True Triaxial Apparatuses with Two Rigid Boundaries

A small-scale and a large-scale true triaxial apparatuses (where σ₁≠σ₂≠σ₃) are recently developed at Institute of Industrial Science, University of Tokyo, Japan and described in this paper. In these apparatuses, a comprehensive loading system that can control both strain rate and stress rate are used for the vertical (axial) direction. In the small-scale true triaxial apparatus, one horizontal load is applied by using a hydraulic system (stress control) while in the large-scale true triaxial apparatus it is applied by using a motor-driven gear system (strain control). Another horizontal load is applied by air or water pressure in both apparatuses. The stresses in three orthogonal directions are controlled independently by a personal computer. High-resolution local measurement transducers are set up in these apparatuses to evaluate normal strains in the three orthogonal directions. These apparatuses have been used in a number of research topics such as anisotropy, time effect, behavior of geo-materials from small to large strains and cyclic loading behavior, among others. It helps to obtain advanced knowledge and understanding of properties of various types of geomaterials including gravelly soils.