Tests of friction joints in mining yielding supports under dynamic load

A mining yielding support is used for securing dog headings against the static and dynamic impact of the rock mass. Steel frames and friction propos are used to produce the support. Their essential part decisive for load-bearing capacity and yield capacity are friction joints. The article presents the results of theoretical studies and stand tests concerning the work of friction joints at their dynamic load. During the stand tests, a joint was loaded axially onto which a cross-bar was rested with a mass freely falling from a specifi c height. The forces occurring within the stirrups and the displacement of the yielding shaped section were recorded for the fi rst time during the tests with a high-speed camera. Variations in the force transmitted through a friction joint were also recorded. The physical and mathematical models of the joint had been developed based on the stand tests, which were then used for a simulation analysis of joint work under impulse loading. The friction joint model developed and a new measuring system used in the stand tests and the results of such tests should be used for operating, designing and selecting a yielding support matching the dynamic load risk conditions.