Analysis of design method of large diameter and over length caisson pile

Static tests and calculating bearing capacity and settlement of largediameter and overlength caisson pile are carried out; and design method is discussed. The Q-S curve of large diameter and overlength caisson pile doesn’t have apparent characteristic point, it is slow transformation .The settlement of the pile head is composed of the elastic compression of pile body, the compression of the soil below the pile tip by the load from the pile stem and pile tip. It is shown that the bearing force of largediameter and overlength caisson pile can be determined by displacement control method. Usually, the design bearing capacity is the test load when the pile head’s settlement is one percent of its diameter. Elastic compression of pile body has a great influence on pile settlement, the calculated pile settlement by elastic method is bigger than that of test, and the settlement from static tests should be adopted when designing.