Motorized Unconfined Compression Testing Machine
Applies constant vertical strain rate (0.5 to 2.0 mm/min) with electronic load cell monitoring force P.
Civil Engineering / Unconfined Compression Test
FREE TO EXPLORELABORATORY 23 · CIVIL ENGINEERING
Unconfined Compressive Strength & Undrained Shear Strength of Cohesive Soil
Determine the unconfined compressive strength (q_u), undrained shear strength (c_u), and stress-strain deformation modulus (E_u) of undisturbed and remolded cohesive soil according to ASTM D2166 / AASHTO T208. Explore interactive structural mechanics, materials simulation, and civil engineering telemetry.
STRUCTURAL MATERIALS · MECHANICS · GEOTECHNICAL · HYDRAULICS · HIGHWAYS · SURVEYING
Your virtual civil engineering laboratory.
AXIAL DEVIATOR STRESS Σ_D—
CIVIL INFRASTRUCTURE TELEMETRY
Ready to sample with Axial Strain = 3.0 %.
Adjust Axial Strain, 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 (1.0 to 6.0 %). Undisturbed silty clay specimen (diameter D_0 = 38.0 mm, length L_0 = 76.0 mm). Peak UCS q_u = 171.0 kPa, undrained shear strength c_u = q_u / 2 = 85.5 kPa. Linearized initial elastic response relates deviator stress σ_d to strain ε with slope 28.5000 kPa/% (E_u = 2.850 MPa).
Laboratory apparatus & testing equipment.
Precision Electronic S-Type Load Cell
Measures compressive force up to 5.0 kN with 0.5 N resolution and digital display.
Digital Linear Displacement Transducer (LVDT)
Measures vertical axial specimen deformation ΔL to 0.001 mm precision.
Soil Specimen Trimming Lathe & Wire Saw
Trims cylindrical specimens to exact 38.0 mm diameter and 76.0 mm height.
Precision Vernier Calipers & Analytical Balance
Measures specimen diameter, length, and wet weight to 0.01 mm and 0.01 g.
Thermostatic Drying Oven
Maintains 110 ± 5 °C for post-test moisture content determination.
FOLLOW THE METHOD
A reason behind every step.
Determine the unconfined compressive strength (q_u), undrained shear strength (c_u), and stress-strain deformation modulus (E_u) of undisturbed and remolded cohesive soil according to ASTM D2166 / AASHTO T208. Standardized parameter settings: 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 %.
01
Specimen Trimming & Dimensional Verification
Trim an undisturbed cohesive soil core to 38.0 mm diameter and 76.0 mm height (L/D = 2.0) on the soil lathe; measure diameter at ends and middle; record initial length L_0 and mass M_0.
02
Platen Alignment & Machine Centering
Place specimen centrally on lower platen of the UCS machine; raise platen until upper spherical bearing platen just makes contact; zero load cell and LVDT channels.
03
Strain-Controlled Axial Compression
Engage motorized drive at a constant deformation rate of 1.0 mm/min (~1.3% strain/min); record compressive load P and axial deformation ΔL at 15-second intervals.
04
Cross-Sectional Area Correction
Calculate axial strain ε = ΔL / L_0; compute corrected cross-sectional area A = A_0 / (1 - ε) at each interval assuming constant specimen volume.
05
Failure Point Identification
Continue loading until compressive load P peaks and begins dropping, or until axial strain reaches 15%; record peak load P_max and unconfined compressive strength q_u.
06
Fracture Angle Inspection & Moisture Testing
Sketch failure mode (single diagonal shear plane vs bulging barrel); measure shear failure angle θ; dry specimen in oven at 110 °C to determine moisture content w.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into civil engineering insight.
Points are your recorded observations. The solid regression line validates Unconfined Compression Test mathematical scaling.
LINEAR REGRESSION FIT · y = mx + b
σ_d = 28.5000 · ε
| # | Axial Compressive Strain ε (%) | Axial Deviator Stress σ_d (kPa) | Axial strain ε (%) | Axial compressive stress σ_d (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.
For saturated clay tested in unconfined compression, undrained shear strength c_u is related to peak compressive strength q_u by:
The standard length-to-diameter (L/D) aspect ratio for an unconfined compression soil specimen is:
If initial area is A_0 and axial strain is ε, the corrected cross-sectional area A during undrained compression is:
A soil with a sensitivity ratio S_t of 10 is classified as:
THEORY AND STRUCTURAL CONTEXT
Civil engineering background & physical principles.
The Unconfined Compressive Strength (UCS) test provides the most rapid, economical, and widely used laboratory method for determining the undrained shear strength (c_u) of cohesive fine-grained soils. Standardized under ASTM D2166, the test is a special limiting case of the unconsolidated-undrained (UU) triaxial compression test where confining cell pressure is zero (σ_3 = 0). A cylindrical undisturbed cohesive soil specimen (typically 38 mm or 50 mm diameter, with standard length-to-diameter aspect ratio L/D = 2.0 to 2.5) is mounted between flat end platens and loaded axially in compression without lateral lateral restraint. Loading is applied at a rapid strain rate of 0.5% to 2.0% per minute so that testing is completed within 10 to 15 minutes, ensuring that zero water can drain from low-permeability clay pores (undrained condition). As axial compressive force P increases, axial strain ε = ΔL / L_0 increases, and cross-sectional area expands from initial area A_0 to corrected area A = A_0 / (1 - ε). Deviator stress σ_d = P / A rises to a peak unconfined compressive strength q_u. According to the Mohr–Coulomb failure criterion for total stress with friction angle ϕ_u = 0, the Mohr circle passes through the origin (σ_3 = 0) and has diameter q_u. Consequently, the undrained shear strength is exactly half the unconfined compressive strength: c_u = q_u / 2. In this laboratory, cohesive soil specimens are tested across axial strains from 1% to 6% to calibrate the undrained modulus E_u and evaluate undrained shear strength c_u.
σ_d = 28.5000 · ε
Undisturbed silty clay specimen (diameter D_0 = 38.0 mm, length L_0 = 76.0 mm). Peak UCS q_u = 171.0 kPa, undrained shear strength c_u = q_u / 2 = 85.5 kPa. Linearized initial elastic response relates deviator stress σ_d to strain ε with slope 28.5000 kPa/% (E_u = 2.850 MPa).