Bishop Stress Path Triaxial1. Description This equipment is a Bishop Stress Path Triaxial Apparatus (BTU-TTS-5S), designed based on the Bishop-type stress path pressure cell. It
is specifically used for studying the mechanical properties of
saturated soils under complex stress paths. The system is equipped
with a high-precision submersible load cell, an LVDT displacement
sensor, a multi-channel data acquisition unit, and multiple
pressure/volume controllers, enabling fully automatic control from
saturation and consolidation to stress path shearing. The software
includes advanced modules such as linear stress paths (p-q or s-t,
with 6 forms), low-frequency cyclic loading, and k0 consolidation. 2. Test Standards - ASTM D7181(Consolidated Drained Triaxial Compression Test)
- ASTM D4767(Consolidated Undrained Triaxial Compression Test)
- ASTM D2850(Unconsolidated Undrained Triaxial Compression Test)
- BS 1377(British Standards for soil testing)
- SL 237-1999(Chinese specification for soil testing)
3.Specification (Parameter) | Parameter | Specification | | Model | BTU-TTS-5S | | Max. cell pressure | 2000 kPa | | Max. axial force | 10 kN | | Specimen sizes | 39.1mm / 50mm (specimen cap and base) | | Submersible load cell | 5kN / 10kN optional, accuracy ±0.05% FS | | Displacement sensor | LVDT, range 0-50mm, accuracy ±0.15% FS | | Pore water pressure sensor | 2MPa, accuracy 0.1% FS | | Data acquisition unit | BTU-DAI-10, 10 channels (2 digital + 8 analog), 16-bit AD, RS232 | | Axial pressure/volume controller | 3MPa / 250cc | | Back pressure/volume controller | 2MPa / 250cc | | Cell pressure/volume controller | 2MPa / 250cc | | Software modules | B-check, back pressure saturation, consolidation, UU, CU, CD,
stress paths (6 types), low-frequency cyclic, k0 consolidation,
sensor calibration |
4. Detail (technical details) - Bishop stress path pressure cell: Bishop-type design suitable for saturated soil tests; max cell
pressure 2000 kPa, axial force 10 kN.
- Submersible load cell: Mounted inside the pressure cell to avoid piston friction;
accuracy as high as ±0.05% FS; optional ranges 5kN or 10kN.
- LVDT displacement sensor: British brand, accuracy ±0.15% FS, range 50mm, suitable for
conventional specimen deformation measurement.
- Three independent volume controllers:
- Axial pressure: 3MPa / 250cc
- Back pressure: 2MPa / 250cc
- Cell pressure: 2MPa / 250cc
Enables independent and precise control of cell pressure, back
pressure, and axial pressure, as well as volume change measurement. - Data acquisition unit: 10 channels, supporting 2 digital signals (e.g., LVDT, load cell)
and 8 analog signals (e.g., pore pressure, volume change); 16-bit
resolution.
- Stress path module: Provides 6 types of linear stress paths (p-q or s-t forms);
custom paths can be defined – suitable for simulating complex
stress histories.
- Low-frequency cyclic module: Supports low-frequency cyclic loading under load control mode,
for simulating seismic or traffic loading.
- k0 module: Enables k0 consolidation and swelling tests.
5. Application - Stress path studies on saturated soils: simulate stress changes during excavation, filling, unloading,
and other practical engineering scenarios
- Constitutive model parameter calibration: e.g., Cam-clay model, Duncan-Chang model
- Foundation and slope engineering: strength and deformation characteristics under different stress
paths
- Cyclic loading tests: soil response under subway or traffic loading (low-frequency
cyclic module)
- k0 consolidation tests: determine coefficient of lateral earth pressure at rest
- Teaching and research laboratories: advanced soil mechanics testing
6. Advantages - Bishop-type pressure cell: optimized for saturated soil stress paths, reducing errors
- High-precision submersible load cell: directly measures specimen load, avoiding piston friction
- Three independent volume controllers: independent control of cell pressure, back pressure, and axial
pressure; accurate volume change measurement
- Rich software modules: covers conventional triaxial to advanced stress paths,
low-frequency cyclic, k0 consolidation
- Cost-effective configuration: 10kN axial force, 2000kPa cell pressure – sufficient for most
saturated soil testing needs
- Modular upgradability: additional stress path forms or cyclic loading functions can be
added as needed
7. What To Choose (selection guide) | Requirement | Recommended configuration | Reason | | Routine saturated soil UU/CU/CD tests | Basic configuration + standard software | Meets standard triaxial test requirements | | Complex stress path simulation (6 linear paths) | Standard stress path module | Enables p-q, s-t linear stress paths | | Low-frequency cyclic loading (traffic/seismic loads) | Optional advanced loading module | Supports load-controlled low-frequency cycling | | k0 consolidation and swelling tests | Optional K-0 module | Determines coefficient of lateral earth pressure at rest | | Higher axial force needed (>10kN) | Not suitable for this model | Recommend BTU-TTS-20S or higher | | Larger specimen needed (>50mm) | Not suitable for this model | Recommend TTS-6S or above | | Comprehensive teaching lab requirements | TTS-5S + full software suite | One machine covers multiple advanced tests |
8. Process Flow - Specimen preparation→ Prepare saturated soil specimen of Ø39.1mm or 50mm
- Mount pressure cell→ Install specimen, submersible load cell, LVDT; connect
cell/back/axial pressure lines
- Saturation stage→ Back pressure saturation and B-check to verify saturation level
- Consolidation stage (optional)→ Isotropic consolidation or k0 consolidation
- Shearing or stress path stage:
- Conventional CD/CU/UU shearing
- Linear stress path (p-q or s-t, 6 forms)
- Low-frequency cyclic loading (requires advanced loading module)
- Data acquisition→ 10-channel DAQ simultaneously records axial force, displacement,
pore pressure, volume change, cell pressure, back pressure
- Post-processing→ Software generates stress path diagrams, stress-strain curves,
effective stress paths, failure envelopes, etc.
- Report output→ Automatically generates standard-compliant tables and curves;
supports printing and export
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