An investigation has been made into the reproducibility of measurement of joint orientation in rock. The rocks studied were sandstone, mudstone and limestone exposed in the Kielder aqueduct tunnels; the same limestone exposed in a nearby quarry was also studied. It was found that for six observers measuring a 10m long scanline, the orientation of particular joints recorded can have a mean maximum variation of + or - 10 degrees for dip direction and + or - 5 degrees for dip angle without there being any real difference in the joint orientation. However, the joint orientation diagrams produced by the six observers were in broad general agreement, and allowed the major joint sets to be identified. When the effects of the observed variation were compared with the joint orientation rating adjustment in bieniawski's rock mass classification it was seen that they were insignificant. However, the effects of variation need to be taken into account when dealing with the stability of individual blocks of rock. (Author/publisher)
Abstract