INVESTIGATION OF EQUATION OF STATE OF POROUS EARTH MEDIA
Final rept., 15 June 1964-26 Jul 1965
STANFORD RESEARCH INST MENLO PARK CA
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Earlier experimental work has been extended to evaluate the effect of moisture on the Hugoniot of playa. For engineering applications the Hugoniot of moist playa can be predicted with sufficient accuracy from the Hugoniot of dry playa and water and the assumption of pressure equilibrium. Isentropic release data were obtained for moist and dry playa. The steep release curve in the P-V plane from high pressure implies an irreversible phase change. Some low pressure data in the elastic-plastic region are presented. A theoretical discussion of various forms of the Mie-Gruneisen equation and the physical basis of asymptotic statistical models is presented. Shock stability is reviewed. Phase transitions in which delta V 0 are classified according to the signs of the slopes of the coexistence curves. Relative slopes of Hugoniots and isentropes in the mixed phase region are calculated. The results of the theoretical discussion are applied to transitions in bismuth, iron, and quartz. Agreement of values of dPdT deduced from shock data and measured directly are good for bismuth and poor for quartz and iron. Calculations of spherical shock propagation in a hypothetical medium that undergoes a phase change are presented. The calculations show qualitatively some types of pulse shapes that may be expected in a transforming medium. It is concluded that the proper treatment of phase changes is an outstanding problem in predicting equations of state for earth materials.
- Soil Mechanics