A large number culvert pipes are installed every year in North Carolina. While the loading and structural requirements for these pipes are considered during the selection process, the exposure condition of these culverts receives less attention. Many pipe choices exist including reinforced concrete, galvanized steel, aluminum, aluminized, and various types of plastic. Choosing the right pipe for the right installation is a non-trivial task that carries significant financial impact. Factors such as structural capacity, environmental durability, anticipated life-span, required pipe size, site conditions, and available construction expertise are all important when selecting a pipe. Existing NCDOT selection tables provide some limited guidance, but often result in highly-conservative selections being made, particularly from the perspective of matching pipe materials to site environmental conditions. Selection of the wrong pipe material (or an overly-conservative pipe material) can result in significant excess cost. If materials degrade too quickly, costly re-work is required, and additional costs and risks may be incurred due to reduced performance of the degraded pipe. If high-cost and high-performance materials are selected in areas where they are not needed, then initial construction costs can increase dramatically. For example, in many situations, aluminized corrugated steel pipe can likely provide the same useful service life as corrugated aluminum pipe at a dramatically reduced cost. Aluminum pipe may be justified in regions with salt-water exposure, however, it is likely an over-conservative choice for regions where contact with salt will be incidental. Accounts from NCDOT personnel have indicated widespread use of aluminum pipe in regions where it is likely not needed (i.e., regions with limited salt exposure).

The North Carolina Department of Transportation (NCDOT) routinely performs road improvement projects where a portion of the right-of-way might be contaminated. Based on the field evaluations carried out by NCDOT, at times subsurface utilities including water and/or drainage pipes are present, or need to be installed, in environments where soil and groundwater contamination exists. The currently funded project (RP 2017-08 with end date on July 31, 2019), is focused on the laboratory evaluation of contaminant migration through concrete pipes, as well as evaluation of the effect of contaminants on the mechanical performance of PVC pipe and three gasket materials (Neoprene, Buna-N, and Viton) when exposed to contaminated water. In addition, modeling of hardening methods and evaluating their efficacy is conducted as a part of the ongoing project.

The North Carolina Department of Transportation (NCDOT) routinely performs road improvement projects where a portion of the right-of-way might be contaminated. Potential sources of contamination include underground storage tanks in the vicinity of the road improvement site, old unlined landfills, or abandoned industrial and agricultural operations with practices leading to soil and/or groundwater contamination. It has been reported by NCDOT in RNS#7406 that in several situations, subsurface utilities including drainage pipes are present in environments where soil and groundwater contamination exists. The effect of the contamination on the integrity and durability of the subsurface drainage pipes and gaskets is largely unknown but such integrity is a function of the type of contamination and the physicochemical properties of pipe, gasket, and other materials forming a given subsurface utility. In addition to the variety of contaminants and concentrations that prevail at these sites, a wide variation in soil geological formation and hydrogeological conditions exist across the state. While in general the groundwater table is expected to be high in the North Carolina (NC) Coastal Plain Physicographic region, it is expected to be deep in the Mountains. On the other hand, it is more likely that groundwater will feed surface water springs and streams in the NC Mountains. Therefore, a "typical" contaminated site is difficult to define. Accordingly, the adverse effect of subsurface contamination on drainage pipes and the efficacy of hardening measures are usually developed on a site-specific basis. Objectives of this project are to (i) catalog the prevalent types of contaminants and their concentrations at sites where subsurface utilities are installed, (ii) document the typical materials used in subsurface utilities and drainage systems in NC, (iii) quantify the effect of contaminants on the long-term durability of commonly used hardened and unhardened materials that are used in construction of subsurface utilities, (iv) quantify the rate and extent of migration of common contaminants through concrete utilities, (v) recommend effective hardening methods for different materials, and (vi) provide documentation and better understanding of the effect of subsurface utility installation on the contamination of groundwater and surface water through simulation of several typical scenarios. These objectives will be achieved through a multidisciplinary effort of the research team as outlined in the project plan. Objective (i) will be achieved through examination of available data from the NC Department of Environmental Quality (DEQ). If necessary, limited sampling of groundwater and surface water will be conducted in consultation with NCDOT in areas where subsurface utilities have been installed and contamination is known to exist or expected to occur. Objectives (ii), (iii), and (iv) will be accomplished through literature review and accelerated coupon testing in our laboratory. Objective (v) will be achieved by analyzing test results and literature data. Objective (vi) will be accomplished through numerical simulations.

A research project on reinforced concrete filled pipe piles concluding in May of 2013 had the following objectives: (1) Develop recommendations for strain limits for use in seismic design at key design limit states as a function of diameter/thickness (D/t) ratio and material properties, (2) Develop an equation (via computation) for the plastic hinge length of ?below ground hinges?, (3) Quantify the impact of reinforcing steel on performance and confirm that strain compatibility can be used for prediction of the force-displacement response. These three objectives have been studied through the use of large scale experimental testing, and the analysis of pile members. In addition, work in the project provided recommendations for equations to estimate equivalent viscous damping, which are required for implementation in a direct displacement-based design approach. This proposal builds upon the work previously conducted through the following tasks: (1) Large scale testing of reinforced concrete filled pipe piles in soil; and (2) FEA and fiber-based SSI analysis. The specific goals of this proposed research project are to examine the impact that soil stiffness has on: (1) Pipe pile strain limit states; (2) Plastic hinge length and integration of curvature for deformations; (3) Proposed analysis methods, and (4) Damping

The North Carolina Department of Transportation (NCDOT) has funded a research project (will be referred to as Phase I study) to develop criteria for situations where soft soils need to be undercut and replaced and/or stabilized with mechanical or chemical measures (undercut refers to the removal of soft subgrade during the construction or reconstruction of new pavement sections). In this funded study, a large scale laboratory testing program was conducted to evaluate the performance of undercut subgrade stabilization measures under construction traffic loading, prior to final paving. Twenty-two simulated undercut sections, with four different stabilization configurations, were built in a large-scale test pit. Undercut areas backfilled with aggregate base course (ABC) and reinforced with geosynthetics showed improvement over unreinforced sections, but only when reinforcement was placed at depth approximately equal to the loaded area diameter and after initial displacements mobilized the strength of the geosynthetic. The soft nature of the subgrade and its consequences on the ability to compact the ABC layer showed the importance of carefully analyzing the results when viewed on a comparative basis, and the need for documented field performance. In this case, a trend of an accelerated deformation rate was observed during the first two hundred load cycles, with a steady state deformation rate emerging after approximately 1000-2000 loading cycles. It is not clear, however, whether this is a situation specific to the results from the laboratory testing, due to the limitation of the laboratory-sized equipment, or it is a behavior representative of field performance, and is occurring due to the limited ability to compact backfill over the soft subgrade layer. The main objective of the proposed project is to validate the findings from the Phase I laboratory study at a construction site in the Piedmont geologic area of North Carolina. The proposed work will seek to investigate the applicability of the proposed undercut criteria in the Piedmont Physiographic region and validate approaches to improving soil bearing properties investigated in the laboratory. The proposed plan includes the field implementation of four instrumented test pads for performance monitoring. In addition to a control pad, one pad will implement undercutting and replacement with select fill, a second will include undercutting in conjunction with ABC and the use of geosynthetics, and a third will include chemical stabilization. The research work will address the following objectives: i. Identify test sites in the Piedmont Physiographic region for implementation of alternative or supplemental approaches to undercut, including the use of geosynthetics and/or chemical stabilization. ii. Instrument test pads at the identified site and monitor performance in terms of induced rut depth, maximum curvature, tension cracks development, and stress attenuation with depth under repeated truck loading. iii. Perform Dynamic Cone Penetrometer (DCP) testing to validate proposed undercut criteria for site conditions. In addition, perform FWD testing to supplement the DCP data for comprehensive subgrade characterization. iv. Use field data to verify performance of alternative or supplemental approaches to undercut to limit volume change and improve soil properties and workability. Accordingly, update and verify the undercut criteria and comparative cost analyses developed during Phase I. Provide a recommendation of the relative cost of each measure and the most suitable stabilization measure(s).

The main objective of the proposed project is the more economical design of temporary slopes and retaining structures in North Carolina (NC) residual soils. In general, the current design methods and procedures for temporary slopes and temporary excavation support systems do not consider the short-term characteristics of NC residual soils, and therefore may result in overly conservative designs and unnecessary construction costs. Even though the geotechnical engineers are aware of the over conservatism of the current design methods and procedures, they do not have rational means by which to improve the design cost effectiveness. It is the development of these rational design procedures that is the heart of the proposed research.

Asset management is a relatively new concept in geotechnical engineering. In general, the nature of earth structures within the realm of highway engineering renders the concept of asset management a valuable tool for operation efficiency and cost control. Asset management includes a database of assets, tools to manage the database, asset condition assessment models, and strategies for assessment, mitigation, rehabilitation, and replacement. At present, there is no systematic tool to provide electronic documentation and analysis of earth structures including the retaining wall inventory maintained by the North Carolina Department of Transportation (NCDOT). The objective of this research is to design and develop a database archival and retrieval system for electronic documentation, management, qualitative analysis, and display of retaining walls, especially critical walls such as those adjacent to bridges. Such structures include MSE, soil-nail, tie-back, gravity, cantilever, and pile panel walls. The prototype database to be created will include wall location, geometry, internal configuration, local geology, and external signs of stress such as tilt and cracking. The development of rating criteria models that are specific to particular wall types will also be explored in consultation with NCDOT. The development of a systematic means for cataloging and condition assessment of highway retaining structures will represent a major contribution to the ability to establish effective and sustainable maintenance and replacement priorities. The primary project product is referred to herein as a database and includes a definition of all data tables and the attributes they contain. The final report will provide these definitions as well as sample data for 12 existing retaining walls populating all tables. Data collection procedures will include both wall spatial as well as wall attribute (characteristics) data. The spatial data will be organized in such a way as to be able to link to existing NCDOT systems. The proposed database (of key parameters defining the various types of retaining walls within the state) is intended to assist NCDOT engineers and contractors in evaluating the need for maintenance and replacement as well as capture often-lost assets for effective master planning, engineering, design, maintenance, and management of highway retaining structures.

Problems with reflective cracking in asphalt concrete (AC) overlays on cracked flexible pavements have been observed for many years in North Carolina. Left untreated, such cracks can severely degrade the service life of asphalt pavements. Intrusion of water into the subgrade and/or base material quickens the deterioration process, leading to early and costly failure of the whole pavement structure. Therefore, it is in the economic interest of the state of North Carolina to investigate methods that reduce or, at the very least, retard reflective cracking in AC overlays.

The dynamic evolution of landforms under stress can lead to catastrophic loss of either functionality or of mass itself. This project will examine the dynamics of landforms undergoing a transition from one state to another (e.g., barrier island collapse, wetland loss, dune erosion) in order to determine critical defining features of the resilient natural and developed landforms. This descriptive dynamic will be translated into design parameters for restoration of protective or beneficial landforms (e.g., beaches, dunes, barrier islands, wetlands). In addition, this analysis will be used to provide improved metrics for communicating hazard and risk as well as incorporating hazard and risk into land use plans. This project lies at the interface between Coastal Hazards Science and Planning for Resilience focus areas and has the potential to provide insights to the Hazards, Human Behavior and Economic Resilience focus area.