophysics....
- Seismic Refraction Tomography- bed rock profile, fault/ fracture/ shear zones.
- Resistivity Imaging- detailed subsurface images even in velocity inversion zones
- ReMi/ MASW- Shear wave profile from surface surveys, without any boreholes
- Crosshole/ uphole/ downhole surveys- P&S wave velocities for detailed analysis of various layers and dynamic moduli.
- Crosshole/ uphole/ downhole surveys- P&S wave velocities for detailed analysis of various layers and dynamic moduli.
- Seismic Reflection- tunnel route investigation
- Electrical Resistivity- Earth Grid Design
Dam Site Investigations- Advanced Geophysics....
- Seismic Refraction Tomography- bed rock profile, fault/ fracture/ shear zones.
- Resistivity Imaging- detailed subsurface images even in velocity inversion zones
- ReMi/ MASW- Shear wave profile from surface surveys, without any boreholes
- Crosshole/ uphole/ downhole surveys- P&S wave velocities for detailed analysis of various layers and dynamic moduli.
- Crosshole/ uphole/ downhole surveys- P&S wave velocities for detailed analysis of various layers and dynamic moduli.
- Seismic Reflection- tunnel route investigation
- Electrical Resistivity- Earth Grid Design
Limitations & Reasons for Failures?
- Wrong tool selection
- Method lacking desired resolution
- Geology ignored
- Calibration ignored
- Only single tool used
- Wrong initial model
Understanding Tomography...
Conclusion:
Geological investigations and site characterization by making drifts has been a standard procedure for large dams. This provides very valuable information about dam site. Making drifts is a time consuming and expensive activity. To gain more advantage and cover more area, conducting seismic tomography between drifts is a cost-effective option.
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