Calculation of 1-D Consolidation Settlement

Calculation of 1-D Consolidation Settlement

? A general theory for consolidation, incorporating three- y dimensional flow is complicated and only applicable to a very limited range of problems in geotechnical engineering.

? A simplification for solving consolidation problems, drainage and deformations are assumed to be only in the vertical direction. q kPa GL Sand

x z

z

water squeezed out

saturated clay Sand

reasonable simplification if the surcharge is of large

lateral extent

Calculation of 1-D Consolidation Settlement

The consolidation settlement can be determined knowing: - Initial void ratio e0. - Thickness of layer H - Change of void ratio e

It only requires the evaluation of e

Calculation of 1-D Consolidation Settlement

Settlement Calculation

Sc H Ho H f (h1 h2)

Sc

(h1

h2)

H H

o o

Sc

(

h1 hs

h2)H h1

Sc

(

(h1 (hs

h2) h1)

/ /

hs hs

)H

H

h1

Ho hs

Voids S=100% h2 Solids hs

Hf Solids

Sc

(

eo ef 1 eo

)H

Sc

e 1 eo

H

It only requires the evaluation of e

One-dimensional Laboratory Consolidation Test

? 1-D field consolidation can be simulated in laboratory.

? Data obtained from laboratory testing can be used to predict magnitude of

consolidation settlement reasonably, but rate is often poorly estimated.

Wide foundation GL

Saturated clay field

simulation of 1-D field consolidation in Lab

Sand or Drainage layer

porous stone

Undisturbed soil specimen

metal ring (oedometer)

lab

One-dimensional Laboratory Consolidation Test

The one-dimensional consolidation test was first suggested by Terzaghi. It is performed in a consolidometer (sometimes referred to as oedometer). The schematic diagram of a consolidometer is shown below.

The complete procedures and discussion of the test was presented in CE 380.

Consolidometer or Oedometer

Dial gauge

Load

Water

Porous stone Soil specimenSpecimen ring

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