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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