Now showing items 1-20 of 50

    • Development of Landslide Warning System

      Riad, Beshoy; Zhang, Xiong (2019-11)
      Landslides cause approximately 25 to 50 deaths and US$1 - 2 billion worth of damage in the United States annually. They can be triggered by humans or by nature. It has been widely recognized that rainfall is one of the major causes of slope instability and failure. Slope remediation and stabilization efforts can be costly. An early warning system is a suitable alternative and can save human lives. In this project, an early warning system was developed for a 40-foot-high cut slope on the island of Hawaii. To achieve the objective, subsurface investigations were performed and undisturbed samples were collected. For the purpose of unsaturated soil testing, new testing apparatuses were developed by modifying the conventional oedometer and direct shear cells. The unsaturated soil was characterized using two separate approaches and, later, the results were discussed and compared. The slope site was instrumented for the measurement of suction, water content, displacement, and precipitation. The collected climatic data along with the calibrated hydraulic parameters were used to build an infiltration-evapotranspiration numerical model. The model estimations were compared with the field measurements and showed good agreement. The verified model was used to determine the pore-water pressure distribution during and after a 500-years return storm. Later, the pore-water pressure distribution was transferred to a slope stability software and used to study the slope stability during and after the storm. Based on a 2D slope stability analysis, the slope can survive the 500-year storm with a factor of safety of 1.20. Instrument threshold values were established for water content sensors and tensiometers using a traffic-light-based trigger criterion.
    • Development of a Computer Vision-Based Three-Dimensional Reconstruction Method for Volume-Change Measurement of Unsaturated Soils during Triaxial Testing

      Zhang, Xiong; Xia, Xiaolong (2019-10)
      Problems associated with unsaturated soils are ubiquitous in the U.S., where expansive and collapsible soils are some of the most widely distributed and costly geologic hazards. Solving these widespread geohazards requires a fundamental understanding of the constitutive behavior of unsaturated soils. In the past six decades, the suction-controlled triaxial test has been established as a standard approach to characterizing constitutive behavior for unsaturated soils. However, this type of test requires costly test equipment and time-consuming testing processes. To overcome these limitations, a photogrammetry-based method has been developed recently to measure the global and localized volume-changes of unsaturated soils during triaxial test. However, this method relies on software to detect coded targets, which often requires tedious manual correction of incorrectly coded target detection information. To address the limitation of the photogrammetry-based method, this study developed a photogrammetric computer vision-based approach for automatic target recognition and 3D reconstruction for volume-changes measurement of unsaturated soils in triaxial tests. Deep learning method was used to improve the accuracy and efficiency of coded target recognition. A photogrammetric computer vision method and ray tracing technique were then developed and validated to reconstruct the three-dimensional models of soil specimen.
    • Laboratory and Field Evaluation of Modified Asphalt Binders and Mixes for Alaskan Pavements

      Liu, Jenny; Liu, Jun (2019-08)
      In order to properly characterize modified asphalt binders and mixes for Alaskan pavements, this study evaluated properties of 13 asphalt binders typically used in Alaska from three different suppliers, and 10 hot mix asphalt (HMA) mixtures which were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (G*), and phase angle (δ) at high performance temperatures, multiple stress creep recovery rate and compliance, bending beam rheometer stiffness and m-value, Glover-Rowe parameter, ΔT, rheological index, and crossover frequency for binders, and rut depth, critical strain energy release rate (Jc), Indirect tensile (IDT) creep stiffness and strength for mixtures. Binder cracking temperatures were determined using asphalt binder cracking device. Mixture cracking temperatures were determined with IDT creep compliance and strength data. It was found that rutting and cracking resistances of the mixtures with highly modified binders were better than the mixture with unmodified asphalt binder (PG 52-28). Future recommendations for highly modified asphalt binders applications and research were provided based on laboratory testing results and field survey evaluation.
    • Highly Abrasion-resistant and Long-lasting Concrete

      Liu, Jenny; Murph, Diane (2019-08)
      Studded tire usage in Alaska contributes to rutting damage on pavements resulting in high maintenance costs and safety issues. In this study binary, ternary, and quaternary highly-abrasion resistant concrete mix designs, using supplementary cementitious materials (SCMs), were developed. The fresh, mechanical and durability properties of these mix designs were then tested to determine an optimum highly-abrasion resistant concrete mix that could be placed in cold climates to reduce rutting damage. SCMs used included silica fume, ground granulated blast furnace slag, and type F fly ash. Tests conducted measured workability, air content, drying shrinkage, compressive strength, flexural strength, and chloride ion permeability. Resistance to freeze-thaw cycles, scaling due to deicers, and abrasion resistance were also measured. A survey and literature review on concrete pavement practices in Alaska and other cold climates was also conducted. A preliminary construction cost analysis comparing the concrete mix designs developed was also completed.
    • A Bio-Wicking System to Prevent Frost Heave in Alaskan Pavements: Phase II Implementation

      Galinmoghadan, Javad; Zhang, Xiong; Lin, Chang (2019-11)
      Water within pavement layers is the major cause of pavement deterioration. High water content results in significant reduction in soil’s resilient behavior and an increase in permanent deformation. Especially in cold regions, frost heave and thaw weakening cause extensive damage to roads and airfields. Conventional drainage systems can only drain gravity water not capillary water. Both preliminary lab and field tests have proven the drainage efficiency of a newly developed H2Ri geotextile with wicking fabrics. In this report, continuous research was conducted to verify the effectiveness of the wicking fabric in mitigating frost boil issues in Alaskan pavemnets. Two test sections were selected at two low volume roads on the campus of the University of Alaska Fairbanks. Soil moisture and temperature sensors were installed within the road embankments. The monitored data was used to analyze the soil migrations and evaluate the drainage performance of the wicking fabric. Preliminary monitoring results showed that the wicking fabric was effective in mitigating the frost boil problem.
    • Use of Cellular Concrete for Air Convection Embankment to Protect Permafrost Foundations in Cold Regions: Feasibility Study

      Liu, Jenny; Wu, Hanli (2019-08-15)
      The air convection embankment (ACE) is a technique used to protect permafrost from thawing in road construction in cold regions. However, the desired materials needed for ACE are not readily available, which prevents its extensive use in Alaska. To overcome the limitation of traditional ACE, and further improve the cooling effect of ACE, this study investigated the feasibility of using cellular concrete as an alternative material for ACE in cold regions. The heat transfer patterns of the cellular concrete ACE, the crushed-rock ACE, and the sand/gravel embankment were studied using the numerical simulation. The results of the present study show that the cooling performance of both cellular concrete ACE and crushed-rock ACE are superior to the traditional sand/gravel embankment. The cellular concrete ACE has better heat insulation property in the summer, and the crushed-rock ACE has stronger natural convection in winter. For the annual cooling efficiency of the two different ACE techniques, the proposed cellular concrete ACE has a better cooling effect on the foundation soil than the crushed-rock ACE. These results indicate that the thermal conductivity and specific heat capacity of construction materials have significant impacts on the performance of the ACE.
    • The Impact of Snowfall on Airport Operations and Delays

      Lee, Jukwan; Yan, Jia (2019-03-31)
      Flight delays or cancelations due to snowfall are a costly inconvenience, not only to airports but also to airlines, passengers and society as a whole. However, no quantitative research has ever been done to provide an analytical explanation about the issue. Though being a reliable alternative to melt snow on the runway and mitigate flight delays, the Heated Pavement System is not adopted in any US airports because of concerns over the initial investments and maintenance costs being higher than the economic loss from delays during unpredictable snowfall days. Combining weather and domestic flight data in Boston and Los Angeles regions, we analyze the benefits and costs associated with installing the Heated Pavement System. Using two advanced econometric methods, the Difference in Difference in Difference (DDD) and the nearest neighbor matching, we first develop a Delay Analysis model to evaluate the exact effect of snowfall on flight delays, and then we calculate the delay costs. Based on the empirical findings, we conduct cost-benefit analysis of installing HPS at the three airports in Boston area. Our results indicate that HPS is feasible for airports with a great number of flights and passengers, such as Boston Logan airport.
    • Examination of the Variability in Grout Test Results

      Ahn, Il-Sang; Friend, Trenton (2019-08-31)
      Keyway grouting is an operation that connects decked bulb-tee girders into one system. The quality of grout should be well maintained through reliable material test procedures. Due to the issues of discrepancy and variability, there have been several cases in which grout materials did not satisfy the compressive strength standard specified in the DOT&PF Standard Specifications for Highway Construction. This research examined the causes of such issues. Six factors – grout material, mix consistency, workmanship, initial curing/storing, curing method, and test equipment – were identified as the causes of strength variation. Their effects on strength variation were investigated by testing compressive strength of cube and cylinder specimens made from 5 grout materials that were used or considered to be used in DOT&PF projects. Grout material characteristics such as grout material and mix consistency have significant effect on strength variation. Workability and consolidation can be different from one material to another. Consequently, they affect compressive strength and its variation. Workmanship and test equipment were evaluated in this research to have moderate effect on strength variation. Especially, strength variation can increase when the workmanship factor combines with the grout material characteristics factor.
    • Pre-Stress Loss Due to Creep in Precast Concrete Decked Bulb-Tee Girders Under Cold Climate Conditions

      Vandermeer, Drew; Ahn, Il-Sang (2019-07-31)
      Accurate estimation of pre-stress losses is one of the important issues for the design of precast, pre-stressed concrete bridge girders. While this subject has been long studied by many researchers, studies on pre-stress losses in cold climates are minimal. In the present research, long-term pre-stress loss due to concrete creep was studied based on concrete creep test. Two concrete creep test frames were fabricated and placed indoors and outdoors. Concrete strains were measured by Demountable Mechanical Strain Gauge (DEMEC) from two 612 high-strength concrete cylinders in each frame. The concrete strains were collected for 11 months (7/26/2017 – 6/21/2018) after loading, and outdoor ambient temperature dropped below 0C between 100 and 250 days. Between 50 and 100 days, two curves from the two frames are similar in their patterns and values. After 100 days, the total strain from the indoor frame slowly increased reaching 1,600 and 1,700 after 250 days. However, the total strain from the outdoor frame varied between 1,000 and 1,500 and the averaged total strain was 1,300 after 250 days. In cold temperature, the occurrence of concrete creep and shrinkage was suppressed.
    • A Novel Systematic Strategy Towards Air-Purifying, Corrosion Resistant and Self-Healing Concrete Infrastructure

      Yang, Zhengxian (2019-09-15)
      Transportation causes major emissions of harmful gases (NOx, CO, VOCs). These pollutants also travel long distances to produce secondary pollution such as acid rain. The most popularly used photocatalytic cementitious composites based on TiO2 achieve the air purification function under ultraviolet sunlight, significantly impeding a broader application of photocatalytic cementitious composites. This study focused on developing an environmentally friendly and durable cementitious system based on the multifunctional photocatalytic Graphitic carbon nitride (g-C3N4). The photocatalytic cementitious composites (PCC) were prepared in three manners: (1) incorporating g-C3N4 nanosheets (CNNs) in cement at three mixing dosages (0.5%, 1% and 2% by weight of cement), (2) applying CNNs at various concentration levels as the coating on recycled asphalt pavement aggregate, (3) applying CCNs s with vinyl chloride/vinyl ester/ethylene copolymer (as a binder) as the coating on cement mortar. The photocatalytic performance and durability of the newly developed cementitious composites were evaluated systematically and the results showed that the PCC hold marked efficiency in terms of NOx removal and self-cleaning when the CNNs were applied in a proper way. The obtained knowledge sheds light on a future perspective of developing a novel systematic strategy towards air-purifying, corrosion resistant, and self-healing concrete infrastructure.
    • Cost-Effective Use of Sustainable Cementitious Materials as Reactive Filter Media (Phase I)

      Li, Wenbing; Shi, Xianming (2019-08-31)
      This report presents a laboratory study on the use of nano SiO2 as modifier in crushed fines recycled concrete (CFRCs), coupled with thermal treatment, with the goal of fabricating a sustainable reactive medium to capture the chloride anions in deicer-laden stormwater runoff. A uniform design (UD) scheme was employed for the statistical design of experiments. Predictive models were developed based on the experimental data to quantify the influence of each design parameter on the effectiveness of removing Cl- ions from simulated stormwater. The models were verified, and then employed for predictions. Finally, the samples of different CFRCs modified by nano SiO2 and heating regimes were prepared under the optimal parameters identified via the Response Surface Methodology (RSM). The optimal processing of CRFCs include the use of admixing nano SiO2 at 0.3% (by mass), then heating the material at 525oC for 3h. The structure and properties of these CFRCs materials were characterized by XRD, FTIR, BET, SEM and EDS. These advanced characterization tools revealed that the modified CFRCs achieved great potential to chemically bind chloride anions. This work is expected to produce substantial benefits for highway agencies and other stakeholders of deicer stormwater runoff, through enhanced understanding of the efficacy and appropriateness of cementitious filter media in passive reactive systems for decreasing contaminant loading in stormwater runoff. The use of CRFCs as a low-cost sorbent will be economically attractive and environmentally sustainable, diverting them from waste stream and landfill and towards sustainable stormwater management.
    • Numerical Simulation of Snow Deposition Around living Snow Fences

      Petrie, John; Zhang, Kun; Shehata, Mahmoud (2019-09-13)
      In this study, computational fluid dynamics (CFD) was used to investigate the air flow around porous snow fences to gain insight into snow transport and deposition in the vicinity of fences. Numerical simulations were performed to validate the CFD approach using experimental data from a wind tunnel study. Subsequent simulations were used to test the use of a porosity model to represent fence geometry and determine the effect of fence spacing for fences comprised of multiple rows. The results demonstrate that CFD simulations can reproduce the aerodynamics around porous fences. Additionally, the flow field generated with a porosity model is in close agreement with that from a model with explicit representation of fence porosity. Simulations of fences comprised of two rows spaced at various distances demonstrate that when the row spacing is small the fence behaves as a single row.
    • Mapping the Wolverine Way: Identifying Conservation Corridors and Transboundary Linkages in the Canadian Crown of the Continent Region

      Clevenger, Anthony P. (2019-09-13)
      The Canadian Crown of the Continent (CCoC) is one of three zones where wolverines can move between Canada and the US, providing the last links for recruitment and ultimately gene flow to the highly fragmented population in the US Rocky Mountains. However, a combination of rapidly expanding logging, energy development and motorized recreation, along with a growing road network, threatens to fragment and diminish connections in this critical transboundary linkage between the US and Canada. This report summarizes a project to complete a 3-year sampling effort in the CCoC, which in turn completed a larger 6-year effort over a vast area of the central and southern Canadian Rockies. In 2016, the research team surveyed the last unsampled portion of the Alberta Rockies (south of Kananaskis Country to Highway 3) in addition to a substantial portion of the East Kootenay region of the British Columbia Rockies (BC; >9000 km2). This follow-up effort allowed the team to complete an entire ecoregion-wide wolverine survey in the Canadian Rockies ecoregion, from the US-Canadian border north to Banff and Yoho National Parks. From this data, researchers created density estimates and occupancy models of wolverine distribution and its multiple landscape stressors across an extensive and complex region of the Great Northern Landscape. The report summarizes research findings and makes recommendations regarding management strategies.
    • A New Sustainable Additive for Anti-Icing Pavement

      Zhang, Yan; Shi, Xianming (2019-08-30)
      Based on a review and synthesis of the state-of-the-art literature on asphalt pavement with anti-icing additives, this laboratory study developed an anti-icing asphalt pavement that incorporates innovative salt-storage additives with a sustained salt-release rate. These additives were prepared through a surface treatment approach, in which zeolite containing CaCl2 was coated by a porous epoxy layer. The anti-icing performances and mechanical properties of asphalt mixture with the obtained additives were investigated. The experimental results indicated that the anti-icing capability of asphalt mixture at both -3.9 °C (25°F) and -9.4 °C (15°F) was significantly improved by the addition of the additives, and the friction coefficient of the pavement at 60 min after moisture spray was 0.75 at -3.9 °C to 0.55 at -9.4 °C. Reducing the size of additives resulted in a further improved anti-icing capability. Under simulated conditions, the estimated effective anti-icing period of asphalt pavement with additives #8, #16, and #30 were 5.8 years, 9.9 years and 15.3 years, respectively. The incorporation of the additives exhibited negligible effect on the moisture damage resistance of asphalt mixture, and almost all the mixtures passed the WSDOT specification as well as the Wisconsin and Iowa specifications. The rutting resistance, mid-temperature (fatigue) cracking resistance, and low-temperature (thermal) cracking resistance of asphalt mixture improved due to the addition of these anti-icing additives to various extents.
    • Evaluating Management Options to Increase Roadside Carbon Sequestration

      Ament, Robert; Hartshorn, Tony; Powell, Scott (2019-01-30)
      We estimated the amount of carbon sequestered along Montana Department of Transportation (MDT) roads and tested 3 different highway right-of-way (ROW) management techniques to increase carbon stocks. Using Geographic Information System techniques, the total ROW acreage owned by MDT was found to sequester 75,292 metric tons of carbon per year and to consist mostly of grasslands (70%). From 2016-2018 we tested 3 ROW management techniques to increase carbon stocks- increase mowing height, plant woody shrubs, or add legumes to reclamation seed mixes of disturbed soils - at 3 sites (Three Forks [3F], Bear Canyon [BC], and Bozeman Pass [BP]) along Interstate 90 in southwestern Montana. Soil samples generally averaged 0.75–1.5% soil organic carbon (SOC) at the 3F site, 2.5–4% SOC at the BC site, and 1.5–2.5% SOC at the BP site. Average SOC levels were always lower in 2018 than in 2016. Soil respiration rates were generally highest in June or July at the BC site, averaging ~4 μmol CO2 m-2 second-1. Soil respiration rates were lower at the BC site in November 2016, at the BP site in June 2018, and at the 3F site in July 2018 (all ~2–3 μmol CO2 m-2 s-1). Aboveground biomass carbon estimates generally mirrored belowground SOC estimates. Taken together, our findings suggest that of the three treatments implemented (raised mowing height, shrub planting, and disturbance), minimizing disturbance to soils likely makes the greatest contribution to the medium- and long-term carbon-storage potential of these roadside soils.
    • SIZING HYDRAULIC STRUCTURES IN COLD REGIONS TO BALANCE FISH PASSAGE, STREAM FUNCTION, AND OPERATION AND MAINTENANCE COST

      Blank, Matt; Dockery, David; Pohl, Christina (2019-03)
      The purpose of this research was to evaluate how characteristics of hydraulic structures, such as slope or size, used at crossings over waterways relate to operation and maintenance (O&M) effort, fish passage, and stream function. Data on O&M concerns, fish passage concerns, and crossing characteristics were collected from 45 road-stream crossings in Prudhoe Bay, Alaska, during lower and higher water periods in both 2014 and 2015 (four events total). Logistic regression and generalized mixed models were used to examine relationships between O&M effort (response) and five explanatory variables. For all data from all years combined, there were no observable associations among O&M and culvert type or constriction ratio. However, lower constriction ratios were observed for sites with O&M needs in the June 2014 data set. The proportion of sites with both fish passage and O&M concerns was 0.52; comparatively, the proportion of sites with no fish passage concern but with O&M concern was 0.35.
    • Near-Roadway Air Pollution: Evaluation of Fine Particulate Matter (PM2.5) and Ultrafine Particulate Matter (PM0.1) in Interior Alaska

      Aggarwal, Srijan; Kadir, Abdul; Belz, Nathan (2019-01-28)
      This report presents a study of fine (PM2.5) and ultrafine (PM0.1) particles in the Fairbanks North Star Borough (FNSB) in Interior Alaska, with specific emphasis on the relationship of ultrafine particles (UFPs) to vehicular traffic. Chapter 1 provides a summary of published literature on particulates in air from vehicular emissions. Chapter 2 provides a novel and robust GIS-based data analysis approach to PM2.5 data collected by the FNSB. This analysis approach is convenient for identifying hotspots, as well as locations where PM2.5 changes either abruptly or continuously or does not change at all. The results reveal that average on-roadway PM2.5 concentrations are higher in North Pole than in Fairbanks, and mean levels are higher in stationary background monitoring data than in mobile monitoring on-roadway data. Not surprisingly, significant negative correlations were found between temperature and PM2.5. Chapter 3 presents the results from the data collection campaign to measure UFPs at roadside locations in Fairbanks and North Pole and investigate the relationship of UFPs with traffic and meteorological parameters. Multilinear predictive models were developed for estimation of UFPs and PM2.5 based on weather and traffic parameters. Overall, this study improves our understanding of on- and near-roadway particulates in a cold-climate region.
    • Evaluating the Potential Effects of Deicing Salts on Roadside Carbon Sequestration

      Fay, Laura; Ament, Rob; Hartshorn, Tony; Powell, Scott (2019-01)
      This project sought to document patterns of road deicing salts and the effects of these salts on the amount of carbon being sequestered passively along Montana Department of Transportation roads; it was designed collaboratively with a related roadside project that tested three different highway right-of-way management techniques (mowing height, shrub planting, disturbance) to determine whether they have the capacity to increase soil organic carbon. Our sampling did not reveal elevated salt levels at any of the nine locations sampled at each of the three I-90 sites. The greatest saline concentrations were found at the sample locations farthest from the road. This pattern was consistent across all three sites. The range of soil organic matter (SOM) was broad, from ~1% to >10%. Generally, SOM values were lowest adjacent to the road and highest farthest from the road. We found no or weak evidence of a relationship between our indices of soil salinity and SOM levels, with electrical conductivity, exchangeable calcium, and cation exchange capacity. Results imply that if road deicing salts are altering patterns of roadside SOM and potential carbon sequestration, this effect was not captured by our experimental design, nor did deicing salts appear to have affected roadside vegetation during our most recent sampling effort. Our findings highlight the value of experimentally separating the multiple potentially confounding effects of winter maintenance operations on roadside soils: roads could focus the flow of water, salts, and sands to roadside soils. How these types of mass inputs to roadside soils might influence medium- or long-term carbon dynamics remains an open question, but their fuller characterization and possible flow paths will be essential to clarifying the role of roadside soils in terrestrial soil organic carbon sequestration strategies.
    • A Targeted Approach to High-Volume Fly Ash Concrete Pavement (Phase I)

      Du, Sen; Shi, Xianming (2018-12)
      Unlike the conventional method of admixing nanomaterials directly in fresh concrete mixture, a more targeted approach was explored. Specifically, nanomaterials were used to improve the interface between coarse aggregate and cement paste, by coating the coarse aggregate with cement paste that contained graphene oxide or nanosilica. Using coated coarse aggregates, the mechanical and transport properties of high-volume fly ash (HVFA) concrete were tested to evaluate the effect of nanomaterial coating on the interface transition zone of concrete. The compressive and splitting strengths of HVFA concrete at 3, 7, 14, and 28 days and the water sorptivity and chloride migration coefficient at 28 days were studied. Results show that nanomaterial-coated coarse aggregate can improve the transport properties of HVFA concrete by reducing permeability. However, no improvement was seen in the compressive and splitting strengths when incorporating coated coarse aggregate, compared with direct mixing of nanomaterials in fresh concrete. Resistance to freezing/thawing cycles and scanning electron microscope/energy dispersive X-ray spectroscopy of concrete samples were also investigated to obtain a more comprehensive and mechanistic understanding of nanomaterial coating.
    • Environmentally Friendly Pervious Concrete for Treating Deicer-Laden Stormwater: Phase II

      Xu, Gang; Shi, Xianming (2018-12)
      In Phase I of this project, graphene oxide (GO)-modified pervious concrete was developed using coal fly ash as the sole binder. The primary objectives of Phase II of this project were (1) to evaluate the stormwater infiltration capacity of GO-modified fly ash pervious concrete; (2) to evaluate the durability performance of GO-modified fly ash pervious concrete using freeze/thaw and salt resistance testing methods; and (3) to use advanced analytical tools to fully characterize the GO-modified fly ash binder. Test results indicate different degrees of reduction in concentrations of possible pollutants in stormwater—copper, zinc, sulphate, chloride, ammonia, nitrate, and total phosphate. The incorporation of GO significantly improved the resistance of pervious concrete to freeze/thaw cycles and ambient-temperature salt attack. The specimens were examined using X-ray diffraction, which revealed that the mineralogy and the chemical composition of fly ash pastes differ considerably from those of cement pastes. Nuclear magnetic resonance was used to study the chemical structure and ordering of different hydrates, and provided enhanced understanding of the freeze/thaw and salt scaling resistance of fly ash pervious concrete and the role of GO.