Strength Characteristics of Secura Hollow Groutable Cable Bolts

The strength properties of Secura Hollow Groutable Cable-bolts (HGC) were examined for tensile and shear failures. The 30 mm diameter, nine strand, cable bolt consisted of a mixture of five 7.5 mm plain and four 7.0 mm indented strands wrapped around a central 14 mm steel grouting hole to make a round cable with lay length of 500 mm with bulbs at 500mm centres of diameter 35mm. The tensile strength of the cable was tested in accordance with the British Standard (BS7861-part 2:2009) using the double embedment pull test. The shear strength of the cable bolt was tested by both the BS7861 single and UOW double shear methods. The single shear double test used a guillotine shear frame of double embodiment tendon/grout assembly in a steel tube, while the double shear method enabled shear testing of the cable bolt in concrete to simulate rock. It was found that the tensile strength of the cable was in the order of 680 kN, the shear load by single shear test, based on the average of three tests, was around 448 kN. The shear failure load of the cable bolt from double shear testing based on two tests averaged around 786 kN which is significantly higher than achieved from the single shear test. Thus the shear value, obtained from the double shear method was between 13 and 18 % greater than the single shear test method. The use of the guillotine shear frame for the single shear method was considered an unrealistic method of evaluating the shear characteristics of the cable bolts in rock.