Repository logo

Browsing by Author "Schaeffer, Steven L., committee member"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    A novel direct shear apparatus to evaluate internal shear strength of geosynthetic clay liners for mining applications
    (Colorado State University. Libraries, 2016) Soleimanian, Mohammad R., author; Bareither, Christopher A., advisor; Shackelford, Charles D., committee member; Schaeffer, Steven L., committee member
    The use of geosynthetic clay liners (GCLs) in engineering practice has grown extensively over the past three decades due to application of this material containment applications such non-hazardous solid waste, residential and commercial wastewater management, roadways, and other civil engineering construction projects. This growth has been supported by an enhanced understanding of the engineering properties of GCL as well as hydraulic and mechanical behavior for different applications. In particular, the internal shear strength of GCLs is an important design consideration since GCLs often are installed on sloped surfaces that induced internal shear and normal stresses. The objective of this study was to develop a direct shear testing apparatus to measure the internal shear strength of GCLs for use in mining applications. The direct shear apparatus was designed to support the following testing conditions for needle-punched reinforced GCLs: hydration and testing in non-standard solutions (e.g., pH ≤ 1 or pH ≥ 12); testing under high normal stresses (up to 2000 kPa); and testing at elevated temperatures (up to 80 °C). Ultra-high molecular weight polyethylene GCL shear boxes were developed to facilitate testing 300-mm-square and 150-mm-square specimens under displacement-controlled conditions. Experiments were conducted on 150-mm-square and 300-mm-square GCL specimens to (i) evaluate gripping surface effectiveness as a function of peel strength and normal stress, (ii) assess hydration procedures to adopt into a systematic shear-testing protocol, (iii) assess stress-displacement behavior for 150-mm and 300-mm GCL shear tests, and (iv) develop failure envelopes for peak shear strength (τp) and large-displacement (τld). Shear behavior and peak and large-displacement shear strengths measured on both 150-mm and 300-mm square GCL specimens compared favorably to one another as well as to data from a previous study on a similar GCL. These comparisons validated the direct shear apparatus developed in this study and support the use of small GCL test specimens to measure internal shear behavior and shear strength of reinforced GCLs. Furthermore, the pyramid-tooth gripping plates developed to transfer shear stress from the interfaces between geotextiles of the GCL and shear platens to the internal region of a GCL were effective for a needle-punched GCL with peel strength of 2170 N/m and at normal stress ≥ 100 kPa.
  • Thumbnail Image
    ItemOpen Access
    Analysis of industrial oilseeds: production, conversion to biofuels, and engine performance from large to small scale
    (Colorado State University. Libraries, 2015) Drenth, Aaron C., author; Olsen, Daniel B., advisor; Johnson, Jerry J., advisor; Cabot, Perry E., committee member; Schaeffer, Steven L., committee member
    Most of the biofuel produced in the U.S. as an alternative to petrodiesel is derived from soybean oil. Three major problems of using soy and other traditional biofuel feedstocks are: (1) the high commodity cost of the feedstock results in higher cost fuel than the petroleum equivalent, (2) land use requirements are too great to offset a significant portion of petroleum use, and (3) many traditional biofuel feedstocks also have food uses, which creates market competition and a “food versus fuel” debate. The problems above are addressed by exploring the feasibility of biofuel production from a new class of oilseeds known as industrial oilseeds, and industrial corn oil as a biofuel feedstock. Industrial oilseeds are alternative low-cost oilseeds also known in the literature as low-impact oilseeds or non-food oilseeds. Due to their non-food nature, they steer us clear of any food versus fuel debates. They have several advantages over conventional oilseeds, such as a short growing season, high oil yield and quality, ability to thrive on marginal lands, and low water and fertilizer inputs. These advantages can equate to lower oil costs. Since these oils can be optimized for fuel instead of food, plant scientists can maximize the erucic and other long chain fatty acids, which increase fuel conversion rates and fuel quality. For several of these plant species, little or no engine research has been done; some in the agronomic community still consider some of these plants weeds. This research includes compression ignition engine performance and emissions studies, measurement of important fuel properties, and investigation into the feasibility of several fuel pathways. Corn is not classified as an oilseed by the USDA; however, the corn kernel contains a small amount of oil (~3.5%) which can be extracted during the production of ethanol. Only the starch portion of a corn kernel is converted to ethanol; the remaining solids (including the oil) remain in the distillers grain coproduct. Recently, the ethanol industry has discovered economical methods to extract this corn oil from the meal stream. As corn oil extraction technology has matured and ethanol margins have tightened, the ethanol industry has started widely adapting this technology as an additional revenue-generating coproduct. Since most ethanol plants are non-food grade facilities, corn oil from an ethanol plant can also be categorized as an industrial oilseed. Corn oil represents a relatively new, abundant, and inexpensive source of biofuel feedstock. This research includes compression ignition engine performance and emissions of corn oil based fuels, feasibility of using corn oil as an on-farm biofuel feedstock, research into fuel production and processing methods, and measurement of important fuel properties.