Model Experimental Research on Machanical Characteristics of Large Diameter Overlength Pile-group Foundation in Loess
黄土地基中大直径超长群桩基础受力特性的模型实验研究

By means of indoor model experiment, the bearing-settlement relation of the large diameter overlength pile group foundation in loess, the soil additional stress distribution and development under pile cap, the pile and soil's bearing, the mechanical characteristics of pile at different positions were studied respectively. Results show that the load-settlement curve of large diameter overlength pile group foundation in loess presents a mild change type and has no obvious inflexion. Therefore the ultimate bearing capacity of pile group foundation should be determined by settlement-time logarithm s-lgt curve and load-settlement Q-s curve integratedly. The distribution of soil additional stress under pile cap is big on the edge and small at the center. The bearing behavior of pile at different positions is various: as a whole, the corner pile (6#pile) is the biggest, the side pile (5# pile) takes second place, the center pile (1# pile) is the minimum. Meanwhile, the side friction resistance and axial stress of each pile change diversely along the pile length.