A Mohr circle method for 3D strain measurement using the geometry of no finite longitudinal strain and the RXZ strain ratio

This paper proposes a new method for 3D finite strain analysis. This method utilizes a Mohr circle construction combined with stereographic projection of the geometry of no finite longitudinal strain and with the strain ratio on the XZ-plane of the finite strain ellipsoid. The method is described using numerical examples and then it is tested by applying it to the deformed Deh Vazir conglomerate in the southwestern part of the Sanandaj-Sirjan HP-LT metamorphic belt, within the Zagros orogenic belt in Iran. The results of this method compare well with previous finite strain measurements using strain ratios on three principal planes of finite strain. Calculation of finite strain from strain ratios on the XY and YZ principal planes is advantageous when preparation of 3 perpendicular sections is difficult or impossible.

► The paper proposes a new method for 3D finite strain analysis.
► 3D strain analysis based on the geometry of the surface of no finite longitudinal strain.
► It is possible to determine the strain ratio in the other two principle planes by using a Mohr circle.