SUMMARYEvidence for threshold gradients is reviewed. The consolidation problem, with threshold gradient, is properly formulated and solved numerically. An approximate analytical solution is also developed. The influence of a threshold gradient on the time rate of settlement is examined, and it is shown that by modifying the definition of the degree of consolidation a good approximation to the threshold gradient problem can be obtained directly from the Terzaghi solution. It is also shown that threshold gradients will have no influence on odometer testing and their effect is, therefore, to reduce the primary compression below that predicted from standard tests.
This paper describes the flow behaviour of certain non-Newtonian fluids through a porous medium. A generalized Bingham rheological model of power-law in the presence of a yield stress has been considered. Several problems of fluid mechanics, which appear currently in oil reservoir engineering, have been investigated and the rheological behaviour effect has been emphasized. The short time solutions have been formulated in terms of a moving boundary problem. The approximate solutions in a closed form were obtained by means of the integral method. Several dimensionless groups have been found to be relevant in evaluating the rheological effect on the steady and unsteady flow behaviour. The deviation from Newtonian flow behaviour has been illustrated using several numerical examples.
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