Date of Award

Spring 2019

Project Type

Dissertation

Program or Major

Civil Engineering

Degree Name

Doctor of Philosophy

First Advisor

Jennifer M Jacobs

Second Advisor

Paul H Kirshen

Third Advisor

Eshan V Dave

Abstract

The climate is changing, and these changes are expected to accelerate. In the northeast region of the United States, temperatures and sea levels are projected to rise with climate change. These changes have the potential to impact coastal communities in many ways, but this dissertation focuses on climate-change impacts to pavement life. A well-maintained and fully functional roadway system is essential to maintaining a high quality of life and economic vitality in a region. When pavements fail prematurely, the agency and user costs of full-pavement rehabilitation or reconstruction are much higher than the costs of routine maintenance and pavement over-lays. Pavement life is sensitive to changes in temperature and the moisture content of the under-lying layers. This research investigates the individual and combined effects of rising groundwater from sea-level rise (SLR) and rising temperatures on pavement life. Adaptation strategies are evaluated with respect to performance, cost, and long-term viability.

A three-dimensional groundwater model is used to characterize groundwater rise caused by SLR in coastal New Hampshire and to establish a groundwater-rise zone (GWRZ). Roads vulnerable to reduced pavement life caused by increasing moisture content in underlying pavement layers from rising groundwater are identified. A top-down, or scenario-based, approach is used to quantify projected pavement life reductions in years 2030, 2060, 2090, and 2100 under a high emissions SLR scenario using pavement layered-elastic analysis. Adaptation options including layer-thickness and base-layer material modifications are evaluated.

A hybrid bottom-up/top-down approach is then introduced to evaluate seasonal and long-term changes in pavement life due to climate-change induced temperature rise over a 60-year pavement management period. This approach differs from the top-down approach by beginning with a sensitivity analysis of pavement performance with incremental temperature rise over the entire range (low to high emissions scenarios) of projected temperature rise. Pavement performance is quantified using an optimal hot-mix asphalt (HMA) thickness or the thickness required to achieve a minimum of 85% reliability under the simulated conditions. Next, downscaled Global Climate Model (GCM) output is used to determine the timing of the effects. Finally, a pavement adaptation framework consisting of the hybrid bottom-up/top-down approach, adaptation pathway mapping, and cost analysis is introduced and demonstrated at a case-study site in coastal New Hampshire for the combined effects of temperature and groundwater rise.

This research shows that climate change, specifically temperature and SLR-induced groundwater rise, will produce significant reductions in coastal-road pavement life without adaptation planning and implementation. Pavement adaptation in the form of structural modifications can maintain the pavement’s design life with climate change but choosing the best adaptation strategy and the timing of its’ implementation is challenging with an uncertain climate future. Developing adaptation pathways, consisting of a series of performance-based adaptation actions with regular re-evaluation, will result in a cost-effective, stepwise, and flexible adaptation plan that that can help transportation agencies avoid the high cost of premature pavement failure or robust over-design.

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