True Triaxial Systems

The Advanced True Triaxial Test System has the defining characteristic that all three principal stresses can be controlled independently, unlike conventional triaxial apparatus with just two stresses. This allows a wide range of complex stress paths to be performed. This dynamic cyclic system is powered by advanced electromechanical actuators or optional hydraulic actuators and is an extremely sophisticated research tool. Vertical and one horizontal axis are loaded via the dynamic actuators (axis 1 and 2), stress control is provided for the 2nd horizontal axis, (axis 3) via cell pressure.





  • Stress or strain is applied to different sample sizes like 75 x 75 x 150 mm, 100 x 100 x 200 mm or smaller on request independently on three axes. Two pairs of matched dynamic rams for axes 1 and 2, and a confining fluid provides pressure for the 3rd axis on load readings.
  • Test procedures under saturated and optionally unsaturated conditions with axis translation technology are available
  • Each actuator is supplied with an internal submersible load cell to ensure friction effects will be not measured.
  • Different displacement sensors are available to ensure best strain measurement conditions for each size or strain range.
  • The new developed, generation of electromechanical actuators are more effective in frequency, displacement accuracy and load range
  • The high capacity models with frequency ranges up to 50 Hz include high end technologies in servo-hydraulic solutions like special manufactured frictions-less servo-hydraulic cylinder with hydrostatic bearings.
  • Each pair of actuators are synchronized in real-time and can be controlled in any test mode. That means all kinds of static applications, ramps functions, low and high frequencies can be realized in stress, strain or position controlled mode
  • Electromechanical actuators provide an easier to use and environmentally friendly solution for accurate testing to 10 Hz. In comparison to servo-hydraulic actuators electromechanical do not require regular maintenance of hydraulic power pack or to protect system users from noise generated by a power pack.
  • The seal-less hydraulic actuators are custom designed by Wille Geotechnik. This improves the actuator performance up to 50Hz and reduces whole-life servicing costs as there are no piston seals to replace. Each actuator pair can be controlled in “static-mode” with either constant, ramp or slow cyclic targets in terms of load, stress or displacement.
  • Full sample preparation equipment for cohesive and non-cohesive samples is provided with the system including a specially designed soil lathe for producing prismatic or cubical samples.
  • Static cell pressure control system with minimizing pressure ripples generates in cyclic test procedures
  • Large glass windows in the cell doors up to 250 mm diameter allow a continuous observation of the sample


4 (for 2 main stress axis)

 Axial Transducer Accuracy  <±0.05%
 Force Resolution  Depending on range (e.g. <0.001N for 5kN)
 Computer Interface  Ethernet
 Displacement Accuracy  <±0.15%
 Displacement Range  50mm per actuator (100mm per axis)
 Displacement Resolution  <0.0001mm
 Actuator Load Range (kN)

 5/10/15/20kN (electromechanical)
or 20/25/30kN (servohydraulic)

 Actuator Frequency Range  0-5/0-10Hz (electromechanical)
or 0-10/0-50Hz (servohydraulic)
 Operating Frequency (Hz)  Depending on material and application
 Power   400V, 3 phase
 Confining Pressure Accuracy  <±0.05% (depending on chosen pressure controller)
 Confining and Pore Pressure  1 or 2 MPa
 Sample Sizes  Max 100 x 100 x 200mm (custom sample sizes on request)
  • Local strain measurement
  • Bender elements
  • Unsaturated testing
  • Bender element system (vertical, horizontal, S and P waves),
  • Local strain measurement (axis 3 only),
  • Unsaturated testing and dynamic cell pressure (5Hz).
  • Not available
  • Not available
  • Detailed information will follow soon