Development of a new true tri-axial apparatus

A true tri-axial apparatus is usually applied to measure the mechanical characteristics of soil under the three-dimensional principle stress condition. A new true tri-axial apparatus with a new structural cell is developed by Geotechnical Engineering Institute of Xi’an University of Technology. By comparing loading ways of different true tri-axial apparatuses at home and abroad, the characteristics of the new true tri-axial apparatus are summarized as follows: ① A kind of hydraulic and volume apparatus with stepper motor servo-driven is developed, which is used to load independently the principal stress, and the corresponding automatic control system is developed. ② The cubic sample is loaded by a pair of vertical steel plate and two pairs of lateral latex film vesicas. ③ The neighboring vesicas are separated by the steel plate, which can flex elastically in the radial direction and turn elastically on the horizontal plane. Furthermore, the true tri-axial tests on remolded loess are executed by use of the new true tri-axial apparatus. The characteristics of the stress-strain curve of the true tri-axial tests on the remolded loess and the strength of the loess remodeling are analyzed under different water contents. The new true triaxial apparatus is simple in structure, convenient in operation, true in stress state, exact in measuring the strain state and manageable in testing process.