Services Ground Penetrating Radar

Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR data are acquired by transmitting pulses of radar energy into the ground from a surface antenna, reflecting the energy off buried objects, features, or bedding contacts and then detecting the reflected waves back at the ground surface with a receiving antenna.

Applications of GPR include locating buried voids/cavities, underground storage tanks, sewers, buried foundations, ancient landfills. It can also be used to characterize bedrock, ice, the internal structure of floors/walls, water damage in concrete, and the internal steelwork in concrete.

On location at Ground Zero: Marking the position of rebar to enable the contractor to drill holes in an existing slab and anchor a metal plate.

Drawing of rebar arrangement in RADAN (Radar Data Analyzer) based on Radar Data at a multi-storey BuildingRADAN

GPR uses transmitting and receiving antennae. The transmitting antenna radiates short pulses of the high-frequency (usually polarized) radio waves into the ground. When the wave hits a buried object or a boundary with different dielectric constants, the receiving antenna records variations in the reflected return signal. The greater the contrast in electrical (and to some extent magnetic) properties between two materials at an interface, the stronger the reflected signal, and therefore greater the amplitude of reflected waves.  When travel times of energy pulses are measured, and their velocity through the ground is known, distance (or depth in the ground) can be accurately measured.

The depth range of GPR is limited by the electrical conductivity of the ground, and the transmitting frequency. Higher frequencies do not penetrate as far as lower frequencies, but give better resolution. Optimal depth penetration is achieved in dry sandy soils or massive dry materials such as granite, limestone, and concrete. In moist and/or clay laden soils and soils with high electrical conductivity, penetration is sometimes only a few inches.

Applications:

Concrete Slab Imaging (Structure Scan)

Safely locates embedments within concrete structures prior to drilling, cutting or coring up to a depth of 18 inches. With the high-resolution antennae, even small targets are located within minutes. Only single sided access is required to perform surveys, and a large area can be inspected in one day. The compact data acquisition system provides clear and reliable data, while remaining user-friendly at the same time.

Locates subsurface object and its depth on the job-site. The Structure Scan handcart is first rolled over the desired survey area (wall, floor or ceiling) and when an object is spotted on the data screen; we simply back up the hand cart and mark the target. Structure Scan provides immediate results when timing is crucial, with no need to close off work areas. Multiple antenna options (1.5 GHz and 900 MHz) also ensure that appropriate depth results are acquired.

Ground-penetrating radar as a three-dimensional mapping technique:

GPR produces three-dimensional images by creating pulses of radar energy at a surface antenna, transmitting those pulses into the ground and measuring the elapsed time between when they were sent, reflected off buried targets, and received back at a surface antenna. As the antenna is pulled over the ground surface, a two-dimensional vertical slice showing the significant reflections in the ground is obtained.   Approximate depth in the ground for each of the reflections can be determined when radar travel times are converted to depth.  When many transects are collected in a closely spaced grid, a three-dimensional cube of reflection data are available for processing and image production.

  • Floor, ceiling and wall inspection
  • Locate rebar, tension cables, and conduits
  • Estimate cover and spacing of rebar
  • Estimate wall and slab thickness
  • Identify the size of footing
  • Ungrouted vs. grouted concrete masonry unit cells

Utility Locating and Mapping (Utility Scan)

Utility Scan is used for the non-destructive location of all subsurface utilities. With Utility Scan, we can immediately locate and mark buried service utilities like gas, electric and sewer lines. This system can also easily detect depth and location of objects like water mains, underground storage tanks, terra cotta pipes, tree roots and voids. Utility Scan penetrates manmade or natural surfaces, returning data with unsurpassed quality. Utility Scan with 400MHz or 200MHz antennae is ideally suited for detection and mapping of utility pipes, as well as shallow engineering and environmental applications. It is effectively used to locate buried utilities, drums and underground storage tanks; to identify depth and location of objects of all construction materials, i.e., concrete pipes, plastic drums, .berglass tanks and to identify voids under man-made structures such as roads, runways and buildings.

The Utility Scan system allows us to collect 3D data in real time automatically instead of waiting to view data in the software program RADAN (Radar Data Analyser). Three-dimensional visualization helps you to see the whole picture, giving you a powerful tool to interpret complex utility layouts.

  • Locate metallic and non-metallic targets
  • Locate buried service utilities like gas, electric and sewer lines
  • Estimate depth and location of objects like water mains, underground storage tanks, terra cotta pipes and voids
  • Geological investigation

Subsurface void and cavity Mapping

  • Determine position and size of sink holes
  • Detect voids in structures

Geological & Mining Applications

  • Deep bedrocks profiling
  • Karst mapping
  • Fractures characterization
  • River & lake bottom profiling
  • Soil & aggregate mapping
  • Groundwater resources

Environmental Application

  • Groundwater resources
  • Site assessment
  • Hazardous Waste site assessment
  • Landfills delineation
  • Underground Storage Tank location

Road Inspection and Evaluation

  • Determine pavement layer thickness
  • Perform base and sub-base evaluations with data densities

Bridge Deck Assessment

  • Determine the condition of aging bridge decks, parking structures, balconies and other concrete structures
  • Concrete cover depth
  • Measure slab thickness
  • Void detection and location
  • New York
  • New Jersey
  • New Delhi