Determination of Local Strain from the Contour Line

4 Determination of Local Strain from the Contour Line 

The extent of settlement in the subgrade of a geomembrane is described in various ways. Depth of settlement, radii of curvature along the contour line of settlement or local deformations is used. Ambiguity often exists, e g. how a permissible local strain of HDPE geomembranes can be converted into a radius of curvature or in a depth of settlement, which are still acceptable. 

Finally one has, using the usual expression for the local radius of curvature of a contour line  

Here 3 ( ) ss well as dy/dx denote the first derivative of curve j(x) and y x) ox cFyld stand for the second derivative. 

The maximum local strain Emax in the volume element is given by  

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