Large Triaxial Testing Apparatus

This special facility can perform static and cyclic triaxial tests on large dimensions samples. The rigid reaction frame is provided with an electro-hydraulic piston designed to minimise friction effects.

The computer controlled system can operate both under strain controlled and stress controlled conditions, thus any designed stress path can be reproduced.

Main features:

  • 3000 kN load frame;
  • sample dimensions: diameter 30 cm, height 60 cm
  • confining stress up to2.5 MPa
  • back-pressure up to 1 MPa
  • isotropic or anisotropic consolidation
  • static and cyclic tests
  • 1200 kN double acting piston
  • cycles frequency in the range 0.1 Hz (ε=6%) to 5 Hz (ε=0.2%)

In the monotonic tests the samples are consolidated, isotropically or anisotropically, under stress controlled conditions, then during the shearing stage the deviator stress is applied in a strain-controlled mode, imposing to the piston a constant rate of vertical displacement.

In the cyclic tests the servo controlled electro-hydraulic system pilots the proportional valve to apply the required axial load amplitude (stress ratio) or a cyclic load at constant rate of strain.

Continuous data acquisition during the test is assumed by a DAQ. The axial load is measured by a 1000 kN load cell: The axial deformation can be measured either by external or internal transducers. Volume changes and pore pressure evolutions are measured by specific transducers.