The THN type support arch is an element used in underground mining and in tunnels to support the walls of the excavations and prevent their collapse. It is a steel arch formed by an Omega-shaped profile (quality 31Mn4 according to DIN21544 standard and >350N/mm2), which can be curved in the opposite direction, which overlap each other by means of joining clips to form the complete arch. . This structure allows to distribute the load of the rock and keep it in place, thus protecting the workers and machinery that are in the mine.

THN support arches are also called sliding arches and this is one of their main characteristics because, thanks to their overlap, these arches can be stretched or contracted during installation to adapt to the excavated section. Once the staples are installed, depending on the type, they have a certain degree of slippage that absorbs the stresses of the section when moving, helping to absorb the loads before arch fatigue occurs.