PARSAN Overseas (P) Limited

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Integrated Geophysical Approach for Rapid & Cost Effective
Site Investigations for Water Resources
Presented at: India Water Week- April 8-12, 2013
Presented by: PARSAN Overseas (P) Limited
1
About PARSAN……
PARSAN Overseas
•
An ISO 9001:2008 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 Exploration2008
– Innovative use of geophysical methods for high
resolution non-destructive testing of dams
•
Highly experienced and trained staff.
•
Offices in Delhi, Kolkata, Bahrain, Egypt (agent) &
Sudan (agent).
•
Work experience in India, Singapore, Oman,
Afghanistan, Greece, Saudi Arabia, Bahrain,
Kuwait, Iran, Algeria, Georgia…….
3
About Speaker
•
Professional Geophysicist, with 22 years
of work experience. Gold Medalist,
University of Roorkee (Now IIT-Roorkee)
•
Member of various working committees
for development of Code of Practices and
Standards.
•
Completed geophysical investigations of
72 hydro power projects.
•
Have conducted 28 training programs on
Geophysics for various companies in 4
countries.
•
Successfully used integrated geophysical
approach for investigations across
flowing rivers & for dam safety
•
Conferred Golden Achievement Award
2011.
4
Geophysical
Subsurface
Investigations……
5
Why Use Geophysics…….
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Low Cost
•
Rapid Coverage
•
No Exposure to buried hazards
•
Non Destructive
•
Minimal Surface Disturbance
•
Easy to integrate
•
Integrated capability
6
Geophysics- Huge ROI...
•
Detailed investigation of site…Saving huge costs towards changed
plans, project delays when surprises crop up….
•
No drilling, No digging…Vast information at fraction of cost of traditional
methods.
•
Early stage application…Better planning, smooth execution.
7
Method
Sensitive To...
Typical Applications
Seismic Refraction
Changes in strata type (soil, weathered
rock, rock), rock quality (jointed,
weathered), elastic properties
Rock interface, overburden mapping,
rock quality, degree of weathering/
jointing, faults, fracture mapping
Resistivity Imaging
Soil-rock profile, water table
Moisture content variations, conductivity, determination, weak zone delineation,
water table, porosity
detection of weak zones under rock
interface, buried channels.
Determination of shear wave profiles
(to determine liquefaction potential,
earthquake response)
ReMi (Refraction Micro-tremor)
Change in shear properties of medium
Crosshole/ downhole/ uphole
Detailed analysis to obtain P and S
wave velocities with depth for
Difference in elastic properties.
dynamic moduli: Poisson’s Ration,
Variations in S Wave or P Wave velocity.
shear modulus, bulk modulus,
Young’s modulus
Seismic Reflection
Difference in acoustic impedance
(velocity x density)
Detects interfaces, maps faults/
fractures/ water lenses/ shear zones
along tunnel routes
Ground Penetrating Radar
Change in dielectric properties
Detection of buried pipes and cables,
with exact location and depth. Also
used for inspection of concrete
structures.
Micro Gravity
Changes in Density of Subsurface
Detection of buried voids/ cavities
8
Electrical
Tomography…..
9
What for……
Applications:
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Determine the underground water resources
•
Bedrock quality and depth measurements
•
Mineral prospecting
•
Dam structure analysis
•
Landfill
•
Contamination source detection
Advantages:
•
Excellent 2-dimensional display of ground resistivity.
•
Delineation of small features like cavity, contamination plumes, weak zones in
structures like dams etc.
10
Example……
Photo Courtesy: www.mragta.com
11
Example……
12
Example……
Photo Courtesy: GeoInvest
13
Water Well Planning……
Photo Courtesy: GeoInvest
14
Water Table Contamination……
Time-lapse monitoring
Photo Courtesy: GeoInvest
15
3D Modeling……
16
Photo Courtesy: GeoInvest
Detection of soft zone under rock (Hydropower)……
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Cave/ Cavity……
18
Contamination…….
19
River Crossings…….
20
River Crossings…….
21
River Crossing……
22
River Crossing- Shear Zone…….
23
River Bottom Profile…….
24
Photo Courtesy: GeoInvest
Seismic
Refraction…….
25
Velocity Model…….
26
Velocity Model…….
27
Seismic Refraction- Applications
•
•
•
•
•
•
•
•
•
Bedrock profile, rock quality and depth.
Thickness of overburden
Fractures and weak zones
Topography of ground water
Rippability assessment in mines
Slope stability studies
Pipeline route studies
Seismic velocity increases markedly from unsaturated to
saturated zone.
The acoustic velocity of a medium saturated with water is
greatly increased in comparison with velocities in the vadose
zone. Thus, the refraction method is applicable in determining
the depth to the water table in unconsolidated sediments.
28
Ground Penetrating
Radar…..
29
Field Operation………
30
GPR- Features………
• Penetration of more than 40 meters in certain formations
(penetration dependent on conductivity and frequency of
antenna)
• Data acquisition at walking speed.
• Identification of objects measuring on few centimeters.
• Light portable equipment
• Results available immediately
31
Water Table Mapping…….
32
Water Table Mapping…….
33
Fractures……
34
GPR- Contaminant Hydrogeology & Soil Stratigraphy
GPR is extremely sensitive to variations in water content. It has
been widely used to map water tables and the corresponding
stratigraphy that controls groundwater flow. In addition, GPR is
very sensitive to changes in water chemistry, particularly soluble
inorganic materials that change conductivity. Inorganic materials
such as DNAPL (chlorinated solvents) can alter the groundwater
distribution resulting in GPR detectable responses.
35
36
Dam Investigations
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Electrical Resistivity Imaging- Dam Axis………
39
Electrical Resistivity Imaging- Dam Axis………
40
SP Anomaly due to leakage………
41
Dam Investigation (integrated with SP)…….
300
200
Streaming Potential (mV)
100
0
200
400
600
800
1000
1200
1400
1600
1800
2000
-100
-200
-300
Chainage (ft)
42
Ground Penetrating Radar
43
43
GPR- Submerged Area
44
GPR-Tomography
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Seismic Tomography
•
•
•
•
•
Acoustic Waves Travel Time
Properties for Each Cell
Colour Tomogram of Dam
Weathered Concrete, Fractures
Highly Detailed Information
46
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Pipeline Leak
Detection…..
47
Pipeline Leak Detection using Seismograph…….
48
Leak Detection using GPR………
49
Leak Detection using GPR ………
50
Leak Detection using GPR ………
51
Leak Detection using GPR ………
52
Case Study
53
Problem…….
• Project site was for cable stayed bridge across a river.
• A cavity was detected in otherwise massive sandstone, while
drilling.
• It was of utmost importance to determine nature and extent of
this cavity before finalizing the design.
Investigations:
• Geophysical investigations consisting of crosshole seismic and
electrical tomography were conducted to determine depth and
extent of the cavity.
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Results…….
55
Conclusions……….
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Conclusions…….
• Geophysical Techniques- Quick assessment of subsurface
conditions in non-destructive manner
• Geophysical Techniques- Detailed and continuous information
as against drilling
• Geophysical Techniques- Eliminates surprises during project
execution
57
Thanks for your attention
Dr. Sanjay Rana
[email protected]
+91-9811168288
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