REPRESENTATION OF TECTONIC STRESS

Rok, strany: 1995, 13 - 17

A diagram for the presentation of the stress tensor is proposed. The diagram is an equal side triangle whose left side is labelled as [n (σ₁–σ₂)] / σ₁, right side as [n (σ₂–σ₃)] / σ₁ and base as R. The R value is computed as the stress ratio of Etchecopar et al. (1981); R = (σ₂–σ₃) / (σ₁–σ₃) If σ₁ = 1and σ₃ = 0, the remaining stress magnitude σ₂ is equal to R. Left and right side of the triangle are scaled to fit positive infinite interval to a finite interval <0, n>. Lines connecting the same values indicated by a left side are parallel to the right side and vice versa. The base is proportionally calibrated to indicate interval of R = <0, 1>. Lines connecting this calibration with the upper apex indicate stress ellipsoids with the same stress ratio, just progressively increasing the size of the greatest Mohr circle towards the base. Line having the R value 0.5 indicates the plane stress. Lines parallel to the left side show stress ellipsoids with the same σ₂–σ₃ values, progressively changing the R value. Left side is a special line obeying in addition σ₂ = σ₃ thus indicating the axial compression increasing towards the base. Lines parallel to the right side show the stress ellipsoids with the same σ₁–σ₂ values, progressively changing the R value. Right side is a special line obeying in addition σ₁ = σ₂, thus indicating the axial extension increasing towards the base. Upper apex indicates the hydrostatic stress state with all principal stress magnitudes equal. Graph visualizes ellipsoidal shapes. The upper apex represents sphere and the line with R = 0.5 indicates ellipsoids with σ₂ = (σ₁ + σ₃) / 2. Left and right apexes represent an ideal cigar and pancake shape, respectively. Points of the diagram to the right from the plane stress line show stress ellipsoids with control constriction, points to the left from the plane stress control flattening. It is felt that this diagram ignoring the volume effect by a putting ellipsoids into a finite space provides a possibility either to compare the shapes of ellipsoids or to study continuous mutual changes of the stress axes.

ISO 690:

Nemcok, M. 1995. REPRESENTATION OF TECTONIC STRESS. In Geologica Carpathica, vol. 46, no.1, pp. 13-17. 1335-0552.

APA:

Nemcok, M. (1995). REPRESENTATION OF TECTONIC STRESS. Geologica Carpathica, 46(1), 13-17. 1335-0552.