CONSOLIDATION SETTLEMENT FOR CLAYS

PrePre--Consolidation PressureConsolidation Pressure

log Vv

void

rat

io

Vppreconsolidation pressure

is the maximum vertical

effective stress the soil element has ever been subjected to

Oedometer test to get Cc and Cs values

Expulsion of water from soils accompanied by increase in effective stress and strength

Amount can be reasonably estimated in lab, but rate is often poorly estimated in lab

Only partially recoverable

Primary ConsolidationPrimary Consolidation

Secondary CompressionSecondary Compression

Creep phenomenon No pore pressure change Commences at completion of primary

consolidation cD/Cc | 0.05

ccDD = = ''ee

log log ((tt2 2 / t/ t11))

Terminology for ConsolidationTerminology for Consolidation

Preconsolidation stress (pressure)The maximum effective stress which has been The maximum effective stress which has been

applied to an element of soilapplied to an element of soil

OverconsolidatedA soil is called A soil is called overconsolidatedoverconsolidated (OC) if:(OC) if:

Normally consolidatedA soil is called normally consolidated (NC) if:A soil is called normally consolidated (NC) if:

Current Effective StressCurrent Effective Stress PreconsolidationPreconsolidation StressStress