Xf X V k

This equation is Laplacian and involves the two co-ordinate variables xt and z. It can be solved by a flow net provided that the net is drawn to a vertical scale of z and a horizontal scale of

2.22 Calculation of seepage quantities in an anisotropic soil

This is exactly as before:

and the only problem is what value to use for k.

Using the transformed scale a square flow net is drawn and Nf and Nd obtained. If we consider a 'square' in the transformed flow net it will appear as shown in Fig. 2.25a. The same figure, drawn to natural scales (i.e. scale x = scale z), will appear as shown in Fig. 2.25b.

Let k' be the effective permeability for the anisotropic condition. Then k' is the operative permeability in Fig. 2.25a.

Flow a

Flow

(a) Transformed Fig. 2.25 Transformed and natural 'squares'.

(b) Natural

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