. Early geophysical papers of the Society of Exploration Geophysicists. Petroleum; Prospecting. ELASTIC WAVES IN AMHERST SANDSTONE 15 character of the rock. In other words, the "moisture cycle" appears to be reversible. This is evidenced by the fact that points 1 and 2 fall so nearly on the curve determined by the remaining points. This fact must be taken into consideration in seeking for an explanation of the observed phenomena. Figure 5 is a graph derived from the observed data. In this figure the calculated velocities in feet per second are plotted against the percentage of water
. Early geophysical papers of the Society of Exploration Geophysicists. Petroleum; Prospecting. ELASTIC WAVES IN AMHERST SANDSTONE 15 character of the rock. In other words, the "moisture cycle" appears to be reversible. This is evidenced by the fact that points 1 and 2 fall so nearly on the curve determined by the remaining points. This fact must be taken into consideration in seeking for an explanation of the observed phenomena. Figure 5 is a graph derived from the observed data. In this figure the calculated velocities in feet per second are plotted against the percentage of water added to the dry bar, the weight of the latter being taken as the base. This curve shows most clearly the very small. WATER ADDED IN PER CENT BY WEIGHT Fig. 5.—Variation of bar velocity of elastic waves in Amherst sandstone as water content is changed. amount of moisture necessary to cause a great decrease in velocity. The addition of slightly more than 2 per cent of water to the dry bar decreases its velocity from 7,640 feet per second to 4,600 feet per second, which is a reduction of 40 per cent. The addition of 4 per cent more water, however, decreases the velocity to 4,415 feet per second, which is a further reduction of only 2 per cent. In order to formulate an explanation for the phenomena described, it is first necessary to determine what property of the bar is affected by the moisture. The bar velocity is a function of the value of Young's modulus and the density of the bar, being given by the relationship v = \/E/p where v is the bar velocity E is Young's modulus and p is the density of the bar. A decrease of velocity may therefore be caused by an increase in density, by a decrease in the value of Young's modulus, or by both. The addition of water does, of course, increase the density, but this 675. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrati
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