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.


The areas of application of the arches type THN are principally in underground mining and tunnel construction. The arches are used in different stages of the process of excavation and are especially useful in the following situations:

For areas with unstable rock or weak soil: THN arches are used to support the excavation walls and prevent their collapse, especially in areas where the rock or soil is unstable or weak.

Construction of long tunnels: THN arches are used in long tunnels to maintain the stability of the walls and prevent their collapse.

Construction of tunnels with steep slopes: THN arches are used in tunnels with steep slopes to maintain the stability of the walls and prevent their collapse.

Stabilization of slopes and embankments: CT bolts are used in the stabilization of slopes and embankments in construction and mining to prevent landslides and the collapse of the terrain.

Construction of vaults and arches: THN arches are used to build vaults and arches in tunnels and other underground structures.

Construction of tunnels with small section galleries


Onix Underground THN Specificaitons


The use of THN type support arches has several advantages, some of the most notable are:

Safety: THN arches increase safety in underground excavations by reducing the risk of collapses and accidents. This is especially important in underground mining, where worker safety is a priority.

Adaptability: THN arches, thanks to their overlapping design, can be easily adapted to the excavated section, making them a versatile solution for stabilizing underground excavations.

Easy installation: THN arches are relatively easy to install and do not require special equipment or machinery, reducing installation time and costs.

Reuse: This type of arches can be easily salvaged and reused for another installation.

High strength: THN arches are made with high-strength steel, which allows them to support large loads and offer a long service life.

Transport: Thanks to their Omega-type section, they are easily storable and transportable profiles.

Cost reduction: The use of THN arches can reduce underground excavation costs by increasing excavation speed and reducing downtime for wall stabilization.