Abstract: In some projects there are restrictions in static loading tests and thus the characteristic load bearing capacity is unable to be determined. Through analyzing a project of cement-soil pile composite foundation, the ultimate bearing capacity of the piles and composite foundation is predicted with “gray model” under limited test conditions. Meanwhile, the ratio of the bearing capacity to the characteristic bearing capacity determined from relative deformation is defined as safety reserve index “K”, and 113 groups of static loading test are analyzed to obtain the K value of this region. The statistical result is confirmed by the project. It should be noticed that K is a regional and experiential value, and it can be used to predict the ultimate bearing capacity of cement-soil pile composite foundation based on the known bearing capacity determined by relative deformation.

Key words: cment-soil piles, static loading test, bearing capacity of composite foundation, safety reserve, gray model