Browsing by Author "Siller, Thomas J., committee member"

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Open Access
Comparison of direct shear and triaxial tests for measurement of shear strength of sand
(Colorado State University. Libraries, 1991) Rahman, Jamshed, author; Nelson, John D., advisor; Siller, Thomas J., committee member; Mielke, Paul W., committee member
To ascertain the shear strength parameters of soils for engineering purposes is fundamental to soil mechanics and basic for designing earth-bearing and earth-retaining structures. Direct shear and triaxial tests are the most popular laboratory methods to determine these parameters. The direct shear test is used widely because it is simple and quick. The test has several disadvantages, however. The non-uniform stress-strain behavior, the rotation of principal planes during the test, and the imposition of the failure plane are chief among them. The triaxial test was designed as a possible alternative that eliminates some of these disadvantages. Direct shear test results are always comparable to those of the triaxial test; the difference usually is negligible from a practical point of view. Researchers have tried to unfold the intricacies involved in the direct shear test especially the complicated stress-strain behavior that a soil experiences during this test. Data, however, are lacking that determine the difference and establish a correlation between the results of the two tests. This study compares the two tests for measurement of shear strength parameters of sand. Triaxial and direct shear tests were performed on silica sand under the same density and normal stress conditions. Five sets of triaxial tests and 20 direct shear tests each were performed using four different makes of direct shear machines. The results of the direct shear tests were compared with those of the triaxial tests considering the latter as benchmarks. The possible effect of the structural features of the direct shear equipment on results was briefly studied. The results showed that the shear strengths from direct shear tests are higher than those from the triaxial tests. All four direct shear machines gave cohesion values different from each other and higher than the benchmark value. The Soiltest and Wykeham Farrance machines gave almost the same friction angle that was higher than the benchmark value by 4 degrees. The friction angle value from the ELE machine was higher by 2.7 degrees while those from Clockhouse machine were lower by 4.5 degrees as compared to the benchmark value.
Open Access
Development of the piezovane for estimating liquefaction potential of saturated sands
(Colorado State University. Libraries, 1994) Butler, Leo Wm., author; Charlie, Wayne A., advisor; Siller, Thomas J., committee member; Doehring, Donald O., committee member
The Piezovane was developed for determining in situ liquefaction potential of saturated sands by measuring the porewater pressure response oi saturated sand during and after shearing of the soil. A negative porewater pressure response is an indication that the material is in a dense (dilative) state; therefore is not susceptible to liquefaction failure. Positive porewater pressure response is an indication that the sand is in a loose (contractive) state and is susceptible to liquefaction-type failure. This project included design, fabrication of the Piezovane apparatus and the calibration chamber for the initial laboratory testing. Sands were placed within the calibration chamber at densities greater than or less than densities at the steady state which had been developed by using CU triaxial and CD direct shear tests. Trends indicate that the Piezovane testing can predict contractive or dilative behavior of soils. Additional testing both in the laboratory and in the field is required to determine whether these measured porewater pressure responses and measured shear resistances provide parameters needed for evaluating liquefaction potential and their possible use for design. A patent for the Piezovane has been awarded.
Open Access
Exploring the relationships among creativity, engineering knowledge, and design team interaction on senior engineering design projects
(Colorado State University. Libraries, 2012) Ibrahim, Badaruddin, author; De Miranda, Michael A., advisor; Gloeckner, Gene W., committee member; Siller, Thomas J., committee member; Makela, Carole J., committee member; Folkestad, James E., committee member
In the 21st century, engineers are expected to be creative and work collaboratively in teams to solve or design new products. Research in the past has shown how creativity and good team communication, together with knowledge, can impact the outcomes in the organization. The purpose of this study was to explore the relationships among creativity, engineering knowledge, and team interaction on senior engineering design product outcomes. The study was conducted within the College of Engineering, Department of Mechanical Engineering, at Colorado State University. A purposeful sampling of 55 students who enrolled in Mechanical Engineering Design capstone course completed the instruments during this study, which included the Torrance Tests of Creative Thinking (TTCT) Figural Form A, and a pre and post Team Climate Inventory. Students were assigned to twelve design project teams at the beginning of the fall term, 2011, and the project outcomes were evaluated in the spring of 2012, during the senior design showcase. Eleven professional engineers and three graduate students were trained to evaluate the senior design outcomes. The students' engineering grade point average (GPA) was used as a proxy to represent engineering knowledge. Descriptive statistics were utilized to describe the sample in terms of their engineering GPA, creativity score, and team interaction score. Correlational analyses were executed to examine the relationships among the constructs of the study. At the design team level, results from this research indicate that there was no statistical significant relationship between the teams' creativity composite score and the design outcome. There was also no statistical significant relationship between the team interaction score and the design outcome. The team composite creativity score had no significant relationship with the team interaction score. The composite of team engineering knowledge had no significant relationship to the team interaction score. At the individual level, the correlation analysis indicated there was no statistically significant relationship between student engineering knowledge and the creativity score. Exploratory data analysis (EDA) was used to assess the interaction of the main constructs on the engineering design outcome. The EDA results indicate that only one team met the hypothesis that a team scored above average on engineering knowledge and creativity, and a positive team interaction climate would expect to score above average on their design outcome score. Two design teams scored above average on creativity and engineering knowledge, and positive team interaction climate yet scored below average on their design outcome, which went against the original hypothesis. One design team scored above average on their design outcome, but scored below average on the other three main constructs of the study. The remaining eight design teams did not show any consistent pattern of relationships among the three constructs and the design outcome score. This research adds to the body of work within creativity, engineering knowledge, and team interaction climate in engineering design, as well as engineering education. The findings suggest that creativity, engineering knowledge, and team interaction climate had little impact on the engineering design outcomes. The limitations and implications of the study and future research are also discussed.
Open Access
Fractures within the Irish Canyon-Vermillion Creek area, northeastern Uinta Mountains, northwestern Colorado
(Colorado State University. Libraries, 2009) Detring, John Peter, author; Erslev, Eric A., advisor; Schutt, Derek L., committee member; Siller, Thomas J., committee member
In the northeast Uinta Mountains, fold axes are observed to be consistent with Laramide ENE-WSW shortening and Sevier NW-SE shortening. The structural trends and fracture patterns may be due to the cumulative effects of Laramide and Sevier deformation. This research addresses the timing and mechanisms of fracturing within eastern Uinta Mountains, as well as the controls on post-orogenic fracturing. These results will hopefully aid in testing current regional tectonic models, as well as aid in predictions of fracture permeability in analogous water and hydrocarbon producing, basement-involved orogenic basins worldwide. This study analyzes the kinematic indicators and structural geometries within the extreme northeastern Uinta arch, NW Colorado, USA, to resolve its complex strain history. Fracture systems provide permeability as well as create traps in petroleum reservoirs. An understanding of the orientation and timing of fracture systems can test current tectonic models and allow for predictions of fracture orientation as well as allow for predictions of which fractures are open, closed, and fluid conducting. Systematic fracture data collection, detailed field mapping, kinematic analyses, and a combination of 2D seismic interpretations and cross-section analyses were used to address questions concerning the structural geometry and fracture history within the northeastern Uinta Mountains. Data from geologic mapping, 722 slickensided minor faults, 996 joints and the interpretation of a 2D seismic line were used to determine the fracture history and geometry of the Irish Canyon-Vermillion Creek area. Fracture data were collected at 34 stations in pre- and post-Laramide rocks to obtain average joint orientations and to calculate the ideal σ1 orientations of minor faults. Restoration of 2D structural models, constrained by map and 2D seismic data, were conducted using line length balancing techniques which showed that a significant amount of interlayer slip is necessary for a viable structural interpretation. Fault analyses indicate multidirectional deformation with ENE-WSW and NNE-SSW σ1 orientations. There is a predominance of left-lateral faulting associated with the first stage of deformation and a predominance of right-lateral faulting associated with the second stage of deformation. Evidence for this sequence is the observation of right-lateral faults associated with the NNE-SSW σ1 cross-cutting left-lateral faults associated with the ENE-WSW σ1. Joint measurements are trimodal in distribution, with average strikes of N71E, N1E, and N40W. Abutting relationships suggest that the N71E-striking joints are primary and the N1E-striking joints are secondary. The N40W-striking joint set is only found within the Oligocene Bishop Conglomerate and Miocene Browns Park Formation and their strike parallels regional normal faults. Therefore, this set is likely due to extension during the Miocene to Holocene and post dates Laramide deformation. Folding of the Mancos Shale and back-thrusting of the Browns Park Formation were observed in the northeastern portion of the field area. This deformation is possibly in response to the overlying Browns Park Formation gravitationally sliding down dip along its contact with the Mancos Shale. The tectonic history of the Irish Canyon-Vermillion Creek area is consistent with three stages of deformation. The first stage is characterized by N59E-directed thrusting, conjugate strike-slip faulting, and the N71E-striking joint set. The second stage is characterized by an E-W extension resulting in a system of NNW-directed right-lateral faults, localized NNE-directed transpressional thrust faulting, and the N1E-striking joint set. The third stage is by characterized by NE-SW extension resulting in N52W-striking normal faults and the N40W-striking joint set. The first stage of deformation can be attributed to Laramide compression. The second stage of deformation was probably due to a poorly documented late-Sevier/late-Laramide, or post-Laramide event, or a combination of these events. The third stage of deformation can be attributed to a Miocene to Holocene NE-SW extension.
Open Access
Microalgae to biofuels evaluation through experimentally validated models
(Colorado State University. Libraries, 2011) Quinn, Jason, author; Bradley, Thomas H., advisor; Marchese, Anthony J., committee member; Willson, Bryan D., committee member; Siller, Thomas J., committee member
To view the abstract, please see the full text of the document.
Open Access
Proof of concept of an automated CoCoRaHS rain gauge
(Colorado State University. Libraries, 2016) Lin, Jieqi, author; Johnson, Gearold R., advisor; Troxell, Wade O., committee member; Siller, Thomas J., committee member
CoCoRaHS is the Community Collaborative Rain, Hail and Snow Network, collecting daily precipitation reports from volunteers’ reading of a low-cost plastic 4-inch diameter rain gauge. Nolan Doesken, the Colorado State Climatologist following the disastrous Fort Collins flood of July 1997, created the network. Today there are more than 20,000 rain gauges in service. There are three limitations in the present CoCoRaHS rain gauge. The first limitation is limited temporal granularity, i.e., data measurements are only available once each 24-hours, in the best cases. The second limitation is not being able to capture data during an extreme event as it is occurring. The third limitation is because this is a volunteer activity other activities may interfere with the ability to collect daily data. The question is can the CoCoRaHS rain gauge be modified to eliminate these three restrictions while keeping the design as similar to the current system as possible. The design is to turn the present rain gauge into a weight-based automated rain gauge. An in-lab tested prototype was built requiring only that the rain gauge bracket needed modification. The result is a modified bracket holding a load-cell, microcontroller and Wi-Fi communications subsystems. A number of experiments were designed and conducted to prove the feasibility of the rain gauge. The conclusion is that a low-cost, high-accuracy weight-based automated CoCoRaHS rain gauge is achievable.
Open Access
Structural engineering masters level education framework of knowledge for the needs of initial professional practice
(Colorado State University. Libraries, 2012) Balogh, Zsuzsa Eniko, author; Criswell, Marvin E., advisor; Grigg, Neil S., committee member; Van de Lindt, John W., committee member; Siller, Thomas J., committee member; De Miranda, Michael Anthony, committee member
For at least the last decade, engineering, civil engineering, along with structural engineering as a profession within civil engineering, have and continue to face an emerging need for "Raising the Bar" of preparedness of young engineers seeking to become practicing professional engineers. The present consensus of the civil engineering profession is that the increasing need for broad and in-depth knowledge should require the young structural engineers to have at least a Masters-Level education. This study focuses on the Masters-Level preparedness in the structural engineering area within the civil engineering field. It follows much of the methodology used in the American Society of Civil Engineers (ASCE) Body of Knowledge determination for civil engineering and extends this type of study to better define the portion of the young engineers preparation beyond the undergraduate program for one specialty area of civil engineering. The objective of this research was to create a Framework of Knowledge for the young engineer which identifies and recognizes the needs of the profession, along with the profession's expectations of how those needs can be achieved in the graduate-level academic setting, in the practice environment, and through lifelong learning opportunities with an emphasis on the initial five years experience past completion of a Masters program in structural engineering. This study applied a modified Delphi method to obtain the critical information from members of the structural engineering profession. The results provide a Framework of Knowledge which will be useful to several groups seeking to better ensure the preparedness of the future young structural engineers at the Masters-Level.