Browsing by Author "Roy H. Borden, Committee Member"

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Complex Modulus Determination of Asphalt Concrete Using Indirect Tension Test
(2004-11-29) Momen, Mostafa; Murthy N. Guddati, Committee Member; Roy H. Borden, Committee Member; Y. Richard Kim, Committee Chair
The purpose of this research is to present the results from an analytical/experimental study on the dynamic modulus testing of hot mix asphalt (HMA) using the indirect tension (IDT) mode. The analytical solution for dynamic modulus determination in IDT was developed by Kim (14) using the theory of linear viscoelasticity. To verify the analytical solution, temperature and frequency sweep tests were conducted on 24 asphalt mixtures commonly used in North Carolina, using both axial compression and IDT test methods. In doing so, a modified dynamic modulus test protocol is introduced that reduces the required testing time by using more frequencies and fewer temperatures based on the time-temperature superposition principle. A comparison of results from the axial compression and IDT test methods shows that the dynamic modulus mastercurves and shift factors derived from the two methods are in good agreement. It was also found that Poisson's ratio is a weak function of the loading frequency; its effect on the phase angle mastercurve is discussed. After verification of the analytical solution, another study was conducted to evaluate the effect of aggregate size on the variability of test results, where the coefficient of variation (CV) was computed for each aggregate size and the results were compared. It was found that mixes with a larger nominal maximum size of aggregate (NMSA) had a greater CV than those with a smaller NMSA. Digital image Correlation was used to further support the findings and reveal physical explanations for the results obtained from this statistical analysis.
Cone Tip Apex Angle Effects on Cone Penetration Testing
(2006-04-27) Browning, John Adam; M. Shamimur Rahman, Committee Member; Roy H. Borden, Committee Member; Mohammed A. Gabr, Committee Chair
Research work in this thesis deals with the Cone Penetrometer Test's (CPT) cone tip apex angle effects on penetration resistance, and the soil parameters that can be derived from its value. Five tips with apex angles of 50, 60, 75, 90 and 120° were pushed in a controlled laboratory environment and at three separate field sites in North Carolina. The laboratory study was performed to investigate the relative effect, as compared to the standard 60o apex angle, of different angles on the thrust needed to push the cone. The field testing was completed to investigate the tip apex angle effect in naturally occurring conditions. In general, the results showed that the tip apex angle has an increasing effect on tip resistance with increasing relative density. This finding agrees with Nowatzki and Karafiath's (1972) suggestion that two tip geometries, one with an acute apex angle (2α< 90°) and one with an obtuse apex angle (2α&8805;> 90°), should be pushed at every site if a failure mechanism within a given soil is to be discerned. Following such approach, if the two tip resistances are relatively the same, the soils are loose (Dr ≥ 34%) and compression controls the failure mode and therefore the thrust magnitude. On the other hand, if the two tip resistances vary significantly, the soils are medium dense to dense (Dr > 34%) and failure is controlled by shear strength. Based on the field testing it is determined that as the tip angle increases in dense soils, the acute angle tips (50, 60, and 75°) provide higher tip resistances than the obtuse angle tips (90 and 120°). Since the non-standard, obtuse angle tips are more advantageous because they require less thrust to penetrate dense soils than the standard 60 degree tip, previously established relationships between tip resistance and soil parameters for the 60 degree tip were modified for non-standard tip geometries. Based on field testing and previously established relationships for the standard 60° tip angle, empirical relationships are developed for the five tips tested to relate normalized cone resistance to the soil behavior type index (as defined by Robertson 1990), relative density, friction angle, and normalized SPT N60.
Development of Resistance Factors for Axial Capacity of Driven Piles in North Carolina
(2003-02-11) Kim, Kyung Jun; Roy H. Borden, Committee Member; M. Shamimur Rahman, Committee Co-Chair; Mohammed A. Gabr, Committee Chair; C. C. Tung, Committee Member
Resistance factors were developed in the framework of reliability theory for the Load and Resistance Factor Design (LRFD) of driven pile's axial capacity in North Carolina utilizing pile load test data available from the North Carolina Department of Transportation. A total of 140 Pile Driving Analyzer (PDA) data and 35 static load test data were compiled and grouped into different design categories based on four pile types and two geologic regions. Resistance statistics were evaluated for each design category in terms of bias factors. Bayesian updating was employed to improve the statistics of the resistance bias factors, which were derived from a limited number of pile load test data. Load statistics presented in the current AASHTO LRFD Bridge Design Specifications were used in the reliability analysis and the calibration of the resistance factors. Reliability analysis of the current NCDOT practice of pile foundation design was performed to evaluate the level of safety and to select the target reliability indices. Resistance factor calibration was performed for the three methods of static pile capacity analysis commonly used in the NCDOT: the Vesic, the Nordlund, and the Meyerhof methods. Two types of First Order Reliability Methods (Mean Value First Order Second Moment method and Advanced First Order Second Moment method) were employed for the reliability analysis and the calibration of the resistance factors. Recommended resistance factors are presented for the three methods of static pile capacity analysis and for seven different design categories of pile types and geologic regions. The resistance factors developed and recommended from this research are specific for the pile foundation design by the three static capacity analysis methods and for the distinct soil type of the geologic regions of North Carolina. The methodology of the resistance factor calibration developed from this research can be applied to the resistance factor calibration for other foundation types.
Evaluation of Rutting Behavior of Density Deficient Asphalt Mixtures
(2003-11-18) El-Haggan, Omar Sherif; Roy H. Borden, Committee Member; Y. Richard Kim, Committee Chair; Murthy N. Guddati, Committee Member
The purpose of this research has been to evaluate the effect of change in density on the rutting performance of the asphalt pavement. This investigation helps in determining the appropriate penalty for density deficient pavements based on the rutting performance. Permanent deformation tests were performed at 30, 40, and 50C on specimens with four different air void contents: 8, 8.75, 9.5, and 11%. More permanent deformation was observed at higher air voids and temperature. Complex modulus tests were also performed at the same four air void contents. Results showed that dynamic modulus decreases with the increase of both temperature and air void content as the asphalt mixture becomes softer at higher temperatures and air voids. Finally, a case study was performed to see the effect of air voids on the rutting behavior of the asphalt pavement. In this case study, the yearly rut depth for a certain pavement structure was predicted for both 8% and 11% air voids. Rut depth was determined to be 0.0074 inches for the 8% air voids pavement and 0.0168 inches for the 11% air voids pavement. This means that the pavement with 3% deficiency in air voids had an amount of rutting which is 2.3 times that of the in-specification pavement.
Fatigue Performance Prediction of North Carolina Mixtures Using Simplified Viscoelastic Continuum Damage Model
(2009-08-10) Hou, Tian; Y. Richard Kim, Committee Chair; Murthy N. Guddati, Committee Member; Roy H. Borden, Committee Member
Fatigue performance modeling is one the major topics in asphalt concrete modeling work. Currently the only standard fatigue test available for asphalt concrete mixtures is the flexural bending fatigue test, AASHTO T-321. There are several issues associated with flexural fatigue testing, the most important of which are the stress state is not uniform but varies over the depth of the specimen and equipment for fabricating beam specimens is not widely available. Viscoelastic continuum damage (VECD) fatigue testing is a promising alternative to flexural fatigue testing. Different researchers have successfully applied the VECD model to asphalt concrete mixtures using constant crosshead rate direct tension test. However, due to the load level limitation of the new coming Asphalt Mixture Performance Tester (AMPT) testing equipment, there is an immediate need to develop a model that can characterize fatigue performance quickly using cyclic test data. In this study, a simplified viscoelastic continuum damage model developed at NCSU is applied to various North Carolina mixtures, which are used in the NCDOT HWY-2007-7 MEPDG local calibration project. It is shown that the simplified VECD model can predict fatigue tests fairly accurately under various temperature conditions and strain levels. It is also shown that the model can be further utilized to simulate both the strain controlled direct tension fatigue test and the traditional beam fatigue test. In this thesis, simulation results are presented. Conclusions regarding the applicability of the new model are advanced as well as suggestions for further work.
A Fundamental Investigation of Well Injection Depth Extraction (WIDE) System Performance Aspects in Fine-Grained Soil Contaminated with Trichloroethylene
(2003-12-06) Warren, Kimberly Anne; Mohammed S. Rahman, Committee Member; Roy H. Borden, Committee Member; Mohammed A. Gabr, Committee Chair; Robert C. Borden, Committee Member
This research consisted of three components: the field demonstration, laboratory experimentation, and finite element analysis. Global WIDE system performance (in-situ ground water and contaminant transport) was investigated during the field demonstration, PVW performance was examined during laboratory experimentation, and contaminant partitioning tendencies were evaluated as a function of time and operational scheme during the finite element analysis. The field demonstration was conducted at a site located in Ashtabula, Ohio. With the exception of a silt seam located approximately 1.8 m to 2.4 m below the ground surface, the subsurface consisted of clay (CL) and the in-situ permeability was determined to be approximately 1x10-6 cm/s. TCE contamination levels as high as 300,000 mg/kg were detected on the soil, and concentrations as high as 475 mg/L were detected in the ground water. A 21.0 m by 18.3 m WIDE demonstration system was installed over an area that encompassed a TCE plume. The test area was divided into four quadrants and 494 PVWs were installed to a depth of 6.1 m. Concurrent injection extraction, alternating row extraction, and full quadrant extraction operations took place over a nine month demonstration. Vacuum pressure, injected and extracted fluid volumes, TCE concentrations (gas and soluble-phase), and water table levels were monitored. A 10 kPa laboratory tracer test experiment was conducted using a 1.0 m3 clay slurry sample with a high permeability soil seam, similar to field conditions. The test box was lined with a geocomposite to provide a constant head reservoir boundary around the test sample. Three settlement plates, 23 piezometers, and 27 tracer tubes were installed to monitor settlement, pressure head, and chloride (Cl) tracer concentration, respectively. The zone of influence and PVW geometry effects were evaluated. NAPL Simulator (a three-dimensional finite element analysis model) was calibrated using hydraulic field data and then used to simulate soluble and gas-phase contaminant transport in saturated and unsaturated soil media. Using a reference case, a parametric evaluation was initially performed to establish the input variables that significantly affect contaminant transport. System performance and contaminant partitioning tendencies were evaluated as a function of time and operational scheme. Finally, a sensitivity analysis, consisting of 36 simulations, was performed to evaluate contaminant partitioning tendencies as a function of the PVW spacing, extraction water flow rate, and mass transfer coefficient.
Fuzzy and Neural Network Models for Analyses of Piles
(2007-11-19) Jeon, JongKoo; M.S.Rahman, Committee Chair; Roy H. Borden, Committee Member; Mohammed A. Gabr, Committee Member; Murthy N. Guddati, Committee Member; Deepak Sirdeshmukh, Committee Member
Mechanics of Compressibility and Strength of Solid Waste in Bioreactor Landfills
(2002-11-28) Hossain, Md. Sahadat; Roy H. Borden, Committee Member; Shamim Rahman, Committee Member; Mortan A. Barlaz, Committee Member; Mohammed A. Gabr, Committee Chair
Bioreactor landfills are operated to enhance refuse decomposition, gas production, and waste stabilization. A major aspect of bioreactor landfill operation is the recirculation of collected leachate back through the refuse mass. While there are significant economic advantages to the operation of landfills as a bioreactor, our understanding of the mechanics governing accelerated waste degradation and its impact on waste geotechnical properties is limited. As such, there is a need to explain and quantify such impact on compressibility and shear strength parameters; these parameters are needed for the three design phases of landfill construction, operation, and post-closure. The overall objective of the research was to develop an understanding of change in refuse compressibility and strength during accelerated waste decomposition in landfills operated as bioreactors. An experimental program was performed to provide data on parameters describing MSW compressibility and strength properties as a function of the state of decomposition, gas generation, and physical characteristics of waste particles. The research links the measured parameters to the physical and biological changes that take place as waste decomposition is accelerated. The research provides data on the significance of using relatively small equipment and shredded waste relative to field-estimated properties. The research develops a model of waste settlement that considers the effect of high moisture content and time-dependent property changes on waste compressibility. This research also develops a model for shear stress-displacement behavior of MSW in bioreactor landfills. Refuse samples representing various stages of decomposition, from fresh refuse to well decomposed refuse, were generated in laboratory-scale reactors that were operated under conditions designed to simulate decomposition in both traditional and bioreactor landfills. The reactors were destructively sampled to obtain refuse at various states of decomposition, based on the reactor's methane production rate curve. In addition, the state of decomposition was quantified by measurement of the concentrations of cellulose (C), hemicellulose (H), and lignin (L), and (C+H)/L ratio. Reactors were sampled at each of four time points to obtain refuse in the anaerobic acid phase, the accelerated methane production phase, and early and late in the decelerated methane production phase. The experimental program was performed using oedometer and direct shear tests to determine the compressibility parameters and shear strength parameters and illustrate the effect of shredding and equipment size on compressibility and strength parameters for refuse (at different degrees of degradation). The extent of degradation was documented by gas production rates as well as (C+H)/L ratios. Oedometer test conducted on 63.5 mm, 100mm, 200mm diameter equipment with constant R, specimen to equipment size ratio, indicate that compressibility parameters are dependent on R. Compressibility parameters are similar with constant R even though the equipment size varies. Shredding of MSW affects mainly initial compression as observed from the test results on same equipment with variable R. For example, initial compression for MSW in 200mm equipment is 31% and 35% for R =0.34 and 0.17, respectively. Creep and biological strain rate of MSW is not affected by shredding. The variation of the magnitude of biological indices with varied R is minimal. The shear strength is affected by shredding as the light-weight reinforcing materials are shredded into smaller pieces during specimen preparation. The measured shearing angles are 31° and 27° for R=0.50 and 0.25, respectively. The larger components in the specimen act as better reinforcing element than shredded smaller components during the shear test. Compressibility increased with increasing gas production as solid-to-gas conversion took place. Testing results indicated a correlation between the coefficient of primary compression (Cc) and (C+H)/L ratio. The coefficient of primary compression (Cc) for all samples showed an increasing trend with decreasing (C+H)/L. Results indicated the creep index (Cα) to be independent of the state of waste decomposition. The creep index range was 0.02 to 0.03 for traditional and bioreactor samples in various states of decomposition. The magnitude of the biological indices varied with the state of decomposition and yielded the highest values (Cβ=0.19) when samples were actively decomposing and had substantial methane potential remaining. The amount of plastic, a non-degradable waste component, within test sample remains the same where as the paper content decreases with degradation as their structure matrix breaks down. The experimental results found that with degradation of degradable material, percentages of plastic content increases and contributes to decrease in friction angle. Accordingly, testing results indicated a correlation between strength parameters and (C+H)/L ratio. For example, measured shearing angle for bioreactor samples decreased from 32° to 24° as (C+H)/L ratio decreased from 1.29 to 0.25. The predicted shear behavior by the developed constitutive model for shear stress displacement was matched with the experimental results. Settlement prediction using a developed model considered all the aspects of biological decomposition, creep and matrix stiffness change as decomposition takes place with time. Seven field case studies show that the model predicts landfill settlement quite well including the biological decomposition component.
Quantifying the Benefits of Improved Rolling of Chip Seals.
(2009-04-23) Lee, Jaejun; Roy H. Borden, Committee Member; Richard L. Lemaster, Committee Member; Y. Richard Kim, Committee Chair; Akhtarhusein A. Tayebali, Committee Member
This dissertation presents an improvement in the rolling protocol for chip seals based on an evaluation of aggregate retention performance and aggregate embedment depth. The flip-over test (FOT), Vialit test, modified sand circle test, digital image processing technique, and the third-scale Model Mobile Loading Simulator (MMLS3) are employed to evaluate the effects of the various rolling parameters and to measure chip seal performance. The samples used to evaluate the chip seal rolling protocol were obtained directly from field construction. In order to determine the optimal rolling protocol, the effects of roller type, number of coverages, coverage distribution on the sublayers of a multiple chip seal (i.e., the split seal and triple seal), and rolling pattern are evaluated using the results of aggregate retention performance tests, the modified sand circle method, and the digital image process. It is found that two types of roller, the pneumatic tire roller and the combination roller, are recommended as the optimal rollers for the chip seal. In addition, it is found that the optimal number of coverages for the chip seal, as determined from measurements of the aggregate, is three coverages. Moreover, the performance of the triple seal without coverage at the bottom layer does not affect the aggregate retention performance, although the split seal does require coverage at the bottom layer. Finally, it is found that the rolling pattern is strongly related to a delayed rolling time between the aggregate spreader and the initial rolling time. Therefore, it was recommended that two pneumatic tire rollers applied initial one coverage with optimal delayed rolling time (between 2 min. and 4 min.) to entire lane width, and then the combination roller applied two additional coverages. Further, it is confirmed that the delayed rolling time is related to the aggregate moisture condition and the ambient temperature.