STUDY ON BEARING BEHAVIORS OF PILE TIP RESISTANCE OF SUPER-LENGTH PILES

In order to investigate the bearing behaviors of pile tip resistance, based on the field testing data of 32 piles in 15 sites, with illustration, unitary disposal method, mathematic model regression method, the mobilization behaviors of pile tip resistance with pile tip settlement for large diameter and super-length piles are studied. It is found that there exists 3 types for pile tip resistance versus pile tip settlement, that is type 1 (approximate linear increasing type), type 2 (double linear increasing type), type 3 (double linear increasing type that pile resistance having arrive at ultimate state), that three kinds of type denote that there are two types for the failure of large diameter and super-length piles, the failure of penetrating into and the failure of shearing of pile tip. The regression effect of unitary curves of pile tip resistance versus pile tip settlement with Boltzmann mathematics model is good, and the correlativity coefficients R2 are more than 0.95; the pile tip settlement is from 0.444d to 123.433d, but is from 1.00mm―40.00mm mostly when the pile tip resistance arrives at ultimate state; the pile tip resistance after pile tip grouting is more 2.5 times than the pile tip resistance before pile tip grouting. The following conclusion can be drawn that pile tip resistance cannot be ignored, and it should be utilized.