Study On Piled Raft Foundation By Model Tests

Piled raft foundations are ordinarily adopted for the tall buildings and heavy structures because it possesses large capacity and well performance of reducing settlements and balancing differential settlements. The load ratio between pile and raft and the settlement of foundation are the most abstruse and focal problems in design. To achieve to the design objects, it is crucial to logically estimate and quote the calculating data. A series of field model experiments in large scale has been completed on the single pile, the slab, the slab with a pile and the piled raft with a frame the stiffness of which is equivalent to the super-structure in the uniform or close stratum. The piled raft foundation includes the following combination such as, natural groundsill, equably disposed piles, varied distance of piles, varied length of piles, varied diameter of piles etc. It is found that the load ratio and the settlement distribution of piled raft foundation are related to the super-structure and the disposed piles with varied stiffness. The interactive effect coefficient of pile to soil and the shaft friction and bottom resistance of the single pile and the group of piles as the parts of foundation are discussed. The effects of pile dimension such as length, diameter and distance, upon the load ratio, differential settlements and local inclination are studied. The satisfactory combination of piles and raft has been found out in which the differential settlements "ami local inclination tire tower and the bearing capacity is sufficient for relative flexible raft foundation with the field stratum. The settlement pattern and raft contacting pressure and load in different pile measured from the test are accorded with those calculated by the mixed finite element method based on Mindlin's solution and Gedde's stress factor.