Materials employed for support

The following materials are commonly used for mine supports entirely as such or in combination:—

(1) Timber, usually sal (and in some areas, teak) is used for props, bars, chocks or cogs, and laggings,

(2) Iron and steel in the form of bars, props, arches, corrugated sheets and roof bolts.

(3) Brick or building stone in masonary walls, or archings.

(4) Reinforced concrete or precast concrete blocks as roadway lining.

(5) Roadway ripping, dirt bands and shales as packwalls.

(6) Sand, earth, boiler ash, washery rejects, mill tailings, slag from blast furnace for smelting iron and crushed stone as packing of goaf and filling or voids.

Research into strong, lightweight materials for underground supports has shown that the most promising one is glass fibre-reinforced plastics. These have not been introduced in our mines as yet. Tests in Russia have shown the CBAM framed supports for development roads weigh one seventh or one eighth as much as precast reinforced concrete and one third as much as timber frames. CBAM is a Soviet glass fibre product.

Precast concrete assemblies as support have been seldom used in our mines. They have the serious disadvantage of great weight and difficulty in handling.

The type of support to be built up depends on the importance of the place to be supported, the period for the support, its cost and availability.