settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

2. Meyerhof(l956,!965,1974)
3. DeBeer (1965)
4. Thomas (1968)
5. Schmertmann (1970)
6. Berardi et al. (1991)
7. Robertson (1991)
5.3.1 DeBeer and Martens (1957)
The method presented by DeBeer and Martens (1957) and also described by DeBeer (1965)
is based on the semi-empirical Terzaghi-Buisman formula for calculating settlements:
S = (2.3/C) log [(p' 0
+ Ap')/p'oJ H
[5.88]
where:
s = settlement
C =constant of compressibility
p'o = effective overburden stress
ll.p' = increment of stress at depth due to the footing stress
H = thickness of the layer
Settlement from individual soil layers can be calculated and then summarized to give the total
settlement.
The constant of compressibility, C, is obtained from the CPT tip resistance, q" as:
C = 1.5 qjp'o [5.89]
The method was intended to provide a "safe upper limit of settlements" and compared with the
settlements of several bridge abutments and piers generally gave estimates of about 2 times the
observed settlement.
The value of ll.p' is obtained from Bousinesq stress distribution charts. The maximum depth
of the zone of influence may be taken as the depth below the foundation to which the change in
vertical effective stress equals 1 0% of the applied surface stress.
If the cone tip resistance, q" is constant with depth, it is suggested to use the Boussinesq
equation to determine Ap' as:
Ap' = (3q cos 5 8)/211z 2 [5.90]
If q, increases with depth, use the Buisman equation to determine Ap' as:
95