Date of Award

2017

Degree Type

Thesis

Degree Name

Master of Science in Ocean Engineering

Department

Ocean Engineering

First Advisor

Christopher Baxter

Abstract

Ground-penetrating radar (GPR) is increasingly being used in transportation projects to monitor the performance of roadways and bridges and to identify buried structures. The objective of this thesis was to evaluate the use of GPR for the identification of bridge scour and to estimate the depth of shallow rock for geotechnical site investigations. The ability to understand and predict scour at bridges is a requirement for safe, economical foundation design and is important for the development of feasible scour monitoring systems. Accurate assessment of the depth to rock is essential for designing and constructing foundations for buildings and transportation infrastructure. Misinterpretation of the depth to bedrock can dramatically increase construction costs.

GPR surveys were performed at two bridge locations across shallow streams, on land at four shallow rock locations, and at three other test sites in Rhode Island.

During the bridge site tests, the GPR was maneuvered in a small pontoon boat across the water surface from one river side to the other while towed from the bridge deck. The acquired two-dimensional data sets from the shallow streams accurately image the channel bottom, demonstrating that the GPR is an effective and safe tool for measuring or monitoring scour. However, infilled scour features could not be identified due to the presence of cobble armoring layers.

During the tests on land, the GPR was placed on a survey cart and pushed along to create a linear profile. The acquired two-dimensional data sets from the shallow rock locations were compared to boring logs and shear wave velocity profiles taken previously at the sites and showed good agreement between the different estimated depths to rock. These results showed that GPR is a useful, cost effective tool for the identification of shallow rock layers.

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