Synchronization of the yield as a way to increase bearing capacity of frame supports
Results of testing of a yield frame support having synchronized clutches. Testing of the frames in situ and in a laboratory showed that opposite clutches yield by turn, one after another that is compliant with thermodynamics of irreversible processes. Such behavior causes blocking of the clutches, longitudinal twist of frame profile, its plastic deformation, breaking of the clutch components, asymmetrical yield of the clutches, buckling and shifting of the frames, what reduces their bearing capacity. Synchronization of the opposite clutches yielding is a key solution to provide stable operation of the frame saving and maintaining their bearing capacity. Synchronization of the opposite clutches was provided using a flexible link, for example, steel rope joining opposite clutches. New frame design proved to be much more efficient than a traditional prototype frame equipped with independent clutches. SC always demonstrated practically the same yield and synchronous paths of pliancy. Yield of SC occurred by smaller portions, average value of which was 1.962±2.29 mm, whereas corresponding elementary yield of IC extended to 6.641±6.7 mm, what increased probability of clutches blocking and destroying. Possibility of the IC jamming increases additionally because standard deviation of IC yield exceeds 100%, whereas standard deviation of SC yield in four tests was 0.43% only. Average resistance of the frame equipped with SC was 1.23 times more in comparison with IC prototype. Irreversible work of the SC resistance was 1.73 times more than corresponding work of IC. In addition, SC facilitate stable operation of the frame because variance of its resistance is 20% versus 67% for the frame having IC, and variance of the work is 10% for SC versus 50% for IC. The most important advantage is that weak but specific action of a frame equipped with SC induces strong interactions among blocking rock fragments, which produce self-supporting effect that increases stability of underground roadway.