geotek draft.pptx

7/21/2019 GEOTEK DRAFT.pptx

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CONSOLIDATION

TEST



Consolidation Settlement• It occurs due to the process of the consolidation.

•

Clay and Organic soil are most prone to consolidationsettlement.

• Consolidation is the process of reduction in volumedue to lost of water under an increased load.

• It is a time related process occurring in saturated soil

by draining water from void.

• It is often confused with Compaction.

• Consolidation theory is required to predict both rateand magnitude of settlement.



What is Consolidation?• When a saturated soil is loaded externally the

water is squee!ed out of the soil and the soil

shrin"s.



Concept of Consolidation• #s the time passes the water comes out of the

soil void and so the volume of soil decreases thisis cause of the settlement.

The decrease in volume of soil = The volume ofsqueezed out water



Settlement due toconsolidation

• Settlement is the vertically downward movementof structure due to the shrin"age in volume of

soil due to consolidation



Settlement$%oid ratio&elation

• 'quating the two expression for average vertical

strain



Settlement vs. (ime

• (his leads to settlement occurring over a long timewhich could be several years depending upon the

permeability of the soil



Oedometer test

•(he soil characteristics during one$dimensionalconsolidation or swelling can be determined bythe oedometer test.

• #n oedometer test measures asoil*s consolidation properties.

•Oedometer tests are performed by applyingdi+erent loads to a soil sample and measuring

the deformation response.•(he results from these tests are used to predicthow a soil in the ,eld will deform in response toa change in e+ective stress.



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Concept

• Oedometer tests are designed to simulate the one$dimensional deformation and drainage conditions that

soils experience in the ,eld.• (o simulate these conditions rigid con,ning rings are

used to prevent lateral displacement of the soil sample.

• 1orous stones are placed on the top and bottom of thesample to allow drainage in the vertical direction.

• (o better simulate one$dimensional strain a diameter$to$height ratio in the sample of 345 or more is used. 6ecausethe process of consolidation involves movement of waterout of a soil it is important to prevent drying of the soil



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CO'88ICI'2( O8 CO2SO9I-#(IO2

• (here are two methods for determining the coe+icientof consolidation4

i. Casagrande or log :time; or <=> consolidationii. (aylor or time or @=> consolidation

• (he coe+icient of consolidation can be determined bythis equation



(aylor method



Casagrande method



&esult 'xample

geotek draft.pptx

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