Shear testing of 28 mm hollow strand "TG" cable bolt

Cable bolts were introduced to the coal mining industry in the early 1980’s mainly for roadway reinforcement as a secondary means of support. Their application is dictated by the nature of the stratification, ground stress conditions and the size of the opening. Double shearing tests were carried out on the 28 mm hollow strand Jennmar “TG” cable bolt, two tests were conducted to evaluate the shearing characteristics of the bolt and to gain a better understanding of the shearing behaviour of the cable. The first test was limited by a 50 mm travel on the testing machine and produced a shear load of 900 kN (92 t) at the maximum 50 mm displacement, with axial load generated on the cable bolt reaching 238 kN (24.3 t). In the second test the machine travel was increased to 75 mm, cable failure due to shear loading was achieved at 1 354 kN (138 t) load and a vertical displacement of 59 mm, with cable axial load in the order of 385 kN (39.3 t). Analysis of the failure mode and loads achieved indicate that the cable strands bent and the concrete crushed along the shear plane, the shear loading across the concrete and grouted cable then reached the tensile strength of the steel wires.