Education

Research Description

Dr. Gabr's research programs are the results of work by his colleagues and graduate students and experience accumulated through interaction and cooperation with colleagues in various places including North Carolina State University (NCSU), Norwegian Geotechnical Institute (NGI), Woodward-Clyde Consultants, West Virginia University (WVU), the Waterways Experiment Station (WES), and the UNC Coastal Studies Institute. Dr. Gabr's research is multifaceted in nature and encompasses the areas of in-situ soil flushing, waste characterization and properties, scour, limit states of protective earth structures, geosynthetics, and shallow and deep foundations. Details on some of the research activities are summarized as follows: 1. Base Support and Reinforcement: We have conducted research in the area of soil reinforcement focused on strain-based analysis in terms of defining the contribution of reinforcement to the soil modulus as well as characterizing the variation in strain within the soil mass with reinforcement. Our work branched out to include the effect of polymeric reinforcement on crater forming under explosions as a part of a project we conducted at US Army Corps of Engineers, Waterways Experiment Station. At present, on-going work is extending the soil reinforcement research to discern the behavior of a soil mass with various reinforcement types for the stabilization of soft subgrade soils under cyclic loading. The results of this work will be incorporated in a constitutive model for the design/analysis of reinforced soils under cyclic loading. 2. In Situ Assessment of Scour: We have developed an in situ erosion evaluation device called ISEEP to allow for rapid assessment of the scour potential of soil with depth around hydraulic structures throughout their designated lifetime, but especially prior to, and after, storm events. The ISEEP has been tested in coastal sands, coastal peat as well as in the Laboratory. The ISEEP development has been documented in ASTM Standard. 3. Levees Stability and Seepage Limit states (Strain-Based Approach): We have conducted research in cooperation with the Department of Homeland Security and the Waterways Experiment Station (WES) related to the development of methods for analyzing and assessing the risk of failure of levees. We have introduced the concept of Strain-Based Limit States for protective earth structures investigated the consequences of repeated storm loading on the functionality for a given limit state. 4. Piles and Drilled Shafts: Our research in the area of deep foundation has developed methods for analysis of drilled shafts on slopes as well as the use of in situ tests for analysis of laterally loaded shafts. We have extended this work to investigate the buckling behavior of piles taking into account the presence of the soil to provide lateral support with variable lateral subgrade distribution, as well as the impact of various boundary conditions on piles behavior. We have performed research on the use of in situ measurement techniques for obtaining parameters used in pile/shaft design. We have conducted research to investigate the effect of embedment in soft weathered rock profiles on lateral shaft behavior as well as the influence of various degree of fixity on the measured P-y curves. We have introduced a simple model for estimating the point of fixity in laterally loaded piles for use in bridge design. We are currently conducting research on the use of micropiles for anchoring offshore renewable energy devices. 5. Well Injection Depth Extraction (WIDE) System for Enhanced Soil Flushing: An achievement in this research area is the pioneering use of prefabricated vertical wells (PVWs) for accelerated soil flushing. The technology termed Well Injection Depth Extraction (WIDE) aims at reducing the clean up time in soils with a large fines fraction. The research was proclaimed as a success story by the Department of Energy. The WIDE technology was subjected to a level II independent peer review process conducted by the American Society of Mechanical Engineers, Institute for Regulatory Science. 6. Surfactant Flushing of PAH’s and DNAPLs in Clayey Soils: In conjunction with the development of an enhanced pump and treat system, we have conducted research in the area of surfactant flushing of Polycyclic Aromatic Hydrocarbons (PAH’s) and Dense Non-Aqueous Phase Liquids (DNAPLs). The research was focused on soil clogging as a result of introducing surfactant and investigated the redistribution of the contaminant within the soil/liquid/air phases during flushing, the quantitative measurement of the contaminated soil’s hydraulic conductivity and its variation during the flushing process, and the effect of the clay content on flushing levels. 7. Recycle of Industrial By-Products and Waste Characterization: We have established a research program on the use and recycling of by-product industrial material for the development of grout and flowable fill materials as well the utilization of geosynthetics to facilitate such applications. Results of the research on grout development have been successfully implemented by the US Bureau of Mines at a site in Waynsburg, Pennsylvania, for the abatement of acid mine drainage. As fly ash differs from natural soils in aspects related to physical and chemical characteristics, we have developed design criteria for the long term assessment of filtration and clogging of nonwoven geotextiles retaining fly ash fill material as well as methods pertaining to sample preparation techniques and the impact of such techniques on filtration and drainage behavior.

Honors and Awards

• Alumni Association Distinguished Graduate Professor, North Carolina State University, 2019
• Outstanding Teacher Award, American Society of Engineering Education-Southeastern Region, 2016
• Diplomate, Academy of Geo-Professionals, American Society of Civil Engineers (ASCE) , 2015
• College of Engineering Recipient- Board of Governors Award for Excellence in Teaching, 2011
• Alumni Distinguished Undergraduate Professor, 2009
• Alumni Outstanding Teacher Award, North Carolina State University, 2008
• Member, Academy of Outstanding Teachers, North Carolina State University , 2008
• Outstanding Teacher Award, North Carolina State University, 2008
• Kimely-Horn Faculty Award, 2005
• Fellow, American Society of Civil Engineers (ASCE), 2000
• Edmund Friedman Professional Recognition Award, American Society of Civil Engineers, 1996
• Excellence in Teaching Award, Dept. of Civil Engineering, West Virginia University, 1996
• Outstanding Teacher Award, College of Engineering, West Virginia University , 1995
• Outstanding Faculty Advisor, ASCE Student Chapter, West Virginia University, 1994
• Outstanding Researcher Award, College of Engineering, West Virginia University , 1994
• West Virginia Young Engineer of the Year , American Society of Civil Engineers (ASCE), 1993
• Eminent Engineer, Tau Beta PI - National Engineering Honor Society, 1992
• First Place, Student Technical Paper Contest, 3rd US Conf. on Earthquake Engineering, 1986
• Outstanding Teaching Assistant, North Carolina State University, 1985

Publications

Development of a reactive transport model for microbial induced calcium carbonate precipitation in unsaturated conditions

Faeli, Z., Montoya, B. M., & Gabr, M. A. (2024, March 1), CANADIAN GEOTECHNICAL JOURNAL, Vol. 3. https://doi.org/10.1139/cgj-2022-06771

Interpretable machine learning scheme for predicting bridge pier scour depth

Kim, T., Shahriar, A. R., Lee, W.-D., & Gabr, M. A. (2024), Computers and Geotechnics. https://doi.org/10.1016/j.compgeo.2024.106302

Natural Frequency and Foundation Damping of Colocated and Hybrid Systems Sharing Wind Turbine Monopiles under Operational Conditions

Vo, L., Jamaleddin, N., Gabr, M., & Borden, R. (2024), INTERNATIONAL JOURNAL OF GEOMECHANICS, 24(1). https://doi.org/10.1061/IJGNAI.GMENG-8469

Numerical study on micropile group behavior supporting fixed bottom marine hydrokinetic devices in sandy seabed

Jamaleddin, N., Gabr, M., Borden, R., Argall, R., & Lasser, D. (2024), OCEAN ENGINEERING, 293. https://doi.org/10.1016/j.oceaneng.2023.116614

Synergistic Hybrid Marine Renewable Energy Harvest System

Cui, L., Amani, S., Gabr, M., Kumari, W. G. P., Ahmed, A., Ozcan, H., … Bhattacharya, S. (2024), ENERGIES, 17(5). https://doi.org/10.3390/en17051240

Analysis of Wave-Driven Progressive Buildup of Excess Pore Water Pressure in Sands Supporting Marine Hydrokinetic Devices

Rafiei, A., Gabr, M. A., & Rahman, M. S. (2023), Presented at the Offshore Technology Conference. https://doi.org/10.4043/32639-ms

Development of a Reactive Transport Model for Microbial Induced Calcium Carbonate Precipitation in Unsaturated Conditions

Faeli, Z., Montoya, B. M., & Gabr, M. (2023), Canadian Geotechnical Journal, 8. https://doi.org/10.1139/cgj-2022-0677

Efficacy of Permeable Reactive Barriers in Mitigating Tetrachloroethene Ingress into Highway Drainage Concrete Pipe in Saturated Media

Almuaythir, S., Gabr, M., & Pour-Ghaz, M. (2023), JOURNAL OF PIPELINE SYSTEMS ENGINEERING AND PRACTICE, 14(2). https://doi.org/10.1061/JPSEA2.PSENG-1417

Elucidating factors governing MICP biogeochemical processes at macro-scale: A reactive transport model development

Faeli, Z., Montoya, B. M., & Gabr, M. A. (2023), Computers and Geotechnics, 160, 105514. https://doi.org/10.1016/j.compgeo.2023.105514

Estimating live-bed local scour around bridge piers in cohesionless sediments: applicability and bias of selected models

Shahriar, A. R., Gabr, M. A., Montoya, B. M., & Ortiz, A. C. (2023), CANADIAN GEOTECHNICAL JOURNAL, 60(4), 471–487. https://doi.org/10.1139/cgj-2022-0122

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Grants

Linking Scour Evaluation and Data from Geotechnical, Erodibility, and Hydraulic 4 Investigation-An Integrative Approach

NC Department of Transportation(8/01/23 - 7/31/25)

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Linking Scour Evaluation and Data from Geotechnical, Erodibility, and Hydraulic 4 Investigation-An Integrative Approach

Sponsor: NC Department of Transportation

Start Date: 8/01/23

End Date: 7/31/25

Abstract

Traditional practice of bridge local scour estimation relies upon the use of analytical models such as the one specified in Hydraulic Engineering Circulars, HEC-18 and HEC 20 (Arneson et al., 2012). Models such as HEC-18 were however developed based on data collected mainly from flume testing on sand. The data used for HEC-18 model development were mainly for narrow pier erosion in sand (scour depth/pier width>1.4) per Benedict and Knight (2017). Yet the model is applied in practice to intermediate and wide pier cases as well. In addition, the materials classified as “soils” include sand, and/or silt, and/or clay with a grain size distribution that can yield a bed soil behavior that may not be captured by a single parameter, such as D50. Approaches such as the HEC-18 model also lump the flow channel and bridge hydraulic and geometrical parameters with the bed erosion resistance parameters in one equation. While such an approach is simple to use, there is consensus in literature that it yields overly conservative scour estimates. On a fundamental level, the magnitude of erosion and scour can be assessed through knowledge of the flow-induced shear stress, the soil’s erodibility parameters, which include the critical shear stress (τc), co- efficient of erodibility (α'), and m, which is “an exponent defining the functional variation of the soil erosion rate with the flow-induced shear stress.” This approach is fundamentally implemented in the FHWA Hy- draulic Toolbox and adopted by the NextScour Program. In parallel, geotechnical site investigation by the North Carolina DOT commonly involves the performance of SPT, and the retrieval of soil samples for characterization of physical and engineering properties. As such, there is an opportunity to obtain the site- specific erodibility (τc, α', and m) through linking such parameters with the geotechnical data for a rational assessment of site-specific scour magnitude, accounting for variability of channel-bed soil layers with depth.

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Integration of Repair and Remediation Methods into Pipe Material Selection Approach

NC Department of Transportation(8/01/21 - 7/31/23)

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Integration of Repair and Remediation Methods into Pipe Material Selection Approach

Sponsor: NC Department of Transportation

Start Date: 8/01/21

End Date: 7/31/23

Abstract

In a recent research project a pipe material selection software was developed. This software enables estimation of the service life of pipes made from different materials based on their anticipated exposure conditions. The linked GIS database is used to automatically compute the anticipated exposure condition corresponding with GPS coordinates input by the user for a given project. The culvert pipe materials commonly used by NCDOT have been included in the software: reinforced concrete, galvanized steel, aluminized steel, cast iron, mild steel, aluminum alloy, and polymeric pipes. Based on conversations with NCDOT, additional scope for the software is desired and identified as follows: i. The developed software selection guide only considers material type and exposure condition in the selection process. It is desirable to integrate NCDOT’s structural requirements into the selection process such that NCDOT engineers can use a single software to select pipe materials based on both durability and structural requirements. ii. The current software does not provide an estimate of how service life can be extended by repair and rehabilitation. It is desirable to upgrade the software to account for the additional service life expected from various rehabilitation measures, and to develop a comparative analysis of possible repair methods in terms of expected impact on service life. iii. The current software does not account for the effects of approaches to mitigate adverse subsurface exposure on the service life of installed pipes. Addressing the effects of mitigation is desirable since in many projects, backfill soil is different from native soil. The work proposed herein aims to update the current software to include: (i) An upgraded pipe selection guide software that integrates structural requirements, repair and rehabilitation methods, and mitigation strategies into a unified pipe selection guide, and (ii) provisions accounting for the effects of various repair and rehabilitation methods on the service life of the pipe materials.

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Field Evaluation of Hardening Methods for Subsurface Utilities and Drainage Pipes

NC Department of Transportation(8/01/19 - 12/31/21)

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Field Evaluation of Hardening Methods for Subsurface Utilities and Drainage Pipes

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 12/31/21

Abstract

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.

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Durability of Pipe Materials in Soils

NC Department of Transportation(8/01/19 - 12/31/21)

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Durability of Pipe Materials in Soils

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 12/31/21

Abstract

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).

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Compare NCDOT Bridge Scour Calculations to USGS SIR 2016-5121 South Carolina (SC) Scour Envelope Curves Results

NC Department of Transportation(8/01/19 - 5/15/22)

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Compare NCDOT Bridge Scour Calculations to USGS SIR 2016-5121 South Carolina (SC) Scour Envelope Curves Results

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 5/15/22

Abstract

The North Carolina Department of Transportation (NCDOT) routinely performs assessment of scour potential at bridge foundations. The availability of representative approaches for estimating first order scour magnitude is needed as such information is used for the design of new bridges, designating bridges as “scour- critical,” and for deciding on the need for implementing scour countermeasures. As stated by Mr. Jerry Snead, the applicability and potential modification of USGS Scour Envelope Curves, developed for the state of South Carolina, to North Carolina soils is the focus of the research proposed herein. Such investigation is needed to assess the robustness of the first order scour estimates and to provide reliable quality control measure to ensure the reasonableness of bridge scour magnitudes estimated by other means.

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The effects of contaminated soil and groundwater on subsurface utilities, surface water and drainage

NC Department of Transportation(8/01/16 - 7/31/19)

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The effects of contaminated soil and groundwater on subsurface utilities, surface water and drainage

Sponsor: NC Department of Transportation

Start Date: 8/01/16

End Date: 7/31/19

Abstract

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.

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Establishment of Remote-Sensing Based Monitoring Program for Performance Limit State Assessment of the Sacramento Delta Levees

US Dept. of Homeland Security (DHS)(1/01/16 - 6/30/23)

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Establishment of Remote-Sensing Based Monitoring Program for Performance Limit State Assessment of the Sacramento Delta Levees

Sponsor: US Dept. of Homeland Security (DHS)

Start Date: 1/01/16

End Date: 6/30/23

Abstract

The integrity and reliability of flood-control earthen dams and levees are essential components to homeland safety. The failure of such systems due to natural or man-made hazards may have monumental repercussions, sometimes with dramatic and unanticipated consequences on human life and the country’s economy. The levees network in the Sacramento-San Joaquin Delta support exceptionally rich agricultural area (over a $500 million annual crop value). Currently, the risk of levee failure in this area from potential flooding or draught threatens the lives of individuals living behind the levees, but also, the water quality in this water-transfer system. Preliminary risk assessment demonstrated a 40% chance that at least 30 islands within the Delta area would be flooded by simultaneous levee failures in a major earthquake in the next 25 years. The teamwork proposed herein will extend the remote sensing monitoring by InSAR and Joint Scatterer interferometry (JSInSAR) to monitor levees deformation with a resolution on the order of a few millimeters. The research team ay NCSU will participate by integrating the use of measurement data and modeling techniques, using the concept of performance limit states, to effectively achieve a performance based health assessment of the delta levees network.

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Reinforced Concrete Filled Pipe Piles in Soil

State of Alaska, Department of Transportation(8/15/13 - 12/31/16)

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Reinforced Concrete Filled Pipe Piles in Soil

Sponsor: State of Alaska, Department of Transportation

Start Date: 8/15/13

End Date: 12/31/16

Abstract

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

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Retaining Wall Inventory and Assessment System

NC Department of Transportation(8/16/13 - 8/15/15)

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Retaining Wall Inventory and Assessment System

Sponsor: NC Department of Transportation

Start Date: 8/16/13

End Date: 8/15/15

Abstract

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.

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Design of Temporary Slopes and Excavations in NC Residual Soils

NC Department of Transportation(8/16/12 - 6/30/16)

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Design of Temporary Slopes and Excavations in NC Residual Soils

Sponsor: NC Department of Transportation

Start Date: 8/16/12

End Date: 6/30/16

Abstract

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.

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