Subsurface Imaging (GPR)
Locating below-the surface items before digging or demolishing is imperative for the surveying, construction, landscaping, golfing, environmental, development, utilities and many other industries. Diamond Ground Penetrating Radar — GPR safely and accurately, finds and clearly plots targets in their exact location below the surface in concrete or soils. Both metallic and non-metallic objects are detected and mapped. GPR works by sending a pulse of energy at a below-surface target and recording the strength and the time required for the return of the signal. A series of sent and returned signals, over a specific area, will provide a digital window to view below the surface items.
Subsurface Imaging (GPR), Structural Investigation
Client
Sturgis Middle School—Sturgis Public Schools—Sturgis, MI
Project
The Sturgis School Board decided to modernize the Sturgis Middle School which had been built in the 1920’s. Improvements to the facility required significant modification to the existing structure. JDH Engineering was called upon to analyze the structural integrity of the building. By evaluating the original drawings of the building, the engineer could only speculate about the steel arrangement within the concrete. Some of the improvements proposed required that certain structural requirements be met and confirmed. Therefore, JDH asked Diamond to perform GPR (Ground Penetrating Radar) surveys of specific areas of the structure to determine whether the present building was capable of supporting the renovations intended by the school board’s plans.
Process
Subsurface imaging surveys were performed by Diamond using a SIR 20 system with onsite 3D capabilities and Radan software. A Diamond engineer used a 400 mHz antenna to find the location of the footings on the bottom floor. A1500 mHz antenna along with the patented 3D Smart Pad technology was used for diagnostics on the thickness of the concrete slab and location of steel reinforcements. Ten different locations throughout the middle school were scanned, a detailed report was delivered to JHD.
Outcomes
“We have used Diamond’s Ground Penetrating Radar on three projects where information on existing footings was limited or non-existent,” said Larry Hulst from JDH Engineering. “In those cases, Diamond’s Ground Penetrating Radar was able to determine an approximate footing sizes and ground cover which then could be used to assist in preliminary evaluation as well as determine necessary steps for future construction. The use of radar eliminated the need for early invasive investigation and the associated costs and disruption. We have also, in coordination with architectural clients, recommended and used this procedure to determine the presence of under slab mechanical, electrical, or other infrastructure in planning for facility renovation. Our experience has been nothing less than positive and invaluable in being able to determine construction limits, procedures, and design considerations. We have been recommending Diamond’s subsurface imaging to clients as a cost effective, efficient, and successful method of predesign or pre-construction investigation,” concluded Hulst.