ABSTRACT
For the underground rock joints as shown in Figure 1, the normal stress on the rock joint is determined by normal stiffness and normal displacement of the joint. In CNS direct shear test, the constant normal stiffness can be obtained by inserting a spring between a load frame and a joint sample or by adopting a servo-controlled shear machine. Of course, the servocontrolled machine is more versatile and provides more precise results.
