Technical Paper by A. Fakher and C.J.F.P. Jones WHEN THE ...

FAKHER & JONES • When Bending Stiffness of Geosynthetic Reinforcement is Important
ing capacity ratio (Figure 6). The bearing capacity ratio is defined as the ratio between
the bearing capacity of reinforced ground and the bearing capacity of the same case
without reinforcement. When D/B is small, the increase in the bearing capacity ratio,
due to bending stiffness, is significant. As the D/B ratio increases, the influence of the
bending stiffness of the reinforcement diminishes.
The deformed shape of geosynthetic reinforcements for different ratios of D/B is
shown in Figure 7. The maximum heave of the reinforcement modelled as a cable is
located close to the footing when values of D/B are small. When the value of D/B
increases, the reinforcement bending stiffness has little effect on the deformed shape
and the deformation of the reinforcement, modelled as a beam or a cable, are similar.
3.3 Effect of Size of Footing
The width of the footing, B, was varied to investigate the relative influence of the reinforcement
on the behaviour of footings of different dimensions. When, B, increases,
the effect of the reinforcement bending stiffness decreases sharply (Figure 8). This
conforms with the findings of a dimensional analysis study on model loading tests
(Fakher et al. 1996).
The effect of footing width, B, on the deformed shape of the reinforcement is
shown in Figure 9. The location of the point of maximum heave depends on the size of
the footing when cable elements are used in the analysis. This is not apparent when
beam elements are used to model the reinforcement.
3.4 Effect of the Yield Stress of Clay
A series of analyses were performed to investigate the influence of the shear strength of
the underlying clay, C, on the bearing capacity. As expected, the bearing capacity
increases when C increases. An interesting observation is that the positive effect of bend-
3.5
Bearing capacity ratio
3.0
2.5
2.0
1.5
1.0
No reinforcement
Beam element
Cable element
I = 7.64 e-7
s /B = 0.3
Figure 6.
0.5
0.0 0.5 1.0 1.5 2.0 2.5
D/B
The effect of D/B on the bearing capacity ratio.
452 GEOSYNTHETICS INTERNATIONAL • 2001, VOL. 8, NO. 5