Computerized Automated Triaxial Testing Cell System
High-pressure acrylic cell (1700 kPa capacity) with internal tie rods and balanced loading ram.
Civil Engineering / Triaxial CU Shear Test
FREE TO EXPLORELABORATORY 24 · CIVIL ENGINEERING
Triaxial Consolidated-Undrained (CU) Shear Testing with Pore-Water Pressure Measurement
Determine the effective stress shear strength parameters (c', ϕ') and pore pressure parameter (A) of saturated cohesive soil using the triaxial consolidated-undrained (CU) compression test with pore pressure measurement according to ASTM D4767 / BS 1377-8. Explore interactive structural mechanics, materials simulation, and civil engineering telemetry.
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Your virtual civil engineering laboratory.
PEAK DEVIATOR STRESS Q_F—
CIVIL INFRASTRUCTURE TELEMETRY
Ready to sample with Confining σ'_3 = 250.0 kPa.
Adjust Confining σ'_3, then execute civil engineering measurement.
Civil engineering telemetry is evaluated rigorously using 64-bit IEEE 754 precision. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity structural mechanics and geotechnical continuum modeling.
Civil engineering assumptions and boundary condition limits
The civil engineering physical models apply within the specified calibrated operational window (100.0 to 400.0 kPa). Medium-stiff saturated silty clay (CL). Effective stress parameters: effective friction angle ϕ' = 28.5°, effective cohesion c' = 15.0 kPa. Stress path failure slope M = 6 sin ϕ' / (3 - sin ϕ') = 1.3500, intercept = 45.0 kPa.
Laboratory apparatus & testing equipment.
Dual Automatic Pressure-Volume Controllers (APVC)
Microprocessor syringe pumps controlling cell pressure and back pressure to 0.1 kPa and 1 mm³.
High-Accuracy Submersible Load Cell
Internal 10 kN load cell mounted inside cell to eliminate piston friction artifacts.
High-Precision Differential Pore Pressure Transducer
Measures pore-water pressure u at the base of the specimen with 0.1 kPa precision.
High-Quality Latex Rubber Membranes & O-Rings
Encloses 38 mm diameter specimen, isolating soil pore fluid from pressurized cell water.
De-Aired Water Vacuum Conditioning System
Provides dissolved-gas-free water for saturation and cell filling.
FOLLOW THE METHOD
A reason behind every step.
Determine the effective stress shear strength parameters (c', ϕ') and pore pressure parameter (A) of saturated cohesive soil using the triaxial consolidated-undrained (CU) compression test with pore pressure measurement according to ASTM D4767 / BS 1377-8. Standardized parameter settings: 100.0, 175.0, 250.0, 325.0, 400.0 kPa.
01
Specimen Mounting & Membrane Encapsulation
Mount undisturbed 38 x 76 mm saturated clay specimen on triaxial pedestal between saturated porous stones and filter paper; roll latex membrane using stretcher; seal top cap and pedestal with dual O-rings.
02
Cell Assembly & Water Filling
Lower acrylic cell chamber; tighten tie rods; fill cell completely with de-aired water; bleed air from cell top vent valve.
03
Back-Pressure Saturation & B-Check
Increment cell pressure and back-pressure simultaneously in 50 kPa stages up to back pressure of 200 kPa; close drainage valve and increase cell pressure by 50 kPa; verify B = Δu / Δσ_3 ≥ 0.95.
04
Isotropic Consolidation Stage
Open drainage valve to back-pressure controller; elevate cell pressure to target effective confining stress (100, 175, 250, 325, 400 kPa); log volume change until consolidation completes.
05
Undrained Axial Shearing with Pore Pressure Acquisition
Close drainage valve; advance loading ram at 0.05 mm/min (undrained shear); log axial load P, axial displacement ΔL, and pore water pressure u every 15 seconds.
06
Failure Envelope Evaluation
Calculate principal effective stresses σ'_1 and σ'_3 at peak deviator stress; repeat for all confining pressures; plot q_f versus σ'_3 to determine failure slope M and effective shear parameters.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into civil engineering insight.
Points are your recorded observations. The solid regression line validates Triaxial CU Shear Test mathematical scaling.
LINEAR REGRESSION FIT · y = mx + b
q_f = 1.3500 · σ'_3 + 45.0000
| # | Effective Confining Pressure σ'_3 (kPa) | Peak Deviator Stress q_f (kPa) | Effective confining pressure σ'_3 (kPa) | Peak deviator stress q_f = (σ_1 - σ_3)_f (kPa) | Remove |
|---|
No readings yet. Execute a civil engineering trial and record it.
Calculate it yourself.
CHECK YOUR UNDERSTANDING
Explain what the civil engineering metrics mean.
Skempton's pore pressure parameter B for a fully saturated soil (100% saturation) is approximately:
In a Consolidated-Undrained (CU) triaxial test, the drainage valve is:
Heavily overconsolidated clay sheared undrained typically exhibits an A-parameter at failure (A_f) that is:
The primary advantage of CU triaxial testing with pore pressure measurement is:
THEORY AND STRUCTURAL CONTEXT
Civil engineering background & physical principles.
The triaxial shear test is universally recognized as the most versatile, rigorous, and definitive laboratory method for evaluating the shear strength, pore pressure response, and stress-strain-volume constitutive behavior of soils. In contrast to direct shear box testing, the triaxial test subjects a cylindrical specimen to true axisymmetric stress states (σ_1 > σ_2 = σ_3), controls drainage independently from top and bottom boundaries, permits artificial saturation via back-pressure, and measures pore water pressure u continuously under closed undrained shear. Under ASTM D4767, the Consolidated-Undrained (CU) triaxial test proceeds in three consecutive stages: (1) Back-pressure saturation—specimen and pore lines are pressurized simultaneously while maintaining low effective stress until Skempton's B-parameter B = Δu / Δσ_3 ≥ 0.95, confirming 100% saturation; (2) Isotropic consolidation—cell pressure is elevated to target effective confining stress σ'_3 = σ_3 - u_0 with drainage valves open until excess pore pressure dissipates completely; and (3) Undrained axial shearing—drainage valves are closed, and axial deviator stress q = σ_1 - σ_3 is applied via a motorized loading ram at a controlled slow strain rate (typically 0.05% to 0.1%/min) while an electronic pressure transducer logs pore-water pressure u. Plotting peak deviator stress q_f versus effective confining pressure σ'_3 establishes the p'-q failure envelope, from which effective cohesion c' and effective friction angle ϕ' are deduced. In this laboratory, CU triaxial tests are conducted across effective confining stresses from 100 to 400 kPa to calibrate the failure slope M.
q_f = 1.3500 · σ'_3 + 45.0000
Medium-stiff saturated silty clay (CL). Effective stress parameters: effective friction angle ϕ' = 28.5°, effective cohesion c' = 15.0 kPa. Stress path failure slope M = 6 sin ϕ' / (3 - sin ϕ') = 1.3500, intercept = 45.0 kPa.