materials used for supporting underground mine workings. Certain grades of wood (round timber; lumber), as well as metal (iron and steel), concrete, reinforced concrete, and sometimes artificial and natural stone, are used as support material; the use of polymeric materials and glass-fiber-reinforced plastics is increasing.
Support materials are selected according to the design of the mine support, taking into account the conditions of operation, the purpose and service life of the mine working, and the amount and nature of the rock pressure. Wood (usually pine), although it is relatively light and inexpensive, has little strength, is not fire-resistant, and is subject to decay. Therefore, wood supports are used in development workings (outside the stoping zone) with a short service life and low rock pressure. Metal, a strong and durable support material with good construction qualities, is widely used in the form of special channeled sections, flanged I-beams (sometimes channel beams), pipes, reinforced and sectional steel, and iron tubing. The concrete for cast concrete supports is made with a strength of up to 30 meganewtons per sq m (MN/m2), or 300 kilograms-force per sq cm (kgf/cm2); concrete for precast reinforced-concrete supports has a strength of up to 50 MN/m2 (500 kgf/cm2). Artificial stone (concrete stones or blocks) for underground support is made from concrete or based on boiler and metallurgical slags, with added cement and lime.
Trends in the future development of support materials include an increase in strength and resistance to the effect of corrosive mediums and expanded use of polymeric synthetic materials for the manufacture of supports.
M. N. GELESKUL