Date of Award

4-4-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Applied Science

First Advisor

Haydar Al-Shukri

Second Advisor

Hanan Mahdi

Abstract

The Broadway Bridge, constructed in 1923, crosses the Arkansas River in the downtown area of Little Rock, AR and was the main crossing point between Little Rock and North Little Rock. The structural deterioration of the bridge reached a level beyond patch and repair. Accordingly, the Arkansas Highway and Transportation Department (AHTD), in collaboration with the City of Little Rock, allocated the required resources ($98.4M) to demolish and replace the bridge. Due to the age of the bridge site and the limited knowledge of the subsurface utility layout, it became clear that geotechnical work be done in order to map the subsurface utilities. It is important that utility mapping be conducted before any excavation at the site is performed. AHTD identified three critical sites, two on the Little Rock side and one on the North Little Rock, to be precisely mapped using near-surface geophysical equipment. Ground Penetrating Radar (GPR) was selected to perform the work for its known high-resolution capabilities, non-destructive nature, ease of use, and on-site interpretation. Due to the importance of the work requiring narrow margin of error, the research was divided into two main parts. The first is the laboratory and prototype experimentation and analysis in which aspects of the subsurface utilities were studied. This includes metal and PVC pipes with different sizes, cables, and other objects buried beneath the surface. The results of this research helped to design the full-scale field surveys, select the optimal equipment set, and develop the appropriate interpretation method. The second part of the project are the full-scale field surveys at the three sites. A total of 1409 meters (4623 ft.) of GPR data was collected from several profiles at the critical sites. The results show the successful precise mapping of many subsurface pipes and other buried objects.

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