Geotechnical Engineering

DHARM

COMPRESSIBILITY AND CONSOLIDATION OF SOILS 241

Example 7.2: A sand fill compacted to a bulk density of 18.84 kN/m^3 is to be placed on a
compressible saturated marsh deposit 3.5 m thick. The height of the sand fill is to be 3 m. If the
volume compressibility mv of the deposit is 7 × 10–4 m^2 /kN, estimate the final settlement of the
fill. (S.V.U.—B.E., (N.R.)—March-April, 1966)
Ht. of sand fill = 3 m
Bulk unit weight of fill = 18.84 kN/m^3
Increment of the pressure on top of marsh deposit ∆σ = 3 × 18.84
= 56.52 kN/m^2
Thickness of marsh deposit, H 0 = 3.5 m
Volume compressibility mv = 7 × 10–4 m^2 /kN
Final settlement of the marsh deposit, ∆H
= mv.H 0 .∆σ
= 7 × 10–4 × 3500 × 56.52 mm
= 138.5 mm.

Example 7.3: The following results were obtained from a consolidation test:

Initial height of sample Hi = 2.5 cm

Height of solid particles Hs = 1.25 cm

Pressure in kN/m^2 Dial reading in cm

0 0.000

13 0.000

27 0.004

54 0.016

108 0.044

214 0.104

480 0.218

960 0.340

1500 0.420

Plot the pressure-void ratio curve and determine (a) the compression index and (b) the
preconsolidation pressure. (S.V.U.—B.E., (R.R.)—Dec., 1968)

Initial void ratio, e 0 =

()(.. )

.

.

.

HH

H

is

s

−

−

−

=

250 125

125

125

125 = 1.000