Stereometric Analysis of Shear Surfaces during Triaxial Testing.

Three series of cylindrical samples of clay were tested under triaxial stress. Each sample was oriented in two systems of references (with respect to structural coordinates and with respect to the north). All the tests were performed under identical laboratory conditions. The samples were taken from various sites in an anticline of glacitectonic origin. The generated shear surfaces were used for the preparation of stereograms on a Lambret-Szmidt net. From the studies performed it follows that the spatial orientation of shear surfaces changes from a conical system (anticline limb) to an arrangement of two systems of shear surfaces (characteristic of the anticline joint). The observed trace of the intersection of the two systems of shear surfaces has the same orientation as the axis of an anticline of glacitectonic origin.