Abstract: The ultimate axial capacity of pile is an important parameter for the design and construction of pile supported foundations, however, it is difficult to statically load the pile to failure. As a new prediction method, the gray system theory can accurately predict the ultimate axial load at pile failure and needs fewer data points. This paper presents a gray system prediction model based on the deflections of pile head under different loadings in the pile axial static load tests and its application in the ultimate load prediction for other pile axial load tests. The following conclusions can be made: Although some errors might exist, the predicted pile head deflection using the gray system model are generally consistent with the static load test results on piles with various lengths. It is also concluded that the gray system theory has a good result in predicting the ultimate pile capacity of piles.

Key words: Gray System Theory, Static Pile Load Tests, Predictions, First Oder Linear Differential Equations, Load-Settlement Curves