Partially Drained Analysis

The excess pore water pressure can be the result of underconsolidation (i.e., rapid sedimentation rates) or earthquake loading as examples. The ultimate shear stress under these circumstances can be the following  

Assuming a constant excess pore water pressure ratio (rj defined as follows  

A review shows that the drained F.S. is approximately twice the undrained value. 

Factors of safety from infinite slope analysis for partially drained conditions, R = 0.25, ( ) = 25°. 

A general expression for the F.S. including earthquake effects of an infinite homogeneous slope is given by Equation 11.24. 

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Figure 5 Schematic of a lance falling at terminal velocity, Uo, and impacting the seabed. For the evolving partially-drained analysis of embedmentgenerated pore pressures, the coordinate system is fixed to the penetrometer tip.

Another well-established area of mechanical finite-element analysis is in the motion of the structures of the human middle ear (Figure 9.3). Of particular interest are comparisons between the vibration pattern of the eardrum, and the mode of vibration of the middle-ear bones under normal and diseased conditions. Serious middle-ear infections and blows to the head can cause partial or complete detachment of the bones, and can restrict their motion. Draining of the middle ear, to remove these products, is usually achieved by cutting a hole in the eardrum. This invariably results in the formation of scar tissue. Finite-element models of the dynamic motion of the eardrum can help in the determination of the best ways of achieving drainage without affecting significantly the motion of the eardrum. Finite-element models can also be used to optimise prostheses when replacement of the middle-ear bones is necessary. 

Figure 10 shows TEM images of an MEA following an open-circuit endurance test in which was supplied to the anode and to the cathode. The test conditions were a cell temperature of 90 C, 30% relative humidity, anode atmosphere of H, and cathode atmosphere of O. Similar to the results of the load-cycling test, it was found that platinum from the cathode catalyst layer dissolved and was redeposited in the electrolyte membrane. Under these test conditions, redeposited platinum particles were observed near the center of the electrolyte membrane. The position of redeposited platinum particles is determined by a balance between the mixed potential of the electrolyte membrane and the partial pressures of the anode and cathode O. It was estimated that platinum particles would be redeposited near the center of the electrolyte membrane under the conditions used in this test (Fig. 11). Chemical degradation of the electrolyte membrane was observed centered on the band of redeposited platinum particles. An analysis was made of the drain water discharged from the MEA during the test and fluoride ions were detected, which suggests that the electrolyte manbrane was partially decomposed (Ohma et al. 2007).

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