Characters Of High-rise Building Static Pressure Pile Foundation Work

A high-raised building in Zhengzhou, central China, with Press-in Pile (PIP) Foundation is chosen as the specimen, so the specimen is full scaled, and the measurements are accomplished in-situ. The in-between piles (IBEP) soil settlements in different depth in the foundation are obtained in the 22 months course of construction, since the casting of cushion until the finish of whole building, even to the stable settlement stage of the building. After the analysis on PIP foundation working mechanism, deformation characteristics, the profile of affixation stress of IBEP soil, the stress ratio of pile to IBEP soil, some important conclusions are drawn as following.1. For a typical composite foundation, the stress ratio of pile to IBEP soil varies between 3-20. However, the maximum one for PIP foundation is smaller than the one of typical pile foundation, and is bigger than that of composite foundation. The testing results show that the mechanism of PIP foundation is a hybrid one of traditional pile foundation and composite foundation. So, for PIP foundation, the analysis and design may be carried out according to the algorithm of composite foundation.2. The in-situ full scale experiment shows the following tendency. For nature soil, the profile of affixation stress is that the maximum is on the upper surface, and it decreases with the depth increases. However, for PIP foundation, the affixation stress in IBEP soil is much more complicated. On the upper surface of reinforced scope, the stress is rather small, and it increases with the increasing of depth, and the maximum comes into being at the bottom surface of reinforced scope. Then, the stress decreases with the increasing of depth.3. At the initial stage of loading, the stress ratio of pile to IBEP soil is developing linearly. Then, when the load is great enough, the increasing trend turns into horizontal one and even decreasing. The phenomenon shows the function of cushion layer.4. The settlement calculation algorithm for composite foundation may be employed to determine the final accumulated settlement of PIP foundation. Some empirical coefficients for local application are suggested.5. When the main structure on PIP foundation is accomplished, the settlement may be 70-80% of the final accumulation one.For more general conclusions, the Finite Element Method has to be used to check the results of in-situ testing ones.