Abstract: The lateral resistance of the piles in saturated soft soil is important to the stability of tall and large span buildings and other structures. This paper presents three-dimensional numerical analysis results of pile foundations in the vacuum preloading improved mucky silty soft soils. The soil-structure interaction effect was considered in the analysis and the lateral loaded piles in soft soils before and after the preloading were compared. The results indicate that, when a pile in original soft soils under different lateral load, the lateral pile deformation patterns were similar: the point of zero shear is 2～3 meters below the ground. Larger lateral loading results in a larger stress in the pile and the lateral load influence depth is between 0 and 15 meters. When a pile in the vacuum preloading improved soil, with the increase of the soil improvement (limited to 10 meters), the lateral resistance of pile increases with the depth of soil improvement. However, when the soil improvement depth is greater than the limiting depth, the increment of the lateral resistance gradually reduces. Therefore, the improvement depth should be appropriately determined for a cost-effective construction.

Key words: Vacuum Preloading, Lateral Resistance, Foundation Pile, Characteristic Values, Numerical Analysis