Interface shearing stress of a body in contact with water saturated sand
Gatlin, Carl Earl, Jr.
Powell, S. Curtis
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The reduction of shearing stress of a body in contact with sand was studied with the possible application of ungrounding ships. An annular ring with the thirty-six sources was rotated in a bed of sand so as to model an infinitely long ship with a series of pumps (sources) placed on the longitudinal centerline. By means of strain gages placed on four two-dimensional load cells, quantitative data for both normal and shearing stress were obtained. Also, by means of a pressure transducer, a type of strain gage, measurement of the pore water pressure was made. All three quantities: normal stress, shearing stress, and pore water pressure were thus measured simultaneously. Quantitative results showed that there was a reduction of 90% in shearing stress for a nominal value of pore water pressure (25-30 psi). These results were true for all three types of samples tested regardless of their initial coefficient of friction. The coefficient of friction was noted to decrease at higher pore water pressures giving rise to the idea that the dynamometer (force measuring device) may have deflected enough to negate the readings at higher pressures. Lending itself to this possibility was the fact that theoretical or predicted shearing stress was less than the measured stress at low values of pore pressure but greater than the measured stress at higher values of pore pressure. However, the overall results of the tests showed promising possibilities in reducing the number of salvage tugs, days to unground, etc., by employing a keel mounted pump. Suggestions are presented as to possible future research in this area.
This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library Collection for reasons not now known. It has been included in the digital archive for its historical value to NPS. Not believed to be a CIVINS (Civilian Institutions) title.
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