Wirkungsprinzipien eines gegen Gebirgsschläge Widerstandsfähigen hydraulischen Strebausbaus

The stresses which occur in hydraulic support legs as a result of dynamic loading from rockburst events can be more than 50 times greater than those present under static loading. This can result in the destruction of the support unit. Investigations have shown that powered-support safety valves open with a delay of about 4 ms in relation to the moment of load application, with the result that they are ineffective in counteracting the effects of rockburst. In order to prevent the risk of damage to the support system, the Polish coal industry has developed a face support unit in which the hydraulic legs are fitted with a pneumatic plate, which is designed to absorb the load energy generated by the rockburst.