## 1 Introduction  
The purpose of a foundation beneath structures is to transfer the superstructure load to the subsoil. For the proper functioning of the foundation, it is required to design it properly to satisfy the strength and serviceability requirements. The most common types of deep foundation are the pile raft and the pile group. In the pile raft, a raft is in contact with the soil surface, while in the pile group a raft is somewhat above the soil surface. The difference between the pile group and the piled raft response has been studied in the past by a few researchers [1; 2; 3]. The first attempt to use the combination of raft and piles was reported a half-century ago by the pioneer [PERSON] [4; 5] in Mexico City. They used piled rafts for \"Tower Latino Americana\" on the compressible volcanic clay of Mexico. In a piled raft foundation, the length of piles should be long enough to exceed the stress bulb caused by the raft. The response of the pile group to lateral loading is significantly different from that of a single pile due to different interaction factors. The major interaction factors involved are the pile-pile interaction factor and the pile-to-raft factor. These factors are highly dependent on the distance between piles and reduce as the distance between the piles increases. [PERSON] et al. [6] showed that the interaction effects reduce considerably when the pile-to-pile distance is equal to 5d, where \"d\" is the pile diameter. Moreover, [PERSON] et al. [7] and [PERSON] et al. [8] concluded that pile-pile interaction can be ignored when the distance between the piles is more than 6d. In this case, the pile behavior in the pile group is the same as that of a single isolated pile. [PERSON] et al. [9] conducted a study to find the effect of the interaction factors on the response of a single pile and a pile in a pile group. [PERSON] [10] performed a test on a pile group consisting of timber piles with a length of 32 ft installed in sand. The objective was to study the group effects on the timber and concrete piles under lateral loads. The author concluded that at a large deflection the group effects are significant and recommended that at a deflection of less than 6 cm the group effects do not affect the response of the piles in a pile group. [PERSON] et al. [11] conducted pile group tests under a lateral load at the same site as [PERSON] [10] used. The result was that the maximum lateral load was resisted by the front row as compared to the trailing row, which was due to shadowing effects. [PERSON] et al. [12] performed a numerical and experimental study on a single pile and a group of 3 \(\times\) 3 and 7 \(\times\) 3 piles in the sand under loose and medium dense conditions in lateral loading. Many researchers [13; 14; 15] have worked on the vertical load analysis of the piled raft foundation. In the piled raft foundation system, the lateral loads are resisted by the piles, the passive resistance provided by the embedded structure, the frictional resistance along the embedded sides, and the frictional resistance of the raft base [16]. Some researchers have shown that the resistance offered by the embedded raft, the sides of the raft, and the base of the raft is substantial and even more than 50% of the total lateral load [9; 17; 18]. [PERSON] [17], in his work, conducted two tests on a 6-pile raft and considered only the passive resistance of the embedded pile cap. In this work, 50% of the applied horizontal load was resisted by an embedded pile cap or raft. In the same way, [PERSON] et al. [9] performed a test on a group of nine piles subjected to lateral loading and showed that the embedded pile cap lateral resistance was approximately equal to the lateral resistance of the piles. [PERSON] et al. [19] conducted experimental centrifuge (50\(\times\)_g_) tests on a piled raft and its components under horizontal load. The objective of the study was to examine the effects of the pile head connection on the response of the pile raft.