parsan………subsurface utility engineering & geophysical investigations
DESCRIPTION
PARSAN………Subsurface Utility Engineering & Geophysical Investigations Presented at: Geospatial World Forum 2011, Hyderabad Presented by: Dr. Sanjay Rana, Director, PARSAN Overseas (P) Limited. Outline of the Presentation. About PARSAN About SUE Geophysical Subsurface Investigations - PowerPoint PPT PresentationTRANSCRIPT
PARSAN………Subsurface Utility Engineering & Geophysical Investigations
Presented at: Geospatial World Forum 2011, Hyderabad
Presented by: Dr. Sanjay Rana, Director, PARSAN Overseas (P) Limited
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Outline of the Presentation
• About PARSAN
• About SUE
• Geophysical Subsurface Investigations– Seismic Refraction– Ground Penetrating Radar– Electrical Tomography
• Case Study
• Conclusions
About PARSAN……
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PARSAN Overseas
• An ISO 9001:2000 certified geophysical company having international associations for access to latest technology with:
– M/s TerraDat, UK– M/s Radar Systems Inc., Riga– M/s T&A Survey, Netherlands– Landtech Enterprises SA & Earth Research (UK) Ltd
• Recognized as a leader 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– Inclusion of GPR as mandatory survey before trench less projects- 2001 – Passive Seismic Tomography for Oil Exploration- 2008– Innovative use of geophysical methods for high resolution non-destructive testing of dams
• Highly experienced and trained staff.
• Working in India, Singapore, Oman, Afghanistan, Greece, Saudi Arabia, Bahrain, Kuwait, Iran, Algeria, Georgia…….
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About Speaker
• Professional Geophysicist, with 20 years of work experience. Gold Medalist, University of Roorkee (Now IIT-Roorkee)
• Pioneered use of GPR in India in 1996.
• Have conducted 28 training programs on GPR for various companies in 4 countries.
• Experienced of working with most of the available GPR models like GSSI, Mala, Sensor & Software, Pipe Hawk, and Zond. Overseas GPR experience- Canada, Singapore, Saudi Arabia, Oman, Afghanistan and Bahrain.
• Conducted first ever city level utility mapping project for city of Tirupur, way back in 1999.
• Various Papers & Publications, including “Advanced Technologies for Preparation of Utility Maps of Cities”, which initiated many projects in India.
• Expert panel members of various organizations.
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About SUE……
Existing Underground Utilities are the Veins and Arteries of our
Cities and Roads
And yet, we know very little about where they are
CommunicationGas
PetroleumSewerageDrainage
PowerWater
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WHY?
• Expansion
• Modernization
• Changing Utility
Technology
• Changing Facility
Missions
• Referenced to
changed topo
features
• No centralized
records storage
• No standard format
• No responsibility
We keep adding and changing utilities
We don’t keep good records
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Where do we get Utility Info?
• Visual Observation
• Field Survey
Old Project Plans (As-Designed)Old Project Plans (Red-Lined)
Utility Records (As-Designed)Utility Records (As-Built)
Maintenance RecordsRepair Records
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The Engineer uses these sources to compile a utility composite that overlays the
new design
Nowadays, we frequently digitize this data into a CADD
or GIS System…
This can result in even more errors
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The Engineer ends up with utility data of unknown reliability
This makes it extremely difficult to
manage the risks that are created by existing underground utilities
I think the gas line is here, but I’m not really sure. It might be in conflict with this proposed
piling.
I guess we’ll let the contractor worry
about that !
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What are these Risks?
Utility Damages
Affecting the Safety ofConstruction crews, or
the Public
The Telecommunicationsand other industries
recognize this
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There are a lot of other risks too
• Redesign costs
• Higher construction
bids
• Change orders
• Extra work orders
• Construction Claims
• Higher insurance costs
• Higher financing costs • Bad publicity
Money TIME
Intangibles
Project delaysDetours
Fortunately, there’s a way
to handle this risk
SUBSURFACE UTILITY ENGINEERING
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S.U.E. Combines Traditional Engineering Practices, such as …..
Utility Records Research Relocation Cost Estimates
Utility Design/Relocation Design Plotting of Utilities from Records
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with New Technologies
Utility Designating via
Surface Geophysical Methods
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Utility LocatingVia Non-DestructiveVacuum Exposure
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The Most Significant Advancement is the Utility Quality Level Attribute
Quality Level Attributes are attached to plotted utilities
They indicate how utility data was developed
Reliability and Accountability are defined
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“Quality Level D”
• Plotted on plans from records.
• Sometimes a field visit - to look for utility
indications on the site - is made.
• Sometimes “verbal recollections” are plotted.
The least reliable utility data
This level of effortis great for Project Planning purposes, utility “inventories,”and very preliminary utility relocation cost estimates
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• Surface Appurtenances are surveyed and accurately plotted on
a current site plan
• Utility data from records (QL D) are correlated to the
appurtenances
“Quality Level C”The “traditional” utility depiction
Problems with records interpretations still exist:
e.g. schematics, no appurtenances depicted,
utilities not straight between appurtenances, no records exist, and so
on.
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• Surface Geophysical Methods used to search for and trace
existing utilities.
• Designated utilities are then surveyed and plotted on site plan.
“Quality Level B”
Non-recorded utilities found. Utilities’ routes between
appurtenances are imaged.
Typically used in early preliminary design for construction footprint
decisions.
A significant upgrade in quality
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• Utilities exposed via non-destructive air-vacuum means
• Exposed utilities are then surveyed and plotted on site plan
Elevations, Size, Condition, Materials, Precise Horizontal
Positions are measured and documented
“Quality Level A”
Typically used in final design stages. Allows small
adjustments in design for big savings in construction
A guarantee in 3-D
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QL A and QL B upgrades have been successful in reducing risk on tens of thousands of infrastructure projects.
This is a tried and trueprocess
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Yet, SUE has not been used as a professional standard practice in some areas for many reasons.
• No concerted local or regional effort to educate project owners or engineers of benefits
• Lack of interest by agencies
• Development of SUE has been primarily in developed countries
• Few providers
• Lack of a well defined standard of care created little incentive for changing the status-quo
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A January 2000 FHWA / Purdue University study (Publication No. FHWA-
IF-00-014) states the following:
“A savings of $4.62 for every $1.00 spent on SUE was quantified from a total of 71 projects. These projects had a combined construction value in excess of $1 billion. The costs of obtaining Quality Level “B”
(QL B) and Quality Level “A” (QL A) data on these 71 projects were less than 0.5 percent
of the total construction costs, and it resulted in a construction savings of 1.9
percent over traditional Quality Level C (QL C) and/or Quality Level D (QL D) data.” .62 for
every $1.00 spent on SUE
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One individual project had a $206.00 to $1.00 return on investment (North Carolina DOT).
The simple conclusion of this study is that SUE is a viable technologic practice that reduces project
costs related to the risks associated with existing subsurface utilities and, when used in a systematic
manner, will result in significant quantifiable and qualitative benefits.
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Geophysical Subsurface Investigations……
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Why Use Geophysics…….
• Low Cost
• Rapid Coverage
• No Exposure to buried hazards
• Non Destructive
• Minimal Surface Disturbance
• Easy to integrate
• Integrated capability
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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.
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Method Sensitive To... Typical Applications
Seismic RefractionChanges 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 ImagingMoisture content variations, conductivity, water table, porosity
Soil-rock profile, water table determination, weak zone delineation, detection of weak zones under rock interface, buried channels.
ReMi (Refraction Micro-tremor) Change in shear properties of mediumDetermination of shear wave profiles (to determine liquefaction potential, earthquake response)
Crosshole/ downhole/ upholeDifference in elastic properties. Variations in S Wave or P Wave velocity.
Detailed analysis to obtain P and S wave velocities with depth for dynamic moduli: Poisson’s Ration, shear modulus, bulk modulus, Young’s modulus
Seismic ReflectionDifference 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
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Seismic Refraction…….
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Basic Principle……..
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Energy Sources……
• Explosives
• Sledge Hammer
• Weight Drop
• Buffalo Gun
• Etc……….
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Recorded Data……
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Velocity Model…….
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Velocity Model…….
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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
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Ground Penetrating Radar…..
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Basic Principle………
Photographs: Georadar Inc.
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How an image is formed………
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Hyperbola Formation………
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Field Example- Pipes………
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Depth Determination………
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Equipment………
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Field Operation………
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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
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Pavement Assessment…
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Rebars…….
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Rebar Layers……
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Road Subsidence…..
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Cavity……
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Fractures……
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Electrical Tomography…..
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What for……
Applications:
• 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.
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Example……
Photo Courtesy: www.mragta.com
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Example……
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Cave/ Cavity……
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Boulders……
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Contamination…….
Case Study
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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…….
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Conclusions……….
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Conclusions…….
• SUE- Need of the hour for Utility Data Management
• 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
Thanks for your attention
Dr. Sanjay [email protected]