Cross brace is the cross-beam connecting between arches meant to add rigidity to construction of mining

Mining

Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...

 tunnel

Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...

s, more often tubular round diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

 (as a rule, it is made of scraps of pipes), on the ends with clips or apertures for screw fastening; serves as an element stiffening

Stiffening

In bookbinding, stiffening is a process whereby paperback books are reinforced for use in libraries, without change to their fundamental binding structure...

 and stability

Mechanical equilibrium

A standard definition of static equilibrium is:This is a strict definition, and often the term "static equilibrium" is used in a more relaxed manner interchangeably with "mechanical equilibrium", as defined next....

of a design. There are also other forms; at times, this word name ordinary cross-section wooden cross-beam, or even a board.