Soil Mechanics Lab CE 350 Unconfined Compression 1 Experiment No. 8 Unconfined Compression Test /02 ASTM D-2166 /02

Soil Mechanics Lab CE Soil Mechanics Lab CE 350350 Unconfined CompressionUnconfined Compression 11

Experiment No. 8Experiment No. 8

Unconfined Compression TestUnconfined Compression TestASTM D-2166 /02 /02



ContentContent

ObjectiveObjective DefinitionsDefinitions Required ApparatusRequired Apparatus Data and calculationsData and calculations Determination of Shear Strength Determination of Shear Strength

Parameters Parameters ApplicationsApplications


ObjectiveObjective

Determine the shear strength of Determine the shear strength of cohesive soil. cohesive soil.


DefinitionsDefinitions

the unconfined compression test is considered a the unconfined compression test is considered a form of triaxial test in which the major principal form of triaxial test in which the major principal stress is equal to the applied axial stress and the stress is equal to the applied axial stress and the minor principal stress is equal to zero.minor principal stress is equal to zero.

The unconfined compressive strength, qu, is The unconfined compressive strength, qu, is defined as the maximum compressive stress at defined as the maximum compressive stress at failure failure


REQUIRED APPARATUSREQUIRED APPARATUS Unconfined compression device (electrically Unconfined compression device (electrically

driven strain-controlled device is recommended). driven strain-controlled device is recommended). Specimen trimmer (if undisturbed sample is Specimen trimmer (if undisturbed sample is tested).tested).

Remolding device (if remolded sample is tested).Remolding device (if remolded sample is tested). Dial gage for measuringDial gage for measuring axial deformation.axial deformation. Caliper for measuring Caliper for measuring specimen dimensions.specimen dimensions. Timer.Timer. Balance, sensitive to 0.01 g.Balance, sensitive to 0.01 g.


REQUIRED MEASUREMENTSREQUIRED MEASUREMENTS

Diameter specimen, DDiameter specimen, D00

Length of specimen, LLength of specimen, L Initial moisture content, wInitial moisture content, wii

Final moisture content, wFinal moisture content, wff

Total specimen weight before testing, Total specimen weight before testing, WWii

Total specimen weight after test, Total specimen weight after test, WWff

Vertical deformation gage reading at time, tVertical deformation gage reading at time, tii

Proving ring reading at time, tProving ring reading at time, tii


SAMPLE PREPARATIONSAMPLE PREPARATION

Undisturbed SampleUndisturbed Sample Remolded SampleRemolded Sample


Aspect RatioAspect Ratio

2 < H/D < 32 < H/D < 3 H/D < 3 To prevent buckling actionH/D < 3 To prevent buckling action H/D > 2 To prevent fraction between H/D > 2 To prevent fraction between

load plate and surface of specimenload plate and surface of specimen


DATA AND CALCULATIONSDATA AND CALCULATIONSDeformation

. dial reading(div.)

Deformation dh (mm)

Load ring

reading(div.)

Strain(dh/h)

Corrected area

Axial force (P) (N)

Axial stress qu (N/cm2)

R1R1 R1*C1R1*C1 R2R2 dh/hdh/h R2*C2R2*C2

Ac =

Ao/(

1-Δ

h/L

o)

qu =

P/A

c


PRESENTATION OF RESULTSPRESENTATION OF RESULTS

Strain

Ax

ial S

tre

ss

Semi plastic

Stiff Clay

Plastic

Peak

Constant

qu


Mohr’s CircleMohr’s Circle

Normal Stress

Shear Stress

Failure EnvelopCu

qu

qu

qu

00

0

0


Mode Of FailureMode Of FailureShapes of Specimens at FailureShapes of Specimens at Failure

Semi PlasticSemi Plastic PlasticPlasticBrittle FailureBrittle Failure


ApplicationsApplications

Prediction of soil behaviorPrediction of soil behavior Estimation of bearing capacityEstimation of bearing capacity Estimation of bearing capacity of pilsEstimation of bearing capacity of pils Estimation of lateral earth pressureEstimation of lateral earth pressure

Documents

Soil Mechanics Lab CE 350 Unconfined Compression 1 Experiment No. 8 Unconfined Compression Test /02 ASTM D-2166 /02