# Experimental Analysis of the Behaviour of Piled Raft Foundations in Loose Sand
## 3 Results and Discussion
### Piled Raft  
Within this experiment, load distribution between raft and piles, when the model was driven into loose sand, was analysed. Figures 20-32 show \"force-displacement\" graphs of the piled raft for pile lengths of L/d = 40, 20, 10, which is often applicable in practice. The experiment was performed for pile distances of 3d, 4d, and 5d. The same layout was investigated by [PERSON] and others [63] in their experiments. From the graphs shown, it can be observed that, when settlement increases, the raft is activated, and, as the settlement  
Figure 19: Load bearing curves for rafts without piles.  
Figure 18: Raft model 84 \(\times\) 84 \(\times\) 10 mm prior to driving it into the soil.  
further increases, the part of the force carried by the raft also increases. The final settlement criterion was defined to be a settlement of 0.1B, measured from the moment when the raft makes contact with the sand. The graphs show the portion of the load taken by the raft.  
Figures 20 and 21 show the \"force-displacement\" graphs, i.e., \"load bearing capacity-settlement\", for piles with a length of 40d at a distance of 3d. The results show that, if a value of 0.1B is chosen for limit settlement, measured from the moment the raft touches the soil (here, approximatively 7 mm), the piles carry 76% of the total load.  
Figures 22 and 23 show the \"force-displacement\" graphs, i.e., \"load bearing capacity-settlement\", for piles with a length of 20d at a distance of 3d. The results show that, if a value of 0.1B is chosen for limit settlement, measured from the moment the raft touches the soil (here, approximatively 7 mm), the piles carry 72% of the total load.  
Figures 24 and 25 show the \"force-displacement\" graphs, i.e., \"load bearing capacity-settlement\", for piles with a length of 10d at a distance of 3d. The results show that, if a value of 0.1B is chosen for limit settlement, measured from the moment the raft touches the soil (here, approximatively 7 mm), the piles carry 74% of the total load.  
Figure 26: Diagram \"force-displacement\" of piled raft L/d = 40, e/d = 4.  
Figure 27: Load distribution graph for the group of 4 piles with 40d length at the distance of e = 4d.  
Figures 28 and 29 show the \"force-displacement\" graphs, i.e., \"load bearing capacity-settlement\", for piles with a length of 20d at a distance of 4d. The results show that, if a value approximatively 8 mm is chosen for limit settlement, the piles carry 55% of the total load.  
Figures 30 and 31 show the \"force-displacement\" graphs, i.e., \"load bearing capacity-settlement\", for piles with a length of 10d at a distance of 4d. The results show that, if a value approximatively 8 mm is chosen for limit settlement, the piles carry 58% of the total load.  
Figure 32 shows the \"force-displacement\" graphs for piles with a length of 40d at a distance of 5d. The results show that, if a value of approximatively 9 mm is chosen for limit settlement, the piles carry 53% of the total load.  
Previous diagrams show that, when designing piled raft foundations, the calculation should not be based on the required number of piles that should accept the entire load but on the number of piles needed to reduce the settlement to the allowable limits.  
[PERSON] [34] presented the measurement results of a load distribution mechanism for the Messe-Torhaus building in Frankfurt, 30 floors high and 130 m high. The building has a piled raft foundation, with raft dimensions of 24.5 \(\times\) 17.5 m and pile spacing of about 3d. The established load distribution was such that about 25% of the total load was taken over by the raft, which corresponds to measurements obtained in this paper for the pile spacing of 3d. [PERSON] [64] analysed the foundations of the ICC shopping centre in Hong Kong, one of the ten tallest buildings in the world, by means of numerical analysis with PLAXIS software and obtained that 30% of the total load is carried by the raft, which also corresponds to the range of measured results obtained by this experiment.