Volume 8, Issue 1 (March 1985)
A Direct Shear Machine for Testing Rock Joints
Most direct shear machines are designed for soil testing or research and have serious limitations when used for rock joint testing by commercial testing laboratories. To overcome some of these limitations, a machine has been designed that uses split cylindrical specimen holders to encapsulate rock specimens in the field, protecting them against drying, swelling, and mechanical damage in transit to the laboratory and in storage. Molten sulfur is used as an encapsulating material. Field encapsulation saves “downtime” during laboratory testing and virtually eliminates specimen disturbance. The holders are uncoupled only when in the test machine and after a normal load has been applied.
Further features designed to make the machine more versatile and less expensive include pumps, pressure and displacement pages that are demountable so that they can be easily calibrated and used in other testing applications. Two opposing jacks allow reversals of shear direction. Testing procedures are outlined for reversed shearing at increasing increments of normal load.