Laboratory equipment for the strength and deformability studies of the rock materials under m ultiaxial stress state
The special laboratory triaxial compression testing equipment was developed to study the deformational and strength behaviour of the brittle polycrystalline materials in multiaxial stress-strain state. Loading capacities of the equipment permit to realise the experiments with 15 × 15 × 15 cm cubic specimens of rock-like materials such as cement mortar, concrete, sandstone and weak rocks. The concept and design of the equipment permit to realise not only the “classic” triaxial, biaxial or uniaxial experiments, but also to conduct very specific tests for new ideas and theories search, as well as to have detailed studies of pre- and postfailure behaviour. For example, in one of the modes the equipment permits to have the tensor of stresses “sliding” along the strength envelope and the receiving a series of points thus determining the part of the envelope in any state of stress (tri- or biaxial).
The special complex for the experimental data acquisition and processing was developed using personal computer with virtual system of measurements and analysis. The system allows realising the measurements of deformations and loads in multiaxial stress states as well as to register the acoustic emission during the failure progress. The created system manages 20 analogous channels simultaneously with velocity of 1000 measurements per second per channel (the sampling velocity increases when the number of channels in use decreases and can reach up to 10,000 samples per second). Specially developed software and functional basis allows to build relationships between the measuring parameters, “time dependent diagrams”, “real time” data saving, and experiment reconstruction with preliminary data processing and analysis (functions fitting, interpolation, extrapolation, signal filtering).