[en] Different sophisticated numerical tools are developed for modeling the behavior of underground openings and related problems dealing with rocks. This development has been accelerated by the actual low cost of the computer treatment. But drawing good mechanical properties from rocks is a difficult problem which can be solved partly by developing computer driven loading frames.
In our rock mechanics laboratory of the Technical University of Mons (FPMs) we developed a Polyaxial test apparatus using small cubes (3 mm side). This system consists in a rigid three pistons polyaxial cell operated by a hydraulic bench driven by a micro-computer. The software we developed for controlling the testing allows different kinds of tests under a general state of stress: classical compression tests with a constant rate of strain, creep and relaxation tests, and biaxial tests.
To improve the treatment of the results supplied by this device we developed also a software for PC microcomputer. This software realises an automatic treatment of experimental curves and calculate directly some mechanical properties of rocks like Young's modulus, Poisson's ratio, and limiting envelopes (elastic limit and/or failure).
The Polyaxial device has been tested on different types of rocks and gives satisfactory results. This tool permits low cost of the treatment and is useful when someone wants to make many characterizations. In fact, the treatment of the data supplied by one test needs less than 5 minutes. This gain of time by coupling a computer controlled testing machine with an automatic treatment software can encourage more in depth studies of rocks and rock masses by multiplying the number of tests.
