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Technical paper: The design and construction of a new rotary machine for rock joints

Shulin Xu, BSc, MSc, EA Rogers & MH de Freitas, BSc, PhD, MIGeol. This paper was first published in GE’s May 1988 edition.


A ring shear machine in principle similar to the ring shear apparatus for testing rocks designed by Kutter (1974) and that for testing soils designed by Bromhead (1979), has been constructed for testing rock joints. Both peak and residual strength parameters can be obtained with this machine.

A description of the sample preparation for this equipment is given by Xu & de Freitas (1988 a & b) together with the results of proving tests, which have demonstrated that the results obtained with this apparatus are comparable with those obtained using direct shear boxes employed in soil testing, the Hock shear box and the Bromhead ring shear apparatus.

This paper describes the main features of the design of this machine (Fig. 1a and 1b) whose principle attributes are:

(i) the ability to achieve continuous displacement of rock surfaces over distances much greater than any equipment available to date,

(ii) a stiffness that allows post-peak behaviour of the rock surfaces to be studied, and

(iii) an unchanging apparant area of contact between the two halves of the specimen being tested.

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