Shear stress around pores

We have performed finite element analysis on a simple model to demonstrate the concentration of shear stress around the pore wall. Figure 5.12(a) shows the model used and Figure 5.12(b) is a plot of shear stress as a function of distance from the pore wall. It is evident that there is considerable stress concentration in the film around the substrate pores, which can lead to the formation of the half-loop dislocations. 

Figure 5.12 Finite element analysis of shear stress distribution around a circular pore under biaxial stress, (a) The finite element analysis model, showing a single circular pore in a solid brick, (b) Plot of shear stress along a diagonal line in the model as a function of distance from pore wall. The units are arbitrary and the length scale of the stress field is determined by the pore diameter in the model (10 distance units)...

The other shear strain component is caused by the cyclic shear stresses from the wave forces. These repetitive shear stresses cycle around the permanent shear stresses due to the initial in-situ stresses and stresses due to platform weight. The soil elements are thus subjected to unsymmetrical cyclic shear stresses and this will cause a permanent shear strain increase in the direction of permanent shear stress even if there is no excess pore pressure. 

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