STRATA LOADING OF MINE ROADWAY SUPPORTS.

Several tunnels and roadways in U. K. coal mines have been instrumented to establish an improved understanding of the general characteristics of rock pressure loading on steel supports in such excavations. The support loads were measured using three main types of mechanical instrumentation, namely hydraulic load cells employed under the arch leg, flat hydraulic cells located between the steel support and the excavated surface and Demec mechanical strain measuring equipment located on the web of the RSJ support legs. Comparisons are made of all three types of instrumentation. The variable nature of the results indicates that steel supports must be selected with special regard to the geological and mining conditions and due account taken of the degree of roadway deformation permissible in any given set of conditions.