Calculating Methods For The Settlement Of Pile Foundation Based On Energy Conservation Law

Pile foundation is widely used in civil engineering with much its advantages such as large bearing capacity, small deformation and fast construction. In recent years, upper structures such as tall buildings and large span bridges have a stricter demanding to the foundation. It is a challenge as well as opportunity to the theory of settlement calculating of pile foundation.Load transfer method is one of the most classical methods in pile foundation analysis. However, the defect is incapable of calculating the settlement at pile tip caused by lateral friction resistance. By introducing the Mindlin equation and the following Geddes stress coefficient, an improvement of load transfer method is proposed to perfect the classical method in calculating settlement of pile foundation. Randolph's method is used to back analysis the parameter of soil from data recorded in static load experiment.Law of energy conservation is one of the most universal rules in nature which were based on countless experimental facts. Thereby, the settlement of piles must obey the law.Based on this fundamental springboard, elastic mechanics being the basic analyzing tool, the settlement processing of pile foundation is annotated from a view of energy. Assuming no slippage occurred on the interface between pile and soil, an equivalent equation of displacement coordination is obtained to constitute a new method calculating settlement of single pile.Mindlin equation is introduced to analyze reciprocity between piles, associated with method of calculating single piles and bearing properties of rigid and soft caps, four methods are established to calculate settlement of two kinds of caps in conditions when soil reactivity is considered or not.The finite rigid cap is perceived as an elastic sheet, and the theory of sheet bending could be introduced to calculate the displacement modality of finite rigid cap. The displacement modality of cap could be obtained from the coordination of cap and soil under the cap. Then the methods of calculating displacement of pile groups under finite rigidity cap could be proposed in conditions that soil reactivity is involved or not. Reciprocity between the new and old piles is analyzed to calculate annexing settlement of an old pile and settlement discount of a new pile from a view of force and energy separately. The energy analyzing method exhibits its superiority of briefness and efficiency.Using energy method, experimental error in static load tests is analyzed, also, a method to amend the P~S curve is proposed. Conclusions show that the recorded P~S curves over estimate bearing capacity of piles.