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Characteristics of Gas Hydrate Bearing Sediment
Prepared by: Jebina Shrestha Co-worker: Alyanna Arnoco Supervised by: Dr...
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  1. 1. ` Characteristics of Gas Hydrate Bearing Sediment Prepared by: Jebina Shrestha Co-worker: Alyanna Arnoco Supervised by: Dr. Jeffery Priest Lab technicians: Mirsad Berbic, Jiechun Wu Abstract The Arctic region has vast energy resources, in the form of an ice-like material called gas hydrate, which resides in sediments below the permafrost and within deep water marine sediments. The methane gas held within the hydrate can potentially be a cleaner source of energy (relative to coal and oil) and ongoing climate change is making these resources more accessible. In order to research on the gas hydrate, it is important to know the properties of the soil where it is found. Introduction • Gas hydrate can be a potential alternate source of energy • Only limited researches have been conducted • Characteristics of gas hydrate of bearing sediments is useful in assessing the possibility of gas hydrate as a cleaner source of energy Research Approach Similar soil composition was prepared in laboratory using silt (65%) and clay (35%) and following tests were conducted: 1. Plastic limit, liquid limit and plasticity index using tap water vs salt water 2. Preconsolidation effective stress, coefficient of consolidation, compression index and recompression index using oedometer 3. Shear strength for soil using triaxial test Results 1. Table 1: liquid limit, plastic limit and plasticity index with salt and tap water Conclusions 1. The mixture can be classified as a low plasticity clay from tap water sample which is reinforced by salt water sample 2. The soil sample specimen collected were only exposed to the stress of 57 kPa before the consolidation test. Different pressures result in various coefficient of consolidation 3. Sample in triaxial test was heavily overconsolidated based on the shear Terms Liquid limit (LL) is the water content at which a soil changes from a plastic state to a liquid state Plastic limit (PL) is the water content at which a soil changes from a semisolid to a plastic state Plasticity index defines the range of water content for which the soil behaves like a plastic material Preconsolidation stress is the stress that sample was under before being consolidated Compression index is the slope of the normal consolidation line in a plot of the logarithm of vertical effective stress versus void ratio. Recompression index is the average slope of the unloading/reloading curves in a plot of the logarithm of vertical effective stress versus void ratio Coefficient of consolidation is a measure of the rate at which the consolidation process proceeds Shear strength of a soil is the maximum internal resistance to applied shearing forces References References Budhu. (2010) “Soil Mechanics and Foundations”. Wiley Global Edition. Braja M. Das “Soil Mechanics Laboratory Manual”. Sixth edition 2. Table 2: various parameters found using oedometer Table 3: coefficient of consolidation for various pressures Figure 3: void ratio vs effective stress using oedometer 3. Table 4: maximum shear at different confining pressure Figure 2: triaxial test apparatus Figure 4: oedometer test apparatus to find coefficient of consolidation Figure 1: methane bearing gas hydrate

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