QUASI-TRIAXIAL APPARATUS FOR THE DETERMINATION OF MECHANICAL PROPERTIES OF GRANULAR MATERIALS

摘要

The failure properties of granular materials (internal friction, cohesion) are measured with the use of shear cell, in the same way as in soil mechanics. The shear cell is not capable to measure the materials properties (e.g. modulus of elasticity, side pressure coefficient). On the other hand, the material properties are necessary for our calculations. Triaxial measurement apparatuses are used for the determination of the material properties of granular mass, as the uniaxial stress state is not possible inside the granular media. The classical triaxial testing apparatus uses cylindrical specimen. The vertical and the horizontal load are produced by oil- or gas pressure. The magnitude of this pressure is constant or can be controlled by the user. With the increase of axial pressure the granular specimen - like a cylindrical steel sample - can be compressed until its breakage. The failure diagram obtained from this measurement is similar to the failure diagram of the uniaxially loaded steel sample. Inside a silo, the horizontal pressure is caused by the weight of the granular mass, and its magnitude is determined by the mechanical properties of the silo wall. Hence, the triaxial apparatus presented above is not capable to model these circumstances well. Therefore, we developed a quasi-triaxial apparatus. The quasi-triaxial principle was used before, for the examination of rock samples [2].