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Subsurface Utility Engineering & Geophysical Investigations

Learn about the use of geophysical methods such as seismic refraction, ground penetrating radar, and electrical tomography in subsurface utility engineering. Presented by Dr. Sanjay Rana, Director of PARSAN Overseas.

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Subsurface Utility Engineering & Geophysical Investigations

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  1. PARSAN………Subsurface Utility Engineering & Geophysical Investigations Presented at: Geospatial World Forum  2011, Hyderabad Presented by: Dr. Sanjay Rana, Director, PARSAN Overseas (P) Limited

  2. Outline of the Presentation • About PARSAN • About SUE • Geophysical Subsurface Investigations • Seismic Refraction • Ground Penetrating Radar • Electrical Tomography • Case Study • Conclusions

  3. About PARSAN……

  4. 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…….

  5. 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.

  6. About SUE……

  7. Existing Underground Utilities are the Veins and Arteries of our Cities and Roads Communication Gas Petroleum Sewerage Drainage Power Water And yet, we know very little about where they are

  8. Expansion Modernization Changing Utility Technology Changing Facility Missions Referenced to changed topo features No centralized records storage No standard format No responsibility WHY? We keep adding and changing utilities We don’t keep good records

  9. Visual Observation Field Survey Where do we get Utility Info? • Old Project Plans (As-Designed) • Old Project Plans (Red-Lined) • Utility Records (As-Designed) • Utility Records (As-Built) • Maintenance Records • Repair Records

  10. 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

  11. The Engineer ends up with utility data of unknown reliability I think the gas line is here, but I’m not really sure. It might be in conflict with this proposed piling. This makes it extremely difficult to manage the risks that are created by existing underground utilities I guess we’ll let the contractor worry about that !

  12. What are these Risks? Utility Damages Affecting the Safety of Construction crews, or the Public The Telecommunications and other industries recognize this

  13. Redesign costs Higher construction bids Change orders Extra work orders Construction Claims Higher insurance costs Higher financing costs Bad publicity There are a lot of other risks too Money TIME • Project delays • Detours Intangibles

  14. Fortunately, there’s a way to handle this risk SUBSURFACE UTILITY ENGINEERING

  15. S.U.E. Combines Traditional Engineering Practices, such as ….. Utility Records Research Relocation Cost Estimates Utility Design/Relocation Design Plotting of Utilities from Records

  16. with New Technologies Utility Designating via Surface Geophysical Methods

  17. Utility Locating Via Non-Destructive Vacuum Exposure

  18. 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

  19. “Quality Level D” The least reliable utility data • Plotted on plans from records. • Sometimes a field visit - to look for utility indications on the site - is made. • Sometimes “verbal recollections” are plotted. This level of effort is great for Project Planning purposes, utility “inventories,” and very preliminary utility relocation cost estimates

  20. “Quality Level C” The “traditional” utility depiction • Surface Appurtenances are surveyed and accurately plotted on a current site plan • Utility data from records (QL D) are correlated to the appurtenances Problems with records interpretations still exist: e.g. schematics, no appurtenances depicted, utilities not straight between appurtenances, no records exist, and so on.

  21. “Quality Level B” A significant upgrade in quality • Surface Geophysical Methods used to search for and trace existing utilities. • Designated utilities are then surveyed and plotted on site plan. Non-recorded utilities found. Utilities’ routes between appurtenances are imaged. Typically used in early preliminary design for construction footprint decisions.

  22. “Quality Level A” A guarantee in 3-D • 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 Typically used in final design stages. Allows small adjustments in design for big savings in construction

  23. 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

  24. 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

  25. 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

  26. 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.

  27. Geophysical Subsurface Investigations……

  28. Why Use Geophysics……. • Low Cost • Rapid Coverage • No Exposure to buried hazards • Non Destructive • Minimal Surface Disturbance • Easy to integrate • Integrated capability

  29. 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.

  30. Seismic Refraction…….

  31. Basic Principle……..

  32. Energy Sources…… • Explosives • Sledge Hammer • Weight Drop • Buffalo Gun • Etc……….

  33. Recorded Data……

  34. Velocity Model…….

  35. Velocity Model…….

  36. 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

  37. Ground Penetrating Radar…..

  38. Basic Principle……… Photographs: Georadar Inc.

  39. How an image is formed………

  40. Hyperbola Formation………

  41. Field Example- Pipes………

  42. Depth Determination………

  43. Equipment………

  44. Field Operation………

  45. 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

  46. Pavement Assessment…

  47. Rebars…….

  48. Rebar Layers……

  49. Road Subsidence…..

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