Deflection Of Mine Roof Supports

Any design of a mine roof in bedded deposits which ignores differential deflections at the supports can quickly lead to dangerous overstressing. As illustrated by the typical case presented on page 1029, if one support deflects only 0.1 in. more than its neighbor, stresses 50 pct higher than anticipated will result. Previous studies1-3 have assumed that the mine roof acts like a beam clamped at both ends, with no deflection or slope4 at the supports (Fig. 1). Essentially this assumes:5,6 [BA = OD = 0 and dA = dB = 0.]