Geotechnical Engineering

(Jeff_L) #1
DHARM

SHALLOW FOUNDATIONS 615


2.

Firm clay or silty clay
extending to great depth

Df > frost depth and zone of
swelling and shrinkage

Spread footings most appro-
priate for conventional
needs. Piles may be used
only if unusual forces such
as uplift are expected.
3.

Soft clay extending to great
depth

Df > frost depth and zone of
swelling and shrinkage

Spread footing appropriate
for low or medium loading,
if not too close to soft clay.
Deep foundations may be
required for heavy loading.

4.

Loose sand extending to
great depth

Df > frost depth and depth of
erosion

Spread footings may settle
excessively. Raft founda-
tion may be appropriate.
Spread footings may be
used if the sand is com-
pacted by vibrofloatation.
Driven piles or augered
cast-in-place piles may also
be used.
5.

or

Soft clay but firmness in-
creasing with depth extend-
ing to great depth

Friction piles or piers would
be satisfactory if some set-
tlement could be tolerated.
Long piles would reduce
settlement. Raft foundation
or floating foundation may
also be considered.


  1. Deep foundation-piles,
    piers, caissons—bearing di-
    rectly on/in the rock.


××

7.

Hard clay extending to
great depth

Spread footings in upper
sand layer would probably
experience large settlement
because of underlying soft
clay layer. Drilled piers
with a bell formed in the
hard clay layer, or other pile
foundation may be consid-
ered.

(Contd.)...

3 m Firm clay

Df
or

7.5m (Soft)

7.5 m (Medium)
(firmer)

20 m Soft clay

Rock

2.5 m Compact sand

3.5 m Medium clay

Df

Df
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