Drape folding of compressible elastic layers-ii. matrix solution for two-layer folds

A matrix solution for two-layer drape folds in compressible elastic media is used to examine the relative importance of layer compressibility, layer stiffness, and the presence or absence of lower boundary shear on fold form, principal stress direction and maximum shear stress distribution. The most obvious effect of decreasing the shear modulus of the lower layer is a change in principal stress orientation, accompanied by a decrease in maximum shear stress. Principal stress orientation, and to a lesser degree fold shape, can be further altered by changing the compressibility of an easily sheared basal layer. Characteristics of drape folds with welded and non-welded basal contacts, as observed in the field and predicted by a single-layer model of drape folding, are also further explored with the two-layer model.