| Summary: | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. Includes bibliographical references. Natural gas hydrates are formed when, under certain pressure and temperature conditions, gas molecules become encaged by hydrogenbonded oxygen atoms, forming a solid, ice-like crystalline substance. They have been found all over the world in both onshore and offshore environments, as well as in permafrost and tropical regions. The presence of natural gas hydrates in marine sediments are of concern to geotechnical engineers for several reasons, including: (1) their effect on the load bearing properties of ocean sediments, and (2) the effect that their dissociation has on the engineering properties of ocean sediments. The recovery of intact, in-situ samples of gas hydrates can be difficult due to their dependence on pressure and temperature conditions. The development of an electrical resistivity cone for the detection of gas hydrates in marine sediments would be ideal because: (1) there is a dramatic contrast between the electrical properties of gas hydrates and ocean sediments; (2) the resistivity module could be incorporated with standard cone penetrometer testing equipment; and (3) it could allow the in-situ detection of gas hydrates without dramatically affecting the surrounding temperature and pressure conditions. The objectives of this study were to design, fabricate and test an electrical resistivity cone using a two-electrode and four-electrode configuration. The laboratory testing program consisted of pushing the cone through a three-layer soil profile in which the central layer (target layer) consisted of simulated gas hydrates. The target layer thickness varied from 1 to 6 inches (2.5 to 15 cm) and the "hydrate" content varied from 10% to 100% by volume. The objective was to determine the effectiveness of the cone for use in the detection of thin resistive layers and randomly dispersed resistive nodules. The laboratory test results indicated that the four-electrode configuration may be more appropriate for the detection of both thin resistive layers and random resistive nodules. Layers as thin as 1 inch (2.5 cm) and containing as little as 10% "hydrate" nodules were successfully detected using this configuration.
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