Large-scale Coarse-grained Soil Triaxial / Rheological Test System

System Functions

The system can perform stress/strain cyclic loading on specimens, and carry out B-test, back pressure saturation, UU, CU, CD tests, confining pressure loading-unloading cyclic tests, axial pressure loading-unloading cyclic tests, stress path tests, wetting tests, rheological tests, etc.

It can be upgraded to support full-surface deformation image measurement for soil samples, dynamic modulus and damping ratio tests, drying-wetting cycles, freeze-thaw cycles, seepage failure tests and other related tests.

System Performance

• Specimen size: φ150×300 mm / φ300×600 mm.

• Confining pressure: 0~4 MPa.

• Static axial force: 0~1000 kN (customizable).

• Dynamic axial force: 0~750 kN (optional, customizable).

• Vibration frequency: 0.1~1 Hz (optional, customizable).

• Vibration amplitude: 0.5 mm @ 1 Hz ~ 5 mm @ 0.1 Hz (customizable).

• Temperature control: -10~+50 ℃ (optional).

• Strain measurement: full-surface image measurement, accuracy 10⁻⁴ (optional).

Optional Upgrades

• Full-surface digital image measurement for specimen deformation

• Stress-seepage multi-field coupling function

• Stress-temperature coupling function

• Drying-wetting cycle function for coarse-grained soil

• Bender element function

• Ultrasonic velocity test function

Main Unit

• Vertical cylindrical chamber for easy integration of imaging camera, temperature control and other modules.

• Pressure chamber: 304 stainless steel, stress-relieved, high strength, toughness and impact resistance.

• Seals: energy storage type, suitable for -30℃, 5MPa, dynamic and static applications.

• Fittings, plugs and pore pressure sensors rated for -20℃.

• Viewing window (optional): special aluminosilicate glass, 50MPa pressure resistant.

• Temperature control (optional): dual-chamber structure, inner pressure chamber (4MPa), outer temperature control chamber (liquid medium).  Processing Requirements: Position dimensions per drawing; unspecified tolerances comply with **GB/T 1804-m.

Loading System

Axial Loading

• Force path: Hydraulic cylinder → Load cell → Loading shaft → Sample cap → Specimen

• Structure: Hydraulic cylinder fixed on the loading frame. Loading shaft passes through pressure chamber with O‑ring dynamic seal. Load cell connects cylinder piston and loading shaft.

• Process: Same as loading frame.

Confining / Back Pressure Loading

• Force path: Hydraulic cylinder → Volume controller → Pipeline → Pressure chamber (fluid) → (membrane) → Specimen.

• Structure: Cylinder drives volume controller to generate high pressure. Fluid pressurizes specimen via membrane (confining pressure) or directly inside specimen (back pressure).

• Process: Same as loading frame.

Hydraulic System

• Function: Supplies pressurized hydraulic oil for axial and confining pressure driving cylinders.

• Composition: Hydraulic power unit, pipelines, servo valves, and safety protection devices.

• Hydraulic unit parameters: Motor by ABB (Sweden); constant pressure variable pump with accumulator; pressure: 21 MPa; oil volume: 50 L. Servo motor with variable frequency control: low noise, low vibration, low power consumption.

• Servo valve parameters: Brands include Rexroth (Germany), ATOS (Italy), MOOG (USA), etc. Pressure/speed adjustment is non-polar, with low power, low heat generation and low noise.

• Other components: Pipelines and valves from well-known brand FITOK.

• The hydraulic unit supports local and remote start-stop control.

Electrical Control and Data Acquisition System

• Function: Issues operating commands and acquires data for the test system.

• Brand: Main controller – DELTA (USA).

• Control mode: Force / displacement drive, with bumpless switching between the two. The DELTA controller supports dual closed-loop control of force and displacement.

• Control cycle: 250 μs.

• Protection mechanism: In case of DELTA abnormality, the hydraulic unit will be interlocked to stop movement.

• Axial force measurement: Spoke-type load cell.

• Displacement: Magnetostrictive sensor by GEFRAN (Italy).

• Confining pressure / pore pressure: Pressure sensors.

PC Module

• Software development based on LabVIEW and C#.

• Data acquisition via dynamic database from DELTA controller with command transmission.

• Waveform control including sine wave, triangular wave, square wave and user-defined wave.

• Extended functions: full-surface image strain measurement, seepage, stress-strain measurement under seepage failure, bender element test, ultrasonic test, etc.