Stress-Controlled Apparatus for Triaxial Testing

Abstract

A testing machine in which the rate of true stress can be controlled manually or automatically is described. A pneumatic analog computer continuously calculates the cross section of the test specimen and provides the loading unit with a pressure such that the force applied produces a given axial stress. The whole test, up to fracture, is entirely automated. A wide range of stress paths is made possible by this machine. Tests on a saturated kaolinite serve to illustrate some of the capabilities as well as to point out some of the problems that this machine may help investigate.