Unconfined Compression Test ASTM D-2166 /02 Experiment No. 8 Unconfined Compression Test ASTM D-2166 /02 Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Content Objective Definitions Required Apparatus Data and calculations Determination of Shear Strength Parameters Applications Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Objective Determine the shear strength of cohesive soil. Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Definitions the unconfined compression test is considered a form of triaxial test in which the major principal stress is equal to the applied axial stress and the minor principal stress is equal to zero. The unconfined compressive strength, qu, is defined as the maximum compressive stress at failure Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression REQUIRED APPARATUS Unconfined compression device (electrically driven strain-controlled device is recommended). Specimen trimmer (if undisturbed sample is tested). Remolding device (if remolded sample is tested). Dial gage for measuring axial deformation. Caliper for measuring specimen dimensions. Timer. Balance, sensitive to 0.01 g. Soil Mechanics Lab CE 350 Unconfined Compression

REQUIRED MEASUREMENTS Diameter specimen, D0 Length of specimen, L Initial moisture content, wi Final moisture content, wf Total specimen weight before testing, Wi Total specimen weight after test, Wf Vertical deformation gage reading at time, ti Proving ring reading at time, ti Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression SAMPLE PREPARATION Undisturbed Sample Remolded Sample Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Aspect Ratio 2 < H/D < 3 H/D < 3 To prevent buckling action H/D > 2 To prevent fraction between load plate and surface of specimen Soil Mechanics Lab CE 350 Unconfined Compression

DATA AND CALCULATIONS Ac = Ao/(1-Δh/Lo) qu = P/Ac Deformation. dial reading (div.) Deformation dh (mm) Load ring reading Strain (dh/h) Corrected area Axial force (P) (N) Axial stress qu (N/cm2) R1 R1*C1 R2 dh/h R2*C2 Ac = Ao/(1-Δh/Lo) qu = P/Ac Soil Mechanics Lab CE 350 Unconfined Compression

PRESENTATION OF RESULTS qu Peak Constant Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Mohr’s Circle qu qu qu Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Mode Of Failure Shapes of Specimens at Failure Brittle Failure Semi Plastic Plastic Soil Mechanics Lab CE 350 Unconfined Compression

Unconfined Compression Applications Prediction of soil behavior Estimation of bearing capacity Estimation of bearing capacity of pils Estimation of lateral earth pressure Soil Mechanics Lab CE 350 Unconfined Compression