2.  Consolidation is a process by which soils decrease in volume.
 According to Karl Terzaghi "consolidation is any process which involves
decrease in water content of a saturated soil without replacement of
water by air.”
 Reduction in volume takes place by expulsion of water under long
term static loads. It occurs when stress is applied to a soil that causes
the soil particles to pack together more tightly, therefore reducing its
bulk volume.
 When this occurs in a soil that is saturated with water, water will be
squeezed out of the soil.

3. When a saturated clay is loaded externally,
GL
saturated clay
the water is squeezed out of the clay over
a long time (due to low permeability of
the clay).

4. This leads to settlements occurring over a long
time,
settlement
time
which could be several years.

5. -Lowering of the ground water table
-External static loads from structures
-Self weight of recently placed soils
-Desiccation

6.  The consolidation of a soil deposit can be divided into
3 stages :
(1) Initial consolidation
(2) Primary consolidation
(3) Secondary Consolidation

7.  When a load is applied to a partially saturated soil, a
decrease in volume occurs due to expulsion and
compression of air in the voids.
 A small decrease in volume also occurs due to
compression of solid particles .
 The reduction in volume of the soil just after the
application of the load is known as initial
consolidation.

8.  After initial consolidation, further reduction in volume
of soil mass occurs due to expulsion of water from
voids. This is known as primary consolidation.
 In fine grain soils, the primary consolidation occurs,
over a long time.
 On the other hand, in coarse grained soils , the
primary consolidation occurs rather quickly due to
high permeability .

9.  The reduction in volume continues at a very slow rate
even after the excess pore water pressure developed by
the applied pressure is fully dissipated and the primary
consolidation is complete.
 This additional reduction in the volume is known as
secondary consolidation.
 Secondary consolidation becomes important for
certain types of soil, such as peats and soft organic
clays.

10.  Process of reduction of  It is a rapid process of
volume under reduction of volume by
sustained, static loading. mechanical process such
as rolling, tamping.
 It causes reduction in  The volume of partially
volume of a saturated saturated soil decrease
soil due to squeezing out because of expulsion of
of water from soil. air from the voids at the
unaltered water content.

11.  It is a process which  It is artificial process
occurs in nature when which is done to increase
the saturated soil the density of the soil to
deposits are subjected to improve its properties
static load caused by the before it is put to any
weight of the buildings & use.
other structures.

12. Several works in the field show
that a temperature increase
induces firstly an increase of
the permeability and
secondly, for normally
consolidated states, an
irreversible contraction and a
modification of the yield limit.
These results point to the fact
that a temperature increase
could lead to an increase of the
settlement rate and an increase
of the final value of settlement.
This figure shows two kinetics of consolidation process obtained at 25
and at 60°C