A total of 85 structures in northeast Wisconsin were measured using ground penetrating radar (GPR). The overall goal was to determine and map void space values of facing panels and wire face MSE retaining walls along each structure. For each MSE wall, values for offset, distance, height, and void space were identified and reported.
GREEN BAY, Wis., July 2, 2025 /PRNewswire/ — Infrasense was tasked with measuring and quantifying the void space between the back of the facing panels and the front of wire face MSE retaining walls along 85 prescribed structures in northeast Wisconsin. The retaining walls hold up various main interstate structures, including bridge overpasses, on and off ramp walls, and large sections of the roadway. Our high-resolution handheld ground penetrating radar (GPR) system facilitated comprehensive surveying and mapping of void spaces. Direct measurements were made via drill holes at locations selected based on the GPR data results to calibrate the GPR void space results.
GPR data was collected across 9 mobilizations using a 2.7 GHz all-in-one GPR system and custom mounting rods to allow scanning from the ground surface to 30-feet high. The data was collected along parallel traverses; collection on long structures was spaced approximately 2 feet apart horizontally from the base of the wall to the coping beam, while collection on narrower or uniquely shaped structures was collected using vertical traverses.
Infrasense engineers recorded direct measurements of the void space at a minimum of one drill location per evaluated structure. Measurements on any structures more than 200 feet in length were recorded at multiple locations spaced approximately 200 feet apart. Once the direct measurements were completed, epoxy grout was used to fill the holes to prevent water ingress. The location of each hole and their measurements were recorded and used to calibrate the GPR signal velocity and void space measurements.
The GPR data was analyzed to quantify void space thickness and exported to spreadsheet format for graphical presentation of the results. Void thickness values were calculated using the known velocity of air and the travel-time measured in the space between the back of the facing panels and the front surface of the MSE retaining walls. The direct drill hole measurements were used to fine tune the velocity calculations for each structure individually. The finalized spreadsheets were used to create representative void space histograms of each structure, along with statistical values of maximum and minimum void space, and average and measured wall thickness.
About Infrasense, Inc.
Since 1987, Infrasense, Inc. has applied advanced technologies to address the most difficult challenges in subsurface scanning. Infrasense’s engineers nondestructively extract critical information from a diverse range of structures. In addition to providing ongoing subsurface evaluation services to clients across the country, the firm has also conducted numerous research programs to advance the field of subsurface detection and nondestructive evaluation. To learn more about Infrasense and the services we provide, visit our website: http://www.infrasense.com
SOURCE Infrasense, Inc.
