This work focuses on the analytical-numerical analysis of the interaction of two crack-like defects situated at the interface between dissimilar elastic materials and subjected to a remote tensile stress field (the plane problem). These defects are modelled by weak zones (WZs), i.e. cuts subjected to adhesive forces over their entire length. A small but strong microstructural feature of the material, say, a small obstacle, separates the WZs. Contrary to a traction-free crack or a crack with a small or a large process zone at its tips (the so-called cohesive crack), the WZ is normally closed but opens gradually under sufficiently large external tensile stresses and becomes the nucleus of a cohesive crack at some critical load. The adhesive forces can be of very different physical origins — atomic, dislocational, localized porosity,
. Healed cracks in glaciers and in the earth’s crust can be regarded as WZs. The length of WZ can thus range from a few
to hundreds of
. Because of this, it is expedient to investigate the fundamental feature of the interaction between WZs located close to each other. The key questions that will be addressed are: (i) when does one of the WZs become the nucleus of a cohesive crack on its own without linking with the other, and (ii) when do the WZs force the obstacle to rupture allowing the WZs to link with each other before event (i) occurs.