Geotechnical Engineering

DHARM

410 GEOTECHNICAL ENGINEERING

base of the foundation and decreases with depth in a curvilinear fashion based on the theory

used.

This concept will again be used in the determination of the depth of exploratory borings

(Chapter 18).

Dr

gh

z

h

Unit wt.

of soil :g q

G.S.

Dn=5

Stress distribution due to

self-weight of soil

20% stress line

Stress distribution due to

load from superstructure

(Active zone)

q

Fig. 11.11 Active zone in soil due to loading (Jumikis, 1962)

If several loaded footings are placed closely enough, the isobars of individual footings

would combine and merge into one large isobar of the same intensity, as shown in Fig. 11.12.

bbbb

qqqq

Dn=5»1.5 B

dn=5»1.5 b

B

Individual

isobars

0.2 q

Combined

Isobar

0.2 q

G.S.

Fig. 11.12 Merging of closely-spaced isobars into one large isobar of the same intensity,
reaching far deeper than the individual isobars (Jumikis, 1962)
The large isobar reaches about Dn = 5 ≈ 1.5B below the base of the closely spaced footings,
where B is the overall width between the extreme footings.
This concept will again be referred to in chapter 16 with regard to the settlement of a
closely spaced group of friction piles.