Mohamed Elshaer

Bio: Mohamed Elshaer is an academic researcher from Cold Regions Research and Engineering Laboratory. The author has contributed to research in topics: Subgrade & Falling weight deflectometer. The author has an hindex of 5, co-authored 17 publications receiving 89 citations. Previous affiliations of Mohamed Elshaer include University of New Hampshire.

Assessing the Effects of Rising Groundwater from Sea Level Rise on the Service Life of Pavements in Coastal Road Infrastructure

Abstract: Coastal communities with road infrastructure close to the shoreline are vulnerable to the effects of sea level rise caused by climate change. The sea level in coastal New Hampshire is projected to rise by 3.9 to 6.6 ft (1.2 to 2.0 m) by 2100. Climate change vulnerability and adaptation studies have focused on surface water flooding caused by sea level rise; however, little attention has been given to the effects of climate change on groundwater. Groundwater is expected to rise with sea level rise and will intersect the unbound layers of coastal road infrastructure, thus reducing the service life of pavement. Vulnerability studies are an essential part of adaptation planning, and pavement engineers are looking for methods to identify roads that may experience premature failure. In this study, a regional groundwater flow model of coastal New Hampshire was used to identify road infrastructure for which rising groundwater will move into the unbound materials during the design life of the pavement. Multilayer ...

Impact of subsurface water on structural performance of inundated flexible pavements

Abstract: The assessment of the structural performance of inundated pavements is crucial to reduce the induced damage in the aftermath of flooding. The objective of this study is to present a simplified approach to investigate the impact of different subsurface water levels on the performance of pavement structures. The flooded conditions and subsequent water recession were simulated by slowly lowering the subsurface water from the pavement surface down in depth. A hydrostatic water pressure distribution was assigned above and below the water level for different cross sections with different subgrade types. Layer Elastic Analysis was performed to predict the surface deflection, stresses and strains at the bottom of asphalt layer and at the top of subgrade layer to evaluate the impact of saturated and unsaturated pavements. Finally, the influence depth for subsurface water level at which the road can withstand traffic with zero to minimum deterioration was discussed given the pavement structure and soil type...

Methodology to evaluate performance of pavement structure using soil moisture profile

Abstract: Variation of moisture content in the subgrade layer of a flexible pavement may play a significant role in its structural performance by influencing the stiffness of the pavement system. The objective of this study is to develop and test methodologies to incorporate the soil moisture profile into flexible pavement evaluation and to determine how the changes of water table level will affect the pavement deformation. Falling weight deflectometer (FWD) data at two locations in Minnesota and Oklahoma were used to estimate the in situ measured pavement deformation with seasonal changes of water content. Then, a layer elastic analysis approach was adjusted to include the moisture dependency of the subgrade resilient modulus in calculating the deflection basin. The controlling parameters in these set of analyses were asphalt layer temperature, the degree of water saturation in unbound materials, depth to the groundwater table, and depth to bedrock. The environmental data for this study were obtained from the Long...

Assessment of the Impact of Fiber Types on the Performance of Fiber-Reinforced Hot Mix Asphalt:

Abstract: This study aims to evaluate the impact of fiber types on the performance of hot mix asphalt (HMA) mixtures. Specifically, the impacts of fiber type on HMA mix design and laboratory performance are ...

Impact of pavement layer properties on the structural performance of inundated flexible pavements

Abstract: The assessment of the structural performance of flooded pavements remains complicated due to the lack of structural data in the aftermath of flooding and the fact that information about the pavement structure and materials is not always readily available. The objective of this study is to acquire a better understanding of the structural response of pavements that have been inundated and the foreseen changes in capacity using two approaches: a mechanistic approach using layer elastic analysis and the AASHTO empirical approach to determine the structural number. The relative impact of parameters such as unbound material type, layer thickness, traffic loads, and interlayer bond conditions on the reduction in expected strain values at critical locations were evaluated. The results show increases of 15–80% in vertical strains at the top of subgrade layer for low volume and interstate sections and 6–15% increase in horizontal strain at the bottom of asphalt layer for low volume sections and 3–8% for interstate sections. Accurate information on the layer thicknesses, traffic type, and interlayer bond condition were found to be most important for the evaluation of the change in expected horizontal strain. The types of base and subgrade materials are the most important factors for evaluating the change in expected vertical strain. The results of this study provide guidance on the type of information that is most important to collect for the assessment of the structural capacity of a pavement following inundation.

Recent Progress of Fiber-Optic Sensors for the Structural Health Monitoring of Civil Infrastructure.

Abstract: In recent years, with the development of materials science and architectural art, ensuring the safety of modern buildings is the top priority while they are developing toward higher, lighter, and more unique trends. Structural health monitoring (SHM) is currently an extremely effective and vital safeguard measure. Because of the fiber-optic sensor's (FOS) inherent distinctive advantages (such as small size, lightweight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability), a significant number of innovative sensing systems have been exploited in the civil engineering for SHM used in projects (including buildings, bridges, tunnels, etc.). The purpose of this review article is devoted to presenting a summary of the basic principles of various fiber-optic sensors, classification and principles of FOS, typical and functional fiber-optic sensors (FOSs), and the practical application status of the FOS technology in SHM of civil infrastructure.

Impact of climate change on pavement structural performance in the United States

Abstract: This study uses climate projections from multiple models and for different climate regions to investigate how climate change may impact the transportation infrastructure in the United States. Climate data from both an ensemble of 19 different climate models at both RCP8.5 and RCP4.5 as well as three individual prediction models at the same Representative Concentration Pathways (RCP) levels is used. These models are integrated into the AASHTOWare Pavement ME software to predict the pavement performance. Comparisons are made between the predicted performance with respect to typical pavement distresses using both historical climate data as well as climate projection data. Though there is substantial variation for different prediction models in terms of the magnitude of the impact, the consistency in results suggest that projected climate changes are highly likely to result in greater distresses and/or earlier failure of the pavement. This finding is consistent across all the climate zones studied, but varies in magnitude of 2–9% for fatigue cracking and 9–40% for AC rutting at the end of 20 years depending on the climate region of the pavement section and prediction model used. This study also compares the impacts incorporating temperature only projections with temperature and precipitation projections. In this respect, the sections considered in this study do not show any substantial difference in the pavement performance when the precipitation data from the climate predictions are also considered in the climate inputs into AASHTOWare Pavement ME software.

Increasing threat of coastal groundwater hazards from sea-level rise in California

Abstract: Projected sea-level rise will raise coastal water tables, resulting in groundwater hazards that threaten shallow infrastructure and coastal ecosystem resilience. Here we model a range of sea-level rise scenarios to assess the responses of water tables across the diverse topography and climates of the California coast. With 1 m of sea-level rise, areas flooded from below are predicted to expand ~50–130 m inland, and low-lying coastal communities such as those around San Francisco Bay are most at risk. Coastal topography is a controlling factor; long-term rising water tables will intercept low-elevation drainage features, allowing for groundwater discharge that damps the extent of shoaling in ~70% (68.9–82.2%) of California’s coastal water tables. Ignoring these topography-limited responses increases flooded-area forecasts by ~20% and substantially underestimates saltwater intrusion. All scenarios estimate that areas with shallow coastal water tables will shrink as they are inundated by overland flooding or are topographically limited from rising inland. Sea-level rise raises water tables, causing flooding from below and saltwater intrusion. A modelling study predicts that coastal California groundwater flooding will expand 50–130 m inland with 1 m of sea-level rise, with areal flooding extent strongly dependent on topography and drainage capacity.

User ' s manual for the HDM-III model

Abstract: This book describes the Highway Design and Maintenance Standards model (HDM-III) and its constituent components and provides a comprehensive discussion of the submodels, their interaction, and the operational parameters involved. The HDM-III is designed to make comparative cost estimates and economic evaluations of different construction and maintenance options, including different time-staging strategies, either for a given road project on a specific alignment or for groups of links on an entire network. The user can search for the alternative with the lowest discounted total cost and can call for rates of return, net present values, or first-year benefits. If the HDM is used in conjunction with the Expenditure Budgeting Model, the set of design and maintenance options that would minimize total discounted transport costs or maximize net present value of an entire highway system under year-to-year budget constraints can be determined. The HDM-III model is not only a readily usable program for handling voluminous computations automatically, it is also a repository of the most extensive and consistent set of empirical data on the subject. The information includes the qualitative structure and quantitative parameters of relationships among construction standards, maintenance, traffic characteristics, road deterioration, and vehicle operating costs.

Sea-Level Rise Induced Multi-Mechanism Flooding and Contribution to Urban Infrastructure Failure.

Abstract: Sea-level rise (SLR) induced flooding is often envisioned as solely originating from a direct marine source. This results in alternate sources such as groundwater inundation and storm-drain backflow being overlooked in studies that inform planning. Here a method is developed that identifies flooding extents and infrastructure vulnerabilities that are likely to result from alternate flood sources over coming decades. The method includes simulation of flood scenarios consisting of high-resolution raster datasets featuring flood-water depth generated by three mechanisms: (1) direct marine flooding, (2) storm-drain backflow, and (3) groundwater inundation. We apply the method to Honolulu’s primary urban center based on its high density of vulnerable assets and present-day tidal flooding issues. Annual exceedance frequencies of simulated flood thresholds are established using a statistical model that considers predicted tide and projections of SLR. Through assessment of multi-mechanism flooding, we find that approaching decades will likely feature large and increasing percentages of flooded area impacted simultaneously by the three flood mechanisms, in which groundwater inundation and direct marine flooding represent the most and least substantial single-mechanism flood source, respectively. These results illustrate the need to reevaluate main sources of SLR induced flooding to promote the development of effective flood management strategies.