consolidation settlement examples 2_solutions(2)-2

8/21/2019 Consolidation Settlement Examples 2_Solutions(2)-2

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Consolidation Settlement – Examples 2

1. The following results were recorded from a consolidation test on a sample of

saturated clay.

PressurekN/m2

Sample thicknessafter consolidation

mm

0

50

100

200

00

!00

0

25.0

2."

2.

2.2

2#.$

2#.%

2.2

The water content at the end of the test was 2#.1 & and the specific gra'ity of the soil

particles was 2."!. (alculate the 'oid ratio at the end of each pressure stage) and plot

the pressure/'oid ratio cur'e. *etermine the coefficient of compressi+ility for a

pressure range 200,#00kN/m2.

2. - flei+le foundation 10m 25m is to +e constructed at a depth of 2.0m and eerts a

gross uniform contact pressure of #00kN/m2

. The ground conditions comprise a "m

thick layer of sand on top of "m of soft clay o'erlying rockhead. The water ta+le is

#m +elow ground le'el. The saturated unit weights of the sand and clay are 20kN/m#

and 22kN/m# respecti'ely. rom the results of la+oratory tests on samples of the clay

u 253N/m2 and m' %10

,2 m2/3N.

(alculate the final settlement of the foundation at its plan centre due to the elastic and

the consolidation compression of the clay layer.

4ou can assume that the clay layer undergoes 1,* consolidation and the sand a+o'e

the water ta+le is fully saturated. Stein+renners (hart and adums (hart apply.

#. - le'el site has .5m of granular material o'erlying a 1.0m thick layer of normally

consolidated clay) which) itself) o'erlies +edrock. The water,ta+le is at ground le'el.

6n order to utilise the area) the ground,water is permanently lowered +y 2.0m using

land drainage. Su+se7uently) 1.5m of imported fill material is placed o'er the wholesite. The following properties ha'e +een determined from site in'estigation8

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9ranular8 :ulk unit weight ;a+o'e g.w.l< 1!.5kN/m#

;+elow g.w.l< 20.0kN/m#

(lay8 :ulk unit weight 21.5kN/m#

6nitial moisture content 2!&

Particle specific gra'ity 2."5

(ompression 6nde 0.2

6mported ill8 :ulk unit weight 1%.0kN/m#

(alculate the ultimate consolidation settlement of the clay layer which can +e

anticipated from the operation.

. - sample of normally consolidated clay ga'e the following results when su+=ected toa consolidation test) each loading increment was maintained for 2,hours.

Pressure

kN/m2

Sample thickness

mm

0 1%.#2

5 1".!

10! 1".!

21" 1".1!

#2 15.!5

0 1".51

-fter the sample had +een allowed to swell its moisture content was determined as

#0.2&. The particle specific gra'ity was 2."5.

a< Plot the cur'es of the 'oid ratio 'ersus effecti'e stress and the 'oid ratio 'ersuslog10;effecti'e stress and)

ii. +y the compression inde.

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SOLUTIONS

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consolidation settlement examples 2_solutions(2)-2

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