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- Creator:
- Reina, Paulina
- Description:
- Rubbernecking on freeways is a common problem that arises when queuing traffic develops in the opposite direction of a freeway incident. The goals of this study are to evaluate the effects of rubbernecking on traffic, investigate incident and freeway characteristics associated with it, evaluate rubbernecking models, and analyze drivers’ behavior in relationship to rubbernecking. To this end, traffic data around a major incident were analyzed. Results revealed that rubbernecking can instigate significant queue lengths, congestion durations, and traffic delays. In addition, analysis of 637 incidents revealed that 12% of incidents instigated rubbernecking queues. A logistic regression model was also fitted to the data. Results from the model suggest that on-ramps, high-occupancy vehicle (HOV) lanes, and percent of trucks are factors associated with rubbernecking. In addition, validation analyses of rubbernecking models pointed to limitations of estimated statistical models in effectively predicting rubbernecking events. Furthermore, results from a drivers’ behavior self-reporting survey suggest that a majority of drivers tend to decrease their speed around an incident in the opposite direction of traffic. It was also observed that respondents attributed these actions to habits and behavior more frequently than incident and freeway characteristics. Findings from this work can be used to help develop targeted rubbernecking traffic control measures, enhance rubbernecking data collection methods and modeling, and advance behavioral interventions to reduce the onset of rubbernecking queues on freeways.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Kurwadkar, Sudarshan
- Description:
- Ingestion of polycyclic aromatic hydrocarbons (PAHs) contaminated water has potential human-health and ecological consequences. A comprehensive investigation of PAHs' occurrence and distribution in the surface water and sediment samples of the Damodar River Basin was conducted using the Agilent 7890B Gas Chromatograph (GC-FID) coupled with 5977A Mass Spectrometry. The results showed that concentrations of the individual PAHs in surface water and sediments ranged from ND to 36 μg/L and ND to 582 ng/g with the highest detected levels of 3-ring PAH Acenapthylene (ACY) and 4-ring PAH Benzo(a)Anthracene (BaA) with a mean concentration of 6.12 ± 6.06 μg/L and 2.79 ± 4.5 μg/L, respectively. The concentration of 4-ring PAHs such as Fluoranthene (Flur), Pyrene (Pye), Benzo(a)Anthracene (BaA), and Chrysene (Chry) in sediment samples has mean levels of 43 ± 41 ng/g, 32 ± 29 ng/g, 52 ± 50 ng/g, and 83 ± 105 ng/g, respectively. The 4-ring PAH Chry was frequently detected in all sediment samples, while the 3-ring PAH ACY was dominant in surface water samples. The principal component analysis (PCA) and diagnostic ratios suggested that the PAHs contamination in surface water was due to petrogenic and fuel combustion. In sediments, PAHs' primary sources were coal burning, fuel combustion, petrogenic, and pyrolysis. The incremental lifetime cancer risk (ILCR) for children and adults due to ingestion of surface water ranged from ND to 4.25 × 10−5 and ND to 7.21 × 10−5, respectively. In contrast, the Risk index (RI) values ranged from 4.3 × 10−5 and 7.3 × 10−5. For sediment samples, higher toxic equivalent quotient (TEQ = 1865 ng/kg) and mutagenic equivalent quotient (MEQ = 1665 ng/kg) for eight carcinogenic PAHs indicate extremely high toxicity. Improper management of mine drainage, frequent flooding of open cast mines, and hydraulic connection between the surface water, sediments, and groundwater significantly deteriorated overall water quality in the DRB.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Koirala, Janak Das
- Description:
- Every year, millions of scrap tires are either discarded in huge piles across the landscape or dumped in landfills in large volumes all over the world. These tire piles cause environmental pollution while posing fire and health hazards. Being volumetric goods in comparison to other wastes, they occupy large volumes in landfills. Rainwater tends to accumulate in the stockpiled tires, which, then become a breeding ground for mosquitoes that carry dangerous diseases, such as encephalitis. Several states in the United States have, therefore, banned the disposal of used tires in the land. Shredded rubber has been used in a variety of applications in geotechnical engineering including in highway pavements and backfills of retaining walls, but mostly as individual material. In this study, kaolinite and montmorillonite were modified using different sizes and quantities of shredded rubber tires and used to evaluate the improvement in geotechnical properties. Five different sizes and five different proportions of shredded rubber tires were mixed with the clay minerals. Laboratory experiments were carried out to evaluate the changes in density, permeability and unconfined compressive strength of such modified soil with shredded tires. The results showed that for kaolinite, the maximum dry density decreased as the percentage of shredded rubber tire in the mixture was greater than 4% by dry weight. In Montmorillonite, the maximum dry density of the modified soil increased till 2 to 4% of shredded rubber tire was added to the soil. The highest strength was observed at 4% shredded rubber tire content in kaolinite and at 5% shredded rubber tire content in montmorillonite. Permeability increased when smaller sized shredded rubber tire was added to kaolinite. In montmorillonite, permeability values sharply increased up to 2% shredded rubber tire content and thereafter, showed a linear increase in permeability for all sizes of shredded rubber tire used. From this study, it is concluded that shredded rubber can be effectively used to improve the compaction and strength characteristics of weak soils.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Pantha, Krishna Hari
- Description:
- This paper presents the results of a study, whose aim was to determine the undrained shear strength at different over-consolidation ratios, which is a very important parameter to evaluate the stability of natural and man-made slopes in soft clay. The undrained shear strength of clays was determined using a laboratory test method utilizing the Direct Simple Shear (DSS) apparatus in the geotechnical engineering laboratory at California State University, Fullerton. In this study, the change in undrained shear strength of soil with over-consolidation ratio in a mineralogical framework was studied. Four different soil samples were prepared by mixing commercially available clay minerals such as kaolinite and montmorillonite with quartz at different proportions by their dry weight. These samples included 100% kaolinite, a mixture of 70% kaolinite with 30% quartz, a mixture of 50% kaolinite with 50% quartz and a mixture of 50% montmorillonite with 50% quartz. The plasticity characteristics of these samples were evaluated. Each of the first three samples had five different specimens representing five different over-consolidation ratios (2, 4, 8, 16 and 32). The fourth sample had only two specimens for two different over-consolidation ratios, i.e. 2 and 4. The applied consolidation stresses were 600 kPa, 300 kPa, 150 kPa, 75 kPa and 37.5 kPa for five different over-consolidation ratios of 2, 4, 8, 16 and 32, respectively. Using the direct simple shear device, the undrained shear strength of these samples were measured using a strain rate of 5%/hour. The pore pressures generated at different applied stresses was also back calculated from the change in total stresses. The pore water pressure continuously increased up to certain displacement and then after tended to remain constant. The results showed that it was inversely proportional to the over-consolidation ratio. Using the results, the SHANSEP model and Hvorslev’s theory were utilized to check normalized shear strength, and true friction angle and true cohesion of each soil sample, respectively. The result showed that the shear strength depends up on the composition of clay minerals and stress history of the soil. The relationship of the normalized undrained shear strength ratio was directly proportional to the overconsolidation ratio of the soil. Similarly, the true friction angle of the soil depended up on the composition of the clay minerals, but not on the stress history. True friction angles of 19.28°, 20.63°, 21.06° and 35.24° were obtained for Sample Nos.1, 2, 3 and 4, respectively; whereas, the true cohesion of these sample were measured as 8.46°, 7.21°, 4.55° and 0.39° respectively.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Woli, Hari
- Description:
- Global warming is a big concern these days all over the world including in the USA. It has said to trigger landslides all over the world every year due to the global warming. Landslides can damage the structures and block roads and rivers that require much effort and finances to repair. On 11 March 2011, an earthquake with magnitude 9.0 (Mw) occurred in Tohoku, Japan. Approximately 15,893 people were killed, 6,152 people were injured and much of the infrastructure was damaged. Hundreds of landslides occurred at that time. Recently, an earthquake with magnitude 7.8 occurred on 25 April 2015 in Gorkha, Nepal, west of the capital Kathmandu. A major aftershock with magnitude 7.3 occurred on 12 May 2015 near Kodari, east of Kathmandu. As a result of both of these major earthquakes, more than 9000 people were killed and thousands of landslides occurred in various parts of the country. Both earthquakes occurred in the dry season, and hence, a major concern was the increased likelihood of landslides in the rainy season following these earthquakes. This research describes the effect of post-earthquake rainfall on slope stability by examining the landslide distribution pattern in Nepal, following the 2015 Gorkha Earthquake and its aftershocks. A high resolution Google Map was used to locate the landslides triggered in the eastern to mid-western part of Nepal following the earthquake and after the first rainy season. A landslide database was created and contains the angle of inclination, features at risk and landslide area for each landslide identified. To evaluate the stability of slopes following a post-earthquake rainfall event, a 45º slope was modelled in a Plexiglas container and subjected to shaking on a shake table and rainfall in the laboratory. A clayey soil obtained from Mission Viejo, CA was used to prepare a slope model with void ratio 1.2. The slope was instrumented with accelerometers, tensiometers, and copper wires to record acceleration, pore water pressure and deformation of the slope, respectively. A series of sinusoidal waves with 20 cycles at various amplitudes and frequencies (0.1 g, 0.2 g, 0.3 g and 1 Hz, 2 Hz, 3 Hz) were applied to the slope model. After the seismic loading was applied, a rainfall simulator was placed on top of the slope and used to apply rainfall with an intensity of 16.8 mm/hr. The water front from the infiltrating rainwater was marked on either side of the Plexiglas container at different time intervals. Slope instability was not observed during the post-earthquake rainfall event. This was attributed to a decrease in the void ratio due to the seismic shaking leading to a reduction in the seepage rate for the rain water and lower pore pressures on the slope. Hence, the likelihood of further slope instability in the rainy season following an earthquake decreases. The results were verified in the case study from Nepal as there were no reported landslides during the rainy season immediately following the 2015 Gorkha Earthquake and its aftershocks.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Khanal, Prakash Chandra
- Description:
- Based on previous studies, ground reinforcement methods such as stone columns, jet grouting, dynamic compaction, soil cement mixing, etc. are commonly used against potential liquefaction, settlement and to improve the bearing capacity of soil. However, additional benefits of ground improvement such as the possible reduction in seismic ground shaking are not usually considered in the practice or in the current International Building Code (IBC). As seismic damage is a major concern, soil-cement mixing was found to be the most effective in reducing of ground shaking levels. Among soil-cement mixing, compacted soil-cement panels have been considered as one among the most effective improvement techniques for seismic remediation. Past research shows that replacement of a portion of soil up to certain depth using compacted soil-cement mixture works effectively in improving soft clays and loose dry sand. However, field compaction effort requires some preparation and additional cost. The present study compares the results obtained through deep soil mixing panels with the results obtained with compacted clay based soil-cement panel. The compacted soil-cement panels and deep soil mixing panels corresponding to replacement ratios of 10% and 20% were prepared and cured for 14 days. A series of small-scale shake table tests were performed using models with unimproved and improved soil with reinforcement panels at different seismic shaking levels. The research results show that compacted soil-cement panels are more effective in reducing seismic amplification than deep soil mixing panels. The compacted soil cement panels could reduce the seismic amplification by 12% and 25%, whereas the reduction for deep soil mixing panels was 9% and 15% for the replacement ratios of 10% and 20%, respectively.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Avina, Jose L.
- Description:
- Infiltration is an important aspect to the hydrologic cycle as it allows for groundwater recharge. In California especially, groundwater is used for agriculture, industrial usage, and as drinking water. This Thesis presents an analytical model for time dependent infiltration through a variably saturated soil. Water is considered to begin infiltrating soil at the ground surface and moves through the vadose zone towards the datum of the system (the water table) where pressure head is constrained to zero. The developed model calculates important soil characteristic parameters such as hydraulic conductivity, K, water content, θ, and pressure head, ψ, as a function of depth. The solution introduces four parameters (ak,ψk,ac, and ψa) to represent K and θ as exponential functions. The proposed model is then compared to existing exponential function solutions for various times. The comparison illustrates the versatility of using a four parameter exponential representation for infiltration. Furthermore, the proposed solution is validated against the numerical solution of HYDRUS-1D, which employs the widely used van Genuchten-Mualem constitutive model. Additionally, once parameters ak and ψk are known, one can obtain van Genuchten parameters α and n. Finally, the constitutive exponential expressions for hydraulic conductivity and water content are compared to the van Genuchten-Mualem expressions.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Tran, Duc Tan
- Description:
- Landslides, which have been existing around the world, are considered as environmental hazards. The number of landslide hazard is increasing every year. Although there are different causes of landslides, two major causes are rainfall and earthquake. Rainfall increases pore water pressure, changes the degree of saturation and causes a loss of strength in the soil. Therefore, the equilibrium can no longer be maintained in the slope, and a failure occurs. Likewise, when an earthquake occurs, the seismic force associated with the earthquake triggers mass movement such as rock fall, debris flow, and others forms of mass movement. In an attempt to evaluate the effect of rainfall in triggering landslides, a series of physical slope models were prepared in laboratory at different soil void ratios, and slope inclinations. Slope stability and deformation analyses were carried out in order to not only further understand the effect of rainfall on slope stability, but also obtain a relationship between void ratio, intensity and duration of rainfall, and slope inclination on soil slope stability. Collected soil samples from a compacted fill area in Mission Viejo, CA were placed into the Plexiglas container and compacted to the desired void ratios to form physical models at the inclinations of 40 and 45 degrees to introduce targeted rainfall with a rain simulation system in order to measure the seepage rate, moisture content, degree of saturation and surface erosion with time. After these static slope experiments, another experimental model was prepared and shaken on the shake table to determine the relationship between void ratio, seismic acceleration, seepage velocity and slope stability. The soil sample was placed into the same Plexiglas container and compacted to a void ratio of 1.2 to form the same 60 cm thick model, which was later cut into a 40 degree slope. Accelerometers were then placed on the slope to measure the amplification of seismic acceleration at different depths during shaking. Tensiometers were also installed on the slope at different locations to measure the variation of pore water pressure with time. The slope was shaken with different accelerations and frequencies for multiple cycles. Rainfall stimulator device was then placed on the top of the slope immediately after the shaking event. The targeted rainfall was introduced to evaluate the stability of the slope after shaking event. The results were used to perform slope stability and finite element analyses in Geo-Studio 2012- Slope/W, Seep/W, Sigma/W and Quake/W. Overall, the results of static slope stability modeling showed that pore water pressure and the velocity of wetting front of the slope do not increase uniformly over the entire slope during the rainfall period. Time required to saturate the soil decreases with an increase in the void ratio for the same intensity of rainfall. The velocity of movement of wetting front decreased for the slopes prepared at larger angle of inclination compared to the one prepared at smaller angle of inclination when subjected to same intensity and duration of rainfall. The values of factor of safety of the slope for the same intensity and duration of rainfall dropped with an increase in void ratio. In addition, a slope having smaller angle of inclination is more stable than the one having lager angle of inclination for same void ratio, and intensity and duration of rainfall. The results of seismic slope stability analysis subjected to post-seismic rainfall event showed that there was no significant change in pore water pressure during shaking and no catastrophic failure occurred during post-shaking rainfall event. The velocity of movement of wetting front decreased for the post-shaking rainfallinduced slopes compared to the static condition. Besides, the slope subjected to rainfall without shaking event exhibited 10% lower factor of safety compared to the slope subjected to post-seismic rainfall event. The deformation obtained from numerical analysis for both of static and seismic slopes were larger than that obtained from the laboratory experiments. Moreover, the numerical analyses for the case study matched well for the results obtained from the laboratory experiments.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Ahj Obaid, Zahraa Tawfeeq
- Description:
- Large amounts of waste materials such as waste tires, rubbers, etc. are discarded into our surrounding environment. Thus, they are a major cause of contamination and pollution, which, as a result, could eventually lead to many problems including health hazards and fire. Therefore, engineers, environment scientists and researchers face a challenge of how to deal with discarded tires. Undoubtedly, the best solution to not only get rid of waste tires but also make use of them through recycling. Thus, recycling tires would ultimately yield a cleaner environment and prevent public health degradation. Moreover, shredded tires have been used in many geotechnical as well civil engineering applications such as highway embankments, bridge abutments and backfills behind retaining structures. Shredded tire material has also been used to modify soils. Certain clay properties such as poor drainage, high compressibility, and low shear strength make it unfavorable for civil engineering applications. Modifications can be made in these properties by mixing clay with shredded tires. This study focuses on improvements obtained in clay properties by using different sizes of shredded rubber tire. Granular kaolin and a mixture of 50% montmorillonite with 50% granular kaolin were modified using different sizes and percentage of shredded rubber tire. Laboratory experiments were carried out to evaluate the changes in unit weight, permeability and unconfined compressive strength characteristics of the modified clay. The results presented in this thesis include the properties of granular kaolin and a mixture of 50% montmorillonite with 50% granular kaolin mixed with shredded rubber tires. According to the test results, the maximum dry unit weight occurs at 2 to 4% of shredded rubber tires are added to the clay soil samples for all sizes of shredded rubber tire. The highest strength for the mixture of granular kaolin and tire was obtained at when 3 to 4% shredded rubber tire was added into the soil. The maximum unconfined compressive strength for a mixture of 50% montmorillonite with 50% granular kaolin was obtained at approximately 4% shredded rubber tire for all sizes. Moreover, when less than 10% shredded rubber tire was added to granular kaolin, little changes in the coefficient of permeability were observed. When more than 10% shredded rubber tire was added, the coefficient of permeability increased as the percentage of shredded rubber added increased.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
- Creator:
- Nassruldin, Lafa Taher
- Description:
- Soil is unlike other construction materials such as steel and concrete for which humans can control their properties. Therefore, it is important to investigate and test soil in order to predict its response to the construction loading. The coefficient of consolidation (Cv) and coefficient of permeability (k) are two of the dominant and fundamental geotechnical parameters that are used in many applications within the civil engineering discipline. These coefficients are used in dam construction on soft bedrock, erection of retaining walls in weak bearing soil and foundation design on poorly compaction soil. In this study, four types of minerals montmorillonite, kaolinite, illite and quartz were mixed in different proportions, and used to conduct one- dimensional consolidation tests, as summarized in Tiwari and Ajmera (2011). Seven different vertical pressures 3.47 psi, 6.94 psi, 13.89 psi, 27.78 psi, 55.56 psi, 111.11 psi and 222.22 psi were applied. In order to examine the influence of pore fluid chemistry, the soil samples were prepared with distilled water as well as with saline water as the pore fluid. Casagrande’s Logarithm of Time Method were used to estimate the coefficient of consolidation values for forty – two samples with distilled water as the pore fluid and twenty – four samples with saline water as the pore fluid. Also, Terzaghi’s equation was used to determine the coefficient of permeability for the mineral mixtures. The variations of the Cv and k with consolidation pressure and index properties for all mixtures with distilled water and saline water as the pore fluids were examined. It is observed that Cv for kaolinite and illite mixtures with distilled water and saline water as the pore fluids increases with an increase in the consolidation pressure. On the other hand, Cv values for the montmorillonite mixtures with distilled water as the pore fluid decrease with an increase in the consolidation pressure. The Cv values for the montmorillonite mixtures with saline water as the pore fluid increase with an increase in the consolidation pressure. All the soil mixtures with distilled water and saline water as the pore fluids experienced reduction in the values of the coefficient of permeability with the increase in the consolidation pressure. The coefficient of consolidation decreases with an increase in the liquid limit for the kaolinite, illite and montmorillonite mixtures with distilled water and saline water as the pore fluids. The relationship between the coefficient of consolidation and plasticity index for the mineral mixtures with distilled water and saline water as the pore fluids has the same trend as that with the liquid limit. Specifically, the coefficient of permeability decreases with an increase in the liquid limit and plasticity index for the kaolinite mixtures with distilled water and saline water as the pore fluids. Finally, the coefficient of permeability decreases with an increase in the liquid limit and plasticity index for the montmorillonite mixtures with distilled water and saline water as the pore fluids.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Civil and Environmental Engineering
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