# Experimental Analysis of the Behaviour of Piled Raft Foundations in Loose Sand
## 4 Conclusions  
Based on experimental results, the following conclusions were reached:  
1. Application of small-scale 1g models for pile bearing capacity estimation in loose sand is justified for this research because there is no significant scale effect that could originate from the curved strength envelope for dense sand.  
Figure 41: Load bearing capacity of piled rafts and rafts without piles for different pile lengths and piles at a distance of 5d.  
Figure 40: Load bearing capacity of piled rafts and rafts without piles for different pile lengths and piles at a distance of 4d.  
2. For the same external force, a raft with smaller contact area, i.e., smaller e/d ratio, and smaller pile slenderness (L/d) has higher settlements.
3. For the same external force and same e/d ratio, an increase in pile slenderness ratio L/d reduces settlement of the raft.
4. The scientific contribution of this paper is showing that the influence of scale effect on estimation of pile bearing capacity in loose sand that has a constant value of the angle of shearing resistance is negligible. In other words, application of 1g models on assessment of the bearing capacity of piles in loose sand is not essentially related to the size of the model. By contrast, in dense sand, the shear resistance envelope is curved. This means that the mobilized angle of shearing resistance at smaller pile dimensions is smaller; i.e., the average normal stress is lower and vice versa, or, in other words, the scale effects become significant.
5. Piled raft foundation systems with smaller contact surfaces at the same load levels have higher settlements than systems with larger contact surfaces; the increase in the raft contact surface improves the load bearing capacity of the piled raft foundation system at the same settlement values. This improvement in performance is caused by the horizontal pressures in the soil beneath the raft, which increase the friction between the soil and the pile surface, therefore increasing the load bearing capacity of the whole piled raft foundation system.
6. When driving in a group of piles, as soon as the raft makes contact with the sand, the raft is activated, and its load bearing contribution increases as settlement increases.
7. For the case of raft settlement at a value of 0.1B, where B is the width of the pile, depending on the distance between the piles, the pile carries about 24% to 50% of the total load acting on the foundation system.
8. The length of the piles does not play a significant role in the distribution of the load between the raft and the piles.
9. For the pile spacing of 3d, the pile group effect is very pronounced, while, as the spacing increases, the pile group effect decreases. It was concluded that the pile spacing of 5d represents the upper boundary value, after which the pile group effect contribution to the load bearing capacity is lost.  
N.B.--writing--original draft preparation; I.D.--supervision, review, editing; D.K.--methodology, review, editing. All authors have read and agreed to the published version of the manuscript.  
The publication of this research was supported by the company \"Construction Center Ltd.\" from Subotica, Serbia.  
Not applicable.  
The paper presents the results of an experiment conducted for the purpose of writing a doctoral thesis by [PERSON], which has not yet been published. We thank [PERSON] and [PERSON] for their cooperation and donated measuring equipment for the experiment.  
The authors declare no conflict of interest.